Odborné texty pro učební a studijní strojní obory Anglický jazyk
Tvorba odborných textů je součástí projektu spolufinancovaného z Evropského sociálního fondu a státního rozpočtu České republiky, v rámci Operačního programu Vzdělávání pro konkurenceschopnost, registrační číslo CZ.1.07./1.1.10/02.0088
OBSAH OBSAH .................................................................................................... 2 TURNING................................................................................................. 3 MILLING ................................................................................................ 10 DRILLING .............................................................................................. 20 GRINDING ............................................................................................ 24 NUMERICALLY CONTROLLED MACHINES............................................ 29 UNCONVENTIONAL METHODS OF MACHINING ................................ 32 TOOLING MATERIALS ........................................................................... 35 MACHINABILITY OF THE MATERIAL...................................................... 40 STIFFNESS OF THE TECHNOLOGY SYSTÉM ........................................... 52 INDUSTRY, ECONOMY, ENGINEERING AND ITS MANUFACTURING PROCESS IN ENGINEERING ................................................................. 58 PRODUCTION OF PIG IRON ................................................................. 67 CASTING PRODUCTION ....................................................................... 71 INTERNAL STRUCTURE OF MATERIAL AND HEAT TREATMENT .............. 75 NONDESTRUCTIVE TESTING = TESTS OF MATERIAL FAILURE ................ 79 TECHNOLOGICAL PROCESSES ............................................................ 84
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TURNING Soustružení je jedním ze způsobů třískového obrábění, kdy obrábíme rotační plochy vnitřní i vnější – válcové, kuželové, tvarové, a dále plochy rovinné, díry a závity. Soustružení provádíme na soustruhu soustružnickým nožem. Při soustružení se nástroj zařezává ostřím do materiálu, který se proti němu otáčí hlavním řezným pohybem. Nůž při tom koná vedlejší pohyb – posuv, na jehož velikosti je závislá tloušťka odebírané třísky. Požadované hloubky třísky dosáhneme přísuvem = pohybem nože směrem k obrobku. Rotační obrobky se na soustruhu upínají nejčastěji do univerzálního tříčelisťového sklíčidla, pro upnutí součástí nepravidelného tvaru se používá lícní deska. Obrobek musí být upnut pevně, ale nesmí se vlivem působící síly deformovat. Soustružnické nože jsou jednobřité nástroje, které se upínají do nožové hlavy tak, aby špička nástroje byla umístěna výškově v ose obrobku. Nože mohou mít různý tvar a velikost. Jejich rozměry jsou normalizovány. Nože jsou vyrobeny z materiálů, které dobře odolávají zvýšenému mechanickému i tepelnému namáhání. Nejčastěji se používají nástroje, jejichž činná část je vyrobena z keramických materiálů, které jsou velmi tvrdé a odolné proti opotřebení. Odřezáváním třísky a jejím třením o nástroj vzniká teplo, kterým se nástroj zahřívá. Pokud by jeho teplota překročila určitou hranici, nástroj by se nadměrně otupoval. Proto je nutné při obrábění pravidelně a dostatečně chladit a mazat. Soustruhy mohou mít vodorovnou nebo svislou konstrukci a jejich využití je velmi specifické. Nejširší použití má soustruh univerzální hrotový, který se ale hodí pouze pro kusovou výrobu. V sériové a hromadné výrobě se dnes nejčastěji používají soustružnické stroje číslicově řízené, které pracují automaticky podle zadaného programu a zaručují požadovanou kvalitu u všech výrobků. Schéma univerzálního hrotového soustruhu:
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1. 2. 3. 4. 5. 6.
elektromotor vřeteník suport lože koník převody
Turning Turning is one way of chip machining, where the rotary work areas can be divided in internal and external ones – we can speak than about : cylindrical, conical, shape work areas and planar surfaces, holes and threads. The turning is done on a lathe with a turning knife. While the tool is turning, its cutting edge cuts into the material, which is rotated against the main cutting motion. The turning knife makes also another movement done by motion, it can be described as a side – shift movement or displacement, whose size depends on the thickness of the splinter / chip. The chips reach the desired depth-feed = if the knife moves towards the workpiece. The rotational workpieces are clamped on the lathe frequently to a three – jaws universal chuck, a plate is used for clamping of irregular shaped faced materials. Workpiece must be clamped firmly, but not to deform due to operating forces. Turning tools are usually tools with one edge, which are clamped to the blade head so that the tip of the instrument is placed vertically in the axis of the workpiece. Knives can have different shape and size and their dimensions are standardized. The knives are made of materials that can withstand the increasing mechanical well and heat stress. The most commonly used tools have the active part made from ceramic materials and they are very hard and wear resistant. Cutting the chip and its friction on the tool generates heat, which also heats the tool. If the temperature exceeds a certain threshold, the tool would be unduly blunted. Therefore, when working regularly and sufficiently you have to keep your eyes on cooling and lubrication. Lathes can have a horizontal or a vertical construction and their use is very specific. The widest use of the lathe has a universal cylindrical lathe, but it is only suitable for a single-piece production. The serial and mass production now mainly uses lathes that are numerically controlled machines, which can operate automatically according to the specified program and ensure the required quality for all products.
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Diagram of a universal lathe point-contact:
1. 2. 3. 4. 5. 6.
electro motor headstock slide bed tailstock transfers
EXERCISES : Find the mistakes and correct it : 1. Colling 2. Haedstock 3. Knifes 4. Friktion 5. Workpeace Read the text about medieval and renessaince lathes: 1. The lathe is an ancient tool, dating at least to the Egyptians and, "known and used in Assyria, Greece, the Roman and Byzantine Empires.“ The earliest depiction of a lathe comes from a Ptolemaic tomb painting. Primarily a tool of tradesmen known as "turners" or "throwers" (the term "bodgers" came later), the lathe was also used by pulley makers, seal makers, wheelwrights, chairmakers, joiners, pewterers, bell founders, and others. Early evidence of wood turning in England dates from the 4th to the 7th century, and by 1180 there appears to have been a turner's guild established in Cologne, Germany. 2. There are several reasons why this simple machine has been in use for thousands of years. From a practical point of view, the lathe can easily produce truly round objects, invaluable in making wheels for carts and parts for mills and pumps. Turned spindles can also be easily assembled into complex objects such as chairs, beds, tables,
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etc. This same machine also simplifies the making of woodenware for eating, drinking, and storage. From a more aesthetic perspective, turning can create a sort of surface decoration impossible to achieve by hand alone. The combination of mechanical simplicity, versatility, and decorative appeal has made turning a steadily practiced trade throughout European culture. 3. The idea of the lathe is simple: a piece of wood is made to turn on an axis while a sharp tool cuts or scrapes the wood into a desired shape. 4. One of the earliest reliable references to lathes is Theophilus' "On Divers Arts," probably written in the 11th century by a metalworker named Roger of Helmarshausen. In this treatise, he mentioned two lathes. The first is a hand-cranked lathe for turned heavy bell cores. The other is a pewterer's lathe, which he describes as "set up in the same way as the one on which platters and other wooden vessels are turned." This lathe is pulled by "a boy," presumably pulling back and forth on a cord wrapped around the piece being worked. Such reciprocol motion is charactistic of most early lathes, particularly those used in woodworking.
Turner, from the "Mendel Housebook," c. 1436.
A turner and some of his wares, from the "Book of Trades," 1568.
Decide if these statements are true or false: 1. Ptolemaios used a lathe. T 2. The first turners were from England. T 3. It is a simply machine. T 4. Woodenware is used for eating. T 5. „ Book of Trades“ was published in the 16th century. T
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Fill in the words, the picture may help you : offset the tailstock tailstock spindle handwheel
gear box
clamped
F F F F
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Tailstock
Tailstock with legend, numbers and text within the description refer to those in the image: The ________ is a toolholder directly mounted on the spindle axis, opposite the headstock. The _______ (T5) does not rotate but does travel longitudinally under the action of a leadscrew and ________ (T1). The spindle includes a taper to hold drill bits, centers and other tooling. The tailstock can be positioned along the bed and _______ (T6) in position as required. There is also provision to __________ (T4) from the spindles axis, this is useful for turning small tapers. The image shows a reduction _______ (T2) between the handwheel and spindle, this is a feature found only in the larger center lathes, where large drills may necessitate the extra leverage. Solution: The tailstock is a toolholder directly mounted on the spindle axis, opposite the headstock. The spindle (T5) does not rotate but does travel longitudinally under the action of a leadscrew and handwheel (T1). The spindle includes a taper to hold drill bits, centers and other tooling. The tailstock can be positioned along the bed and clamped (T6) in position as required. There is also provision to offset the tailstock (T4) from the spindles axis, this is useful for turning small tapers. The image shows a reduction gear box (T2) between the handwheel and spindle, this is a feature found only in the larger center lathes, where large drills may necessitate the extra leverage.
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Describe the picture :
Vocabulary assemble ......................................... shromáždit, smontovat axis ................................................... osa bed ................................................... lože blade head ...................................... nožová hlava blunt ................................................. tupý, ztupit, otupit ceramic materials ........................... keramické materiály clamp ............................................... svěrák, upnout do svěráku cooling ............................................. chlazení cutting edge .................................... ostří depiction.......................................... vylíčení drill bits ............................................. vrtáky edge ................................................. břit, ostří friction .............................................. tření handwheel....................................... ruční kolo headstock........................................ vřeteník chip machining ............................... třískové obrábění lathe ................................................. soustruh lubrication ........................................ mazání pulley makers .................................. výrobce kladky reduction gear box ......................... redukce převodovky slide .................................................. suport spindle axis ...................................... osa vřetene tailstock............................................ koník taper ................................................. kužel tool ................................................... nástroj, nářadí toolholder ........................................ upínání nástrojů
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transfers ............................................ převody turning knife ..................................... soustružnický nůž turners .............................................. soustružník turning .............................................. soustružení unduly .............................................. příliš, nadměrně withstand.......................................... odolat, vydržet wear resistant .................................. odolný proti opotřebení workpiece........................................ obrobek
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MILLING Frézování je jedním z nejuniverzálnějších způsobů třískového obrábění. Frézováním lze obrábět plochy rovinné, šikmé, tvarové, rotační, výřezy, drážky, ozubená kola a závity. Frézování provádíme na stroji, který se nazývá frézka, pomocí nástroje zvaného fréza. Jedná se o vícebřitý nástroj, který se při obrábění otáčí kolem své osy. Obrobek upnutý na pracovním stole frézky se proti fréze pohybuje většinou přímočarým, případně otáčivým a přímočarým pohybem. Tloušťka odřezávané vrstvy materiálu se nastavuje pomocí přísuvu. Obrobky se na frézce upínají nejčastěji do univerzálního svěráku, velké součásti se upínají přímo na pracovní plochu stroje pomocí upínek a pro upnutí tvarových součástí lze použít přípravky, což jsou speciální upínací zařízení zhotovená pro konkrétní součást. Důvodem je snaha upnout součást co nejrychleji a nejpřesněji, aby byla výroba dostatečně produktivní. Frézy jsou vícebřité nástroje, které se upínají za kuželovou stopku do kuželové dutiny vřetena frézky pomocí redukčního pouzdra. Redukční pouzdro přizpůsobí kužel na stopce frézy rozměru kuželové dutiny vřetena frézky. Frézy se člení podle mnoha hledisek. Mohou být válcové, kuželové nebo tvarové, jemnozubé nebo hrubozubé, celistvé nebo se vsazenými zuby, stopkové nebo nástrčné. Jsou vyrobeny z materiálů, které dobře odolávají zvýšenému mechanickému i tepelnému namáhání. Odřezáváním třísky a jejím třením o nástroj vzniká teplo, kterým se nástroj zahřívá. Pokud by jeho teplota překročila určitou hranici, nástroj by se nadměrně otupoval. Proto je nutné při frézování pravidelně a dostatečně chladit a mazat. Frézky mohou mít vodorovnou nebo svislou konstrukci a jejich využití je velmi široké. Nejširší použití má frézka univerzální konzolová nebo frézka rovinná, ale nejčastěji se dnes používají tzv. obráběcí centra. Jedná se o frézovací stroj, který je vybaven dalšími obráběcími jednotkami – např. vrtací nebo soustružnickou. Na nich lze opracovat součást ze všech stran při jednom upnutí, čímž se zvýší přesnost výroby a zároveň se zkrátí výrobní čas.
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Schéma rovinné frézky: 1
.......................................................... .............................. .......................................................... ..........................................................
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1. 2. 3. 4. 5.
Stojan Příčné rameno Vřeteník Pracovní stůl Lože
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4 5 Milling A milling machine (also see synonyms below) is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines. Unlike a drill press, which holds the workpiece stationary as the drill moves axially to penetrate the material, milling machines also move the workpiece radially against the rotating milling cutter, which cuts on its sides as well as its tip. Workpiece and cutter movement are precisely controlled to less than 0.001 in (0.025 mm), usually by means of precision ground slides and leadscrews or analogous technology. Milling machines may be manually operated, mechanically automated, or digitally automated via computer numerical control (CNC). Milling machines can perform a vast number of operations, from simple (e.g., slot and keyway cutting, planing, drilling) to complex (e.g., contouring, diesinking). Cutting fluid is often pumped to the cutting site to cool and lubricate the cut and to wash away the resulting swarf. Types and nomenclature Mill orientation is the primary classification for milling machines. The two basic configurations are vertical and horizontal. However, there are alternate classifications according to method of control, size, purpose and power source. Mill orientation 1. Vertical mill
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Vertical milling machine. 1: milling cutter 2: spindle 3: top slide or overarm 4: column 5: table 6: Y-axis slide 7: knee 8: base In the vertical mill the spindle axis is vertically oriented. Milling cutters are held in the spindle and rotate on its axis. The spindle can generally be extended (or the table can be raised/lowered, giving the same effect), allowing plunge cuts and drilling. There are two subcategories of vertical mills: the bed mill and the turret mill. 1. A turret mill has a stationary spindle and the table is moved both perpendicular and parallel to the spindle axis to accomplish cutting. The most common example of this type is the Bridgeport, described below. Turret mills often have a quill which allows the milling cutter to be raised and lowered in a manner similar to a drill press. This type of machine provides two methods of cutting in the vertical (Z) direction: by raising or lowering the quill, and by moving the knee. 2. In the bed mill, however, the table moves only perpendicular to the spindle's axis, while the spindle itself moves parallel to its own axis. Turret mills are generally considered by some to be more versatile of the two designs. However, turret mills are only practical as long as the machine remains relatively small. As machine size increases, moving the knee up and down requires considerable effort and it also becomes difficult to reach the quill feed handle (if equipped). Therefore, larger milling machines are usually of the bed type. Also of note is a lighter machine, called a mill-drill. It is quite popular with hobbyists, due to its small size and lower price. A mill-drill is similar to a small drill press but equipped with an X-Y table. These are frequently of lower quality than other types of machines.
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2. Horizontal mill
Horizontal milling machine. 1: base 2: column 3: knee 4 & 5: table (x-axis slide is integral) 6: overarm 7: arbor (attached to spindle) A horizontal mill has the same sort of x–y table, but the cutters are mounted on a horizontal arbor across the table. Many horizontal mills also feature a built-in rotary table that allows milling at various angles; this feature is called a universal table. While endmills and the other types of tools available to a vertical mill may be used in a horizontal mill, their real advantage lies in arbor-mounted cutters, called side and face mills, which have a cross section rather like a circular saw, but are generally wider and smaller in diameter. Because the cutters have good support from the arbor and have a larger cross-sectional area than an end mill, quite heavy cuts can be taken enabling rapid material removal rates. These are used to mill grooves and slots. Plain mills are used to shape flat surfaces. Several cutters may be ganged together on the arbor to mill a complex shape of slots and planes. Special cutters can also cut grooves, bevels, radii, or indeed any section desired. These specialty cutters tend to be expensive. Simplex mills have one spindle, and duplex mills have two. It is also easier to cut gears on a horizontal mill. Some horizontal milling machines are equipped with a power-take-off provision on the table. This allows the table feed to be synchronized to a rotary fixture, enabling the milling of spiral features such as hypoid gears. Comparative merits The choice between vertical and horizontal spindle orientation in milling machine design usually hinges on the shape and size of a workpiece and the number of sides of the workpiece that require machining. Work in which the spindle's axial movement is normal to one plane, with an endmill as the cutter, lends itself to a vertical mill, where the operator can stand before the machine and have easy access to the cutting action by looking down upon it. Thus vertical mills are most favored for diesinking work (machining a mold into a block of metal). Heavier and longer workpieces lend themselves to placement on the table of a horizontal mill. Prior to numerical control, horizontal milling machines evolved first, because they evolved by putting milling tables under lathe-like headstocks. Vertical mills appeared in subsequent decades, and accessories in the form of add-on heads to change horizontal mills to vertical mills (and later vice versa) have been commonly used. Even in the CNC era, a heavy workpiece needing machining on multiple sides lends itself to a horizontal machining center, while diesinking lends itself to a vertical one.
