Unit 5 -RECENT TRENDS IN NON-TRADITIONAL MACHINING PROCESSES
- 2. PRINCIPLE Here the machining is done by usage of heat energy. The heat energy is focused on a particular portion for melt & Vaporize the work material Example : 1. Electron Beam Machining (EBM) 2. Laser Beam Machining (LBM) 3. Plasma Arc Machining (PAM)
- 3. ELECTRON BEAM MACHINING (EBM)
- 6. Cross sectional area of 0.01 to 0.02 mm dia. To deflect the electro beam to different spot 10-5 to 10-6 mm of mercury Temp. 2500°C Electron accelerated as 1.6×108 m/s by applying 50 to 200 kV Power density (6500 million W/mm2) Pulse frequency (1 to 16000 Hz) and duration (4 to 65,000 microseconds)
- 7. To avoid collision of accelerated electrons with air molecules Vacuum is required (10-5 to 10-6 mm of mercury) This chamber carries a door, through which the workpiece is placed over the table. The door is then closed and sealed.
- 8. ELECTRON GUN Tungsten filament Connected to the negative terminal of DC power supply Grid cup Negatively based with respect to the filament Anode Connected to the positive terminal of DC power supply
- 9. TYPES OF EBM
- 10. MECHANICS OF EBM Electrons are the smallest stable elementary particles with a mass of 9.109×10-31 kg with a negative charge if 1.602×10-19 coulomb. • The electron velocity at the striking is given by Es – Voltage of the electric field, volt Vs = 600 Es km/s
- 11. • The electron beam power is given by, Ib - Beam current, amp • The electron beam pressure is given by, 𝐼𝑑 − Current density, A/cm2 • The thermal velocity acquired by an electron is given by, Pb = Es Ib, watts Fb = 0.34 𝐼𝑑 𝐸𝑠, dyne /cm2 Va = 2Kθ Ma m/s K – Boltzmann’s constant = 1.38×10-23 J/K/atom θ – Temperature raised, K Ma – Mass of one atom of the workpiece, kg
- 12. Process Parameters The parameters which have significant influence on the beam intensity and metal removal rate are given below Control of current Control on spot diameter Control of focal distance of magnetic lens
- 14. Control on spot diameter i) Effect of thermal velocities:
- 15. ii) Spherical deviation of the focusing lens
- 18. Characteristics of EBM process
- 22. LASER BEAM MACHINING Photon Emission
- 23. Differences .
- 24. PRINCIPLE OF LASER BEAM PRODUCTION
- 28. TYPES OF LASER 1. Gas lasers 2. Solid lasers 3. Liquid lasers 4. Semi Conductor lasers
- 29. SOLID LASER RUBY LASER Synthetic Ruby rod made up of crystal of aluminium oxide
- 31. LASER BEAM MACHINING Flash tube filled with Xenon, argon or krypton Gases 250 – 1000 watts power Few Chromium Atoms are placed in Ruby rod for absorbing Green light
- 32. Cooling of ruby rod is necessary – Because they are less efficient in high temperature
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- 34. .
- 35. MACHINING APPLICATIONS OF LASER 1. Laser in Metal Cutting 2. Laser in Drilling 3. Laser in Welding 4. Laser in Surface Treatment 5. Trimming 6. Blanking 7. Micromachining applications
- 36. LASER IN METAL CUTTING • .
- 38. Laser in Surface Treatment A thin layer of cobalt alloy coating is applied on Turbine blade for heat and Wear Resistance. A thin Ceramic coating is applied on metal Surface for heat and Wear Resistance. Its also used to seal the micro cracks which are usually present in hard – Chromium electroplates
- 39. Advantages of LBM 1. All Kind of metals are machined 2. Micro holes are possible 3. Soft materials like rubber can be machined 4. No tool wear and contact with w/p 5. Automated process 6. Controlling of beam is easy
- 40. 1. High initial Cost 2. Operating cost is high 3. Required skilled labours 4. Rate of production is low 5. Need safety equipments 6. Life of flash lamp is low 7. The machined holes are not straight and round Disadvantages of LBM
- 41. PLASMA ARC MACHINING OR PLASMA JET MACHINING IONIZED GAS High velocity jet of high temp. ionized Gas
- 42. INTRODUCTION SOLID GAS or LIQUID Heated LIQUID Heated GAS GAS Heated FREE electrons and IONIZED GAS
- 43. PLASMA GAS When a gas is heated to a sufficiently high temperature of the order of 11000 – 28000 degree Celsius, it becomes partially ionized its known as PLASMA PLASMA It’s a mixture of Free electrons + Partially ionized as and Neutral Atoms
- 46. ACCURACY
- 47. GASES USED IN PAM
- 48. TYPES OF PLASMA ARC TORCHES
- 49. Direct Arc Plasma Torch
- 50. In-Direct Arc Plasma Torch .
- 51. • It can be used to cut any metal • Cutting rate is high • As compared to ordinary flame cutting process, it can cut plain carbon steel four times faster • It is used for rough turning of very difficult materials ADVANTAGES OF PAM
- 52. • It produces tapered surface • Protection of noise is necessary • Equipment cost is high • Protection of eye is necessary for the operator • Work surface may undergo metallurgical changes. DISADVANTAGES OF PAM
- 53. Work Material: All materials which conduct electricity. Tool: Plasma jet Velocity of plasma jet: 500 m/s Power range: 2 to 220 kW Current: As high as 600 amp Voltage: 40 – 250 V Cutting speed: 0.1 to 7 m/min MRR: 145 cm3/min CHARACTERISTICS OF PAM