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  1. 1. Non-Traditional Machining ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 1 Singh/Melkote/Colton
  2. 2. Introduction• Machining is a broad term to describe removal of material from a workpiece.• Machining categories: – Cutting involves single-point or multipoint cutting tools, each with a clearly defined geometry. – Abrasive processes, such as grinding. – Nontraditional machining, utilizing electrical, chemical, and optical sources of energy. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 2 Singh/Melkote/Colton
  3. 3. Nontraditional Machining• Ultrasonic Machining (USM)• Water-Jet Machining & Abrasive-Jet Machining• Chemical Machining• Electrochemical Machining (ECM)• Electrical-Discharge Machining (EDM)• High-Energy-Beam Machining – Laser-beam machining (LBM) – Electron-beam machining (EBM) ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 3 Singh/Melkote/Colton
  4. 4. Traditional vs. Nontraditional• Primary source of energy – Traditional: mechanical. – Nontraditional: electrical, chemical, optical• Primary method of material removal – Traditional: shearing – Nontraditional: does not use shearing (e.g., abrasive water jet cutting uses erosion) Water jet machining Grinding 2D cutting process ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 4 Singh/Melkote/Colton
  5. 5. Why Nontraditional Machining?• Situations where traditional machining processes are unsatisfactory or uneconomical: – Workpiece material is too hard, strong, or tough. – Workpiece is too flexible to resist cutting forces or too difficult to clamp. – Part shape is very complex with internal or external profiles or small holes. – Requirements for surface finish and tolerances are very high. – Temperature rise or residual stresses are undesirable or unacceptable. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 5 Singh/Melkote/Colton
  6. 6. Ultrasonic Machining (USM)• Process description – The tool, which is negative of the workpiece, is vibrated at low amplitude (0.013 to 0.08 mm) and high frequency (about 20 kHz) in an abrasive grit slurry at the workpiece surface. – The slurry also carries away the debris from the cutting area. – The tool is gradually moved down maintaining a constant gap of approximately 0.1 mm between the tool and workpiece surface. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 6 Singh/Melkote/Colton
  7. 7. USM (Cont.)• Cracks are generated due to the high stresses produced by particles striking a surface.• The time of contact between the particle and the surface is given by: 1/ 5 5r  c 0  t0 ≈   (10 − 100 µ s ) Force of a particle on surface: c0  v  F = d (mv) / dtr: radius of a spherical particlec0: workpiece elastic wave velocity = E / ρ Average force of a particle striking the surface:v: velocity of particle striking surface Fave = 2mv / t 0 ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 7 Singh/Melkote/Colton
  8. 8. USM (Cont.)• Example: Explain what change, if any, takes place in the magnitude of the impact force of a particle in ultrasonic machining as the temperature of the workpiece is increased. Solution: Here, m and v are constant. 1/ 5 5r  c 0  1 1 t0 =   ⇒ t0 ∝ ∝ c0  v  c04 / 5 E 2/5 When temperature increases, E decreases and t0 increases. Hence, F decreases. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 8 Singh/Melkote/Colton
  9. 9. USM (Cont.) Assuming hemispherical brittle fracture 3 2π  D  V=   3 2 D ≈ 2 dh 2π V= (dh) 3 / 2 3MRR = ηV Z fwhere V = volume removed by a single grain f = frequency of operation Z = number of particles impacting per cycle η = efficiency ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 9 Singh/Melkote/Colton
  10. 10. USM (Cont.)• Applications – USM is best suited for hard, brittle materials, such as ceramics, carbides, glass, precious stones, and hardened steels. (Why?)• Capability – With fine abrasives, tolerance of 0.0125 mm or better can be held. Ra varies between 0.2 – 1.6 µm.• Pros & Cons: – Pros: precise machining of brittle materials; makes tiny holes (0.3 mm); does not produce electric, thermal, chemical damage because it removes material mechanically. – Cons: low material removal rate (typically 0.8 cm3/min); tool wears rapidly; machining area and depth are limited. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 10 Singh/Melkote/Colton