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Alternate classifications In addition to horizontal versus vertical, other distinctions are also important: Criterion
Example classification scheme
Comments
Spindle axis orientation
Vertical versus horizontal; Turret versus non-turret
Among vertical mills, "Bridgeport-style" is a whole class of mills inspired by the Bridgeport original, rather like the IBM PC spawned the industry of IBMcompatible PCs by other brands
Control
Manual; Mechanically automated via cams; Digitally automated via NC/CNC
In the CNC era, a very basic distinction is manual versus CNC. Among manual machines, a worthwhile distinction is non-DRO-equipped versus DRO-equipped
Number of axes (e.g., 3-axis, 4-axis, or more); Within this scheme, also: Control (specifically among CNC machines)
• •
Pallet-changing versus non-palletchanging Full-auto toolchanging versus semi-auto or manual tool-changing
Purpose
General-purpose versus special-purpose or singlepurpose
Purpose
Toolroom machine versus production machine
Overlaps with above
Table design
"Plain" versus "universal"
A distinction whose meaning evolved over decades as technology progressed, and overlaps with other purpose classifications above; Commonly, a "plain table" means the table is fixed in place on the machine and cannot be rotated. A "unversal table" means that the table may be rotated to various angles.
Size
Micro, mini, benchtop, standing on floor, large, very large, gigantic
Power source
Line-shaft-drive versus Most line-shaft-drive machines, ubiquitous circa individual electric motor drive 1880-1930, have been scrapped by now Hand-crank-power versus electric
Hand-cranked not used in industry but suitable for hobbyist micromills
EXERCISES: Answer following questions : 1. What is milling ? 2. What is the difference between a vertical and horizontal milling machine ? 3. How can the milling machines be operated ? 4. Have you ever worked on a milling machine ? If yes, describe it. 5. What is the diference between a milling machine and a CNC machine?
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Look at the following picture, and describe them in detaile, what is the same, where are the differences between those two :
You found the following advertisment in the newspaper. Write a letter of request,about 60 – 70 words, where you want to know, what the price is, what the terms of delivery are and ask for the catalog they offer :
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Start with : Dear Sir or Madam, …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………
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DETAILED DESCRIBTION OF A VERTICAL MILLING MACHINE :
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DETAILED DESCRIBTION OF A HORIZONTAL MILLING MACHINE:
Vocabulary access ............................................. přístup accomplish ...................................... splnit, dodělat arbor................................................. hřídel a vast number of ............................. brovské množství built-in .............................................. vestavěný column ............................................. stojan contouring ....................................... konturování cutting fluid ...................................... řezná kapalina cutting tool....................................... řezný nástroj die sinking ....................................... výroba zápustek drill press .......................................... vrtačka evolve .............................................. vyvinout se, vyvíjet se flat surfaces ..................................... rovné povrchy front view ......................................... čelní pohled
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groove.............................................. drážka, žlábek machine tool ....................................... obráběcí stroj milling head ..................................... frézovací hlava milling machine .............................. frézka, fréza penetrace ........................................ proniknout shape ............................................... tvar, formovat side view .......................................... boční pohled solid materials ..................................... pevné materiály spindle................................................ vřeteno, vřeteník swarf ................................................. tříska, piliny
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DRILLING Vrtání patří mezi nejstarší a nejpoužívanější technologické operace. Je definováno jako zhotovování kruhových děr do plného materiálu. Kromě vrtání do plného materiálu rozlišujeme ještě tzv. vyvrtávání, kterým zvětšujeme díry předvrtané nebo předlité. Hlavní řezný pohyb – otáčivý - vykonává při vrtání nástroj, který se zároveň posouvá do řezu pomocí ručního nebo strojního posuvu. K vrtání se používají různé druhy vrtáků. Jedním z nejstarších vrtáků je vrták kopinatý, který pracuje nepřesně a dnes se prakticky již nepoužívá. Zvláštní uplatnění má vrták hlavňový, používaný pro výrobu hlubokých děr. Na vrtání skla a dalších velmi tvrdých materiálů se používá vrták trojhranný. Nejrozšířenějším a nejpoužívanějším vrtákem je vrták šroubovitý, jehož tělo se dvěma drážkami ve tvaru šroubovice umožňuje účinné odvádění třísek a zároveň zajišťuje dostatečné chlazení. Vrtáky se upínají do vřetena vrtaček za stopku, která může mít válcový nebo kuželový tvar. Materiálem vrtáků může být uhlíková nástrojová nebo rychlořezná ocel, případně lze použít vrták s řeznými destičkami ze slinutých karbidů. Pro vrtání se používají ruční nebo strojní vrtačky nejrůznější konstrukce a velikosti. Rozlišujeme vrtačky stolní, stojanové nebo sloupové, pro náročnější vrtací práce se volí vrtačky otočné radiální, souřadnicové, číslicově řízené nebo vícevřetenové. Obráběné součásti se při vrtání musí upínat takovými pomůckami, které zachycují síly přenášené vrtákem a zajišťují součást v takové poloze, aby střed díry ležel pod středem špičky vrtáku. Nejčastěji se používají různé typy svěráků. Teplo vznikající při vrtání odvádíme chlazením. Nadměrný ohřev špičky vrtáku by mohl způsobit ztrátu jeho tvrdosti a rychlé otupení. Chladíme často vodním roztokem (emulzí) s přísadou mýdla a emulzního oleje. Větší mazací účinek má řezný olej, který ale méně chladí. Výkon vrtáku je stejně jako u každého jiného nástroje závislý zejména na správném naostření. Vrtáky se ostří na speciálně konstruovaných ostřících strojích. Šroubovitý vrták:
zub (břit)
zubová mezera
krček
unášeč
L – délka vrtáku l1 – činná část vrtáku l2 - krček
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l3 – tělo vrtáku l4 - stopka Drilling Drilling is one of the oldest and most widely used technology operations. It is defined as the production of circular holes in the full material. In addition to drilling into the full material it can be also distinguished in so called drilling, pre-drilled holes which are magnifying or precasted. The main cutting motion - rotating - carries the drilling tool, which is also shifted to the cut with hand or power feed. Various types of drills are used for drilling. One of the oldest drill bit is lanceolatum, which works incorrectly and is now practically no longer used. There are several another types that may be used for drilling, e.g. special application to drill the barrel, which are used for production of deep holes. Triangular drill is used for drilling of glass and other very hard materials. Most widespread and most commonly used drill is a twist drill, a body with two grooves in the spiral form enables the effective removal of chips while providing enough cooling. Drills are clamped in the spindle shank drills, which may have a cylindrical or conical shape. Drill material may be carbon or high speed steel tool, or you can use a drill with carbide inserts. We can decide which type of drilling machine we would like to use, there are hand or machine drill and their variety of designs and sizes. We can also distinguish drill table, floor, or pillars, for more demanding drilling we can choose rotary radial coordinate, and numerically controlled multiple spindle drilling The workpiece has to be clamped in the drilling of such devices that capture the forces transmitted by the drill and provide part in such a position that the center of the hole lies below the center of the drill tip. Clamps are the most commonly used various types of such machines. Heat generated during drilling is disposed of cooling. Excessive heating of the tip of the drill could cause the loss of its hardness and rapid blunting. We often use for cooling an aqueous solution (emulsion), with addition of soap and oil emulsion. Greater lubricating effect of the cutting oil, but which is less cool. Performance of the drill is the same as for any other instrument is particularly dependent on proper sharpening. Drills are specially designed for blade sharpening machines. Twist drill
cutting edge
cutting edge gap
neck drill
tenon
21
L – length of the drill l1 – active part of the drill l2 – neck drill l3 – body drill l4 – drill stem Activities: Answer the questions to the article: 1. Which type sof drill machines can you name? 2. Why do we use cooling ? 3. Which kinds of drill bits do you know?
1. Where would you use dribling ? 2. Have you ever used it before? 3. Can you name any advantages and disadvantages of drilling ? Additional reading material Twist drill bits The twist drill bit is the type produced in largest quantity today. It comprises a cutting point at the tip of a cylindrical shaft with helical flutes; the flutes act as an Archimedean screw and lift swarf out of the hole. The twist drill bit was invented by Steven A. Morse of East Bridgewater, Massachusetts in 1861. The original method of manufacture was to cut two grooves in opposite sides of a round bar, then to twist the bar (giving the tool its name) to produce the helical flutes. Nowadays, the drill bit is usually made by rotating the bar while moving it past a grinding wheel to cut the flutes in the same manner as cutting helical gears. Twist drill bits range in diameter from 0.002 to 3.5 in (0.051 to 89 mm)[4][5] and can be as long as 25.5 in (650 mm).[6] The geometry and sharpening of the cutting edges is crucial to the performance of the bit. Small bits that become blunt are often discarded because sharpening them correctly is difficult and they are inexpensive. For larger bits special grinding jigs are available. A special tool grinder is available for sharpening or reshaping cutting surfaces on twist drills to optimize the drill for a particular material. Manufacturers can produce special versions of the twist drill bit, varying the geometry and the materials used, to suit particular machinery and particular materials to be cut. Twist drill bits are available in the widest choice of tooling materials. However, even for industrial users, most holes are drilled with standard high speed steel bits. The commonest twist drill (sold in general hardware stores) has a point angle of 118 degrees, acceptable for use in wood, metal, plastic, and most other materials, although it does not perform as well as using the optimum angle for each material. In most materials it will not tend to wander or dig in. A more aggressive (acute) angle, such as 90 degrees, is suited for very soft plastics and other materials; it would wear rapidly in hard materials. The bit will generally be self-starting and cut very quickly. A shallower angle, such as 150 degrees, is suited for drilling steels and other tougher materials. This style of bit 22
requires a starter hole, but will not bind or suffer premature wear so long as a suitable feed rate is used. Drills with no point angle are used in situations where a blind, flat-bottomed hole is required. These drills are very sensitive to changes in lip angle, and even a slight change can result in an inappropriately fast cutting drill bit that will suffer premature wear. Long series drills are extended length twist drills. They are not the best tool for routinely drilling deep holes as they require frequent withdrawal to clear the flutes of swarf and prevent drill breakages. Gun drills are the preferred drills for deep hole drilling.
Twist drill bit cutting edges
Twist drill bit with Morse taper shank
11/32" (8 mm) drills - long-series morse, plain morse, jobber
Vocabulary clamp ............................................... svěrák cutting edge ............................... zub, břit drill .................................................... vrtačka, vrtání length of the drill ...................................... délka vrtáku main cutting motion ................................ hlavní řezný pohyb sharpening ....................................... ostření
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GRINDING Broušení je dokončovací způsob obrábění, jehož cílem je dosáhnout přesný rozměr a tvar součásti a hladký povrch obrobku. Dále se broušení používá k ostření řezných nástrojů a pro obrábění materiálů, které se běžnými metodami obrábět nedají, protože jsou velmi tvrdé. Brousit lze plochy rovinné, rotační i tvarové, a to vnitřní i vnější, a dále výřezy, drážky, závity nebo ozubená kola. Broušení provádíme na bruskách pomocí brusných kotoučů. Brusný kotouč se při obrábění otáčí kolem své osy. Obrobek upnutý na pracovním stole brusky se pohybuje většinou přímočarým, nebo otáčivým a přímočarým pohybem. Tloušťka odřezávané vrstvy materiálu je velmi malá a nastavuje se pomocí přísuvu. Brusné kotouče jsou mnohabřité nástroje s nepravidelnou geometrií. Jsou tvořeny dvěma složkami – brusivem a pojivem. Brusivo je tvrdá ostrohranná složka různé velikosti, podle které rozlišujeme kotouče na jemné nebo hrubé. Jako brusivo se používá oxid hlinitý, karbid boru, karbid křemíku nebo diamant. Tvar kotouče udržuje pojivo, nejčastěji silikátové nebo keramické. Kotouče mohou mít různý tvar, podle tvaru broušené součásti. Rozlišujeme kotouče ploché, hrnkové, miskové, talířové, tvarové. Jsou vždy rotační, uprostřed mají otvor, za který se upínají na trn brusky. Musí být vždy dobře vystředěny a vyváženy, aby při broušení neházely. Nevyváženost brusného kotouče způsobuje nepřesnosti při výrobě a nelze dosáhnout požadované kvality povrchu. Obrobky se na brusce upínají různými způsoby v závislosti na jejich tvaru a na konstrukci stroje. Rovinné brusky, na kterých se opracovávají rovinné plochy, bývají vybaveny magnetickou upínací deskou. Upínání na magnetické desce je velmi rychlé, spolehlivé a bezpečné, ale upínací plocha obrobku musí být dostatečně velká. Dlouhé rotační součásti se opracovávají na bezhrotých bruskách, kde se obrobek neupíná, pouze se při broušení podepírá opěrnou lištou. Kratší rotační součásti se brousí na bruskách na kulato, kde se upínají většinou mezi hroty. Vnitřní plochy se brousí na bruskách na díry, kde se používají speciální brusná tělíska. Brusné kotouče jsou velmi křehké a mají sklon k praskání. Rozletí-li se prasklý nebo špatně upnutý kotouč, pak při vysoké obvodové rychlosti znamenají letící kusy smrtelné nebezpečí, proto se při broušení používají ochranné kryty. Zároveň je třeba použít ochranné brýle a zapnout při práci odsávání prachu. Schéma horizontální rovinné brusky: 1. 2. 3. 4. 5.
1
Vřeteník brusky Stojan s vedením Podélný stůl Křížový stůl Lože
2 3
4 5 24
Grinding Grinding is the finishing machining method, which aims to achieve the exact size and shape of parts and smooth of the workpiece surface. Further grinding is used for sharpening cutting tools for machining materials which cannot be done by conventional machining methods, because the machining materials are very hard. The grind surface can be not only flat, rotational and shaped, but we can also have here an internal and external surface. Grinding can be also used for cutouts, grooves, threads or gears. Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool, that means grinding is done on grinding machine with grinding wheels. The grinding disc during operation, rotates on its axis. The workpiece, which is placed on the desktop machines are moving mostly in a linear or in a rotary and linear motion. The thickness of cutting layer of material is very small and is configurable with infeed. The tolerances that are normally achieved with grinding are ± 5 um for a grinding a flat material and 8 um for a parallel surface. Abrasive wheels have several edges with an irregular geometry. They consist of two elements – the abrasive and the binder one. The abrasive element is a hard angular component of various sizes, according to which we can divide the wheels into fine or coarse. The abrasive special materials are aluminum oxide, boron carbide, silicon carbide or diamond. The shape of the blade keeps a binder, usually ceramic or silicate. The blades may have a different shape usually according to the shape of the ground component. That is why we can divide the abrasive wheels into : flat wheels, pot, dish, plate, shaped. They are always rotating in the middle with a hole for the mandrel and are clamped on the grinder. They must be well centered and balanced, otherwise the grinding process may be interrupted by deflection of the grinding wheel. The wheel imbalance causes inaccuracies in the manufacture and after that we cannot achieve the required surface quality. Surface grinding uses a rotating abrasive wheel to smooth the flat surface of metallic or nonmetallic materials to give them a more refined look or to attain a desired surface for a functional purposes. The surface grinder is composed of an abrasive wheel, a workholding device known as a chuck, either electromagnetic or vacuum, and a reciprocating table. The workpieces are clamped on the grinder in different ways depending on their shape and design of the machine. The surface grinding machine, which worked on the flat surface, is usually equipped with a magnetic clamping plate. Clamping on a magnetic board is very fast, reliable and safe, but clamping of the workpiece surface must be large enough. Long turned parts machined to the unpointed grinding where the workpiece is not clamped, only buttresses supporting the grinding rail. Shorter rotating components are cut on the grinding round, where they are usually clamped between centers. The inner surfaces are cut on the grinding of holes by the use of special grinding bodies. Abrasive wheels are very fragile and prone to cracking. If an abrasive wheel breaks, then the flying pieces can cause at high peripheral speeds deadly danger. That is the reason why we should use grinding guards. It is also necessary to use protective glasses and turn on the dust collection work.Poslech Fonetický přepis Diagram of a horizontal surface grinding machines: 1 . Headstock Sanders
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2. 3. 4. 5.
1
Stand with management Longitudinal table Cross Table Bed
2 3
4
5 Tasks : •
There is a paragraph which can be removed. Find it.
• •
Use the diagram to describe the grinding process : Answer the following questions : 1. What is grinding? 2. Where can we use grinding? 3. What is an abrasive wheel? 4. Which abrasive materials do you know? 5. What is a surface grinder composed of?
•
Here you see a picture, can you quess what it is? Describe it in own words :
(Sketch of how abrasive particles in a grinding wheel remove material from a workpiece.)
