Non Traditional Machining Processes MIME - 6980

1. Non Traditional Machining ProcessesMIME - 6980 Presented by, • Abhijit Thanedar • Naga Jyothi Sanku • Pritam Deshpande • Vijayalayan Krishnan • Vishwajeet Randhir Electron Beam Machining

2. Introduction - A Brief History • Development of EB technology is closely related with advances in vacuum engineering and electron optics • In 1905, Marcello von Pirani successfully melted Tantalum • In 1938, magnetic lens were introduced to focus EB • It was only in 1965, all techniques were put together and secured a place in production processes list.

3. Classification of NTM processes Classification based on the energy source • Mechanical • Electro-chemical • Chemical • Thermo-electric EBM uses Thermo-electric Energy.

5. GENERATION OF ELECTRON BEAM: The electron beam is formed inside an electron gun, which is basically a triode and consists of: • A cathode which is a hot tungsten filament emitting high negative potential electron • A grid cup, negatively biased with respect to filament , and • An anode at ground potential though which the accelerated electrons pass

7. Energy Conversion at the point of action electrons are accelerated in the electrostatic field of the beam source to attain a kinetic energy, E = e UB • the kinetic energy absorbed by the electrons during their trajectory through the accelerating field is E = (me0/2) ve2 (1 + 3 ve2/4c2 + 5 ve4/8 c4 +…)= e UB

8. Relation between velocity and acceleration voltage

9. BEAM ACTION ON IMPINGEMENT ON MATTER

10. Machine Tools The three major subsystems that make up an electron beam machining system are • power supply, • electron beam gun, and • the vacuum system.

11. Modern EBM Drilling Machine

12. POWER SUPPLY • Pulsed DC • Voltage range up to 150 kv to accelerate electrons • Systems capability can go as high as 12 kw • high-voltage sections of the power supply are submerged in insulating dielectric oil

13. ELECTRON GUN • gun is designed to be used exclusively for material removal applications and can be operated only in the pulse mode • It has a cathode, bias electrode, anode, magnetic coil/lens (to converge the beam), variable aperture, 3 final magnetic coils (used as magnetic lens, deflection coil, and stigmator) and rotating disc.

14. Gun Types • 2 electrode gun

15. 3 Electrode Guns

16. Rogowski gun Telefocus gun Modified 3 Electrode Guns

17. Four Electrode Array gun

18. High-perveance guns Pierce gun

19. Guns with Curved Electron Trajectories

20. Guns with Concave Emmiting Surface and center bore in cathode

21. Beam Guidance

22. MATHEMATICAL MODEL: Energy of Electrons: The kinetic energy of the electrons can be written as: K.E.=Ee=1/2 mV2. Where, m= mass of electron. e= charge on electron.(joules) E= voltage. V= velocity of electron.(cm/sec)

23. Number of electrons per second (N): N= I n. Where , I= beam current. n= electron per second per amp current.

24. Total Power : P= E I Energy Required to vaporize Workpiece: Material removal rate : G = nP/W.(cm3/sec) Where: P = Power.(watts) n= cutting efficiency. W= Specific energy required to vaporize metal. (joules/cm3) W=[C(Tm-20)+C(Tb-Tm)+Hf+Vv] Where: C= Specific Heat, Tm = Melting temperature Tb = Boiling temperature, Hf = Heat of fusion, Hv = Heat of vaporization

25. MRR Vs POWER

26. Parameter Zones

27. Parameters and their influence Power density

28. Drilling of all materials

29. Parameters for drilling various materials

30. Examples of EBM Drilling

31. Examples of EBM Drilling

32. Examples of EBM Drilling

33. Examples of EBM Drilling

34. Hole Diameter Vs Pulse Charge

35. Depth & Diameter Vs Beam Current

36. Depth of Cut, Milling Width Vs Input Energy

37. Relation between material thickness s, hole diameter dB, and perforation rate ns