Advanced Machining Process
Sumber: Manufacturing Engineering and Technology Oleh: Serope Kalpakjian
Mengapa perlu Advanced Machining Process
Material sangat kuat dan sangat keras (> 400 HB) atau material sangat getas. Benda kerja sangat fleksible, sangat tipis ataupun sangat kecil sehingga tidak mungkin u/ diproses dengan permesinan konvensional maupun proses grinding (tidak memungkinkan dikenai gaya potong yang besar maupun tidak mungkin di jepit/clamp pada mesin perkakas konvensional. Bentuk komponen kompleks, dengan fitur-fitur eksternal/internal yang rumit (diameter lubang sangat kecil). Surface finish dan toleransi dimensi yg tinggi, yg tidak bisa dipenuhi oleh proses permesinan konvensional. Benda kerja yang peka terhadap peningkatan temperatur maupun tegangan sisa akibat proses permesinan konvensional 2
Parts Made by Advanced Machining Processes
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Parts Made by Advanced Machining Processes
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Parts Made by Advanced Machining Processes
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General Characteristics of Advanced Machining Process
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Chemical Milling
Figure 27.2 (a) Missile skin-panel section contoured by chemical milling to improve the stiffness-to-weight ratio of the part. (b) Weight reduction of space-launch vehicles by the chemical milling of aluminum-alloy plates. These panels are chemically milled after the plates first have been formed into shape by a process such as roll forming or stretch forming. The design of the chemically machined rib patterns can be modified readily at minimal cost. 7
Chemical Milling and Machining
Permukaan material diberi lapisan (maskant). Material maskant tidak boleh bereaksi dgn zat kimia (reagent) yg digunakan. Permukaan benda kerja harus bersih dan bebas minyak/grease agar pelapis/maskant menempel dengan baik. Maskant dihilangkan dr permukaan yg ingin dibentuk, shg logam bereaksi dgn zat kimia (reagent) agar terjadi pengikisan. 8
Chemical-Machining
Chemical machining dilakukan berdasarkan prinsip bahwa zat kimia atau proses kimia bisa/mampu mengikis logam.
Dengan demikian bagian-bagian tertentu dari logam yg ingin dihilangkan atau dikurangi diekspose pada zat kimia tsb, sehingga terjadi pengikisan logam sesuai dengan bentuk yg diinginkan.
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Chemical-Machining
Figure 27.3 (a) Schematic illustration of the chemical-machining process. Note that no forces or machine tools are involved in this process. (b) Stages in producing a profiled cavity by chemical machining; note the undercut.
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Surface Roughness and Tolerances in Machining
Figure 27.4 Surface roughness and tolerances obtained in various machining processes. Note the wide range within each process (see also Fig. 23.13). Source: Machining Data Handbook, 3rd ed. Copyright © 1980. Used by permission of Metcut Research Associates, Inc. 11
Parts Made by Chemical Blanking
Figure 27.5 Various parts made by chemical blanking. Note the fine detail. Source: Courtesy of Buckbee-Mears, St. Paul. 12
Chemical Blanking
Prinsipnya sama dgn sheet metal blanking, yaitu menghasilkan bentuk/fitur tertentu dengan melubangi benda kerja.
Lubang/fitur terjadi karena pengikisan logam melalui reaksi kimia. 13
Electrochemical Machining (Reverse electro plating)
Figure 27.6 Schematic illustration of the electrochemical machining process. 14
Parts Made by Electrochemical Machining
Figure 27.7 Typical parts made by electrochemical machining. (a) Turbine blade made of nickel alloy of 360 HB. Note the shape of the electrode on the right. (b) Thin slots on a 4340-steel roller-bearing cage. (c) Integral airfoils on a compressor disk. 15
Knee Implants
Figure 27.8 (a) Two total knee replacement systems showing metal implants (top pieces) with an ultra-high molecular-weight polyethylene insert (bottom pieces). (b) Cross-section of the ECM process as applies to the metal implant. Source: Courtesy of Biomet, Inc.
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Electrochemical-Grinding Process
Figure 27.9 (a) Schematic illustration of the electrochemical-grinding process. (b) Thin slot produced on a round nickel-alloy tube by this process. 17
Electrochemical-Grinding Process
Gabungan antara electrochemical machining dgn grinding konvensional.