•
Find the given words in the crossword: Abrasive, are, bed, binder, can, chuck, clamp, cut, diamond, end, fine, flat, grinding, hole, part, plate, safe, shape, size, the
G
T
Z
P
A
R
T
F
X
C 26
y Q C H U C K T •
R M E T A L P H
E I U B S A F E
V C N E Z M Q D
I H G D B P J N
S O Y S I Z E O
A L F H N N X M
R E I A D A G A
B H N P E R T I
A N E E R E N D
Find in the text the opposites to these words:
FINE INTERNAL FLAT RELIABLE SAFE
•
Make the comparative and superlative of these adjectives: FINER INTERNAL FLATTER RELIABLE THE SAFEST
•
USE the adjectives and thein forms to create own sentences :
Poslech Fonetický přepis
27
Vocabulary Abrasive ........................................... brusivo, brusný materiál, brusný, drsný Bed ................................................... lože, lůžko Binder ............................................... tmel, vazač Blade ................................................ čepel, ostří Chuck............................................... upínací pouzdro, koník Clamp .............................................. svorka, upnout do svěráku Coarse.............................................. drsný, hrubý Cut .................................................... řezat, krájet Danger ............................................. nebezpečný, nebezpečí Diamond .......................................... diamant edge ................................................. břit, hrana Fine ................................................... jemný Flat .................................................... rovný, rovinný Grind ................................................ brousit, mlít Hole .................................................. díra Mandrel............................................ trn brusky Reliable ............................................ spolehlivý Safe .................................................. bezpečný Shape ............................................... tvar Size ................................................... velikost Surface ............................................. povrch, plocha, strana, rovina Wheel ............................................... kolo, kotouč Workpiece ....................................... obrobek
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NUMERICALLY CONTROLLED MACHINES Trvalým směrem rozvoje ve výrobních odvětvích je automatizace. Ve velkosériové a hromadné výrobě se dříve používaly výrobní linky a jednoúčelové stroje, u kterých byly jednotlivé činnosti řízené pomocí narážek, vaček a dorazů. Tyto automatizační prvky však lze jen obtížně a zdlouhavě přizpůsobovat změnám ve výrobě. O tomto druhu automatizace hovoříme jako o tvrdé automatizaci. Pro automatizaci v oblasti malosériové, sériové i hromadné výroby se dnes používá strojů, u kterých lze poměrně snadno a rychle provést změnu nebo úpravu výrobního programu. Říkáme, že tyto stroje mají určitou pružnost, protože pružně reagují na změnu výroby, proto se tento druh automatizace nazývá pružnou. V těchto případech se automatický pracovní cyklus zajišťuje převážně číslicovým řízením. Číslicové řízení je druh programovacího řízení, u kterého jsou veškeré informace o požadovaném pracovním cyklu zapsány ve formě alfanumerických znaků tj. pomocí číslic a písmen. Řízení je označováno jako NC – z angl. numerical control. Ovládání pracovních funkcí je prováděno řídícím systémem podle předem vytvořeného programu, ve kterém jsou ve správné posloupnosti obsaženy všechny informace o pracovním procesu. Program je zaznamenán na vhodné médium – nejčastěji CD, flash disc. Informace v programu se člení na geometrické, které popisují dráhy nástroje, technologické, které zadávají řezné podmínky při výrobě a pomocné – například start nebo stop programu, zapnutí chlazení Výhody číslicového řízení: Vlivem zařazení NC strojů do výrobního procesu se značně zjednoduší příprava výroby, oproti použití vaček a narážek se výrazně zkrátí seřizovací čas, zvýší se kvalita i kvantita výroby, odstraní se chyby způsobené obsluhou, zjednoduší se agenda náhradních dílů, protože stačí archivovat pouze program pro danou součást. Mezi nevýhody využití NC strojů bychom pak jistě zařadili vyšší pořizovací cenu NC stroje, vyšší nároky na přípravu výroby, na kvalifikaci údržby a na organizaci práce na pracovištích. Numerically controlled machines Automation is a constant in the direction of development of nowdays industries. Pre-existing production lines and special purpose machines, which were controlled by various allusions activities, cams and stops, which were often used in a large series and mass production. These automation elements, however, are difficult and time consuming to adjust to changes in production. That is why this kind of automation is often called as hard automation. Automation of small-batch, batch and mass production is now using machines where needed changes or adjustments of the production program can be fairly easily and quickly made. We say that these machines have some flexibility as to flexibly respond to changes in production, so this kind of automation is called flexible. In these cases, the automatic cycle ensures mostly numeric control. Numerical control programming is a kind of management in which all information about the required duty cycle are written in the form of alphanumeric characters ie using the numbers and letters. This procedure is known as the NC – from the English abbreviation for numerical control. Controlling the work function of the control system is carried out according to a pre-created program, which contains all 29
information about the process in a correct sequence. The program is recorded on a suitable medium - mostly CDs, flash drives. Information on the program is divided into geometric, describing toolpaths, technology, awarded by cutting manufacturing and ancillary - such as start or stop the program, turn on cooling etc. Advantages of digital / numeric control: Due to the inclusion of NC machines in the manufacturing process it is considerably simplified the preparation of production, compared to the use of cams, and allusions to significantly shorten the adjustment time, increase the quality and quantity of production, eliminate errors caused by the operator, simplifying the agenda of spare parts, because it is sufficient only to archive or save some parts of the program. Disadvantages of digital/ numerical control: Among the disadvantages of using NC we would certainly put a higher cost of NC machines, higher demands on production engineering, qualification and maintenance of workplace policy. Read the text and answer the questions : 1. What kind of automation elements are mentioned in the text? 2. What is the diference between the hard automation and the flexible automation ? 3. Which characters are often used in numeral control programes ? 4. What are the advantages and disadvantages of NC machines ? 5. Where can you find NC machines ? Exercises: 1. Areas of applied numerical control machines. Connect the english word with the czech one: 1. Machine tools 2. forming machines 3. machines for welding 4. machines for cutting with flame, laser and water jet 5. measuring machines 1. 2. 3. 4. 5.
měřicí stroje stroje pro svařování obráběcí stroje stroje pro řezání plamenem, laserem a vodním paprskem tvářecí stroje
2. Development of NC machines Look at the picture and describe the developing stages of CNC machines. Use the words in the box: valve ................................................ relay LSI – Large Scale Integration ....................................... transistor VLSI – Very Large Scale Integration ....................................... PC
. 30
Vocabulary abbreviation .................................... zkratka adjust................................................ nastavit, seřídit advantage ....................................... výhoda allusion ............................................. narážka automation ...................................... automatizace batch ................................................ malosériové cost ................................................... náklady disadvantage .................................. nevýhoda forming machines ........................... tvářecí stroje increase ........................................... vzrůst LSI – Large Scale Integration .......... tranzistory a obvody vysokého stupně .......................................................... Integrace – LSI integrované obvody machines for cutting with flame, laser and water jet .......................................................... stroje pro řezání plamenem, laserem a vodním .......................................................... paprskem machines for welding ..................... stroje pro svařování machine tools.................................. obráběcí stroje measuring machines ...................... měřící stroje numerical kontrol ............................ číslicově řízené relay ................................................. relé stage ................................................ úroveň transistor ........................................... tranzistor valve ................................................ elektronka VLSI – Very Large Scale Integrationobvody velmi vysokého stupně integrace – .......................................................... VLSI integrované obvody Notes :
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UNCONVENTIONAL METHODS OF MACHINING Nekonvenční metody obrábění se používají zejména pro obrábění tvarových součástí, pro opracování těžko obrobitelných materiálů, při výrobě extrémně malých nebo nekruhových otvorů. Mezi nejčastěji používané nekonvenční metody obrábění patří obrábění laserem. Laser je definován jako kvantový generátor světla. Princip metody spočívá v tom, že paprsek světla je soustředěn na velmi malou plošku obrobku. Světelná energie se při dopadu přeměňuje na energii tepelnou, materiál se taví a odpařuje. Laser se používá při řezání všech druhů ocelí, slitin hliníku, plastů, keramiky, pro výrobu velmi malých otvorů, pro gravírování a popisování kovových i nekovových dílů, pro povrchové legování, svařování a dále při měření rychlostí a vzdáleností různých předmětů včetně kosmických těles, v ekologii při měření emisí a v neposlední řadě v lékařství. Další často používanou metodou je obrábění vodním paprskem, při kterém využíváme vysoké rychlosti a vysokého tlaku vody ve velmi úzkém paprsku. Tlak vody dosahuje až několik set MPa. Vodní paprsek se používá pro dělení různých materiálů oceli, skla, betonu, ale také papíru, lepenky a mražených potravin. K obrábění lze využít i svazek elektronů. Podstata metody spočívá ve využití pohybové energie paprsku elektronů soustředěných na velmi malou plochu obrobku. V místě dopadu se kinetická energie přeměňuje na energii tepelnou (teplota dosahuje až 6000°C), vlivem které se materiál taví a odpařuje. Celý proces však nutno provádět ve vakuové komoře z nerezové oceli, která je poměrně drahá. Pro opracování tenkostěnných součástí, tvarově složitých málo tuhých součástí a pro děrování trubek se často používá chemické obrábění. Úběr materiálu nastává odleptáním povrchových vrstev o tloušťce několik desetin milimetru. Používají se k tomu různé druhy kyselin nebo alkálií. Plochy, které nemají být leptány se opatřují ochranným nátěrem nebo se přelepí speciální páskou. Unconventional methods of machining are mainly used for cutting shaped parts for machining difficult to machine materials, the manufacture of extremely small or non-circular holes. The most commonly used unconventional methods of treatment include laser machining. The laser is defined as a quantum generator of light. Principle of the method lies in the fact that the beam is concentrated on a very small facet of workpiece. Light energy is converted to the impact of thermal energy, material is melted and vaporized. Laser is used for cutting all types of steel, aluminum, plastics, ceramics, for the manufacture of very small openings for the engraving and description of metallic and nonmetallic parts, surface alloying, welding, and also in measuring speed and distance of various objects, including space objects, in ecology emissions were measured, and not least in medicine Another frequently used method is the water jet machining, in which the use of high speed and high pressure water in very narrow beam. Water pressure of up to several hundred MPa. Water jet cutting is used for a variety of materials - steel, glass, concrete, but also paper, paperboard and frozen foods. The machines can also use the beam of electrons. Principle is to use kinetic energy electron beam focused on a very small area of the workpiece. In effect, the kinetic energy is converted into heat energy (temperature reaches 6000 ° C), due to 32
which the material melts and evaporates. But the whole process must be carried out in a vacuum chamber made of stainless steel, which is relatively expensive. For cutting thin-walled parts of intricate little parts and solid punching tubes are often used for dry machining. Material removal occurs by etching of the surface layers with a thickness of several tenths of a millimeter. They are used for various kinds of acids or alkalis. Areas not to be etched to procure protective paint or seal on a special tape. Activities: •
Answer the following questions : 1. What is laser ? 2. Where can it be used ? 3. What kinds of methods do you know ? 4. Which materials can be cut by water jet machining?
•
Explain in own words following terms :
Laser energy
beam of electrons
high pressure
kinetic
vacuum chamber
•
Describe the picture : ( warning symbol for lasers)
•
Read the text and decide if the statements are true or false :
Laser cutting is a technology that uses a laser to cut materials, and is typically used for industrial manufacturing applications, but is also starting to appear in schools. Laser cutting works by directing the output of a high power laser, by computer, at the material to be cut. The material then either melts, burns, vaporizes away, or is blown away by a jet of gas, leaving an edge with a high quality surface finish. Industrial laser cutters are used to cut flat-sheet material as well as structural and piping materials. 1. 2. 3. 4. 5. •
Laser cutting is only used in schools. yes / no We use low power laser for the output. yes /no Laser is typically used for industrial manufacturing applications yes / no The material can melt or burn efore i tis finished. yes / no It can cut wide materials too. Yes / no
Create the acronym by using following words: Light Amplification by Stimulated Emission of Radiation
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TOOLING MATERIALS Řezné nástroje jsou při obrábění vystaveny značnému namáhání. Nástroj je při obrábění zatěžován jednak velkými řeznými silami potřebnými k odřezávání třísky, dále tepelným zatížením a zároveň zvýšeným otěrem. Proto jsou kladeny na nástrojové materiály vysoké požadavky. Jejich pevnostní vlastnosti, odolnost proti opotřebení a proti tepelnému zatížení musí být dostatečné, aby si nástroj zachoval své řezné vlastnosti po stanovenou dobu trvanlivosti a životnosti, a to i při vysokých rychlostech obrábění. Požadavky na řezné materiály: 1. tvrdost 2. pevnost 3. houževnatost 4. řezivost Řezné nástroje mohou být vyrobeny jako monolitní, kdy tělo nástroje i jeho řezná část jsou tvořeny jedním kusem. Jsou to nástroje vyrobené většinou z nástrojové oceli, která může být uhlíková, legovaná nebo rychlořezná. Tyto oceli se od sebe liší obsahem legujících prvků, který ovlivňuje použitelnost materiálu za zvýšených teplot. Nejlepší z nástrojových ocelí si svoje řezné vlastnosti zachovává až do teploty 600°C. Kromě monolitních nástrojů se častěji používají nástroje s vyměnitelnými řeznými destičkami. Tělo těchto nástrojů je vyrobeno z konstrukční oceli a činná část nástroje – břity jsou vyrobeny z některého z dalších řezných materiálů – např. ze slinutého karbidu, z řezné keramiky, z cermetu, kubického nitridu boru nebo ze syntetického diamantu. Mají tvar řezné destičky a po otupení se vyměňují. Slinuté karbidy a cermety se vyrábějí tzv. práškovou metalurgií z karbidů těžkých kovů. Nejedná se o slitinu, ale o směs prášků. Jsou velmi tvrdé a křehké a snáší teplotu 900 - 1200°C. Keramické řezné materiály se vyznačují vysokou tvrdostí za studena i za tepla. Výchozí surovinou při výrobě je oxid hlinitý. Pracují při teplotě až 1200°C. Kubický nitrid boru snáší teploty až 2000°C a je vysoce odolný opotřebení. Je však velmi křehký. Nejtvrdším řezným materiálem je polykrystalický diamant. Povlakují se jím řezné destičky ze slinutých karbidů, čímž se značně prodlouží trvanlivost nástroje. Jednobřitý vrtací nástroj s řeznou destičkou:
Řezná destička
Vodící lišta
Tělo nástroje
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Tooling Materials Cutting tools for machining operations are subjected to considerable strain. The tool is first loaded when machining with high cutting forces required for cutting chips, as well as thermal loads and also increased wear. Therefore, high standards are placed on the tool materials. Their strength properties, wear resistance and thermal load must be sufficient to maintain its cutting tool, which features a fixed shelf life and durability, even at high speed machining. Requirements for cutting materials: 1. Hardness 2. Strength 3. Toughness 4. Rustiness Cutting tools can be manufactured as monolithic, when the body and the cutting tools are made of one piece. They are tools usually made of tool steel, which can be made from carbon, alloy, or speed cutting. These steels differ in content of alloying elements which affect the applicability of the material at elevated temperatures. Best of the tool steel retains its cutting properties at temperatures up to 600 ° C. In addition to monolithic tools which are frequently used with replaceable cutting inserts. The body of these tools are made of structural steel and an active part of the tool - blades are made from any of the other cutting materials - such as tungsten carbide, cutting of ceramics, the cermet, cubic boron nitride and synthetic diamond. They have the shape of cutting inserts and after blunting they are usually exchanged. Cemented carbides and cermets are produced by powder metallurgy called carbides of heavy metals. This is not an alloy but a mixture of powders. They are very hard and brittle and can withstand temperature of 900 - 1200 ° C. Ceramic cutting materials are marked with high hardness, in cold and in warm conditions. The starting material for the production is alumina. They work at up to 1200 ° C. Cubic boron nitride withstands temperatures up to 2000 ° C and is highly resistant to wear. However, it is very fragile. The hardest cutting material is polycrystalline diamond. It coats the cutting insert of sintered carbides, thereby it greatly extends tool life. Single point cutting tool with a cutting plate:
cutting plate
guide bar
tool body
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Exercises : 1. Fill in missing words : 1. The cutting materials have to be ………………., ………………… and………………. . 2. The hardest cutting material is ……………………………………… . 3. ……………………………….. is very fragile . 4. The cutting tool can be divided into …………………….., ……………………… and ………………. . 5. …………………… is an active part of the cutting tool. 2. Are the sentences true or false ? 1. 2. 3. 4. 5.
