Introduction to Non-Traditional Machining

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Introduction to Non-Traditional Machining

  1. 1. 6/3/2014 1Hareesha N G, Dept of Aero Engg, DSCE
  2. 2. Review of Machining • Machining is a generic term, applied to material removal processes. • Traditional machining: turning, milling, drilling, grinding, etc. • Metal cutting refers to processes in which excess metal is removed by a harder tool, through a process of extensive plastic deformation or controlled fracture. • Non-traditional machining: chemical machining, ECM, EDM, EBM, LBM, machining of non-metallic materials. 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 2
  3. 3. Nontraditional Machining • Chemilling • Electrochemical machining • Electrical discharge machining • High energy beam machining • Water jet/Abrasive water jet machining • Ultrasonic machining • Machining of non-metallic materials 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 3
  4. 4. Chemical Machining (Chemilling) • Used to produce shallow cavities (<12mm) on large areas. • A maskant is applied over areas you don’t want to machine. • Place the part in a chemical bath (acid or alkali depending upon the metal) • Control temperature and time of exposure to control material removal • Material removal rate is slow, 0.025-0.1 mm/min 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 4
  5. 5. Electro-Chemical Machining (ECM) • Works on the principle of electrolysis • Die is progressively lowered into workpiece as workpiece is dissociated into ions by electrolysis • Electrolytic fluid flows around workpiece to remove ions and maintain electrical current path • Low DC voltage, very High current (700 amps). • Material removal rate is 2.5-12 mm/min depending on current density.6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 5
  6. 6. Electrical Discharge Machining (EDM) • The tool (electrode) usually acts as a cathode and is immersed in a dielectric fluid. • DC voltage (~300V) is applied in modulated pulses (200-500K Hz). • The dielectric breaks down (sparking at around 12,000 deg F) when gap is small. • The sparks erodes the workpiece in the shape of the tool. • The tool is progressively lowered as the workpiece erodes. • Material removal rate is typically 300 mm3/min • Tool wear ratio 3:1 with metallic electrodes, 3:1-100:1 with graphite electrodes6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 6
  7. 7. Die Sinker and Wire EDM • Die sinker EDM – The die (copper or graphite) sinks into the part as it sparks away the workpiece. – Most common injection molding die process. • Wire EDM – The electrode (brass, copper, W, Mo, 0.08-3 mm) is a wire that traverses through the part. – Common for extrusion dies. • Electrical discharge drilling • Electrical discharge grinding 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 7
  8. 8. Examples of Die Sinker and Wire EDM 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 8
  9. 9. Water Jet and Abrasive Water Jet Cutting • High pressure water (20,000- 60,000 psi). • Can cut extremely thick parts (5-10 inches possible). • Thickness achievable is a function of speed. 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 9
  10. 10. Abrasive Waterjet and Waterjet Part Examples 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 10
  11. 11. High Energy Beam Machining (a) Electron beam machining Cutting and hole making on thin materials; very small holes and slots (0.1-0.3mm depending on thickness); heat affected zone; require vacuum, expensive equipment; 1-2 mm3/min. (b) Laser beam machining Cutting and hole making on thin materials; heat-affected zone; does not require a vacuum; but expensive equipment; consume much energy; 0.5-7.5 mm/min depending on thickness.6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 11
  12. 12. Machining of Nonmetallic Materials • Machining of ceramics: – Abrasive machining, including abrasive water jet machining – Laser beam machining – Laser assisted machining Laser assisted machining6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 12
  13. 13. Ultrasonic Machining of Ceramics 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 13
  14. 14. Machining of Plastics and Composites • Plastics need to be carefully supported. • Requires large rake and relief angles, high cutting speed, and low feed. • Trimming of plastic parts using water jet cutting or abrasive water jet cutting. • Common problems in cutting composites – Delamination, poor edge finish, and fiber pull out. • Use abrasive water jet cutting. • Metal matrix composites such as carbide tool bits can be machined using diamond tools, EDM, and ECM. 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 14
  15. 15. Characteristics of Machining 6/3/2014 Hareesha N G, Dept of Aero Engg, DSCE 15

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