  11. 11. USM PartsCeramic ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 11 Singh/Melkote/Colton
  12. 12. Water-Jet Machining (WJM) also called hydrodynamic machiningWJM is a form of micro erosion. It The extreme pressure of the acceleratedworks by forcing a large volume of water particles contacts a small area of thewater through a small orifice in the workpiece and acts like a saw and cuts anozzle. narrow groove in the material. http://www.flowcorp.com/waterjet-resources.cfm?id=360 ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 12 Singh/Melkote/Colton
  13. 13. WJM (Cont.)• Pros: no need for predrilled holes, no heat, no workpiece deflection (hence suitable for flexible materials), minimal burr, environmentally friendly.• Cons: limited to material with naturally occurring small cracks or softer material.• Applications: – Mostly used to cut lower strength materials such as wood, plastics, rubber, paper, leather, composite, etc. – Food preparation – Good for materials that cannot withstand high temperatures of other methods for stress distortion or metallurgical reasons. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 13 Singh/Melkote/Colton
  14. 14. WJM Examples PWB (printed wire board) ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 14 Singh/Melkote/Colton
  15. 15. Abrasive Water-Jet Machining (AWJM)The water jet containsabrasive particles such assilicon carbide, thusincreasing MRR.Metallic materials can becut. Particularly suitable forheat-sensitive materials. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 15 Singh/Melkote/Colton
  16. 16. AWJM Parts Bullet Proof Glass PartSteel rack (75 mm thick) Ceramic Part Source: http://www.waterjets.org/ ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 16 Singh/Melkote/Colton
  17. 17. Abrasive-Jet Machining (AJM)A high-velocity jet of dry air, The gas supply pressure is onnitrogen, or carbon dioxide the order of 850 kPa (125 psi)containing abrasive particles is and the jet velocity can be asaimed at the workpiece surface high as 300 m/s and isunder controlled conditions. controlled by a valve. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 17 Singh/Melkote/Colton
  18. 18. AJM Process Capability• Material removal – Typical cutting speeds vary between 25 -125 mm/min• Dimensional Tolerances – Typical range ±2 - ±5 µm• Surface Finish – Typical Ra values vary from 0.3 - 2.3 µm ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 18 Singh/Melkote/Colton
  19. 19. AJM Applications & Limitations• Applications – Can cut traditionally hard to cut materials, e.g., composites, ceramics, glass – Good for materials that cannot stand high temperatures• Limitations – Expensive process – Flaring can become large – Not suitable for mass production because of high maintenance requirements ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 19 Singh/Melkote/Colton
  20. 20. Chemical Machining (CM)• Chemical machining, basically an etching process, is the oldest nontraditional machining process.• Material is removed from a surface by chemical dissolution using chemical reagents, or etchants, such as acids and alkaline solutions.• The workpiece is immersed in a bath containing an etchant. The area that are not required to be etched are masked with “cut and peel” tapes, paints, or polymeric materials.• In chemical milling, shallow cavities are produced on plates, sheets, forgings, and extrusions for overall reduction of weight (e.g., in aerospace industry). Depths of removal can be as much as 12 mm. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 20 Singh/Melkote/Colton
  21. 21. CM (Cont.)• Chemical blanking is used to produce features which penetrate through the material via chemical dissolution. The metal that is to be blanked is – thoroughly cleaned with solvents. – coated and the image of the part is imprinted. – soaked in a solvent that removes the coating, except in the protected areas. – spray etched to dissolve the unprotected areas and leave the finished part. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 21 Singh/Melkote/Colton
  22. 22. CM (Cont.)• Typical applications – Chemical blanking: burr-free etching of printed-circuit boards (PCB), decorative panels, thin sheet-metal stampings, and the production of complex or small shapes. – Chemical milling: weight reduction of space launch vehicles. Pros: low setup, maintenance, and tooling costs; small, delicate parts can be machined; suitable for low production runs on intricate designs. Cons: slow (0.025-0.1 mm/min); surface defects; chemicals can be extremely dangerous to health. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 22 Singh/Melkote/Colton