Powder metallurgy produces carbids of light metals. T/F Diamonds are used for cutting. T/F Cubic boron nitride cannot withstand temperatures up to 2000 ° C T/F The alloying elements affect the applicability of the material at elevated temperatures. ................ T/F Monolithic cutting tools are made of several pieces. T/F
3. Read the following text and answer following questions :
Tooling Materials Although high speed tool steel has been used in the past it is quickly being replaced by carbide, ceramic, or diamond tooling. Because carbide inserts are long lasting and easily replaced, they lend themselves to high production. Ceramic tools are brittle but can withstand high temperatures. This makes high speed machining possible. Diamond tools are used to achieve a superior surface finish (though they can only be used on non-ferrous materials). 1. Which tooling materials do you know ? 2. What are their advantages and disadvantages ? 3. What is a non – ferrous material ? Find the synonymes to these words :
brittle
lend
high
withstand
superior
achieve
replace
only
Vocabulary achieve ............................................ dosáhnout advantage ....................................... výhoda affect ................................................ ovlivňovat alloy.................................................. legování, legovat
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alumina ............................................ oxid hlinitý applicability..................................... použitelnost blade ................................................ řezná destička blunting ............................................ otupení brittle ................................................ křehký carbid............................................... karbid carbon ............................................. uhlík considerable .................................. značný content ............................................. obsah, obsahovat cutting tools ..................................... řezné nástroje cubic boron nitride ......................... kubický nitrid boru diamond .......................................... diamant differ ................................................. odlišovat se, lišit se disadvantage .................................. nevýhoda durability .......................................... trvanlivost ferrous .............................................. železný, železitý fragile ............................................... křehký hardness .......................................... tvrdost in addition to ................................... kromě monolithic ........................................ monolitní possible ............................................ možný powder metalurgy .......................... prášková metalurgie replace ............................................ nahradit requirements ................................... požadavky resistant to........................................ odolný na strain ................................................. zátěž strength ............................................ pevnost superior ............................................ lepší, vyšší, nadřízený, kvalitnější, vrchní synthetic........................................... syntetický thermal load .................................... tepelná zatížení tool steel .......................................... nástrojová ocel toughness ........................................ houževnatost wear ................................................. nosit, otěr withstand.......................................... odolat, vydržet
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MACHINABILITY OF THE MATERIAL Pod pojmem obrobitelnost rozumíme souhrn vlastností obráběného materiálu posuzovaný z hlediska vhodnosti materiálu pro daný způsob obrábění. Obrobitelnost se určuje pouze vzájemným porovnáváním jednotlivých materiálů podle určitých kritérií, kdy srovnáváme náklady na zhotovení stejné součásti z různých materiálů při jinak stejných podmínkách = používáme stejný nástroj, stejné řezné podmínky, stejné výrobní zařízení, a dosahujeme stejné kvality povrchu povrchu, stejných rozměrů výrobku a stejné přesnosti. Obrobitelnost pak posoudíme podle výšky nákladů - čím nižší náklady, tím lepší obrobitelnost. Velký vliv na obrobitelnost mají fyzikální vlastnosti obráběného materiálu jako je pevnost, tvrdost, tažnost, měrné teplo a tepelná vodivost. Čím je materiál pevnější a tvrdší, tím se samozřejmě hůře obrábí. Druhým faktorem, který ovlivňuje obrobitelnost, je chemické složení materiálu, tedy obsah legujících prvků. Z hlediska chemického složení nelze hodnotit vliv těchto prvků souhrnně, ale je nutné brát v úvahu vliv jednoho prvku v závislosti na obsahu prvků dalších. Např. mangan při nízkém obsahu uhlíku v oceli obrobitelnost zlepšuje, ale při současném vyšším obsahu manganu a uhlíku se obrobitelnost zhoršuje. Většinou je nutno počítat s tím, že legovací prvky obrobitelnost materiálu zhoršují, protože s rostoucím obsahem legur roste pevnost materiálů. Další hlediska, která mohou ovlivnit obrobitelnost materiálu jsou mikrostruktura, způsob výroby a tepelné zpracování. V praxi se posuzuje obrobitelnost především podle tzv. součinitele obrobitelnosti, definovaného jako poměr řezné rychlosti daného materiálu ku řezné rychlosti etalonu=vzorku. Podle součinitele obrobitelnosti jsou materiály roztříděny do čtyř základních skupin: a, b, c, d. Každá skupina se dále členění do 20 tříd - ve třídě 1 jsou materiály nejhůře obrobitelné, ve třídě 20 nejlépe obrobitelné. Machinability of the material The term machinability is hard to describe. In an easy way we can say that it is a summary of all the properties of a workpiece material under consideration for suitability of materials for the machining method. The machinability is determined only by mutual comparison of different materials according to certain criteria. We compare the cost of making the same parts from different materials under otherwise identical conditions = the same tool is used under the same cutting conditions, for the same production facilities, and we have to achieve the same surface quality, the same size and the product shoul achieve even the same precision. The machinability is then easy to be assessed - the most important criteria among all of them is the height of the cost - the lower cost, the better machinability. Physical properties of machined material such as strength, hardness, elongation, specific heat and thermal conductivity have a great influence on the machinability. If the material is stronger and tougher, then it is obviously difficult to machine. The second factor that affects the machinability, is the chemical composition of materials, namely, the content of alloying elements. In terms of chemical composition we cannot assess the impact of these features as a whole, but we must take into account the impact of one element, depending on the content of other elements. Eg. manganese, its low carbon content in steel improves the machinability of the material, but on the other hand a higher content of manganese and carbon 40
can deteriorate the steel machinability. Mostly it is expected that the alloying elements deteriorate the workability of the material because the higher content of alloying elements the bigger is the strength of the used material. . Other aspects which may affect the workability of the material are following listed aspects : the microstructure of the material, the method of manufacture and at the end the heat treatment. The practice is assessed primarily under the "workability coefficient, which is defined as the ratio of the cutting speed of the material to the cutting speed = standard sample. According to the coefficient of workability of the materials, the materials are sorted into four groups: a, b, c, d. Each group is subdivided into 20 classes. In the first class there are the worst-to-machine materials, the best machinable ones can be found in the class 20. 1. Answer the questions to the text : 1. How many classe are the materials divided into ? 2. What can influence the material workability ? 3. What is an alloying element ? 4. What else can affect the machinability of a material ? 2. Machinability ratings are “relative” ratings. They compare the ease of machining an alloy to a standard. The standard used in the USA is 160 Brinel hardness B1112 cold drawn steel machined at 180 surface feet per minute. B1112 was assigned a score of 1.00. The machinability of all other alloys is compared to the standard score of 1.00. The attached tables contain machinability ratings for many alloys. •
Look at the table and find out the best and the worst to be machined materials:
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Tabulka obrobitelnosti vybraných materiálů
Odlitky ze -ŠL
Litá ocel: Válcovaná ocel: 11109,0 11343,0 11353 11373 11375 11500 11600 11700 12010 12020 12060,0 12060,1 12061,0 14100,3 14220,0 14260 15 30,0 16220,1
odlitky přesného lití 15b 15b 15b 14b 15b 13b 12b 11b 15b 13b 12b 13b l1b 12b 13b l0b 13b 12b
422650.14
15b
Al slitiny: 424357,01 424337,03 424330,01 424331,71 424331,03 424331,00
9d l0d l0d 9d l0d l0d
Al válcovaný: 424254,6 424005,21 424413,21
8d 14d 11d
Bronz: 23018,31 423018,51 423016,41
11c l0c l1c
422420 10a podle síly stěny Ocel třídy 19: 19191,3 19312,3 19421,3 19436,0 19452,0 19800,3 19802,3
13b l1b 12b 9b 11b l0b l0b
Měd' válcovaná: 423005,31 423001,31
9c 9c
Mosaz: 423222,31
12c
The use of the machinability rating is a method to assist you in recognizing how easy or how hard a given alloy is to machine in comparison to others. Like any specific appliction method, there is always a plus-or-minus leeway to applying the values. Again, use this as a guideline to understand the difficulty of machining. 3. Put to each type its right czech name : • each type has 4 categories : a – iron b – steel slitiny c - non-ferrous heavy metals + alloys d - light non-ferrous metals + alloys slitiny
a – ocel b– lehké neželezné kovy + jejich c – litiny d – těžké neželezné kovy + jejich
Machinability of metals The condition and physical properties of the work material have a direct influence on the machinability of a work material. The various conditions and characteristics described as "condition of work material," individually and in combinations, directly influence and determine the machinability. Operating conditions, tool material and geometry and workpiece requirements exercise indirect effects on machinability and can often be used to overcome difficult conditions presented by the work material. On the other hand, they can create situations that increase machining difficulty if they are ignored.
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Condition of Work Material The following eight factors determine the condition of the work material: microstructure, grain size, heat treatment, chemical composition, fabrication, hardness, yield strength and tensile strength. Microstructure: The microstructure of a metal refers to its crystal or grain structure as shown through examination of etched and polished surfaces under a microscope. Metals whose microstructures are similar have like machining properties. But there can be variations in the microstructure of the same workpiece that will affect machinability. Grain Size: Grain size and structure of a metal serve as general indicators of its machinability. A metal with small undistorted grains tends to cut easily and finish easily. Such a metal is ductile, but it is also "gummy." Metals of an intermediate grain size represent a compromise that permits both cutting and finishing machinability. Hardness of a metal must be correlated with grain size and it is generally used as an indicator of machinability. Heat Treatment: To provide desired properties in metals, they are sometimes put through a series of heating and cooling operations when in the solid state. A material may be treated to reduce brittleness, remove stress, to obtain ductility or toughness, to increase strength, to obtain a definite microstructure, to change hardness or to make other changes that affect machinability. Chemical Composition: Chemical composition of a metal is a major factor in determining its machinability. The effects of composition though, are not always clear, because the elements that make up an alloy metal, work both singly and collectively. Certain generalizations about chemical composition of steels in relation to machinability can be made, but nonferrous alloys are too numerous and varied to permit such generalizations. Fabrication: Whether a metal has been hot rolled, cold rolled, cold drawn cast, or forged will affect its grain size, ductility, strength, hardness, structure-and therefore-its machinability. The term "wrought" refers to the hammering or forming of materials into premanfactured shapes which are readily altered into components or products using traditional manufacturing techniques. Wrought metals are defined as that group of materials, which are mechanically shaped into, bars, billets, rolls, sheets, plates or tubing. Casting involves pouring molten metal into a mold to arrive at a near component shape that requires minimal, or in some cases no machining. Molds for these operations are made from sand, plaster, metals and a variety of other materials. Hardness: The textbook definition of hardness is the tendency for a material to resist deformation. Hardness is often measured using either the Brinell or Rockwell scale. The method used to measure hardness involves embedding a specific size and shaped indenter into the surface of the test material, using a predetermined load or weight. The distance the indenter penetrates the material surface will correspond to a specific Brinell or Rockwell hardness reading. The greater the indenter surface penetration, the lower the ultimate Brinell or Rockwell number, and thus the lower the corresponding hardness level. Therefore, high Brinell or Rockwell numbers or readings represent a minimal amount of indenter penetration into the workpiece and thus, by definition, are an indication of an extremely hard part. Figure 3.1 shows how hardness is measured. 600 The Brinell hardness test involves embedding a steel ball of a specific diameter, using a kilogram load, in the surface of a test piece. The Brinell Hardness Number (BHN) is
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determined by dividing the kilogram load by the area (in square millimeters) of the circle created at the rim of the dimple or impression left in the workpiece surface. This standardized approach provides a consistent method to make comparative tests between a variety of workpiece materials or a single material that has undergone various hardening processes. The Rockwell test can be performed with various indenter sizes and loads. Several different scales exist for the Rockwell method or hardness testing. The three most popular are outlined below in terms of the actual application the test is designed to address: Yield Strength: Tensile test work is used as a means of comparison of metal material conditions. These tests can establish the yield strength, tensile strength and many other conditions of a material based on its heat treatment. In addition, these tests are used to compare different workpiece materials. The tensile test involves taking a cylindrical rod or shaft and pulling it from opposite ends with a progressively larger force in a hydraulic machine. Prior to the start of the test, two marks either two or eight inches apart are made on the rod or shaft. As the rod is systematically subjected to increased loads, the marks begin to move farther apart. A material is in the so-called `elastic zone' when the load can be removed from the rod and the marks return to their initial distance apart of either two or eight inches. If the test is allowed to progress, a point is reached where, when the load is removed, the marks will not return to their initial distance apart. At this point, permanent set or deformation of the test specimen has taken place. Yield strength is measured just prior to the point before permanent deformation takes place. Yield strength is stated in pounds per square inch (PSI) and is determined by dividing the load just prior to permanent deformation by the cross sectional area of the test specimen. This material property has been referred to as a condition, since it can be altered during heat treatment. Increased part hardness produces an increase in yield strength and therefore, as a part becomes harder, it takes a larger force to produce permanent deformation of the part. Yield strength should not be confused with fracture strength, cracking or the actual breaking of the material into pieces, since these properties are quite different and unrelated to the current subject. Tensile Strength: The tensile strength of a material increases along with yield strength as it is heat treated to greater hardness levels. This material condition is also established using a tensile test. Tensile strength (or ultimate strength) is defined as the maximum load that results during the tensile test, divided by the cross-sectional area of the test specimen. Therefore, tensile strength, like yield strength, is expressed in PSI. This value is referred to as a material condition rather than a property, since its level just like yield strength and hardness, can be altered by heat treatment. Therefore, based on the material selected, distinct tensile and yield strength levels exist for each hardness reading. Physical Properties of Work Materials Physical properties will include those characteristics included in the individual material groups, such as the modulus of elasticity, thermal conductivity, thermal expansion and work hardening. Modulus of Elasticity: The modulus of elasticity can be determined during a tensile test in the same manner as the previously mentioned conditions. However, unlike hardness, yield or tensile strength, the modulus of elasticity is a fixed material property and, therefore, is unaffected by heat treatment. This particular property is an indicator of the rate at which a material will deflect when subjected to
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an external force. This property is stated in PSI and typical values are several million PSI for metals. Hardness is measured by depth of indentations made. Thermal Conductivity: Materials are frequently labeled as being either heat conductors or insulators. Conductors tend to transfer heat from a hot or cold object at a high rate, while insulators impede the flow of heat. Thermal conductivity is a measure of how efficiently a material transfers heat. Therefore, a material that has a relatively high thermal conductivity would be considered a conductor, while one with a relatively low level would be regarded as an insulator. Thermal Expansion: Many materials, especially metals, tend to increase in dimensional size as their temperature rises. This physical property is referred to as thermal expansion. The rate at which metals expand varies, depending on the type or alloy of material under consideration. The rate at which metal expands can be determined using the material's expansion coefficient. The greater the value of this coefficient, the more a material will expand when subjected to a temperature rise or contract when subjected to a temperature reduction. For example, a 100- bar of steel which encounters a 100 F rise in temperature would measure 100.065-. Work Hardening: Many metals exhibit a physical characteristic that produces dramatic increases in hardness due to cold work. Cold work involves changing the shape of a metal object by bending, shaping, rolling or forming. As the metal is shaped, internal stresses develop which act to harden the part. The rate and magnitude of this internal hardening varies widely from one material to another. Heat also plays an important role in the work hardening of a material. When materials that exhibit work hardening tendencies are subjected to increased temperature, it acts like a catalyst to produce higher hardness levels in the workpiece. Metal Machining The term "machinability" is a relative measure of how easily a material can be machined when compared to 160 Brinell AISI B 1112 free machining low carbon steel. The American Iron and Steel Institute (AISI) ran turning tests of this material at 180 surface feet and compared their results for B 1112 against several other materials. If B 1112 represents a 100% rating, then materials with a rating less than this level would be decidedly more difficult to machine, while those that exceed 100% would be easier to machine. The machinability rating of a metal takes the normal cutting speed, surface finish and tool life attained into consideration. These factors are weighted and combined to arrive at a final machinability rating. The following chart shows a variety of materials and their specific machinability ratings: Cast Iron All metals that contain iron (Fe) are known as ferrous materials. The word "ferrous" is by definition, "relating to or containing iron." Ferrous materials include cast iron, pig iron, wrought iron, and low carbon and alloy steels. The extensive use of cast iron and steel workpiece materials can be attributed to the fact that iron is one of the most frequently occurring elements in nature. When iron ore and carbon are metallurgically mixed, a wide variety of workpiece materials result with a fairly unique set of physical properties. Carbon contents are altered in cast irons and steels to provide changes in hardness, yield and tensile strengths. The physical properties of cast irons and steels can be modified by changing the amount of the iron-carbon mixtures in these materials as well as
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their manufacturing process. Pig iron is created after iron ore is mixed with carbon in a series of furnaces. This material can be changed further into cast iron, steel or wrought iron depending on the selected manufacturing process. Cast iron is an iron carbon mixture that is generally used to pour sand castings, as opposed to making billets or bar stock. It has excellent flow properties and therefore, when it is heated to extreme temperatures, is an ideal material for complex cast shapes and intricate molds. This material is often used for automotive engine blocks, cylinder heads, valve bodies, manifolds, heavy equipment oil pans and machine bases. Gray Cast Iron: Gray cast iron is an extremely versatile, very machinable relatively low strength cast iron used for pipe, automotive engine blocks, farm implements and fittings. This material receives its dark gray color from the excess carbon in the form of graphite flakes, which give it its name. White Cast Iron: White cast iron occurs when all of the carbon in the casting is combined with iron to form cementite. This is an extremely hard substance that results from the rapid cooling of the casting after it is poured. Since the carbon in this material is transformed into cementite, the resulting color of the material when chipped or fractured is a silvery white. Thus the name white cast iron. However, white cast iron has almost no ductility, and therefore when it is subjected to any type of bending or twisting loads, it fractures. The hard brittle white cast iron surface is desirable in those instances where a material with extreme abrasion resistance is required. Applications of this material would include plate rolls in a mill or rock crushers. Yield strength is measured by pulling a test specimen as shown. Malleable Cast Iron: When white cast iron castings are annealed (softened by heating to a controlled temperature for a specific length of time), malleable iron castings are formed. Malleable iron castings result when hard, brittle cementite in white iron castings is transformed into tempered carbon or graphite in the form of rounded nodules or aggregate. The resulting material is a strong, ductile, tough and very machinable product that is used on a broad scope of applications. Nodular Cast Iron: Nodular or "ductile" iron is used to manufacture a wide range of automotive engine components including cam shafts, crank shafts, bearing caps and cylinder heads. This material is also frequently used for heavy equipment cast parts as well as heavy machinery faceplates and guides. Nodular iron is strong, ductile, tough and extremely shock resistant. Steel Steel materials are comprised mainly of iron and carbon, often with a modest mixture of alloying elements. The biggest difference between cast iron materials and steel is the carbon content. Cast iron materials are compositions of iron and carbon, with a minimum of 1.7 percent carbon to 4.5 percent carbon. Steel has a typical carbon content of .05 percent to 1.5 percent. The commercial production of a significant number of steel grades is further evidence of the demand for this versatile material. Very soft steels are used in drawing applications for automobile fenders, hoods and oil pans, while premium grade high strength steels are used for cutting tools. Steels are often selected for their electrical properties or resistance to corrosion. In other applications, non-magnetic steels are selected for wrist watches and minesweepers. Plain Carbon Steel: This category of steels includes those materials that are a
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combination of iron and carbon with no alloying elements. As the carbon content in these materials is increased, the ductility (ability to stretch or elongate without breaking) of the material is reduced. Plain carbon steels are numbered in a four-digit code according to the AISI or SAE system (i.e. 10XX). The last two digits of the code indicate the carbon content of the material in hundredths of a percentage point. For example, a 10 18 steel has a 0.18-percent carbon content. Alloy Steels: Plain carbon steels are made up primarily of iron and carbon, while alloy steels include these same elements with many other elemental additions. The purpose of alloying steel is either to enhance the material's physical properties or its ultimate manufacturability. The physical property enhancements include improved toughness, tensile strength, hardenability, (the relative ease with which a higher hardness level can be attained), ductility and wear resistance. The use of alloying elements can alter the final grain size of a heat-treated steel, which often results in a lower machinability rating of the final product. The primary types of alloyed steel are: nickel, chromium, manganese, vanadium, molybdenum, chrome-nickel, chromevanadium, chrome-molybdenum, and nickel-molybdenum. Tool Steels: This group of high strength steels is often used in the manufacture of cutting tools for metals, wood and other workpiece materials. In addition, these highstrength materials are used as die and punch materials due to their extreme hardness and wear resistance after heat treatment. The key to achieving the hardness, strength and wear-resistance desired for any tool steel is normally through careful heat treatment. These materials are available in a wide variety of grades with a substantial number of chemical compositions designed to satisfy specific as well as general application criteria. Stainless Steels: As the name implies, this group of materials is designed to resist oxidation and other forms of corrosion, in addition to heat in some instances. These materials tend to have significantly greater corrosion resistance than their plain or alloy steel counterparts due to the substantial additions of chromium as an alloying element. Stainless steels are used extensively in the food processing, chemical and petroleum industries to transfer corrosive liquids between processing and storage facilities. Stainless steels can be cold formed, forged, machined, welded or extruded. This group of materials can attain relatively high strength levels when compared to plain carbon and alloy steels. Stainless steels are available in up to 150 different chemical compositions. The wide selection of these materials is designed to satisfy the broad range of physical properties required by potential customers and industries. Stainless steels fall into four distinct metallurgical categories. These categories include: austenitic, ferritic, martensitic, and precipitation hardening. Nonferrous Metals and fillos Nonferrous metals and alloys cover a wide range of materials from the more common metals such as aluminum, copper, and magnesium, to high-strength hightemperature alloys such as tungsten, tantalum and molybdenum. Although more expensive than ferrous metals, nonferrous metals and alloys have important applications because of their numerous properties, such as corrosion resistance, high thermal and electrical conductivity, low density, and ease of fabrication. Tools.
