UNCONVENTIONAL MACHINING PROCESS

UNCONVENTIONAL MACHINING PROCESS CLASSIFICATION-MECHANICAL ENERGY METHODS-ELECTRICAL ENERGY METHODS-CHEMICAL ENERGY METHODS-ELECTRO CHEMICAL ENERGY METHODS-THERMALENERGY METHODS.

1. I N T R O D UC T I ON TO UNCONVENTIONALMACHINING PROCESS Prepared by L.LOGANATHAN,M.E,(PhD), Department of Mechanical Engineering, Kamaraj college of Engineering and Technology.

2. Syllabus Unconventional machining Process Need Classification Brief overview

3. WHAT IS UCM? An unconventional(non-traditional) machining process can be defined as a material removal process in which no direct contact between tool and work-piece occurs. In this type of machining process, a form of energy is used to remove unwanted material from a given workpiece.

4. Conventional Machining Process Metal Removal ? Nature of Contact ? Scrap ?

5. Demerits Disposal of Waste By products of chips Work holding Devices for larger cutting force Heat Generation Not possible without chips

6. Unconventional Manufacturing process Unconventional Manufacturing process Unconventional Machining process or Non Traditional Machining Process Unconventional Forming process

7. Unconventional M anuf a c t u rin g pro cess Machining process Metal Removal No Direct Contact b/w tool and work piece Forming process Metals are formed Releases large amount of Energy in very short time i n t e r va l

8. N e ed for UCM • Machining – produces finished products with high degree of accuracy • Conventional machining Utilizes cutting tools (harder than workpiece material). Needs a contact between the tool and workpiece. Needs a relative motion between the tool and workpiece.

9. Need • • • • • • The need for higher productivity, accuracy and surface quality Improve the capability of automation system and decreasing their sophistication (decreasing the investment cost) requirements Very hard fragile materials difficult to clamp for traditional machining When the work piece is too flexible or slender When the shape of the part is too complex Internal and external profiles, or small diameter holes.

10. 12 Unconventional Machining Processes – Based on Energy

11. 13 Unconventional Machining Processes – Based Mechanism

12. 14 Unconventional Machining Processes – Based on Energy used for Removal

13. 15 Unconventional Machining Processes – Based on Transfer of Energy

14. 16 Mechanical Based Processes Working principles Equipment used Process parameters MRR Variation in techniques used Applications AJM WJM A W JM USM

15. 17 Electrical Based Processes Working principle Equipment used Process parameters Surface finish & MRR Electrode/Tool Power & Control circuits Tool wear Dielectric Flushing 10. Applications Electrical EDM WEDM

16. 18 Chemical & Electrochemical Based Processes Working principles Etchants & Maskants Techniques of applying maskants Process parameters Surface finish & MRR Electrical circuits in case of ECM Applications CHM E CM E CG ECH

17. 19 Thermal Based Processes Working principles Equipment used Types Beam control techniques Applications LBM PAM EBM

18. Selection Process Selection Process is based of following parameters Physical Parameter Shapes to be Machined Process Capability Economic consideration

19. Physical Parameter f lui d P aramet e r ECM EDM EBM LBM PAM USM A JM Potential, V 5- 30 50-500 200 x 10 3 4.5 x 10 3 250 2 20 2 20 Current, A 40,000 15-500 0.001 2 600 12 1.0 Power, kW 100 2.70 0.15 20 220 2.4 .22 Gap, mm 0.5 0.05 100 150 7.5 .25 .75 Medium Electrolyte Die electric V a c u u m A i r A r go n N i t r oge n Ab r a s i v e g r a i ns Work M ate r i al M/C di f f T ungs t en carbide All Mtl All Mtl All Mtl Tungsten HSS c a r bide

20. Shapes to be Machined Process Machines Holes ( Micro, Small, deep,Shallow) LBM, EBM,ECM, USM & EDM Precision Work USM & EDM Horning ECM Etching ECM & EDM Grinding AJM & EDM Deburring USM & AJM Threading EDM Profile Cut PAM