  23. 23. Electrochemical Machining (ECM) • Process description: – In ECM, a dc voltage (10-25 v) is applied across the gap between a pre-shaped cathode tool and an anode workpiece. The workpiece is dissolved by an electrochemical reaction to the shape of the tool. – The electrolyte flows at high speed (10-60 m/s) through the gap (0.1-0.6 mm) to dissipate heat and wash away the dissolved metal. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 23 Singh/Melkote/Colton
  24. 24. ECM (Cont.)• The material removal rate by ECM is given by: MRR = C I ηwhere, MRR=mm3/min, I=current in amperes, η=current efficiency, which typically ranges from 90-100%, C is a material constant in mm3/A·min. Feed rate (mm/min): f = MRR / A0 Assuming a cavity with uniform cross-sectional area A0 ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 24 Singh/Melkote/Colton
  25. 25. ECM (Cont.)• Pros: high shape complexity possible, high MRR possible, high- strength materials, mirror surface finish possible.• Cons: workpiece must be electrically conductive; very high tooling (dedicated) and equipment costs; high power consumption.• Applications: complex cavities in high-strength materials, esp. in aerospace industry for mass production of turbine blades. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 25 Singh/Melkote/Colton
  26. 26. EDM-History ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 26 Singh/Melkote/Colton
  27. 27. Electrical Discharge Machining (EDM) EDM is a thermal erosion process whereby material is melted and vaporized from an electrically conducive workpiece immersed in a liquid dielectric with a series of spark discharges between the tool electrode and the workpiece created by a power supply.EDM is one of the most accuratewhile quite affordable mfg process. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 27 Singh/Melkote/Colton
  28. 28. EDM (Cont.)The EDM system consistsof a shaped tool or wireelectrode, and the part. Thepart is connected to apower supply to create apotential difference betweenthe workpiece and the tool.When the potentialdifference is sufficientlyhigh, a transient spark The dielectric fluid 1) acts as andischarges through the insulator until the potential isfluid, removing a very small sufficiently high, 2) acts as aamount of metal from the flushing medium, and 3) providesworkpiece. a cooling medium. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 28 Singh/Melkote/Colton
  29. 29. Process-Basics ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 29 Singh/Melkote/Colton
  30. 30. EDM (Cont.) MRR is basically a function of the current and the melting point of the workpiece material. An approximate empirical relationship is: 4 −1.23 MRR=mm3/min MRR = 4 × 10 I T w I=current in amperes Tw=melting point of workpiece (ºC)Wear rate of electrode:Wt = 11× 10 3 I Tt −2.38 Wear ratio of workpiece to electrode:Wt=mm3/minTt=melting point of electrode material (ºC) R = 2.25 Tr−2.3 Tr=ratio of workpiece to electrode melting points (ºC) ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 30 Singh/Melkote/Colton
  31. 31. MRR - EDM Metal removal is function of pulse energy • Experimental Approach and frequency: h = K1Wn TOOL (-) D= K2Wn where W = Pulse energy, J DC VOLTAGE h = height of crater, mm D = diameter of crater, mm K1, K2 = constants depending h on electrode materials D and dielectric n = constant depending on WORKPIECE work tool combination (+) The crater volume from geometry, π 3  Scheme of Crater Formation Vc = h D 2 + h 2  6 4  MRR = Vc f η π 3 2 2 3nwhere f = frequency of operation and η = efficiency Vc = K1  K 2 + K1 W 6 4  ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 31 Singh/Melkote/Colton
  32. 32. Volume of the crater ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 32 Singh/Melkote/Colton
  33. 33. EDM Process Capability• MRR – Range from 2 to 400 mm3/min. High rates produce rough finish, having a molten and recast structure with poor surface integrity and low fatigue properties.• Dimensional Tolerances – Function of the material being processed – Typically between ±0.005 - ±0.125 mm• Surface Finish – Depends on current density and material being machined – Ra varies from 0.05 – 12.5 µm – New techniques use an oscillating electrode, providing very fine surface finishes. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 33 Singh/Melkote/Colton