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Judging Machinability The factors affecting machinability have been explained; four methods used to judge machinability are discussed below: Tool Life: Metals that can be cut without rapid tool wear are generally thought of as being quite machinable, and vice versa. A workpiece material with many small hard inclusions may appear to have the same mechanical properties as a less abrasive metal. It may require no greater power consumption during cutting. Yet, the machinability of this material would be lower because its abrasive properties are responsible for rapid wear on the tool, resulting in higher machining costs. One problem arising from the use of tool life as a machinability index is its sensitivity to the other machining variables. Of particular importance is the effect of tool material. Machinability ratings based on tool life cannot be compared if a highspeed steel tool is used in one case and a sintered carbide tool in another. The superior life of the carbide tool would cause the machinability of the metal cut with the steel tool to appear unfavorable. Even if identical types of tool materials are used in evaluating the workpiece materials, meaningless ratings may still result. For example, cast iron cutting grades of carbide will not hold up when cutting steel because of excessive cratering, and steel cutting grades of carbide are not hard enough to give sufficient abrasion resistance when cutting cast iron. Tool life may be defined as the period of time that the cutting tool performs efficiently. Many variables such as material to be machined, cutting tool material, cutting tool geometry, machine condition, cutting tool clamping, cutting speed, feed, and depth of cut, make cutting tool life determination very difficult. The first comprehensive tool life data were reported by EW. Taylor in 1907, and his work has been the basis for later studies. Taylor showed that the relationship between cutting speed and tool life can be expressed empirically by: VT = C where: V = cutting speed, in feet per minute T = tool life, in minutes C= a constant depending on work material, and other machine variables. Numerically it is the cutting speed which would give 1 minute of tool life. n = a constant depending on work and tool material. This equation predicts that when plotted on log-log scales, there is a linear relationship between tool life and cutting speed. The exponent n has values ranging from 0.125 for high-speed steel (HSS) tools, to 0.70 for ceramic tools. Tool Forces and Power Consumption: The use of tool forces or power consumption as a criterion of machinability of the workpiece material comes about for two reasons. First, the concept of machinability as the ease with which a metal is cut implies that a metal through which a tool is easily pushed should have a good machinability rating. Second, the more practical concept of machinability in terms of minimum cost per part machined, relates to forces and power consumption, and the overhead cost of a machine of proper capacity. When using tool forces as a machinability rating, either the cutting force or the thrust force (feeding force) may be used. The cutting force is the more popular of the two since it is the force that pushes the tool through the workpiece and determines the power consumed. Although machinability ratings could be listed according to the cutting forces under a set of standard machining conditions, the data are usually presented in terms of specific energy. Workpiece materials having a high specific energy of metal removal are said to be less machinable than those with a lower specific energy. The use of net power consumption during machining as an index of the machinability of the workpiece is similar to the use of cutting force. Again, the data are most useful
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in terms of specific energy. One advantage of using specific energy of metal removal as an indication of machinability, is that it is mainly a property of the workpiece material itself and is quite insensitive to tool material. By contrast, tool life is strongly dependent on tool material. The metal removal factor is the reciprocal of the specific energy and can be used directly as a machinability rating if forces or power consumption are used to define machinability. That is, metals with a high metal removal factor could be said to have high machinability. Cutting tool forces and power consumption formulas and calculations are beyond the scope of this article; they are discussed in books that are more theoretical in their approach to discussing machinability of metals. Surface Finish: The quality of the surface finish left on the workpiece during a cutting operation is sometimes useful in determining the machinability rating of a metal. Some workpieces will not `take a good finish' as well as others. The fundamental reason for surface roughness is the formation and sloughing off of parts of the built-up edge on the tool. Soft, ductile materials tend to form a built-up edge rather easily. Stainless steels, gas turbine alloy and other metals with high strain hardening ability also tend to machine with built-up edges. Materials which machine with high shear zone angles tend to minimize built-up edge effects. These include the aluminum alloys, cold worked steels, free-machining steels, brass and titanium alloys. If surface finish alone were the chosen index of machinability, these latter metals would rate higher than those in the first group. In many cases, surface finish is a meaningless criterion of workpiece machinability. In roughing cuts, for example, no attention to finish is required. In many finishing cuts, the conditions producing the desired dimension on the part will inherently provide a good finish within the engineering specification. Machinability figures based on surface finish measurements do not always agree with figures obtained by force or tool life determinations. Stainless steels would have a low rating by any of these standards, while aluminum alloys would be rated high. Titanium alloys would have a high rating by finish measurements, low by tool life tests, and intermediate by force readings. The machinability rating of various materials by surface finish are easily determined. Surface finish readings are taken with an appropriate instrument after standard workpieces of various materials are machined under controlled cutting conditions. The machinability rating varies inversely with the instrument reading. A low reading means good finish, and thus high machinability. Relative ratings may be obtained by comparing the observed value of surface finish with that of a material chosen as the reference. Chip Form: There have been machinability ratings based on the type of chip that is formed during the machining operation. The machinability might be judged by the ease of handling and disposing of chips. A material that produces long stringy chips would receive a low rating, as would one, which produces fine powdery chips. Materials, which inherently form nicely broken, chips, a half or full turn of the normal chip helix, would receive top rating. Chip handling and disposal can be quite expensive. Stringy chips are a menace to the operator and to the finish on the freshly machined surface. However, chip formation is a function of the machine variables as well as the workpiece material, and the ratings obtained by this method could be changed by provision of a suitable chip breaker. Ratings based on the ease of chip
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disposal are basically qualitative, and would be judged by an individual who might assign letter gradings of some kind. Wide use is not made of this method of interpreting machinability. It finds some application in drilling, where good chip formation action is necessary to keep the chips running up the flutes. However, the whipping action of long coils once they are clear of the hole is undesirable.
Vocabulary affect ................................................ ovlivňovat alloy.................................................. slitina assess ............................................... posoudit, ohodnotit casting ............................................. odlitek comparison ..................................... porovnáná, srovnání condition .......................................... podmínka deteriorate ............................................... zhoršit fabrication ................................................ výroba grain ................................................ zrno, zrnitost, vlákno hardness .......................................... tvrdost heat .................................................. horko, teplo chemical composition.................... chemické složení influence .......................................... vliv iron ................................................... železo leeway ............................................. volnost light................................................... lehké machinability................................... obrobitelnost microstructure ................................. mikrostruktura molten .............................................. tekutý, roztavený mutual .............................................. vzájemný non ferrous metals........................... neželezné kovy ratings .............................................. hodnocení size.................................................... velikost steel .................................................. ocel subdivide ......................................... rozdělit
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STIFFNESS OF THE TECHNOLOGY SYSTÉM When we start to design components, we have to choose the dimensions of each individual component so that we do not get in terms of stress beyond the elastic deformation. We can dimension the components of strength, but we cannot prevent the elastic deformation – we are only able to keep them within established limits. When designing the machine we should pay attention to this elastic deformation, which means that we are dealing with technology system stiffness. The technological system is defined as a system of machine - tool – work piece. Each article of this system can be flexible deformed due to the effect of burdensome power and subsequently amended by the relative position of the work piece to the tool. The resulting distortions have a negative impact on the working machine accuracy, the emergence of vibration during operation, the additional stress of unwanted technology systems and productivity. Stiffness technological system is defined as the ability to resist deformation that means it is a measure of resistance to deformation. Virtually every mechanical part is flexible, ie. that the burden is on the deformation. This distortion disappears after unloading. We can distinguish:- Stiffness in the displacement – which is defined as the ratio of loading force and displacement, which are caused by this force - Stiffness in rotation - the ratio between torque and angle of rotation occurs in the torquetransmitting components such as the electric motor / engine - Bending stiffness - is defined as the ratio of the force and deformation at the load and also we can speak about: Partial rigidity - applies only to one part without assessing the impact of deformation of other parts machine - The overall rigidity - includes the effect of deformation of the group included. The stiffness of machine tool has a great influence on the final precision machining. When we use the machine then thanks to the lower stiffness of a vibration can cause following stuff : the machined surface is corrugated, which may worse the quality of the surface, as occurs gradually,cutting tools become and blunt faster and the wear of machine speeds up. The stiffness of a structure is of principal importance in many engineering applications, so the modulus of elasticity is often one of the primary properties considered when selecting a material. A high modulus of elasticity is sought when deflection is undesirable, while a low modulus of elasticity is required when flexibility is needed. •
Read and answer the questions : 1. What is rigidity ? 2. How can we divide stiffness ? 3. How can be a technological system defined ? 4. How can you calculate stiffness? 5. Do you need it in your job ?
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Find synonyms to these given words : 1. Application 2. Modulus 3. Force 4. Stiffness 5. Start 6. Finish
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7. require
Additional text : •
Look at these calculations: try to explain them, do you know what they mean?
Calculations The stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation. For an elastic body with a single Degree of Freedom (for example, stretching or compression of a rod), the stiffness is defined as
where F is the force applied on the body δ is the displacement produced by the force along the same degree of freedom (for instance, the change in length of a stretched spring) In the International System of Units, stiffness is typically measured in newtons per metre. In English Units, stiffness is typically measured in pound force (lbf) per inch. Generally speaking, deflections (or motions) of an infinitesimal element (which is viewed as a point) in an elastic body can occur along multiple Degrees of Freedom (maximum of six Degrees of Freedom at a point). For example, a point on a horizontal beam can undergo both a vertical displacement and a rotation relative to its undeformed axis. When the Degrees of Freedom is M, for example, a M x M matrix must be used to describe the stiffness at the point. The diagonal terms in the matrix are the direct-related stiffnesses (or simply stiffnesses) along the same degree of freedom and the off-diagonal terms are the coupling stiffnesses between two different degrees of freedom (either at the same or different points) or the same degree of freedom at two different points. In industry, the term influence coefficient is sometimes used to refer to the coupling stiffness. It is noted that for a body with multiple Degrees of Freedom, Equation generally does not apply since the applied force generates not only the deflection along its own direction (or degree of freedom), but also those along other directions (or Degrees of Freedom). For example, for a cantilevered beam, the stiffness at its free end is 12*E*I/L^3 rather than 3*E*I/L^3 if calculated with Equation For a body with multiple Degrees of Freedom, to calculate a particular directrelated stiffness (the diagonal terms), the corresponding Degree of Freedom is left free while the remaining Degrees of Freedom should be constrained. Under such a condition, equation can be used to obtain the direct-related stiffness for the degree of freedom which is unconstrained. The ratios between the reaction forces (or moments) and the produced deflection are the coupling stiffnesses. The inverse of stiffness is compliance, typically measured in units of metres per newton. In rheology it may be defined as the ratio of strain to stress [1], and so take the units of reciprocal stress, e.g. 1/Pa. Rotational stiffness A body may also have a rotational stiffness, k, given by
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where M is the applied moment θ is the rotation In the SI system, rotational stiffness is typically measured in newton-metres per radian. In the SAE system, rotational stiffness is typically measured in inch-pounds per degree. Further measures of stiffness are derived on a similar basis, including: 1. shear stiffness - ratio of applied shear force to shear deformation 2. torsional stiffness - ratio of applied torsion moment to angle of twist Relationship to elasticity In general, elastic modulus is not the same as stiffness. Elastic modulus is a property of the constituent material; stiffness is a property of a structure. That is, the modulus is an intensive property of the material; stiffness, on the other hand, is an extensive property of the solid body dependent on the material and the shape and boundary conditions. For example, for an element in tension or compression, the axial stiffness is
where A is the cross-sectional area, E is the (tensile) elastic modulus (or Young's modulus), L is the length of the element. Similarly, the rotational stiffness is
where "I" is the moment of inertia, "n" is an integer depending on the boundary condition (=4 for fixed ends) For the special case of unconstrained uniaxial tension or compression, Young's modulus can be thought of as a measure of the stiffness of a material. Stiffness is the resistance of an elastic body to deformation by an applied force along a given degree of freedom (DOF) when a set of loading points and boundary conditions are prescribed on the elastic body. It is an extensive material property. The stiffness of a structure is of principal importance in many engineering applications, so the modulus of elasticity is often one of the primary properties considered when selecting a material. A high modulus of elasticity is sought when deflection is undesirable, while a low modulus of elasticity is required when flexibility is needed. •
Choose one of the given names and try to find as many details as possible. Prepare a speaking presentation about him ( 10 – 15 minutes):
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Timeline:
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1. 1452-1519 ............. Leonardo da Vinci made many contributions. 2. 1638: ...................... Galileo Galilei published the book "Two New Sciences" in which he examined the failure of simple structures. 3. 1660: ....................... Hooke's law by Robert Hooke. 4. 1687: ...................... Isaac Newton published "Philosophiae Naturalis Principia Mathematica" which contains the Newton's laws of motion. 5. 1750: ....................... Euler-Bernoulli beam equation. 6. 1700-1782: ............ Daniel Bernoulli introduced the principle of virtual work. 7. 1707-1783: ............. Leonhard Euler developed the theory of buckling of columns. 8. 1826: ...................... Claude-Louis Navier published a treatise on the elastic behaviors of structures. 9. 1873: ...................... Carlo Alberto Castigliano presented his dissertation "Intorno ai sistemi elastici", which contains his theorem for computing displacement as partial derivative of the strain energy. This theorem includes the method of least work as a special case. 10. 1936: ...................... Hardy Cross' publication of the moment distribution method which was later recognized as a form of the relaxation method applicable to the problem of flow in pipe-network. 11. 1941: ...................... Alexander Hrennikoff submitted his D.Sc thesis in MIT on the discretization of plane elasticity problems using a lattice framework. 12. 1942: ...................... R. Courant divided a domain into finite subregions. 13. 1956: ...................... J. Turner, R. W. Clough, H. C. Martin, and L. J. Topp's paper on the "Stiffness and Deflection of Complex Structures". This paper introduces the name "finite-element method" and is widely recognized as the first comprehensive treatment of the method as it is known today. Look at this picture, translate their describtions into English :
1. Vertikální obráběcí centrum MCV 1210, Společnost: TAJMAC-ZPS, a. s. Vertikální obráběcí centrum MCV 1210 je novým strojem, který je díky svému konstrukčnímu uspořádání určen pro širokou oblast obrábění výrobků a nástrojů. Má uplatnění jak při obrábění složitých prostorových tvarů ve 3 nebo 5 osách, tak pro klasické frézování, vrtání, zahlubování a vystružování otvorů, řezání a frézování závitů. Je určen pro plastikářský, automobilový a letecký průmysl pro výrobu forem, 55
lisovacích a tvářecích nástrojů, zápustek pro kování nebo forem pro vstřikování umělých hmot, různých zařízení pro tváření plastů a pryží a jiné tvarově složité strojní výrobky. Stroj vzhledem k vysoké dynamice, velmi vysoké tuhosti a tlumicím vlastnostem konstrukce umožňuje využití výhod HSC technologie.