21. Process Capability or Machining Characteristics Process MRR ( mm 3 /s ) Surface Finish (μm) A c cur a cy (μm) Power (kW/ cm 3 / min LBM 0.10 0.4 – 6.0 25 2700 EBM 0.15 - 40 0.4 – 6.0 25 450 EDM 15 - 80 0.25 10 1.8 ECM 27 0.2 -0.8 50 7.5 PAM 2500 Rough 250 0.90 USM 14 0.2 – 0.7 7.5 9.0 AJM 0.014 0.5- 1.2 50 312.5

22. Process Economy Process Capital Cost Tool & Fixtures Power R e q uire m ent Efficiency EDM Medium High Low High CHM Medium Low High Medium ECM V. High Medium Medium V. Low AJM V. Low Low Low Low USM High High Low Medium EBM High Low Low V. High LBM Medium Low V. Low V. High PAM V. Low Low V. Low V. Low Co n ve n t i o n al V. Low Low Low V. Low

23. Limitation More Expensive Slow Process Commercial

24. UNIT 2 MECHANICAL ENERGY BASED PROCESS B ME 6004 UNCONVENTIONAL MACHINING PROCESSES

25. SYLLABUS Abrasive Jet Machining (AJM) Water Jet Machining (WJM) Abrasive Water Jet Machining (AWJM) Ultrasonic Machining. ( USM) Working Principles – equipment used – Process parameters – MRR-Variation in techniques used – Applications.

26. ABRASIVE JET MACHINING (AJM) Principle In Abrasive Jet Machining process, a high speed stream of abrasive particles mixed with high pressure air or gas which is injected on the work piece through nozzle

27. Schematic Representation

28. Typical AJM Parameters Abrasives used. Aluminum Oxide (Al o    Si l icon C a r b i d e ( S ic) Glass Powder. Dolomite ) 10 to 50 mic 25 to 50 mic 0.3 to 0.6 mm 200 grit size Working Medium.   Dry air Gases ( Nitrogen or carbon dioxide)

29. Nozzle Material Tungsten Carbide Silicon carbonate ABRASIVE MATERIAL Abrasive material Grit size (μin) Orifice diameter (in) Aluminum oxide 10 - 50 0.005 - 0.018 Silicon carbide 25 - 50 0.008 - 0.018 Glass beads 2500 0.026 - 0.05

30. ADVANTAGES Low capital cost Less vibration No heat generated in the work piece Eco friendly Only one tool is required

31. DISADVANTAGES Low metal removal rate Abrasive powder can not be reused The machining accuracy is poor Nozzle wear rate is high

32. Water Jet Machining Principle In WJM, the high velocity of water jet comes out of the nozzle and strikes the material, its kinetic energy is converted into pressure energy including high stress in the work material. when this exceeds the ultimate shear stress of the material, small chips of the material get loosened and fresh surface is exposed.

33. Schematic Representation

34. PROCESS PARAMETERS Material removal rate(MRR) -Depends on the reactive force of the jet Reactive force = Mass flow rate (m) X jet velocity (V) Geometry and finish of work piece Wear rate of the nozzle

35. Advantages of water jet cutting There is no heat generated in water jet cutting; which is especially useful for cutting tool and other metals where excessive heat may change the properties of the material. Unlike machining or grinding, water jet cutting does not produce any dust or particles

36. Disadvantages of water jet cutting One of the main disadvantages of water jet cutting is that a limited number of materials can be cut economically. Thick parts cannot be cut by this process economically and accurately Taper is also a problem with water jet cutting in very thick materials. Taper is when the jet exits the part at different angle than it enters the part, and cause dimensional inaccuracy.

37. Applications Of WJM Process Water jet cutting is mostly used to cut lower strength materials such as wood, plastics and aluminum. When abrasives are added, (abrasive water jet cutting) stronger materials such as steel and tool steel can be cut.