  34. 34. EDM ApplicationsWidely used in aerospace, moldmaking, and die casting to produce diecavities, small deep holes, narrow slots, turbine blades, and intricate shapes. Cavities produced by EDM Stepped cavities ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 34 Singh/Melkote/Colton
  35. 35. EDM Limitations• Limitations – A hard skin, or recast layer is produced which may be undesirable in some cases. – Beneath the recast layer is a heat affected zone which may be softer than parent material. – Finishing cuts are needed at low MRR. – Produces slightly tapered holes, specially if blind. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 35 Singh/Melkote/Colton
  36. 36. Wire EDMA wire travels along a prescribed path,cutting the workpiece, with the dischargesparks acting like cutting teeth. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 36 Singh/Melkote/Colton
  37. 37. Wire EDM (Cont.) MRR in Wire EDM MRR = V f h b where, b = d w + 2sMRR = mm3/minVf = feed rate of wire into theworkpiece in mm/minh = workpiece thickness or dw = wire diameter in mmheight in mm s = gap between wire and workpiece in mm ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 37 Singh/Melkote/Colton
  38. 38. Wire EDM Parts ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 38 Singh/Melkote/Colton
  39. 39. Example• Example: You have to machine the following part from a 85mmx75mmx20mm steel block. You have to choose between EDM and Conventional machining. Your objective is to minimize the cutting power required, which process will you choose? 12.5Assumptions: – EDM process: 40 • Wire diameter: dw=0.2 mm • Gap: s=0.1 mm – Conventional machining: 10 • Negative of the part has to be 12.5 removed 12.5 20 20 20 12.5 ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 39 Singh/Melkote/Colton
  40. 40. ExampleSolution:- EDM process VEDM = lc*(dw+2s)*t = 1440 mm3- Conventional machining VM= Vtotal – Vpart = 99500 mm3- Power comparison u M VM u EDM VEDM We will choose machining if ≤ tM t EDM let’s assume tEDM=αtM u EDM VEDM then machining if α ≤ u M VM ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 40 Singh/Melkote/Colton
  41. 41. Reverse micro-EDM• Fabrication of high aspect ratio micro-electrode arrays• Potential application in machining hole arrays via micro- EDM/ECM ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 41 Singh/Melkote/Colton
  42. 42. Arrays Fabricated via R µ-EDM @IITB 6x6 array 4x4 array ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 42 Singh/Melkote/Colton
  43. 43. Experimental Setup ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 43 Singh/Melkote/Colton
  44. 44. Fabricated Texture ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 44 Singh/Melkote/Colton
  45. 45. High-Energy-Beam Machining • Laser-Beam Machining (LBM) • Electron-Beam Machining (EBM) • Focused Ion-Beam Machining ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 45 Singh/Melkote/Colton
  46. 46. Laser-Beam Machining (LBM)• Laser Concept – Add energy to make electrons “jump” to higher energy orbit – Electron “relaxes” and moves to equilibrium at ground-state energy level – Emits a photon in this process (key laser component) – Two mirrors reflect the photons back and forth and “excite” more electrons – One mirror is partially reflective to allow some light to pass through: creates narrow laser beam ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 46 Singh/Melkote/Colton
  47. 47. LBM (Cont.) Excited StateElectron Ground State Photon Nucleus Orbits Electron is Electron relaxes energized to the to ground state excited state and photon is produced Photon Emission Model ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 47 Singh/Melkote/Colton
  48. 48. LBM (Cont.)• More precise• Useful with a variety of materials: metals, composites, plastics, and ceramics• Smooth, clean cuts• Faster process• Decreased heat- affected zone ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 48 Singh/Melkote/Colton
  49. 49. Schematic of LBM Device ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 49 Singh/Melkote/Colton