2. Hliníkové lepené sendvičové panely Společnost 5M s.r.o. vyrábí sendvičovou výztuhu zadního spoileru automobilů Škoda Octavia RS a Octavia 4x4. Tento spoiler se vyznačuje vysokou tuhostí, přestože je uchycen jen na koncích. Všimněte si někdy na silnicích, kolik jiných věhlasných automobilek to nedokáže a musí si vypomoci "berličkou" v podobě třetí nožky uprostřed.
3. Honda Civic Type R JDM Karoserie je samonosná, typu čtyř dvéřový sedan. Tuhost celé karoserie je v porovnání s modelem DC5 o 50% vyšší. Prvky, které se podílely na zvýšení tuhosti navýšili hmotnost o 1.8 kg. (na obrázku červené) Proti posílení tuhosti šla snaha o snížení hmotnosti celé karoserie (na obrázku zeleně). Úspora činí 13.4 kg. Pokud tedy vezmeme v úvahu navýšení na úkor tuhosti zjistíme, že je karoserie Type R o 11.6 kg lehčí než základní model Civilu 4D. Vyztužení karoserie tedy hmotnost nijak dramaticky nezvýšilo.
Vocabulary assess ............................................... posoudit, odhadnout, stanovit bending stiffness.............................. ohybová tuhost burdensome power ...................... zatěžující síla cause ............................................... způsobit deformation ..................................... deformace degree of freedom.......................... stupeň volnosti distinguish ........................................ rozeznat , rozpoznávat distortions ......................................... narušení elastic deformation ......................... pružná deformace elastic modulus ............................... model pružnosti inertia ............................................... setrvačnost, nečinnost loading force ................................... zatěžující síla negative impact.............................. negativní dopad occur ................................................ nastat, přihodit se overall rigidity .................................. celková tuhost
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partial rigidity................................... částečná tuhost possitive ........................................... pozitivní, kladný ratio .................................................. poměr, koeficient require .............................................. vyžadovat rigidity ............................................. tuhost, neohebnost stiffness ............................................ tuhost stiffness in displacement................. tuhost v posunutí stiffness in rotation ........................... tuhost v rotaci timeline .......................................... časová osa technological system ..................... technologická soustava tension.............................................. napětí torque ............................................... točivý moment, kroutivá síla unconstrained ................................ neomezená uniaxial ............................................ jednoosý
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INDUSTRY, ECONOMY, ENGINEERING AND ITS MANUFACTURING PROCESS IN ENGINEERING V národním hospodářství každého státu má strojírenství velmi důležitou úlohu. Zajišťuje totiž pro ostatní odvětví výrobní techniku tj. moderní výkonné stroje. Ve všech oborech národního hospodářství se dnes projevuje nárůst automatizace a tím se zvyšují nároky na odborníky, kteří se zabývají vývojem nových výrobků, automatizovaných pracovišť a možnostmi využití nových materiálů. Hospodářská soustava státu se člení na výrobní a nevýrobní odvětví. Do výrobního odvětví zařazujeme např. strojírenství, zemědělství, mezi nevýrobní odvětví patří školství, obchod, zdravotnictví. Výrobní proces v podniku začíná soustředěním veškerého materiálu – surovin, materiálu, polotovarů – v areálu výrobního podniku a končí expedicí hotového výrobku zákazníkovi. Suroviny, materiály a polotovary se ve výrobním procesu přeměňují na výrobky. Výrobní proces se rozděluje na 3 etapy: 1. předvýrobní 2. výrobní 3. odbytová Předvýrobní etapa zahrnuje období před započetím vlastní výroby. Před zahájením výroby nového výrobku ovlivněného výzkumem, vývojem a potřebami trhu je třeba zpracovat na základě výpočtů konstrukční a projekční výkresy = vytvořit technickou dokumentaci, dále navrhnout technologické postupy a obstarat potřebné nářadí, materiály, polotovary. Výrobní etapa se zabývá veškerou činností, která přímo souvisí se zhotovováním výrobků. Většinou se jedná o velké množství různých výrobních pochodů, které na sebe bezprostředně navazují. Odbytová etapa tvoří závěr celého výrobního procesu. Patří sem balení výrobků a jeho odeslání zákazníkovi, případně provedení různých garančních zkoušek při předávání zákazníkovi. Většina výrobních podniků poskytuje zákazníkům servisní služby. Úkolem servisní služby je zajištění opravárenských a poradenských služeb včetně zaškolování budoucích pracovníků obsluhy jednotlivých výrobních zařízení.
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Industry, economy, engineering and its manufacturing process in engineering Industry refers to the production of economic goods (either material or a service) within an economy. Many developed countries and many developing/semideveloped countries (People's Republic of China, India etc.) depend significantly on industry. Industries, the countries they reside in, and the economies of those countries are interlinked in a complex web of interdependence. Industry is divided into four sectors. They are: Sector Primary
Definition This involved the extraction of resources directly from the Earth, this includes farming, mining and logging. They do not process the products at all.
This group is involved in the processing products from primary industries. This includes all Secondary factories—those that refine metals, produce furniture, or pack farm products such as meat. Tertiary
This group is involved in the provision of services. They include teachers, managers and other service providers.
Quatenary This group is involved in the research of science and technology. They include scientists. As a country develops people move away from the primary sector to secondary and then to tertiary. There are many other different kinds of industries, and often organized into different classes or sectors by a variety of industrial classifications. Industry classification systems used by the government commonly divide industry into three sectors: agriculture, manufacturing, and services. 1. The primary sector of industry is agriculture, mining and raw material extraction. 2. The secondary sector of industry is manufacturing. 3. The tertiary sector of industry is service production. 4. Sometimes, one talks about a quaternary sector of industry, consisting of intellectual services such as research and development (R&D). Market-based classification systems such as the Global Industry Classification Standard and the Industry Classification Benchmark are used in finance and market research. These classification systems commonly divide industries according to similar functions and markets and identify businesses producing related products. Industries can also be identified by product: chemical industry, petroleum industry, automotive industry, electronic industry, meatpacking industry, hospitality industry, food industry, fish industry, software industry, paper industry, entertainment industry, semiconductor industry, cultural industry, poverty industry 1. labor-intensive industry - capital-intensive industry 2. light industry - heavy industry An economy consists of the economic system of a country or other area, the labor, capital and land resources, and the economic agents that socially participate in the production, exchange, distribution, and consumption of goods and services of that area. There are three main sectors of economic activity: primary, secondary, and tertiary. In modern economies, there are four main sectors of economic activity : 1. Primary sector of the economy: Involves the extraction and production of raw materials, such as corn, coal, wood and iron. (A coal miner and a fisherman would be workers in the primary sector.) 2. Secondary sector of the economy: Involves the transformation of raw
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or intermediate materials into goods e.g. manufacturing steel into cars, or textiles into clothing. (A builder and a dressmaker would be workers in the secondary sector.) 3. Tertiary sector of the economy: Involves the provision of services to consumers and businesses and distribution of manufactured goods, such as baby-sitting, cinema and banking. (A shopkeeper and an accountant would be workers in the tertiary sector.) 4. Quaternary sector of the economy: Involves the research and development needed to produce products from natural resources. (A logging company might research ways to use partially burnt wood to be processed so that the undamaged portions of it can be made into pulp for paper.) Note that education is sometimes included in this sector. Other sectors include the 1. Public Sector or state sector 2. Private Sector or privately-run businesses 3. Social sector or Voluntary sector Engineering has a very important role in the national economy of each country. Engineering is the discipline, art, and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge to design and build structures, machines, devices, systems, materials and processes that safely realize solutions to the needs of society. Its aim is to provide for other sectors of modern production the appropriate technology, new modern powerful machines. Engineering, much like other science, is a broad discipline which is often broken down into several sub-disciplines. These disciplines concern themselves with differing areas of engineering work. Although initially an engineer will usually be trained in a specific discipline, throughout an engineer's career the engineer may become multidisciplined, having worked in several of the outlined areas. Engineering is often characterized as having four main branches: 1. Chemical engineering – The exploitation of chemical principles in order to carry out large scale chemical process, as well as designing new specialty materials and fuels. 2. Civil engineering – The design and construction of public and private works, such as infrastructure (roads, railways, water supply and treatment etc.), bridges and buildings. 3. Electrical engineering – a very broad area that may encompass the design and study of various electrical & electronic systems, such as electrical circuits, generators, motors, electromagnetic/electromechanical devices, electronic devices, electronic circuits, optical fibers, optoelectronic devices, computer systems, telecommunications and electronics. 4. Mechanical engineering – The design of physical or mechanical systems, such as power and energy systems, aerospace/aircraft products, weapon systems, transportation products engines, compressors, powertrains, kinematic chains, vacuum technology, and vibration isolation equipment. Beyond these four, sources vary on other main branches. Historically, naval engineering and mining engineering were major branches. Modern fields sometimes included as major branches include industrial, aerospace, architectural, and nuclear
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engineering. New specialties sometimes combine with the traditional fields and form new branches. A new or emerging area of application will commonly be defined temporarily as a permutation or subset of existing disciplines; there is often gray area as to when a given sub-field becomes large and/or prominent enough to warrant classification as a new "branch." One key indicator of such emergence is when major universities start establishing departments and programs in the new field. For each of these fields there exists considerable overlap, especially in the areas of the application of sciences to their disciplines such as physics, chemistry and mathematics. The increase of automation can be nowdays reflected in all sectors of the economy and it is also connected with a rise in the demand for professionals who are focused on developing new products, automated workstations and the use of new materials. Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but it is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale. Such finished goods may be used for manufacturing other, more complex products, such as aircraft, household appliances or automobiles, or sold to wholesalers, who in turn sell them to retailers, who then sell them to end users – the "consumers". Manufacturing takes turns under all types of economic systems. In a free market economy, manufacturing is usually directed toward the mass production of products for sale to consumers at a profit. In a collectivist economy, manufacturing is more frequently directed by the state to supply a centrally planned economy. In free market economies, manufacturing occurs under some degree of government regulation. Modern manufacturing includes all intermediate processes required for the production and integration of a product's components. Some industries, such as semiconductor and steel manufacturers use the term fabrication instead. The manufacturing sector is closely connected with engineering and industrial design. Examples of major manufacturers in the North America include General Motors Corporation, General Electric, and Pfizer. Examples in Europe include Volkswagen Group, Siemens, and Michelin. Examples in Asia include Toyota, Samsung, and Bridgestone. Manufacturing engineers work on the development and creation of physical artifacts, production processes, and technology. The manufacturing engineering discipline has very strong overlaps with mechanical engineering, industrial engineering, electrical engineering, electronic engineering, computer science, materials management, and operations management. Their success or failure directly impacts the advancement of technology and the spread of innovation.It is a very broad area which includes the design and development of products.This field of engineering first became noticed in the mid to late 20th century The manufacturing process in engineering begins with the company concentrating all materials - raw materials, intermediate products - within the production company and ends with the customer shipment of the finished product. Raw materials and semi-finished materials in the manufacturing process are converted to products. The manufacturing process is divided into 3 stages:
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a. pre-production b. production c. sales 1. Pre-production stage includes the period prior to commencing production. Before the start of a new product, which may be influenced by the research, development and market, there are several activities which have to be done as the result of the production on the basis of design calculations and design drawings = technical documentation has to be created, as well as designed processes and procured the necessary equipment, materials and intermediates needed for the start of a new production. 2. Production stage covers all activities that are directly related to the making of products. Mostly it is a great variety of manufacturing processes, which are directly linked to each other. 3. Sales are the end stage of the manufacturing process. This includes product packaging and sending the customer or implementation of the various tests to guarantee the transfer of the customer. Most production companies provide maintenance services to customers. The challenge is to provide maintenance services for repair and consulting services, including training of future workers handling of the production facilities. EXERCISES : 1. Read the text and find the definitions to these words : a. b. c. d. e.
Industry Economy Engineering Manufacturing Sales
2. Read the folowing quote : „ Scientists study the world as it is; engineers create the world that has never been.“ Theodore von Kármán What do you think about it? Do you or do you not agree with it ? Why ? 3. Which kinds of engineering do you know? Name at least 3 of them:
4. Look at the folowing table with the data of the GDP - Gross domestic product of a country is a measure of the size of its economy. The most conventional economic analysis of a country relies heavily on economic indicators like the GDP and GDP per capita. While often useful, it should be noted that GDP only includes economic activity for which money is exchanged. Compare and contrast 5 countries with the Czech republic, which countries are in the same level, which are on a different one - why, tell and give examples:
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Subject Description GDP based on PPP Austria per capita GDP GDP based on PPP Belgium per capita GDP GDP based on PPP Cyprus per capita GDP Czech GDP based on PPP Republic per capita GDP GDP based on PPP Denmark per capita GDP GDP based on PPP Estonia per capita GDP GDP based on PPP Finland per capita GDP GDP based on PPP France per capita GDP GDP based on PPP Germany per capita GDP GDP based on PPP Greece per capita GDP GDP based on PPP Hungary per capita GDP GDP based on PPP Ireland per capita GDP GDP based on PPP Italy per capita GDP GDP based on PPP Latvia per capita GDP GDP based on PPP Lithuania per capita GDP GDP based on PPP Luxembourg per capita GDP GDP based on PPP Malta per capita GDP GDP based on PPP Netherlands per capita GDP GDP based on PPP Poland per capita GDP GDP based on PPP Portugal per capita GDP Slovak GDP based on PPP Republic per capita GDP GDP based on PPP Slovenia per capita GDP GDP based on PPP Spain per capita GDP GDP based on PPP Sweden per capita GDP United GDP based on PPP Kingdom per capita GDP Country
Units
Scale
2004
2005
2006
2007
Units
US dollars 32231.973
33615.161 35001.979
36409.063
Units
US dollars 30142.015
31243.931 32499.715
33908.408
Units
US dollars 20128.885
21232.209 22334.022
23480.658
Units
US dollars 17220.402
18375.240 19478.158
20596.694
Units
US dollars 33238.732
34737.239 36079.484
37406.122
Units
US dollars 14925.774
16414.034 17802.218
19243.036
Units
US dollars 29951.787
31207.669 32822.390
34162.110
Units
US dollars 28288.394
29316.419 30322.172
31595.121
Units
US dollars 29580.674
30579.396 31571.588
32683.520
Units
US dollars 21161.001
22391.603 23518.767
24732.860
Units
US dollars 16335.592
17404.673 18491.502
19596.967
Units
US dollars 38546.990
40609.775 42858.941
45134.558
Units
US dollars 28097.213
28760.263 29727.270
30790.841
Units
US dollars 11396.117
12621.599 13784.299
14933.484
Units
US dollars 12856.293
14158.421 15442.910
16756.034
Units
US dollars 66546.382
69799.557 72945.456
76215.149
Units
US dollars 19099.502
19739.125 20364.595
21081.347
Units
US dollars 29957.162
30861.515 32061.852
33079.435
Units
US dollars 12292.924
12994.208 13797.201
14609.213
Units
US dollars 18781.657
19334.599 19948.543
20672.795
Units
US dollars 14904.187
16040.740 17239.093
18704.933
Units
US dollars 20573.565
21910.716 23250.323
24592.692
Units
US dollars 25014.038
26320.246 27542.458
28809.508
Units
US dollars 28524.117
29898.076 31235.122
32517.465
Units
US dollars 29294.102
30469.843 31627.577
32993.049
63
Gross domestic product based on purchasingpower-parity (PPP) per capita GDP
International Monetary Fund, World Economic Outlook Database, April 2006
5. Look at the website : http://www.ewb-international.org and answer these questions : 1. 2. 3. 4. 5.
What is the main aim of this organisation ? How can you become a member of it? Is anybody from the Czech republic a member, if yes, find out who. Would you like to join them, if not say why. You want to become a member of this association. What do you have to do ?
6. In 2003, the National Academy of Engineering in the United States published A Century of Innovation: Twenty Engineering Achievements that Transformed our Lives. This work gives detailed historical information on the following list of what the authors consider to be the top twenty engineering achievements of the 20th century or those achievements which had the greatest impact upon life during and following this period. Do you have any idea, what was according them the most important achievement? Here you have 10 words, list them from the first to the last position. The first one is given. If you do not know, try to find out in the Internet : radio and television, automobile, computers, water supply and distribution, airplane, electronics, air conditioning and refrigeration, telephone, agricultural mechanization Electrification, 7. Look at the pictures, what is it ? Describe them :
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Help : Training FMS with learning robot SCORBOT-ER 4u, workbench CNC Mill and CNC Lathe, Mohr's circle, a common tool to study stresses in a mechanical element, An oblique view of a four-cylinder inline crankshaft with pistons.