38. Abrasive Water Jet Machining Principle : In abrasive water jet machining process a high stream of abrasive jet particles is mixed with pressurized water & injected through the nozzle on the work piece.

39. Schematic Representation

40. Advantages of Abrasive water jet cutting In most of the cases, no secondary finishing required No cutter induced distortion Low cutting forces on work pieces Limited tooling requirements Little to no cutting burr Typical finish 125-250 microns Smaller kerfs size reduces material wastages No heat affected zone

41. CONTD… Localizes structural changes No cutter induced metal contamination Eliminates thermal distortion No slag or cutting dross Precise, multi plane cutting of contours, shapes, and bevels of any angle.

42. Disadvantages of Abrasive water jet cutting Cannot drill flat bottom Cannot cut materials that degrades quickly with moisture

43. Ultrasonic Machining Principle  In the Ultrasonic Machining process the material is removed by micro-chipping or erosion with abrasive particles. The tool forces the abrasive grits, in the gap between the tool and the work piece, to impact normally and successively on the work surface, thereby machining the work surface.

44. Contd…. In USM process, the tool , made of softer material than that of the work piece, is oscillated by the Booster and Sonotrode at a frequency of about 20 kHz with an amplitude of about 25.4 um(0.001 in).

45. Schematic Representation

46. Schematic Representation

47. PROCESS PARAMETER Effect of amplitude and frequency of vibration on MRR  MRR is directly proportional to the first power of frequency for a fixed amplitude Theoretical M R R Freq u e n cy Actu a l M R R High am p l i tu d e Low f requ e ncy High fre q u e ncy

48. CONTD… EFFECT `VELOCITY` MRR IS DIRECTLY PROPORTIONAL TO THE PARTICLE VELOCITY M R R Feed force Mean grain diameter S u rface rough

49. CONTD.. EFFECT OF STATIC LOADING OR FEED FORCE: - MRR increases with an increase in feed force. EFFECT OF GRAIN SIZE: 1. - Grain size increases with an increase in MRR

50. Advantages of USM There is no cutting forces therefore clamping is not required except for controlled motion of the work piece Extremely hard and brittle materials can be easily machined There is no heat affected zone. Can machine harder metals Faster than EDM No tool wear at all. No heat affected zone. Better finish and accuracy.

51. USM Applications Hard, brittle work materials such as ceramics, glass, and carbides.   Also successful on certain metals, such as stainless steel and titanium. Shapes include non-round holes, holes along a curved axis. “Coining operations” - pattern on tool is imparted to a flat work surface

52. UNCONVENTIONAL MACHINING PROCESS – UNIT 3 Electrical Energy based processes

53. Electrical Energy based processes Electr i c al ene r gy i s di r ect l y us e d t o cut the material to get the final shape and size Electrical discharge machining (EDM) Wire cut Electrical Discharge Machining (WC EDM)

54. Electrical Discharge Machining (EDM) Principle Metal is removed by producing powerful electric spark discharge between the tool (cathode) and the work material (anode) Also known as Spark erosion machining or electro erosion machining

55. Why EDM? EDM has the following advantages: 1. Cavities with thin walls and fine features can be produced. 2. Difficult geometry is possible. 3. The use of EDM is not affected by the hardness of the work material. 4. The process is burr-free.

56. EDM Construction and Working

57. EDM Dielectric Fluid Fluid medium which doesn’t conduct electricity Dielectric fluids generally used are paraffin, white spirit, kerosene, mineral oil Must freely circulate between the work piece and tool which are submerged in it Eroded particles must be flushed out easily Should be available @ reasonable price Dielectric fluid must be filtered before reuse so that chip contamination of fluid will not affect machining accuracy

58. EDM Functions of dielectric fluid Acts as an insulating medium Cools the spark region & helps in keeping the tool and work piece cool Carries away the eroded material along with it Maintains a constant resistance across the gap Remains electrically non-conductive

