Brno University of Technology Faculty of Mechanical Engineering The Institute of Manufacturing Technology
LESSON 4 Chip Formation
Authors:
Ing. Miroslav PÍŠKA, PhD., Associate Professor
[email protected]
Ing. Petra CIHLÁŘOVÁ
[email protected]
Bc. Michael Lars George HILL
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Obsah 1 Terms, Vocabulary
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2 Examples
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3 Exercises
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4 References
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Terms, Vocabulary 1)
2)
3)
4)
5)
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Machining chip chip flow chip breaker built-up-edge flow zone stagnation zone shear plane abrasion adhesion diffusion undeformed chip deformed chip cutting ratio Physical phenomena fyzikální jevy total force cutting force feed force passive force radial force axial force tangential force friction Heat cutting power power consumption temperature of cutting thermo-duo thermo-couple infra-camera Surface integrity surface roughness residual stresses zbytková napětí cracks, flows structural changes softening hardening Cutting materials HSS (High Speed Steel) cemented carbides ceramics cermet CBN Cubic Boron Nitride polycrystalline diamond CVD (Chemical Vapour Deposition) PVD (Physical Vapour Deposition)
obrábění tříska odvod třísky utvářeč, lamač třísek nárůstek oblast kluzu zóna váznutí (mikrosvarů) rovina střihu abraze adheze difůze nedeformovaný materiál, přeměňovaný v třísku deformovaná tříska poměr hloubky řezu a tloušťky třísky celková síla řezná síla posuvová síla pasivní síla radiální síla axiální síla tangenciální síla tření Teplo řezný výkon řezný příkon teplota řezání termo-duo termočlánek infra kamera Integrita povrchu drsnost povrchu trhliny změny struktury odpevnění zpevnění Řezné materiály rychlořezná ocel slinuté karbidy keramika cermet KNB kubický nitrid bóru polykrystalický diamant chemický způsob povlakování fyzikální způsob povlakování
Examples
LESSON 4 - CHIP FORMATION 1. Chip formation starts with an initial curving and is affected by the combination of cutting data especially the feed rate and depth of cut, rake, the type and condition of material and also the size of the nose radius. A square chip cross-section usually means excessively hard chip compression while a wide, thin band-like chip is formed in to unsuitable strands. When the chip curve becomes smaller for a thicker chip, the chip/tool contact becomes longer with more deformation and pressure as a result. Excessive thickness has a negative influence on the machining process. If the feed is increased to above what the insert geometry has been designed for, the chip will pass over the chip forming geometry, with the effect that machining is 3
performed with a negative instead of positive geometry, with balanced chipbreaking. 2. Comma-shaped or helical chips up to a limited strength are usually found to be most suitable and formed by a carefully designed cutting edge. Although chip formation may in some cases be improved with a more negative rake and harder compression for selfbreaking of the chip, especially when applying small feed rates, a positive rake leads to other advantages. For larger feed rates, a more positive rake can be advantageous in that the initial curving of the chip is not excessively tight. Chipbreaking is thus seen as an important factor in modern machining, for the performance and reliability of the cutting action as well as the removal of chips from the tool, workpieces and machine. 3. Curve, direction, helix and shape of chip is designed into the ability of the cutting edge. Each insert type has a geometry developed to provide satisfactory chip formation within a certain area of feed rate, cutting depth and material type. Controlled chip formation is imperative throughout the various areas of modern cutting. 4. A finishing insert, working mostly with its nose radius will have its geometry concentrated at its corner while a heavy roughing insert will have geometry right across the rake face. Some inserts are capable of providing satisfactory chip formation across a broad intermediate range, having incorporated combinations of chip breakers, moving from the corner radius and across the insert face. 5. There are different ways for a chip to break: a) self breaking - breaking when the chip is stopped by the tool, b) when the chip is stopped by the tool, c) when the chip is stopped by the workpiece. 6. There are advantages and disadvantages with all three alternatives. Self-breaking has been mentioned already, and achieving a suitable direction of chip is one of the more important factors here. Breaking against the tool may be negative if chip hammering takes place against the insert edge. Breaking against the workpiece may be negative if the chip affects workpiece quality or ends up in the cutting zone again. Uncontrolled swarf should always be avoided as it can very quickly lead to tool breakage, inferior results, machine down-time and operator injury. 7. Chip control is, thus, one of the key factors especially in turning and drilling. Milling creates a natural chip length thanks to the limited length of cutting edge engagement. In drilling and boring, chip control is vital because of the limited space inside holes being machined. Also in modern high-performance drilling, chips have to be of exact form so as to be evacuated efficiently from the cutting zone - any congestion, quickly leads to tool breakage. Vocabulary notes: Curving - zakřivení; affect - ovlivnit, poškodit; cutting data - řezné podmínky; nose radius - poloměr špičky břitu; band like chip - stuhovitá tříska; excessive - nadměrný; balanced - vyvážený, uklidněný; comma shaped chip - drobivá tříska; helical - šroubovitý; helix - šroubovice; edge engagement - záběr břitu; swarf - odpad, drť, třísky; inferior - nižší, horší; vital - velmi důležitý, zásadní; evacuate - odsávat, odstraňovat; machine down time - prostoj stroje; congestion - zahlcení, ucpání; breakage - zlomení.