  50. 50. Laser Setup• Laser Processing Center – 100 W SPI single mode fiber laser (Power and frequency modulated) – Optics for variable intensity distribution and spot size – 3 axis (Z decoupled) translational stages and controls “Method and device for generating laser – Provides uniform/Gaussian intensity beam of variable intensity distribution – 7 µm -900 µm spot size possible and variable spot size”, – Hardening/Cladding/Texturing/Brazing Indian Patent Application No. 442/MUM/2011. Machine Tools Laboratory Micromachining Cell
  51. 51. LBM (Cont.)• Important physical parameters in LBM – Reflectivity – Thermal conductivity of workpiece surface – Specific heat and latent heats of melting and evaporation• The lower these quantities, the more efficient the process.• The cutting depth t: t = P / vd P is the power input, v is the cutting speed, and d is the laser-beam-spot diameter. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 51 Singh/Melkote/Colton
  52. 52. Heat Source Modeling• Solution for stationary point using Green’s Theorem: The differential equation for the conduction of heat in a stationary medium assuming no convection or radiation, is This is satisfied by the solution for infinite body, δq ( x − x ) 2 + ( y − y ) 2 + ( z − z ) 2 dT ( x, y, z, t ) = 3 ex p [ − ] 4 a ( t − t ) ρ C (4 π a ( t − t )) 2 sem i − in f in ite 2δ q ( x − x ) 2 + ( y − y ) 2 + ( z − z ) 2 dT ( x, y, z, t ) = 3 ex p [ − ] 4 a ( t − t ) ρ C (4 π a ( t − t )) 2 δq = instantaneous heat generated, C = sp. heat capacity, α = diffusivity, ρ = Density, t = time, K = thermal conductivity. gives the temperature increment at position (x, y, z) and time t due to an instantaneous heat source δq applied at position (x’, y’, z’) and time t’. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 52 Singh/Melkote/Colton
  53. 53. Moving point heat source in semi-infinite bodyIn moving coordinate system: 2δ q ( X − x ) 2 + (Y − y ) 2 + ( Z − z ) 2 dT ( x, y, z, t ) = 3 exp [ − ] 4 a ( t − t ) ρ C (4 π a ( t − t )) 2In fixed coordinate system: 2δ q ( x − vt − x ) 2 + ( y − y ) 2 + ( z − z ) 2 dT ( x, y, z, t ) = 3 ex p [ − ] 4 a ( t − t ) ρ C (4 π a ( t − t )) 2 Note that δ q = Pdt ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 53 Singh/Melkote/Colton
  54. 54. Moving point heat source:Consider point heat source P heat units per unit time moving with velocity v on semi-infinite body from time t’= 0 to t’= t. During a very short time heat released at thesurface is dQ = Pdt’. This will result in infinitesimal rise in temperature at point (x, y, z)at time t given by, t = t 2 Pdt ( x − vt − x ) 2 + ( y − y ) 2 + ( z − z ) 2 dT ( x, y, z, t ) = ∫ t = 0 3 ex p [ − 4 a ( t − t ) ] ρ C (4 π a ( t − t )) 2The total rise in of the temperature can be obtained byintegrating from t’=0 to t’= t
  55. 55. Gaussian Circular • Gaussian beam distribution 2P 2( x 2 + y 2 ) I ( x , y ) = 2 exp[− 2 ] πσ σ • Gaussian circular heat source 2dt ( X − x ) 2 + (Y − y ) 2 + ( Z − z ) 2 dT ( X , Y , Z , t ) = 3 I ( x , y )dx dy exp[− ] 4a(t − t ) ρ C (4π a(t − t )) 2 ∞ ∞ 2dt 2P 2( x 2 + y 2 ) ( X − x )2 + (Y − y )2 + ( Z − z )2dT = 3 πσ 2 ∫ ∫ −∞ −∞ exp[− σ2 ]dx dy exp[− 4a(t − t ) ] ρ C (4π a(t − t )) 2 In fixed coordinate sytem t = t 4P dt (t − t ) −0.5 2(( x − vt ) 2 + y 2 ) z2 T − T0 = ρ C π 4 aπ ∫0 σ 2 + 8a (t − t ) exp[ − σ 2 + 8a (t − t ) − 4 a (t − t ) ] t = ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 55 Singh/Melkote/Colton
  56. 56. Uniform Circular/Rectangular• Circular t σ 2P dt (( x − vt ) − x ) 2 T − T0 = 8 π 2σ 2 K ∫ 0 ( t − t ) ∫ −σ ex p [ − 4 a ( t − t ) ]d x × y − σ 2 − x 2 y + σ 2 − x 2 [ − erf ( ) + erf ( )] 2 a ( t − t ) 2 a ( t − t )• Rectangular 2δ q d t z2 T − T0 = 3 exp[− ] 4 a ( t − t ) 4 b l ρ C ( 4 π a ( t − t ) ) 2 l b ( ( x − v t ) − x ) 2 ( y − y ) 2 ∫l − exp[− 4 a ( t − t ) ]d x ∫ e x p [ − −b 4 a ( t − t ) ]d y ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 56 Singh/Melkote/Colton
  57. 57. LBM Capability• MRR – Cutting speed can be as high as 4 m/min. – Typical material removal rate is 5 mm3/min.• Dimensional Tolerance – Typical ranges from ±0.015 - ±0.125 mm• Surface Finish – Ra varies between 0.4 – 6.3 µm. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 57 Singh/Melkote/Colton
  58. 58. LBM (Cont.)• Process Variations – Laser beam machines can be used for cutting, surface hardening, welding, drilling, blanking, engraving and trimming. – Types of lasers used: pulsed and CW CO2, Nd:YAG, Nd:glass, ruby and excimer. – High-pressure gas streams are used to enhance the process by aiding the exothermic reaction process, to cool and blow away the vaporized or molten material and slag. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 58 Singh/Melkote/Colton