59. EDM Tool materials and tool wear Metallic materials Copper, Brass, Copper-tungsten Non metallic materials graphite Combination of metallic and non metallic Copper – graphite Three most commonly used tool materials are Copper, graphite, copper-tungsten

60. EDM Tool materials Graphite Non-metallic Can be produced by molding, milling, grinding Wide range of grades are available for wide applications It is abrasive and gives better MRR and surface finish But costlier than copper Copper Second choice for tool material after graphite Can be produced by casting or machining Cu tools with very complex features are formed by chemical etching or electroforming Copper-tungsten Difficult to machine and also has low MRR Costlier than graphite and copper

61. EDM Selection of cutting tool is influenced by Size of electrode Volume of material to be removed Surface finish required Tolerance allowable Nature of coolant application Basic requirement of any tool materials are It should have low erosion rate Should be electrically conductive Should have good machinability Melting point of tool should be high Should have high electron emission

62. EDM Tool wear Tool does not comes in contact with the work So, life of tool is long and less wear takes place Wear ratio = vol. of work material removed vol. of electrode consumed Tool wear ratio for Brass electrode is 1:1 Copper of 2:1 Copper tungsten is 8:1 Graphite varies between 5 and 50:1

63. EDM Metal Removal Rate (MRR) Defined as volume of metal removed per unit time Depe n d s up o n c ur r e n t i n t en s ity a n d i t i n cr eases with current U s ual l y a r ou g h cut wi t h he a vy c ur r e n t a n d finishing cut with a less current is performed MRR up to 80Cu.mm/S, can be obtained Surface finish of 0.25 microns is obtained Tolerances of the order of ±0.05 to 0.13 mm are commonly achieved

64. EDM Factors affecting MRR Increases with forced circulation of dielectric fluid Increases with capacitance Increases up to an optimal value of work-tool gap, after that it drops suddenly Inc r eases u p t o an o p timum v alue of s pa r k discharge time, after that it decreases MRR i s m a xim u m , when t h e p r e s s u r e i s be l o w atmospheric pressure

65. EDM Power generating circuits – Resistance capacitance circuit (RC Circuit) – R-C-L Circuit

66. EDM – Rotary pulse generator circuit – Controlled pulse generator circuit

67. EDM Process Parameters Operating parameters Electrical energy Voltage Time interval Instantaneous current Torque Pulse width Taper Surface finish Energy of the pulse Frequency of operation Current density

68. EDM Characteristics of EDM Metal removal technique By using powerful electric spark Work material Electrically conductive materials Tool material Copper, alloy of Zinc, yellow brass, Copper-Tungsten MRR 15 to 80 Cu.mm/S Spark gap 0.005 to 0.05 mm Spark frequency 200 to 500 KHz Volts 30 to 250 V Current 5 to 60 A Temperature 10,000 degree celcius Dielectric fluid Petroleum based HC fluids, Paraffin, White Spirit

69. EDM Applications Production of complicated and irregular profiles Thread cutting in jobs Drilling of micro holes Helical profile drilling Curved hole drilling Re-sharpening of cutting tool and broaches Re-machining of die cavities without annealing Recent developments EDM change from using relaxation circuit to faster and more efficient impulse circuits Instead of using Cu; WC is used as electrode

70. EDM Advantages Can be used to machine various conductive materials Gives good surface finish Machining of very thin section is possible Does not leaves any chips or burrs on the work piece High accuracy is obtained Fine holes can be easily drilled P r oce s s once s t a r t ed doe s no t nee d c o n s t a n t operators attention It is a quicker process Well suited to machine complicated components

71. EDM Disadvantages Used t o ma c hin e on l y electr i c al l y c o n d ucti v e materials No n - m e t al l ic c o m p o u n d s s u c h as p l a s tics, ceramics or glass can never be machined Suitable for machining small work pieces Electrode wear and overcut are serious problems Perfect square corners can not be machined MRR is slow Power requirement is high Th e s ur f a c e mach i ne d ha s bee n f o u n d t o h a v e micro holes