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Exercises
I. Translate the following expressions and build short sentences using each of them: The new design under development, the work on the development of a special design, with the help of a powerful computer, to continue with successful research, close coordination between the research and development efforts, economic growth, a number of successful projects, key objectives, sharing knowledge and expertise, programmes are funded. II. Match the expressions in List A with those in List B:
1.
A approximately proportional
B technical help
a) 4
1
...
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
being developed important advance outlined design technical development considerable increase expert in designing floppy disk technical assistance improved version of a machine by means of draughtsman specified proportion development stage development costs
b) c) d) e) f) g) h) i) j) k) l) m) n) o)
notable rise vdrawer expenditures for development significant progress redesigned machine roughly proportional pre-production stage sketched project given ratio specialist in designing technological progress flexible disk with the aid of under development
2 3 4 5 6 7 8 9 10 11 12 13 14 15
... ... ... ... ... ... ... ... ... ... ... ... ... ...
III. Translate the following expressions: Rough estimate of R&D costs, less industrialised countries, application of high-tech, further improvement in design, standard tolerances, rapid prototyping, completion of the development process, features of the ergonomic design, field of engineering, inter-disciplinary problem, to put considerable effort into, to render technical assistance, assembly of a prototype, remarkably efficient, new product placed on the market, printer, display, for information and dissemination. IV. Build sentences from the following expressions and words: Technological process, pilot plant, pollution, dislocation, raw material, know-how, packaging, discrepancy, loudspeaker, control, remote control, variation, range, British Standard, friction clutch, drawing board, drafting department, combustion engine, lorry, truck. V. Complete the following sentences: 1. Recent advances in science and technology have created . . . 2. . . . to undertake an inquiry into the effects of technological progress on the economy and the character of the society. 3. Having solved a lot of complicated engineering problems the researches decided to. . . 4. The design principles applied are similar to those already proved in . . . 5. The development now in progress indicates that. . . 6. Our improved understanding of the consequences of modern science and technology . . . 7. The highly trained personnel of the computation centre succeeded in . . . 8. The biggest obstacle to the rapid and effective introduction of new technology . . . 9. The negative effects of our technology on our environment are . . . 10. This calculation predicts no difficulties . . . 11. The development extended over five years . . . 12. This demand has lad to the development of . . . 13. These values were not taken into considerations because . . . 14. . . . technological innovation leads to changes in . . . 15. The time period between invention and widespread adoption of new technology . . . VI. Translate the following expressions into English: 1. Nový obráběcí stroj, který se právě vyvíjí v naší firmě, má být připraven ke zkouškám do pěti měsíců. 2. Zde probíhá práce na vývoji nové konstrukce měřicího přístroje. 5
3. Vývoj nového stroje skončil nezdarem. 4. Zavedení nového stroje do sériové výroby brání několik zádrhelů. 5. Ukázalo se, že technicky možný projekt je ekonomicky nerentabilní. 6. Nový pokrok je dnes nemyslitelný bez velkého podílu vědy. 7. Konstruktéři museli náhle řešit těžký a nepředpokládaný problém. 8. Zákazník odsouhlasil a svým podpisem potvrdil provedené změny v dokumentaci. 9. Přístroj takových parametrů asi nebyl dosud vyroben. 10. Tento nový stroj představuje vrchol současných technických možností. VII. Antonyms 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
absolute coordinates accomplished ahead of analysis automatically approve compression dry correct abundant compute dark common safe assumed
a) b) c) d) e) f) g) h) i) j) k) l) m) n) o)
synthesis behind relative coordinates unfinished special rare real estimate light dangerous 10 wrong reject, refuse damp tension manually
1 2 3 4 5 6 7 8 9 ... 11 12 13 14 15
... ... ... ... ... ... ... ... ... ... ... ... ... ...
VII. By adding the prefixes un-/in- to the following words, form their opposites and use each of them in sentences of your own: Completed, common, comparable, complete, important, accurate, efficient, known, solved, certainty, computable, successful, scientific, observed, divisible, calculable, published, significant, reasonable, necessary, capable, expected, explored, satisfactory, finished. IX. Explain the meaning of the following expressions: Jointly financed projects, a highly industrialized country, rapid and large scale industrialization, unwanted effects, successful redesigning, computer hardware/software, staff of expert designers, a rough sketch, social consequences, technically feasible project, economically profitable project, exploiting the results of the technical development, total annual R&D costs, estimated probability of technical success, blueprint copy, in the early twentieth century, deviation from specification, historical evaluation, drawing office, CAD. X. Answer the following questions: 1. How does the technological department influence the productivity of labour? 2. Are computers used at your institute frequently? 3. Are computers important tools for designers? 4. Can you explain the meaning of the term ”know-how”? 5. What is the main purpose of technological development? 6. What is the aim of the EU Standing Committee for Physical and Engineering Sciences? 7. Does the management of your plant formulate long-range plans for its development activity? 8. Why is advertising now so widely used in daily life?