Grinding wheel beropa katoda yg dilengkapi dgn partikel abrasif. 18
Electrical-Discharge Machining Process
Figure 27.10 (a) Schematic illustration of the electrical-discharge machining process. This is one of the most widely used machining processes, particularly for die-sinking applications. (b) Examples of cavities produced by the electrical-discharge machining process, using shaped electrodes. Two round parts (rear) are the set of dies for extruding the aluminum piece shown in front (see also Fig. 19.9b). (c) A spiral cavity produced by EDM using a slowly rotating electrode similar to a screw thread. (d) Holes in a fuel-injection nozzle made by EDM; the material is heat-treated steel. Source: (b) Courtesy of AGIE USA Ltd. 19
Electrical-Discharge Machining Process
Juga disebut electro-discharge atau sparkerosion machining. Pengikisan logam terjadi karena adanya loncatan busur listrik yg keluar dari pahat/tool. Loncatan busur listrik ini akan mengikis permukaan logam (b-kerja). Listrik menggunakan arus searah (DC), voltase 50 – 380 Volt, arus 0,1 – 500 Amp, discharge rate 50 – 500 kHz. Benda kerja direndam dalam fluida dielektrik (fluida yg tidak bisa menghantar arus listrik) 20
Stepped Cavities Produced by EDM Process
Figure 27.11 Stepped cavities produced with a square electrode by the EDM process. The workpiece moves in the two principle horizontal directions (x – y), and its motion is synchronized with the downward movement of the electrode to produce these cavities. Also shown is a round electrode capable of producing round or elliptical cavities. Source: Courtesy of AGIE USA Ltd.
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The Wire EDM Process
Metal removal rate : MRR 4 10 4 ITw1.23 where I current in amperes Tw melting temperature of workpiece, C
Figure 27.12 Schematic illustration of the wire EDM process. As many as 50 hours of machining can be performed with one reel of wire, which is then discarded.
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The Wire EDM Process
Prinsipnya = EDM. Pahat berbentuk kawat (wire), karena Wire EDM ini digunakan untuk proses potong. Diameter kawat 0,3 mm (u/ roughing cut) dan 0,2 mm (u/ finishing cut). Kawat bergerak dgn kecepatan 0,15 – 9 m/menit. 23
Wire EDM
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(b)
Figure 27.13 (a) Cutting a thick plate with wire EDM. (b) A computercontrolled wire EDM machine. Source: Courtesy of AGIE USA Ltd. 24
Laser-Beam Machining (LBM) Figure 27.14 (a) Schematic illustration of the laser-beam machining process. (b) and (c) Examples of holes produced in nonmetallic parts by LBM. (d) Cutting sheet metal with a laser beam. Source: (d) Courtesy of Rofin-Sinar, Inc.
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Laser-Beam Machining (LBM)
Sumber energy dr LBM adalah sinar laser, yg sinarnya difokuskan di permukaan b-kerja yg diproses. Highly-focused & high-density energy laser melelehkan & menguapkan b-kerja, shg didapatkan bentuk yg diinginkan.
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General Applications of Lasers in Manufacturing
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Electron-Beam Machining Process High-velocity Electrons strike surface Of the work-piece and Generate heat. Electrons speed is 5080% of the speed of Light.
Figure 27.15 Schematic illustration of the electron-beam machining process. Unlike LBM, this process requires a vacuum, so work-piece size is limited to the size of the vacuum chamber. 28
Electron-Beam Machining (EBM)Process
High-velocity electrons strike surface of the work-piece and generate heat. Mesin menggunakan tegangan 50-200kV untuk mempercepat elektron smpai 50-80% kecepatan cahaya.
EBM dilakukan dalam kondisi vakum, shg ukuran b-kerja harus bisa masuk ke vacuum chamber. 29
Water-Jet Cutting Process
Figure 27.16 (a) Schematic illustration of the water-jet machining process. (b) A computer-controlled water-jet cutting machine cutting a granite plate. (c) Examples of various nonmetallic parts produced by the water-jet cutting process. (Enlarged on next slide). Source: Courtesy of Possis Corporation
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Water-Jet Cutting Process
Proses ini juga disebut dgn hydro-dynamic machining. Air diberi tekanan sebesar 400-1400 MPa (60-200 ksi). Diameter jet nozzle 0,05-1 mm. Proses pemotongan bisa dimulai di mana saja (di permukaan b-kerja) tanpa memerlukan predrilled-holes. Bisa digunakan untuk material tipis maupun tebal (s/d 25 mm atau lebih). 31
Nonmetallic Parts Made by Water-Jet Cutting
Enlargement of Fig. 27.16c. Examples of various nonmetallic parts produced by the water-jet cutting process. Source: Courtesy of Possis Corporation 32
Abrasive-Jet Machining
(b)
Figure 27.17 (a) Schematic illustration of the abrasive-jet machining process. (b) Examples of parts produced through abrasive-jet machining, produced in 50-mm (2-in.) thick 304 stainless steel. Source: Courtesy of OMAX Corporation. 33
Abrasive-Jet Machining
Udara kering (juga bisa menggunakan nitrogen maupun karbon dioksida) yg diberi partikel abrasive, diberi tekanan hingga 850 kPa (125 psi), dengan kecepatan s/d 300 m/det; diarahkan ke permukaan b-kerja yg akan dipotong. Partikel abrasive berukuran 10-50 mikron.
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