72. Wire Cut Electrical Discharge Machining (WC-EDM) Principle Metal is removed by producing powerful electric spark discharge between the tool (cathode) and the work material (anode) Also known as Spark erosion machining or electro erosion machining

73. Wire Cut Electro-Discharge Machining (WC EDM)

74. WC EDM

75. WC EDM Applications Be s t s u i t e d f o r p r o du c tion o f g e a r s , t ools , d i e s , rotors, turbine blades and cams Disadvantages Capital cost is high Cutting rate is slow Not suitable for large work pieces

76. WC EDM Features / Advantages of WC EDM Manufacturing electrode Electrode wear Surface finishing Complicated shapes Time utilization Straight holes Rejection Economical Cycle time Inspection time

77. UNCONVENTIONAL MACHINING PROCESS – UNIT 4 Chemical and Electrochemical Energy Based processes

78. Chemical Energy Based processes Metal is removed from the work piece through a controlled etching of work piece material in contact with the chemical solution Example – Chemical Machining (CHM)

79. Electrochemical Energy Based processes Material is removed by ion displacement of work piece material in contact with a chemical solution Example Electro-Chemical Machining (ECM) Electro-Chemical Grinding (ECG) Electro-Chemical Honing (ECH) Electro-Chemical deburring (ECD)

80. Chemical Machining (CHM) Also called as Chemical Milling (CHM)

81. CHM Etchant Chemical reagent used to removed the metal from work piece Metal is removed by the chemical conversion of metal into metallic salt S. No Material Etchant 1 Aluminum Caustic soda 2 Steel HCl / HNO 3 Acid 3 Stainless steel FeCl 4 Magnesium HNO 3 Acid 5 Titanium HNO 3 Acid

82. CHM Maskant – A r eas of w or k p i e ce which ar e c o v e r ed with a resistant material called a maskant or resist Methods of masking Scribed or peeled maskants Photo resists maskants S. No Material Maskant 1 Aluminum Butyl rubber, neoprene rubber 2 Magnesium Polymers 3 Titanium Translucent chlorinated polymers 4 Nickel Neoprene 5 Ferrous metals Polyvinyl chloride, polyethylene

83. CHM Metal Removal Rate Depends upon selected etchant Fast with certain etchant Etch rate is limited to 0.02 to 0.04 mm/min E t ching r a t e and dept h of cut ar e h i gh f o r har d materials and low for softer materials Surface finish of the order of 5µ are produced Size of work piece depends upon the size of tank W i th o p timum t i me, t em p e r a tu r e and solut i o n control; accuracies of order ±0.01 mm is obtained

84. CHM Classification of CHM Chemical blanking Material is etched entirely on the work piece Used to cut out the parts from thin sheet metal or foil sheets Chemical machining Material is selectively etched from certain areas on work piece Used to remove material from thicker work pieces Application of CHM Used in manufacturing burr free components Applied where the depth of metal removal is critical to few microns and the tolerances are close

85. CHM Advantages of CHM Burr free components are produced Most difficult to machine components are machined High surface finish is obtained Stress free components are produced No need of skilled labor Tooling cost is low Complex contours can be easily machined Hard and brittle materials can be machined Both faces of work piece are simultaneously machined

86. CHM Disadvantages MRR is low Manufacturing cost is high Large floor area is needed Not possible to produce sharp corners Work piece thickness that can be machined is limited

87. Electro Chemical machining (ECM) Principle Faraday’s first law Amou n t o f m a t erial dissol v ed o r d e posi t ed is proportional to the quantity of electricity passed Faraday’s second law Amou n t o f cha r g e p r oduce d i n the m a t e r ial is proportional to its electrochemical equivalent of material W or k piec e c onnec t ed t o pos i t i v e t erm i nal (cathode) Tool connected to negative terminal (anode)