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9. What are the effects of modern CAD/CAM technology on work and employment? 10. Has your company formulated specific objectives for its development activity? XI. Gerund and infinitive phrases. Back to your roots: Re-write each of the statements about education, beginning with the word given, so that it has exactly the same meaning. Follow this example: To complain to your parents was impossible. It was impossible to complain to your parents. 1. Staying on at school after the age of 16 is uncommon in Britain. It . . . 2. It is the prime aim of primary schooling to teach children to read and write. Teaching . . . 3. It is alarming to discover that 93 per cent of British teenagers do not go to university. Discovering . . . 4. Becoming literate and numerate is the first step towards a successful life. To . . . 5. It is a basic requirement in the modern world to be able to deal with figures. Being . . . 6. It is interesting to discover that girls are usually better at mathematics than boys. To . . . 7. Attending university is not always the best way to learn about life. It . . . 8. It is important to remember that truancy is often the result of family pressures. Remembering . . . 9. To play truant as a child is a principal cause of problems in adult life. It . . . 10. It can make children violent and disaffected to punish them physically. To. . . XII. Synonyms
1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
A appendix access check apparatus assistance importance characteristic back advance chief
B a) b) c) d) e) f) g) h) i) j)
device supplement main progress significance reverse feature inspection help approach
XIII. Computer Numerical Control Programming
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... ... ... ... ... ... ... ... ... ...
1. Define ”absolute programming”. 2. Define ”incremental programming”. 3. Explain ”rapid traverse” motion. 4. Which interpolation will produce the required straight-line motions by driving the slides at different speeds? 5. What is the difference between linear and circular interpolation? Explain each term in the following line of program. 6. List some ”non-dimensional” words in a program. 7. Explain the term ”origin” in programming and list the different types of origins one can encounter in a program. 8. Explain the term ”tool length compensation” and justify the need for this process. 9. Is it critical to position the fixture on the machine table exactly according to the set–up drawing? 10. Which code for cutter diameter compensation left is used? 11. Which code for cutter diameter compensation right is used? 12. How many tool parameters are assigned into the offset register? 13. Is it important to know the actual length of the cutting tools before the start of the program? 14. What is the essential concept of cutter diameter compensation? 15. What are the major advantages of cutter diameter compensation? 16. What is tool length compensation used for? 17. Is there an axis restriction in setting up tool length compensation? 18. What are canned cycles? 19. What is the peck-drilling canned cycle code and how does the cycle work? 20. Write a CNC program for the part shown in Fig. . . . , using canned cycles for contour turning. 21. Write a CNC program for the part shown in Fig. . . . , using canned cycles for peck drilling. 22. Write a CNC program for the part shown in Fig. . . . , using canned cycles for tapping. 23. Explain the facing canned cycle process, by comparing it to straight turning. 24. What is the difference between a subroutine and a standard canned cycle? 25. Why are subroutines used? 26. Is there a limitation in the number of times a subroutine can be called? 27. Give two examples of typical applications for subroutines. 28. Give an example of a program line containing a subroutine call. Explain each word. 29. Write a CNC program for turning of the part illustrated in Fig. . . . . Modify the comparative probing program to measure or probe the 12.00 and the 45.00 dimensions along the Z axis. XIV. Food Breakfast: orange/grapefruit juice, bananas, fruits, lemon squeezer, a package of milk, corn flakes, a glass of milk, roll, sliced bread, cereals, pepper pot, saltcellar, sugar basin, boiled/scrambled eggs, margarine, butter, porridge, toaster, toasts, Passport, identity card, customs, a cup of coffee/tea, cream pot, a jar of strawberry jam, honey, sausages, beans, bacon, tomatoes, paté, ham. Lunch: pizza, hamburger, sandwich, prawn cocktail, omelette, fish and chips, mixed salad, crisps, chips, hot dog, a 8
tin of beer, a bottle of beer, a glass of water, apples, grapes, pear, tea pot, a piece of pie, Brussel sproutes, lettuce, cabbage, asparagus, celery, lentils, green pears, leek, onion, chives, garlic, radish, carrot, horseradish, parsley, beetroot, cauliflower, gherkins, green pepper/paprika, cheese, biscuits, doughnuts, sweets, chocolate gateau. Dinner: tomato soup, roast chicken, roast beef, steak, steak and chips, mixed vegetables, meat pie (shepherd’s pie), fried beans, salad, spaghetti, pasta, plums with custard, ice cream, red/white wine, pineapple. melon, mandarin, hazelnut, coconut, trifle, sundae.
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