Vocabulary agriculture ....................................... zemědělství association. ..................................... asociace branch.............................................. odvětví chemical engineering .................... chemické inženýrství civil engineering ............................. stavební inženýrství consulting ........................................ poradenství cover ................................................ pokrývat, zahrnovat developed countries ...................... rozvinuté země developing countries ...................... rozvojové země economy ......................................... ekonomika, hospodářství electrical engineering ................... elektrotechnika electrification .................................. elektrizace electronics ....................................... elektronika engineering ..................................... inženýrství, strojírenství goods ............................................... zboží gross domestic product .................. hrubý domácí produkt interdependence ............................ vzájemní závislost link .................................................... spojit, propojit maintenance services .................... údržba manufacturing ................................. výrobní, výroba mechanical engineering................ strojírenství overlap ............................................. přesah, překrytí purchasing-power-parity ............... kupní síla obyvatelstva
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R&D ................................................... výzkum a věda quote ................................................ citát tool ................................................... nástroj, nářadí, pomůcka service.............................................. služba, servis, provoz voluntary .......................................... dobrovolný Industry ............................................ průmysl automotive industry ........................ automobilní průmysl chemical industry ........................... chemický průmysl electronic industry .......................... elektrotechnický průmysl food industry .................................... potravinářský průmysl heavy industry ................................. těžký průmysl light industry .................................... lehký průmysl meatpacking industry .................... jateční průmysl petroleum industry .......................... ropný průmysl
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PRODUCTION OF PIG IRON V přírodě se chemicky čisté železo nevyskytuje, v podobě sloučenin je však po kyslíku, křemíku a hliníku nejrozšířenějším prvkem v zemské kůře. Čistého železa se ale používá pouze ke zvláštním účelům, ve strojírenské praxi se s ním nesetkáváme. Tam se používá tzv. technické železo. Technické železo má hustotu 7,84 kg/dm3, jeho teplota tavení je 1536 oC. Není chemicky čisté, obsahuje uhlík a další prvky zejména fosfor, síru, mangan a křemík. Tyto prvky vlastnosti čistého železa podstatným způsobem mění. Základní surovinou pro výrobu železa je železná ruda. Surové železo se vyrábí ve vysokých pecích redukcí železných rud. Vsázka do vysoké pece obsahuje: 1. železnou rudu 2. palivo 3. struskotvorné přísady 4. horký vzduch Železné rudy se ve velkém procentu se dovážejí z Ruska, Švédska a Německa. Nejznámějším druhem železné rudy je magnetovec, který obsahuje 40 – 70 % železa, a krevel. Palivem pro vysokou pec je hutnický koks. Struskotvorné přísady mají čistící funkci, jsou schopny vázat na sebe nečistoty a nežádoucí prvky. Ze železné rudy a koksu vzniká struska, která se usazuje na povrchu roztaveného železa a chrání kovovou lázeň před oxidací. Horký vzduch je pro vlastní proces ve vysoké peci velmi důležitý – podporuje proces hoření, umožní vyšší žár v peci a šetří palivo. Vzduch se dopravuje pomocí různých typů dmychadel. Hlavním produktem vysoké pece je surové železo, vypouští se (odpichuje) v intervalech 3 – 6 hodin. V podstatě se jedná o roztok železa s uhlíkem, obsah uhlíku je 1,8 – 4,5 %. Dalším produktem je struska, která se používá ve stavebnictví při výrobě cementových směsí nebo v zemědělství jako hnojivo. Třetím produktem vysoké pece je vysokopecní plyn, využívá se jako cenné palivo. Veškerá technická železa se používají pro výrobu oceli nebo litiny. Technická železa určená pro výrobu oceli musí mít maximální obsah uhlíku 2%. Production of pig iron The nature of chemically pure iron is not present in the form of compounds, however, after oxygen, silicon and aluminum, it is the most common element in the earth's crust. Pure iron is only used for special purposes, but we do not use it in engineering processes. What is usually used there is technical iron. Technical iron has a density of 7.84 kg/dm3, its melting temperature is 1536 °. It is chemically pure material, containing carbon and other elements, especially phosphorus, sulfur, manganese and silicon. These elements can easily change the quality of pure iron. The basic raw material for the manufacture of iron is iron ore. Pig iron is produced in blast furnaces by reduction of iron ore. Input into the blast furnace contains: 1. Iron ore – 2. fuel – 3. slag making ingredients – 4. hot air Iron ore is imported from Russia, Sweden and Germany in a large percentage. The best known type of iron ore is magnetite, which contains 40-70% iron, and 67
hematite. The fuel for the blast furnace is a metallurgical coke. The slag making ingredients have cleaning function and are able to bind dirt and unwanted elements. The slag arises from the iron ore and coke, which is deposited on the surface of the molten iron bath and protects the metal from oxidation. Hot air is for the process in a blast furnace very important - it supports the combustion process,it allows more heat in the oven and saves fuel. The air is transported through various types of blowers. The main product of blast furnace is the pig iron, deleted at intervals of 3-6 hours. Basically it is a solution of iron and carbon, the carbon content is 1.8 - 4.5%. Another product is the slag, which is used in the construction industry in the manufacture of cement mixtures or in agriculture as fertilizer. The third product of the blast furnace is gas, used as a valuable fuel. All kinds of technical iron are used in the manufacture of steel or cast iron. Technical iron for the manufacture of steel contains at least 2% of the maximum carbon content. Poslech Fonetický přepis Slovník - Zobrazit podrobný slovník Exercises: True or false ? 1. 2. 3. 4. 5.
Hot air is not important for the production of pig iron. The slag can be used for other purposes. Iron ore is seldom imported. The melting temperature of iron is higher than 1536° C. Fuel protects the metal from oxydation.
T/F T/F T/F T/F T/F
What do the following numbers refer to : 1. 1536 2. 2 3. 1,8 4. 40 5. 7,84 Describe the picture: 1. BOF conventor 2. EAf steelplant 3. Production of pig iron
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a)
c)
b) The picture shows Vítkovické steelworks in the 19. ͭ ͪ century. It is part of the European cultural heritage. Do you know what it means ? Explain it.
Vocabulary Allow ................................................ umožnit blast furnace ................................... vysoká pec BOF conventor ................................. kyslíkový konventor EAF steelplant .................................. elektrická oblouková pec European cultural heritage ............ evropské kulturní dědictví Fertilizer ............................................ hnojivo Fuel ................................................... palivo Hot air ............................................... horký vzduch Iron ore ............................................. železná ruda Manganese ..................................... mangan melting temperature ....................... teplota tavení
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metallurgical coke.......................... metalurgický koks mixture ............................................. směs pig iron ............................................. surové železo protect ............................................. chránit, ochraňovat purpose ............................................ účel, důvod slag ................................................... struska Steelworks ........................................ železárny
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CASTING PRODUCTION Odlévání je způsob výroby součástí z kovů nebo jiných tavitelných materiálů, při kterém se roztavený kov – tavenina – vlije do formy, jejíž dutina má tvar a velikost odlitku. Ztuhnutím taveniny ve formě vznikne odlitek. Odlitek je buď již hotový výrobek nebo se ještě dále mechanicky opracovává. Odlitky se odlévají ze šedé litiny, z oceli na odlitky, ze slitin hliníku, mědi, hořčíku, zinku, některých plastů. Materiál používaný k výrobě odlitků musí mít dobrou zabíhavost, aby vyplnil celý prostor formy. Technickým podkladem pro výrobu odlitku je výkres součásti. V oddělení přípravy výroby se zhotoví výkres polotovaru – odlitku, podle kterého modelárna vyrobí modelové zařízení tj. modely, jaderníky, šablony. Pomocí tohoto zařízení se ve formovně zhotovují formy. Mají-li se v odlitku vytvořit dutiny, používá se k tomu jader vyráběných v jadernících. Odlévání se provádí nejčastěji do pískových forem, které se formují ručně – při kusové výrobě - nebo za pomoci formovacích strojů – při sériové výrobě. Formovacím materiálem bývá křemenný písek, jeho soudržnost zajišťuje hlína nebo jíl. Roztavený kov do formy proniká vtokovým kanálkem - vtokem, vzduch z formy uniká výfukem. Většina forem se odlévá na syrovo, ostatní formy se suší. Vysušením se forma stává pevnější a prodyšnější. Tekutý kov se připravuje v tavicích pecích, na místo odlévání se dopravuje v licích pánvích. Po odlití a ztuhnutí se forma rozbije, odlitek se vyjme (vytluče), zbaví se vtokové soustavy a očistí se od zbytků písku. Dobrý odlitek musí vyhovovat všem technickým podmínkám, to znamená, že nesmí mít žádnou vadu. Vady odlitků vznikají zejména nevhodnou konstrukcí odlitku, neodborným tepelným zpracováním nebo použitím nevhodného formovacího materiálu. Vyrobené odlitky tedy procházejí technickou kontrolou, při kterých se zjišťují zejména velmi nebezpečné vnitřní vady. Používají se k tomu různé druhy defektoskopických zkoušek – např. zkouška ultrazvukem. Odléváním se vyrábějí většinou předměty složitého tvaru, které by se jinou technologií (kováním nebo obráběním) vyráběly jen s obtížemi nebo složitě. Velikost odlitků je v širokém rozmezí hmotnosti od několika gramů do desítek tun. surový odlitek výfuk licí jamka
vtoková soustava
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Casting production Casting is a method of producing parts from metal or other meltable materials at which the molten metal - melt – is poured into a molding form whose cavity has the shape and size of the casting. The solidification of the melt occurs in the form of the casting. The casting can be a finished product or is ready to be mechanically machined too. The castings are casted from following materials : cast iron, steel for castings, aluminum alloy, copper, magnesium, zinc and some plastics. The material used for castings shall be of a good cohesive quality to fill the entire space of the forms. Technical basis for the production of cast components is drawing. The preproduction department has to produce a drawing of the semi - casting, the pattern shop produces then according to it needed model equipment ie models, core boxes, patterns. This device is afterwards used to make it into the forming mold. If a cavity has to be created inside of the casting,than it is usually made with the help of cores produced in the core boxes. The casting is most often performed into sand molding forms that are shaped by hand - at piece - or with the assistance of molding machines – in the serial production. The molding material is quartz sand, its consistency ensures loam or clay. The molten metal passes into a mold inlet duct - inlet, the air escapes through the exhaust from the mold. Most forms are produced with the raw casting, other forms are dried. Thanks to the drying, the form becomes more stable and breathable. Liquid metal is prepared in a melting furnace and than it is transported in ladles to the place of casting. After the casting and solidification is finished, the molding form is broken, the casting is removed (beat), the inlet system has to be removed and the residue is purified from the sand. A good casting must comply with all the technical terms, this means that it must not have any defects on it. If there are still some casting defects than they are mainly caused by improper design of casting, heat treatment or improper use of inappropriate material molding. Produced castings then undergo an inspection in which all dangerous internal faults shall be determined. The faults can be found with the help of many kinds of tests as the different types of NDT tests - such as ultrasound examination. Casting objects are made mostly of complex shape that would be a different technology (forging or machining) produced only with difficulty or trouble. The size of castings is in a wide weight range from a few grams to tens of tons.
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raw casting
exhaust
pouring hole
inlet system
EXERCISES : • Read and answer : 1. What is casting ? 2. Which materials are used for casting ? 3. Which material is used for molding ? 4. What can cause casting defects ? •
Describe the casting production with the help of following words : MOLD DRAWING FORM LIQIUD METAL INSPECTION
•
Fill in the given words to complete the sentences : cavity break sand examination weight 1. The casting can_________ from few grams to several tones. 2. They often used _________molds for casting. 3. You have to __________ the mold form. 4. Ultrasound ___________ is one of the tests used to find casting faults. 5. Another word for __________ is a hole.
Notes : …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………...........................
Vocabulary aluminum alloy................................ slitina hliníku breathable ....................................... prodyšná casting ............................................. odlitek, odlévání cast iron ........................................... šedé litiny cause ............................................... způsobit cavity ............................................... dutina clay .................................................. jíl copper ............................................. měď
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core box .......................................... jaderník defect ............................................... chyba, závada exhaust ............................................ výfuk heat treatment................................. tepelné zpracování inappropriate................................... nevhodný inlet system ...................................... vtoková soustava loam ................................................. hlína melt .................................................. tavenina melting furnace ............................... tavící pec molding form .................................. forma na odlitek occur ................................................ vyskytovat se pattern.............................................. šablona, vzor pouring hole .................................... licí jamka quartz sand ...................................... křemenný písek raw.................................................... surový remove............................................. odstranit residue ............................................. zbytek sand molding forms ........................ písková forma solidification .................................... ztuhnutí stable ............................................... stabilní steel for castings ............................. ocel na odlitky ultrasound examination.................. zkouška ultrazvukem undergo ........................................... podstoupit weight .............................................. váha
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INTERNAL STRUCTURE OF MATERIAL AND HEAT TREATMENT Podle druhu vnitřní stavby rozdělujeme materiály do dvou základních skupin. První skupinu tvoří látky nekrystalické – amorfní. Tyto látky mají atomy neuspořádané a patří sem většinou nekovové materiály – např: sklo. Druhou skupinu tvoří látky krystalické, které krystalizují podle určité krystalické mřížky. Rozmístění atomů u těchto prvků je pravidelné a je typické zejména pro kovové materiály. Krystalická mřížka může mít různou podobu, ale u kovových materiálů se nejčastěji setkáváme s mřížkou krychlovou, která se vyznačuje největší pravidelností. Strukturu u kovů lze pozorovat buď pouhým okem nebo lupou - pak hovoříme o zkoumání makrostruktury a sledujeme ji na lomu nebo na řezu pilkou, anebo mikroskopem se zvětšením min. 100x a pak sledujeme mikrostrukturu. Pokud sledujeme mikrostrukturu materiálu, musíme provést odběr vzorku, jeho preparaci = zalití do pryskyřice, dále broušení, leštění a leptání. Na vzorku pak pod mikroskopem sledujeme různé fáze a složky v materiálu. Krystalizace kovů probíhá při teplotě tuhnutí. Krystalická mřížka se začíná tvořit kolem tzv. krystalizačního zárodku, který bývá tvořen atomy s nejmenší vnitřní energií, nečistotami s vyšší teplotou tání nebo tzv. očkovadly. Očkovadla jsou látky, které se úmyslně přidávají do kovové lázně, aby se zvýšil počet krystalizačních zárodků a tím vznikla jemnější struktura. Velikost zrna závisí na krystalizační schopnosti, tedy schopnosti tvořit krystalizační zárodky, a krystalizační rychlosti = jak rychle rostou krystaly. Velikost zrna je také výrazně ovlivněna rychlostí ochlazování materiálu, z čehož vychází princip a význam tepelného zpracování materiálů. Tepelné zpracování je technologický postup, kdy řízeným ohřevem a ochlazováním získáme u materiálu lepší vlastnosti jako důsledek změn ve struktuře materiálu. Nejznámějším druhem tepelného zpracování je kalení, jehož cílem je získat u materiálu větší tvrdost, a dále lze provádět různé druhy žíhání – například žíhání na měkko, žíhání normalizační nebo žíhání ke snížení vnitřního pnutí. Nástroje vyrobené z nástrojové oceli se rovněž často popouštějí. Internal structure of material and heat treatment Materials depending on the internal structure can be divided into two groups. The first group consists of non-crystalline substances - amorphous. They have disordered atoms and includes mostly non-metallic materials . An amorphous or non-crystalline solid is a solid that lacks the long-range order characteristic of a crystal. In part of the older literature, the term has been used synonymously with glass. Nowadays, "amorphous solid" is considered to be the overarching concept, and "glass" the more special case: A glass is an amorphous solid that transforms into a liquid upon heating through the glass transition. Other types of amorphous solids include gels, thin films, and nanostructured materials. The second group consists of crystalline substances, which crystallize under a crystal lattice. A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The points can be thought of as forming identical tiny boxes, called unit cells, that fill the space of the lattice. The lengths of the edges of a unit cell and the angles between them are called the lattice parameters. The symmetry properties of the crystal are embodied in its space group. A crystal's structure and symmetry play a role in determining many of its 75
physical properties, such as cleavage, electronic band structure, and optical transparency. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The word crystal is derived from the Ancient Greek word κρύσταλλος (krustallos), meaning "rock-crystal" but also "ice", from κρύος (kruos), "icy cold, frost". The word once referred particularly to quartz, or "rock crystal". Most common metals are polycrystals. Crystals are often symmetrically intergrown to form crystal twins. Distribution of numbers of these elements is regular and is particularly common for metallic materials. Crystalline lattice can take different forms, but in metallic materials, the most commonly encountered is cubic lattice, which is characterized by the greatest regularity. The structure of metals can be observed either by a naked eye or magnifying glass - then we are talking about macrostructure examination and follow it to fracture or cut saw, or a microscope with magnification minutes. 100x and then follow the microstructure. If we follow the microstructure of the material – the piece of material must be sampled, it needs some preparation = embedding in resin, as well as grinding, polishing and etching. The sample under a microscope can be observed of the various phases and components in the material. Crystallization takes place at a metal temperature hardening. The Crystalline Grid is starting to form around the embryo called the crystallization, which is made up of atoms with the lowest internal energy, impurities with higher melting point or socalled inoculant. Inoculants are substances that are intentionally added to the metal bath to increase the number of crystallization germs and thus suffered a finer structure. The grain size depends on the crystallization ability, the ability to form crystalline germs, and the crystallization speed = how fast the crystals grow. The grain size is also strongly influenced by cooling rates of the material, which is based on the principle and the importance of thermal processing of materials. Heat treatment of the technological process, the controlled heating and cooling is obtained with better material properties as a result of changes in the structure of the material. The best known species is the hardening heat treatment, aiming to attract greater hardness of the material, and can perform various types of ignition - for example, soft annealing, annealing or normalization annealing to reduce internal stresses. Instruments made of tool steel are also often annealed. Read the text and answer the questions : 1. What is a crystallization speed ? 2. How can we observe the structure of a material ? 3. What is crystallography ? 4. What is a crystal lattice ? 5. Which kinds of crystal lattice do you remember ? Look at the system of crystal lattice and try to describe it : •
Lattice systems
These lattice systems are a grouping of crystal structures according to the axial system used to describe their lattice. Each lattice system consists of a set of 76
three axes in a particular geometrical arrangement. There are seven lattice systems. They are similar to but not quite the same as the seven crystal systems and the six crystal families. The simplest and most symmetric, the cubic (or isometric) system, has the symmetry of a cube, that is, it exhibits four threefold rotational axes oriented at 109.5° (the tetrahedral angle) with respect to each other. These threefold axes lie along the body diagonals of the cube. The other six lattice systems, are hexagonal, tetragonal, rhombohedral (often confused with the trigonal crystal system), orthorhombic, monoclinic and triclinic.