88. E CM

89. E CM

90. E CM Analysis of metal removal M i ld D . C . V ol t a g e of about 5 t o 30 V i s a p p l ied between the tool and work piece Cu r r e n t f l o w s t h r oug h t h e elect r oly t e with charged ions – Th e f oll o wi n g r e a ctions a r e possibl e a t the cathode (tool) Na + + e - = Na Na + H 2 O = Na(OH) + H + 2H + + 2e - = H 2 – Th u s the r e i s n o deposit i o n on t oo l a n d o n l y hydrogen gas is evolved

91. E CM Similarly following reaction occur at the anode Fe 2+ + 2e - F eC l 2 Fe Fe ++ + 2Cl - Fe ++ + 2 (OH) - FeCl 2 + 2(OH) Fe(OH) 2 Fe (OH) 2 + 2Cl - This shows that work piece goes into solution and machined By combining the faraday’s first and second law of electrolysis we get Where, W – mass of ions dissolved in Kg E – Equivalent weight of substance dissolved T- time in S Faradays Constant = 96,500 Coulombs = 26.8 Amp.Hr

92. E CM Tool material, tool design and insulation A n y m a t er i al which i s a g oo d c o n du c t o r of electricity can be used as tool material The general requirement of tool material in ECM are Must be a good conductor of electricity Must be chemically inert to the electrolyte Must be easily machinable Must be rigid enough to take up the load due to fluid pressure The tool is made hollow for drilling holes Ou t er s ur f a c e of the t oo l m u s t b e in s ul a t ed by vinyl, teflon, enamels or high temperature varnish

93. E CM While designing the tool, the following aspects are taken into consideration Determine the tool shape Design the tool by considering the electrolyte Electrolyte Carries current between tool and work piece S. No Material Electrolyte 1 Fe based alloys 20% NaCl solution in water 2 Ni based alloys Mixture of brine and sulphuric acid 3 Ti based alloys 10%HF + 10%HCl + 10%HNO 3 4 Co-Cr based alloys NaCl 5 WC based alloys Strong alkaline solutions

94. E CM The essential characteristics of electrolyte are Should be a good conductor of electricity Should have non-corrosive property Should be non-toxic Should have low viscosity Surface finish Depends mainly on Machining voltage Tool feed rate Temperature of electrolyte Concentration of electrolyte

95. E CM Applications To machine complicated profiles like jet engine blades, turbine blades, turbine wheels To drill small deep holes in nozzles To machine cavities and holes of irregular shapes To machine blind holes and pockets in forging dies To machine hard and heat resistant materials Limitations Sharp internal corners cannot be machined Post machining cleaning is needed Tool design is very complicated – Co n t r o l me c hanis m is n e e d e d t o mai n t ain high tolerances

96. E CM Characteristics Metal removal technique Faraday’s law of electrolysis Work material Difficult to machine Tool material Copper, brass or steel Voltage 5 to 30 v Current 50 to 40000 A MRR 27 Cu.mm/S Electrolyte 20% NaCl solution in water, mixture of brine in sulphuric acid Surface finish 0.2 to 0.8 µ Tolerance 0.005mm Specific power consumption 7 W/Cu.mm/min

97. E CM Advantages MRR is high Wear and tool tear is negligible Machining is done at low voltage I n tr i ca t e and c o m pl e x s hape s c an b e mach i ned easily Machined work surface is free of stress No cutting forces are involved High surface finish of order 0.2 to 0.8µ is obtained Tolerance of 0.005mm can be obtained No burrs are produced

98. E CM Disadvantages Non conducting materials can not be machined Initial investment is quite high More space is required Machining process is comparatively low Power consumption is 100 times more than conventional machining Difficulty in designing a proper tooling system Constant monitoring is required

99. E CM S. No EDM ECM 1 Work piece is submerged in dielectric fluid Work piece need not to be submerged in electrolyte 2 Tool wear takes place No tool wear 3 Control system is required No control system is required 4 Machining can not be done at low voltages Machining can be done at low voltages 5 MRR is slow compared to ECM MRR is high compared to EDM 6 Less energy is consumed More energy is consumed