  59. 59. LBM (Cont.)• Applications – Multiple holes in very thin and thick materials – Non-standard shaped holes and slots – Prototype parts – Trimming, scribing and engraving of hard materials – Small diameter lubrication holes• Limitations – Localized thermal stresses, heat affected zones, recast layer and thermal distribution in thin parts – Difficulty of material processing depends on how close materials boiling and melting points are – Hole wall geometry can be irregular – The cutting of flammable materials is usually inert gas assisted ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 59 Singh/Melkote/Colton
  60. 60. Electron-Beam Machining (EBM) How it Works• A stream of electrons is started by a voltage differential at the cathode. The concave shape of the cathode grid concentrates the stream through the anode.• The anode applies a potential field that accelerates the electrons.• The electron stream is then forced through a valve in the electron beam machine.• The beam is focused onto the surface of the work material, heating, melting, and vaporizing the material. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 60 Singh/Melkote/Colton
  61. 61. EBM (Cont.)The entire process occurs in a vacuum chamber because a collisionbetween an electron and an air molecule causes the electrons to veeroff course. LBM doesn’t need vacuum because the size and mass of aphoton is numerous times smaller than the size of an electron. ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 61 Singh/Melkote/Colton
  62. 62. EBM Characteristics• Mechanics of material removal – melting, vaporization• Medium – vacuum• Tool – beam of electrons moving at very high velocity• Maximum MRR = 10 mm3/min• Specific power consumption = 450 W/mm3/min• Critical parameters – accelerating voltage, beam diameter, work speed, melting temperature• Materials application – all materials• Shape application – drilling fine holes, cutting contours in sheets, cutting narrow slots• Limitations – very high specific energy consumption, necessity of vacuum, expensive machine ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 62 Singh/Melkote/Colton
  63. 63. Comparative Performance ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 63 Singh/Melkote/Colton
  64. 64. Focused Ion Beam Technologies• Ga+ ion beam raster over the surface similar to SEM• Milling of small holes and modifications in the structures can be done• Most instruments combine nowadays a SEM and FIB for imaging with high resolution, and accurate control of the progress of the milling• Process is performed in vacuum ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 64 Singh/Melkote/Colton
  65. 65. MechanismRate of etch depth Where, Y is sputter yield of surface atoms per incoming ion, using a probe of current I is given by A is the etched area, ρ is the density of target material, M is atomic mass of target material and e is charge ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 65 Singh/Melkote/Colton
  66. 66. Dual Beam System ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 66 Singh/Melkote/Colton
  67. 67. ME 338: Manufacturing Processes IIInstructor: Ramesh Singh; Notes: Profs. 67 Singh/Melkote/Colton
  68. 68. Focused Ion Beam Technologies• FIB finds application in: – Ablation of hard materials: diamond, WC – Polishing of single crystals – Deposition – Site-specific analysis – FIB lithography – TEM samples• Capital investment ~ 5 Crore ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 68 Singh/Melkote/Colton
  69. 69. Process Capabilities of FIB• Deposition• Etching• Low material removal• Very high cost• Nanometric imaging resolution• Can process conducting and non conducting materials ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 69 Singh/Melkote/Colton
  70. 70. Summary• Process description and capability – Ultrasonic Machining (USM) – Water-Jet Machining & Abrasive-Jet Machining – Chemical Machining – Electrochemical Machining (ECM) – Electrical-Discharge Machining (EDM)• High-Energy-Beam Machining – Laser-beam machining (LBM) – Electron-beam machining (EBM) – Focused Ion Beam (FIB) ME 338: Manufacturing Processes II Instructor: Ramesh Singh; Notes: Profs. 70 Singh/Melkote/Colton
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