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Vocabulary Annealing ........................................ žíhání Axe ................................................... osa Crystallization .................................. krystalizace Crystalline grid ................................ krystalická mřížka Cube ................................................ krychle, kostka Grain ................................................ zrno, zrnitost Heat treatment ................................ tepelné zpracování Ignition ............................................. zapálení, zážeh Influence .......................................... ovlivňovat Internal structure ............................. vnitřní stavba Lattice system .................................. mřížka Resin ................................................. pryskyřice Size ................................................... velikost soft annealing .................................. žíhání na měkko Speed ............................................... rychlo
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NONDESTRUCTIVE TESTING = TESTS OF MATERIAL FAILURE Materiál, hutní polotovary, strojní součásti i konstrukce obsahují většinou různé povrchové nebo vnitřní vady. Defekty vznikají již při výrobě nebo následně při provozu. Tyto skryté vady ohrožují bezpečnost provozu a omezují životnost strojů a zařízení, protože zeslabují nosný průřez, vyvolávají vnitřní pnutí v materiálu nebo způsobují netěsnost výrobků. Ke kontrole hotových součástí nelze použít běžné zkoušky – provádí se zkoušky bez porušení. Patří sem: 1. Vizuální metoda, kdy součást kontrolujeme pouhým okem nebo endoskopem pomocí nějakého záznamového zařízení - kamery, fotoaparátu. 2. Kapilární metoda Je založena na vzlínavosti kapalin v jemných dutinách a pórech (kapilární elevace). Ke zkoušce se používají barevné nebo fluorescenční kapaliny. Na očištěný a odmaštěný povrch materiálu se nanese detekční kapalina a nechá se určitý čas působit. Přebytek kapaliny se otře a nanese se vrstva pigmentu (např: křída). Detekční kapalina, která zatekla do povrchové trhliny začne po určité době vzlínat a zbarví pigment na povrchu součásti. Tato metoda je použitelná pro všechny druhy materiálů. 3. Magnetická metoda polévací Používá se pro zjišťování vad u výrobků z feromagnetických materiálů. Indikace vady probíhá na základě změny magnetického toku ve zmagnetizovaném materiálu. Povrchová vada vyvolá ve feromagnetickém zmagnetizovaném předmětu rozptylové magnetické pole – na obvodu vady se vytvoří magnetické póly. Detekční kapalina (olej + železné piliny) se na obrysu trhliny zachytí a vyznačí tak místo vady. 4. Zkoušky ultrazvukem Ultrazvuková metoda využívá průchodu ultrazvukových vln zkoušeným materiálem. Ultrazvukové vlny se v homogenním prostředí šíří přímočaře, na rozhraní dvou prostředí se odráží a lámou. Na rozhraní kov – vzduch dochází ke stoprocentnímu odrazu. Princip metody je založen na odrazu ultrazvukových vln od vnitřních vad. Zkoušky ultrazvukem jsou nezávadné, rychlé, lze je použít i pro materiály, jejichž tloušťka je větší než jeden metr. Ultrazvuk se používá ke kontrole odlitků, vývalků, výkovků nebo svarů. 5. Zkoušky Rtg zářením Rtg záření je elektromagnetické vlnění, které má schopnost pronikat kompaktními materiály. Při průchodu se zeslabuje v závislosti na tloušťce materiálu a na jeho atomové hmotnosti. Záření je neviditelné, působí na fotografickou emulzi a způsobuje fosforescenci. Princip metody je založen na rozdílném zeslabení záření vlive hrubých materiálových vad. Rtg. záření se využívá ke zjišťování staženin, trhlin, bublin a vměstků v odlitcích a hrubých vad svarů. Má škodlivé biologické účinky. Při práci s rentgenovými přístroji je proto nutno zachovávat bezpečnostní předpisy, aby nedošlo k poškození
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zdraví obsluhy. Nondestructive testing = tests of material failure Nondestructive testing (NDT) is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage. The terms Nondestructive examination (NDE), Nondestructive inspection (NDI), and Nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly-valuable technique that can save both money and time in product evaluation, troubleshooting, and research. Common NDT methods include ultrasonic, magnetic-particle, liquid penetrant, radiographic, remote visual inspection (RVI),eddy-current testing, and low coherence interferometry . NDT is a commonly-used tool in forensic engineering, mechanical engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and art. Methods NDT methods may rely upon use of electromagnetic radiation, sound, and inherent properties of materials to examine samples. This includes some kinds of microscopy to examine external surfaces in detail, although sample preparation techniques for metallography, optical microscopy and electron microscopy are generally destructive as the surfaces must be made smooth through polishing or the sample must be electron transparent in thickness. The inside of a sample can be examined with penetrating electromagnetic radiation, such as X-rays or 3D X-rays for volumetric inspection. Sound waves are utilized in the case of ultrasonic testing. Contrast between a defect and the bulk of the sample may be enhanced for visual examination by the unaided eye by using liquids to penetrate fatigue cracks. One method (liquid penetrant testing) involves using dyes, fluorescent or non-fluorescing, in fluids for non-magnetic materials, usually metals. Another commonly used method for magnetic materials involves using a liquid suspension of fine iron particles applied to a part while it is in an externally applied magnetic field (magnetic-particle testing). Thermoelectric effect (or use of the Seebeck effect) uses thermal properties of an alloy to quickly and easily characterize many alloys. The chemical test, or chemical spot test method, utilizes application of sensitive chemicals that can indicate the presence of individual alloying elements. NDT is divided into various methods of nondestructive testing, each based on a particular scientific principle. These methods may be further subdivided into various techniques. The various methods and techniques, due to their particular natures, may lend themselves especially well to certain applications and be of little or no value at all in other applications. Therefore choosing the right method and technique is an important part of the performance of NDT. 1. Acoustic emission testing (AE or AT) 2. Blue Etch Anodize (BEA) 3. Dye penetrant inspection Liquid penetrant testing (PT or LPI) 4. Electromagnetic testing (ET) 5. Ellipsometry 6. Guided wave testing (GWT) 7. Hardness testing 8. Impulse excitation technique (IET)
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9. Infrared and thermal testing (IR) 10. Laser testing 11. Leak testing (LT) or Leak detection 12. Magnetic resonance imaging (MRI) and NMR spectroscopy 13. Optical microscopy 14. Positive Material Identification (PMI) 15. Radiographic testing (RT) (see also Industrial radiography and Radiography) 16. Scanning electron microscopy 17. Surface Temper Etch (Nital Etch) 18. Ultrasonic testing (UT) 19. Visual inspection (VT) 20. Corroscan/C-scan 21. IRIS - Internal Rotary Inspection System 22. 3D Tomography 23. Heat Exchanger Life Assessment System 24. RTJ Flange Special Ultrasonic Testing Exercises : Answer : 1. Explain what is the NDT good for ? 2. Which basic methods of testing do you know ? 3. Which methods ans techniques can be used not only in the engineering ? 4. Name at least 3 basic methods and describe them in your own words: Are these sentences true or false : 1. Thermoelectric effect rarely uses thermal properties of an alloy characterize many alloys. .................... T/F 2. Microscopy can be used to examine internal surfaces in detail. T/F 3. X-rays or magnetic resonance can be used by human beings. T/F 4. None of the NDT methods is based on a scientific principle. T/F 5. Common NDT methods don´t include laser testing. T/F
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Look at the picture and match it with its describtion :
1. Developer is applied, rendering the crack visible. 2. 2. Excess penetrant is removed. 3. Section of material with a surface-breaking crack that is not visible to the naked eye. 4. Penetrant is applied to the surface. Look at the dates and find the correct endings of the right event : Notable events in early industrial NDT 1. 1854 Hartford, Connecticut: a boiler … 2. 1895 Wilhelm Conrad Röntgen …. 3. 1880 - 1920 The "Oil and Whiting" method of crack …. 4. 1920 Dr. H. H. Lester begins development of industrial radiography …. 5. 1927 - 1928 Magnetic induction …. 6. 1930s Robert F. Mehl demonstrates … 7. 1935 - 1940 Liquid … 8. 1940 - 1944 … 9. 1950 The Schmidt Hammer….. 10. 1950 J. Kaiser …. • • • • • •
…at the Fales and Gray Car works explodes, killing 21 people and seriously injuring 50. Within a decade, the State of Connecticut passes a law requiring annual inspection (in this case visual) of boilers. …for metals. 1924 — Lester uses radiography to examine castings to be installed in a Boston Edison Company steam pressure power plant. …(also known as "Swiss Hammer") is invented. The instrument uses the world’s first patented non-destructive testing method for concrete. …introduces acoustic emission as an NDT method. …discovers what are now known as X-rays. In his first paper he discusses the possibility of flaw detection. …detection is used in the railroad industry to find cracks in heavy steel parts. (A part is soaked in thinned oil, then painted with a white coating that dries to a powder. Oil seeping out from cracks turns the white powder brown, allowing
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• • • •
the cracks to be detected.) This was the precursor to modern liquid penetrant tests. …radiographic imaging using gamma radiation from Radium, which can examine thicker components than the low-energy X-ray machines available at the time. …Ultrasonic test method developed in USA by Dr. Floyd Firestone. Ultrasonic test method developed in USA by Dr. Floyd Firestone. …penetrant tests developed (Betz, Doane, and DeForest) …system to detect flaws in railroad track developed by Dr. Elmer Sperry and H.C. Drake.
Vocabulary aeronautical engineering .............. letecký průmysl acoustic emission testing ............... akustické měření emisí alloy.................................................. slitina alter .................................................. změnit apply ................................................ použít civil engineering ............................. stavebnictví common .......................................... společný, běžný defect ............................................... vada dye ................................................... barvivo electrical engineering .................... elektrotechnika electromagnetic radiation ............. elektromagnetické záření evaluate ........................................... hodnotit, vyhodnotit examine ........................................... zkoumat external surface .............................. vnější plocha fatigue cracks ................................. únavová trhlina fine iron particles ............................. jemné částice železa fluorescent ....................................... fluorescenční infrared and thermal testing ........... infračervené a tepelné testování leak testing ...................................... zkoušky těsnosti liquid penetrant ............................... kapilární liquid suspension ............................. kapalná suspenze magnetic-particle ........................... magnetické částice magnetic resonance imaging ....... magnetická rezonance mechanical engineering................ strojírenství permanently .................................... natrvalo properties of a material .................. vlastnosti materiálu research ........................................... výzkum sample ............................................. vzorek save .................................................. šetřit, ušetřit sound ............................................... zvuk sound wave ..................................... zvuková vlna troubleshooting ............................... řešení problémů ultrasonic ......................................... ultrazvuk volumetric ........................................ objemové x – ray............................................... rentgen
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TECHNOLOGICAL PROCESSES Ve strojírenských podnicích probíhá výrobní proces - tedy činnost, při které se výchozí polotovar přeměňuje na hotový výrobek za účasti výrobního zařízení a pracovní síly. Postup jednotlivých prací je předem naplánován – je vypracován technologický postup. Technologický postup je plán výrobního pochodu od polotovaru k hotovému výrobku. Má umožnit zhotovení výrobku při minimálních nákladech s vysokou produktivitou práce a s maximální jakostí. V technologickém postupu jsou uvedeny údaje důležité pro výrobu, jako například popis prací a metod ve vhodném sledu, počet zhotovovaných kusů, použité výrobní prostředky (stroje, pomůcky, měřidla, přípravky, nástroje), technologické podmínky, rozměry polotovaru před obráběním. Technologický postup se člení na jednotlivé části. Základní částí technologického postupu je operace, definovaná jako pracovní činnost vykonávaná na jednom pracovišti jedním pracovníkem nebo četou a to souvisle bez přerušení. Částí operace je pak úsek což je činnost prováděná na jedné ploše obrobku jedním nástrojem za stejných řezných podmínek. U podrobně rozpracovaných postupů se provádí členění ještě na úkony a pohyby. Podle výrobního postupu se určuje čas potřebný k provedení jednotlivých činností a kapacita = potřebný počet pracovišť a pracovníků. Postup zároveň slouží jako podklad pro odměňování a pro organizaci a plánování výroby. Podkladem pro vypracování technologického postupu je výrobní výkres součásti, výkres výchozího polotovaru a údaj o počtu vyráběných kusů. Technologický postup zpracovává technolog postupář v oddělení Technické přípravy výroby. Postup musí být úplný, správný, stručný, jednoznačný, srozumitelný, přehledný a hospodárný. Pro sériovou výrobu se vypracovává velmi podrobně, někdy je doplněn i návodnými obrázky. Technological processes the manufacturing process takes place in engineering companies - that is, an activity in which the source is converted into semi-finished product with the participation of manufacturing equipment and manpower. The procedure of work is planned in advance – a technological process is developed. The technological process is the production plan to march from the semi finished product. It should allow the construction of the product at minimal cost with high productivity and maximum quality. The processes are data which are relevant to production, such as a description of the work and methods in an appropriate sequence, number of manufactured units, used means of production (machines, tools, gauges, jigs, tools), technological conditions, semi-finished dimensions before cutting etc. Technological process can be broken down into individual parts. The essential part of the technological process is an operation defined as work done by one clinic worker or a platoon, and it is done continuously without any interruption. The operation is a part of the section which is an activity carried on one surface, one piece cutting tool under the same conditions. For detailed procedures for implementing the unfinished subdivision we can divide it into operations and movements. According to the production process we can determine the needed time to implement various activities and needed capacity = number of workplaces and 84
workers. The procedure also serves as a basis for reward and for the organization and planning. The basis for the development of the technological process is a manufacturing drawing, a component drawing of the initial preparations and with the number of units produced. Technological process is handled by a technologist in the Department of Technical preparation of production. The process must be complete, correct, concise, clear, understandable, easy and economical. For serial production it will be conducted in great detail, sometimes accompanied by a picture. •
Question to the text : 1. What is a technological process ? 2. What is an operation ? 3. What do we need to start a technological progress? 4. What does the the Department of Technical preparation of production do?
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Read the following definitions and explain in own words what is an ITP ?
Integrated Technology Processes (ITP) include all the requirements, know-how, means necessary for the design office, manufacturing, quality control to define and produce an elementary part or an assembly within a known supply chain. •
According to the text name at least 3 technologies where the processe are used:
Technology processes (i.e. “Techno Processes”) are end-to-end processes aligned with a specific manufacturing or assembly technology. E.g. Techno processes are used for technologies such as : 1. Tubing, 2. Sheet Metal, 3. Mechanical Parts, 4. Jigs and Tools, 5. Composites, 6. Electricity, 7. Thermoplastics, The "end-to-end" appellation means Techno Processes address all the activities from design to manufacture and assemble of an elementary part or an assembly. Several Techno Processes are most of the time required to build a final product. Find the given words in the crossword : Clear, easy, element, end, most, need, part, product, sheet, techno, tool, use
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Vocabulary accompany..................................... doprovázet align ................................................. sladit, postavit do řady appellation ..................................... označení assemble ......................................... shromáždit, smontovat basis ................................................ základ break down ..................................... rozdělit complete ......................................... úplný composites ...................................... kompozita concise ............................................ stručný correct ............................................. správný cost ................................................... náklady department ...................................... oddělení design .............................................. návrh easy.................................................. jednoduchý economical ..................................... hospodárný electricity ......................................... elektřina essential ........................................... základní final ................................................... konečný, koncový handle .............................................. řešit, zabývat se, manipulovat jigs .................................................... přípravek know how ........................................ znalost operation ......................................... operace, úkon mechanical parts ............................ mechanické součásti motion .............................................. pohyb reward .............................................. odměna require .............................................. vyžadovat, požadovat quality control ................................. kontrola kvality serial production ............................. sériová výroba sheet metal ...................................... plech technological processes ................ technologické postupy thermoplastics ................................. termoplasty tool ................................................... nástroj tubing ............................................... sonda
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