100. Electro Chemical Grinding (ECG) Materials that cannot be easily shaped due to their extreme hardness can be ground Example Cemented carbides Hardened steel Principle Work is machined by the combined action of electrochemical effect and conventional grinding operation

101. E C G

102. E C G

103. E C G Process parameters Current density Electrolyte Feed rate Grinding wheel speed Applications Best suited for high precision grinding of hard metals like WC Also suited to cut thin sections of hard materials without any damage

104. E C G Advantages Tool wear is negligible Work is free of surface cracks and not subjected to any structural changes Burr and stress free components are produced Good surface is obtained Surface finish of 0.2 to 0.4µ are produced Accuracy of 0.01mm can be achieved Intricate paths can be machined without any distortion

105. E C G Disadvantages Initial cost is high Power consumption is high MRR is low Non conductive materials cannot be machined Maintenance cost is high Tolerance achieves is low Preventive measures are needed against corrosion of electrolyte

106. Electro Chemical Honing (ECH) Similar to ECG ECH uses rotating and reciprocating, non- conducting bonded honing stones instead of a conducting grinding wheel

107. E CH Advantages MRR is faster with reduced tool wear Burr and stress free components are produced Less pressure is required between honing stones and work piece Used to machine burred edges Noise and distortion are reduced

108. UNCONVENTIONAL MACHINING PROCESS – UNIT 5 Thermal Energy Based process

109. Thermal Energy based Processes Heat energy is concentrated on a small area of work piece to melt and vaporize the tiny bits of work material Required shape is obtained by the continued repetition of the process Example Electron Beam Machining (EBM) Laser Beam Machining (LBM) Plasma Arc Machining (PAM)

110. Electron Beam Machining (EBM) A beam of high velocity electrons travelling at half the velocity of light (1.6 X 10^8 m/S) are focused on the work piece to remove the metal Principle When high velocity beam of electrons strike the work piece its kinetic energy is converted into heat This concentrated heat raises the temperature of work piece material and vaporizes a small amount of it, resulting in removal of material from work piece

111. EBM Types Machining inside the vacuum chamber Machining outside the vacuum chamber

112. EBM

113. EBM Process parameters Control of current Control of spot diameter Control of focal distance of magnetic lens Applications Used for micromachining operations Used to drill holes in pressure differential devices Used to remove small broken taps from holes Used to machine low thermal conductivity and high melting point materials

114. EBM Accelerating voltage 50 to 200 KV Beam current 100 to 1000µA Electron velocity 1.6X10^8 m/S Medium Vacuum Work piece materials All materials Depth of cut Up to 6.5mm MRR Up to 4.Cu.mm/S Specific power consumption 0.5 to 50 KW Power density 6500 billion W/mm^2

115. EBM Advantages Excellent process for micromachining Very small holes and holes of different sized can be machined No mechanical contact between tool and work piece Quick process Easily automated Close tolerances are obtained Brittle and fragile materials can be machined Physical and metallurgical damage to work piece are less

116. EBM Disadvantages MRR is very low Cost of equipment is high Not suitable for large work pieces Little taper is produced on holes Vacuum requirements limits the size of work piece Not suitable to produce perfectly cylindrical profiles Applicable for thin materials Energy consumption is high

117. Laser beam Machining (LBM) LASE R – Lig h t Am p l i fi c a tion b y S timul a t ed Emission of Radiation Like EBM; LBM is also used to drill micro holes up to 25µ o n t h e w ork p i ece by Principle – Laser beam is focused means of lens t o gi v e e x t r e me l y h i gh ene r gy density to melt and vaporize the work material

118. LBM

119. LBM

120. LBM Accuracy T o g e t b e s t po s sibl e r e s ults , the m a t erial shou l d be placed within a tolerance of ±0.2mm focal point Lasing materials Solid laser Ruby laser, neodymium doped Yttrium – Aluminum –Garnet (Nd-YAG) laser and neodymium doped glass laser Gas Laser Can be operated continuously P r o du c es e x ce p tiona lly hig h mon o c h r o m a ti c ity and high stability of frequency Example Carbon dioxide Laser Helium-Neon Laser

121. LBM Processing with LASER S. No Special characteristics of a LASER beam Cutting process characteristics 1 Can be focused to a maximum or minimum intensity as needed MRR is maximum to minimum 2 Can be moved rapidly on work piece Cutting of complex shapes 3 Projected on the work piece at a particular distance from the lens Remote cutting over long stand-off distances 4 Dedicated to on-line processes Re-routing is not necessary 5 Power is shared on a job Two or more cuts simultaneously

122. LBM Machining applications of LBM Laser in metal cutting Laser in drilling Laser in welding Conduction limited welding Deep penetration welding Laser for surface treatment Other applications Sheet metal trimming Blanking Resistor trimming

123. LBM Characteristics Metal removal technique Heating, melting & vaporization of material by using high intensity of laser beam Work material All materials expect those having high thermal conductivity Tool Laser beam of wavelength range 0.3 to 0.6µ Power density 10^7 W/sq.mm Output energy laser 20 J MRR 6 Cu.mm/min Pulse duration 1 millisecond Dimensional accuracy ±0.025mm Medium Atmosphere Efficiency 10 to 15 % Specific power consumption 1000 W/Cu.mm/min

124. LBM Advantages Micro sized holes are produced Soft materials like rubber can be machined No tool wear No direct contact between tool and work piece Dissimilar materials can be easily welded Easily automated Hardness of material does not affect the process Heat affected zone is very small Deep holes of short diameter can be easily drilled

125. LBM Disadvantages Initial investment is high Operating cost is also quite high Highly skilled operators are needed Rate of production is low Safety procedures to be followed strictly Overall efficiency is extremely low Life of flash lamp is short Machined hole is not round and straight

126. Plasma Arc Machining (PAM) or Plasma Jet machining (PJM) Principle – Material is removed by directing a high velocity jet of high temperature [11000 to 28000 deg. celcius] ionized gas on the work piece, which in turn melts the material from work piece

127. P AM

128. P AM

129. P AM Gases used in PAM – Gas used should not affect the electrode or work piece to be machined S.No Gas or Gas Mixture Material to be machined 1 Ni t r o g e n - h y d r o g e n , Argon-hydrogen Stainless steel, non ferrous material 2 Nitrogen-hydrogen, Compressed air Carbon & alloy steel, cast iron 3 Nitrogen, nitrogen-hydrogen Argon-hydrogen Aluminum, Magnesium

130. P AM Types Direct arc plasma torch Indirect arc plasma torch Accuracy of PAM Accuracy of 1.4mm is obtained Accuracy on width of slots and diameter of holes is ordinarily from ±4mm to 150 mm thick plates

131. P AM Characteristics Metal removal technique Heating, melting and vaporising by using plasma Work material All materials which conduct electricity Tool Plasma jet Velocity of plasma jet 500 m/S Power range 2 to 200 KW Current As high as 600 A Voltage 40 to 250 V Cutting speed 0.1 to 7 m/min MRR 145 Cu.mm/min

132. P AM Process parameters Stand off distance T h ermo p h y si c al a n d m e t allu r gi c al p r o p erti e s of plasma Cutting speed or velocity of plasma jet Applications Used for profile cutting U s ed f o r tur n ing a n d milling o f ha r d t o machi n e materials Can be used for stack cutting, shape cutting Uniform thin film spraying of refractory materials Used to cut alloy steels, SS, copper, nickel, titanium, Aluminum and alloy of copper and nickel

133. P AM Advantages Used to cut any material Cutting rate is high Can cut plain carbon steel four times faster than ordinary flame cutting process Used for rough turning of very difficult materials Disadvantages Produces tapered surface Noise protection is necessary Equipment cost is high Protection of eyes is necessary for the operator Work surface may undergo metallurgical changes