Unit IV-Unconventional Machining Processes.pptx

AJM

1. COURSE: MACHINING PROCESSS CODE: A40315 V Semester Regulation: R-23 G. Pullaiah College of Engineering and Technology (Autonomous) Pasupula , Kurnool- 518002 Dr G Praveen Kumar Assistant Professor Mechanical Engineering Prepared by

2. Course objectives:   Gain knowledge on working principle of different metal cutting processes and familiarize with cutting forces, machining calculations and cutting fluids. Make the student learn about principles of lathe and Drilling machines. Make the student learn about principles of Grinding and Milling machines. To acquire knowledge in the elementary mechanism and machinability of materials with different Mechanical and Electrical energy-based Machining Processes. To make student familiar with various advanced machining operations.  

3. Course Outcomes (COs) After the completion of the course, the student will be able to: A40315.1 - Operation of various machines like lathe, drilling, grinding, slotting, shaping, milling etc. A40315.2 - Practical exposure on flat surface machining, milling and grinding operations. A40315.3 - Illustrate advanced machining processes, cutting tools and cutting fluids for a specific material and part features. A40315.4 - Differentiate Electrical Energy Based machining processes, mechanism of metal removal, machine tool selection. A40315.5 - Interpret Electro Chemical machining process, economic aspects of ECM

4. Course Syllabus UNIT I Elementary treatment of metal cutting theory – Elements of cutting process – Geometry of single point tool and angles, chip formation and types of chips – built up edge and its effects, chip breakers. Mechanics of orthogonal cutting –Merchant‘s Force diagram, cutting forces – cutting speeds, feed, depth of cut, heat generation, tool life, coolants, machinability –economics of machining. cutting Tool materials and cutting fluids –types and characteristics.   UNIT II Engine lathe – Principle of working- specification of lathe – types of lathes – work holders and tool holders –Taper turning, thread cutting operations and attachments for Lathes. Drilling, Boring Machines, Shaping, Slotting and planning machines - Principles of working, specifications, types, Tools and tool holding devices – operations performed, machining time calculation.  

5. UNIT III Milling machine – Principles of working – specifications – classifications of milling machines – methods of indexing, milling cutters - machining operation, Accessories to milling machines. Grinding machine –Theory of grinding – classification– cylindrical and surface grinding machine – Tool and cutter grinding machine – Grinding wheel specification - types of abrasives – bonds, Truing and Dressing of wheels. Lapping, Honing and Broaching machines – comparison of grinding, lapping and honing. Principles of design of Jigs and fixtures and uses, Classification of Jigs & Fixtures – Principles of location and clamping –types. UNIT IV Mechanical Energy Based Processes: Abrasive Jet Machining, Water Jet Machining, Abrasive Water Jet Machining, Ultra Sonic Machining – Working Principle, Description of Equipment, Process Parameters, Metal Removal Rate, Applications, Advantages and Limitations. Electrical Energy Based Processes: Electric Discharge Machining – Wire cut EDM - Working Principles, Process Parameters, Applications Advantages and Limitations.

6. UNIT V Chemical and Electro Chemical Energy Based Processes: Chemical Machining and Electro Chemical Machining – Working Principle, Etchants, Maskants , Techniques of Applying - Process Parameters, Electro Chemical Grinding, Electro Chemical Honing, Applications, Advantages and Limitations. Thermal Energy Based Processes: Laser Beam Machining and Drilling, Plasma Arc Machining, Electron Beam Machining – Working Principle, Process Parameters, Applications, Advantages and Limitations.

7. . Books and References   Text Books: 1. Manufacturing Technology-Kalpakzian- Pearson Seventh edition. (2018) 2. Production Technology by R.K. Jain and S.C. Gupta, Khanna Publishers, 17th edition. 3. Jain V.K., Advanced Machining Processes, 1st Edition, Allied Publishers Pvt. Ltd., New Delhi, 2007. 4. Jain V.K., Advanced Machining Processes, 1st Edition, published by CRC Press (Taylor & Francis), September 7, 2022   Reference Books: 1. Pandey P.C and Shan H.S., Modern Machining Processes, 1/e, McGraw Hill, New Delhi, 2007. 2. Modern Machining Processes by Anand Pandey, published by Ane Books Pvt. Ltd, 2019 3. Production Technology by H.M.T. (Hindustan Machine Tools),TMH, 1st edition, 2001 4. Manufacturing Technology Vol II by P.N. Rao, Tata McGraw Hill, 4th edition, 2013 5. Machine Technology Machine tools and operations by Halmi A Yousuf & Harson, CRC Press Taylor and Francies. 6. Workshop Technology – Vol II, B.S.Raghu Vamshi, Dhanpat Rai & Co, 10th edition, 2013

8. Chapter : 4 Mechanical Energy Based Processes: Abrasive Jet Machining, Water Jet Machining, Abrasive Water Jet Machining, Ultra Sonic Machining – Working Principle, Description of Equipment, Process Parameters, Metal Removal Rate, Applications, Advantages and Limitations. Electrical Energy Based Processes: Electric Discharge Machining – Wire cut EDM - Working Principles, Process Parameters, Applications Advantages and Limitations.

9. Machining – Produces finished products with high degree of accuracy. Tradition Machining Processes (like turning, drilling ,milling) use a sharp cutting tool to remove the from work piece by shear deformation . Introduction to Non Traditional Machining

10. Extremely hard and brittle materials or difficult to machine by traditional machining processes The work piece: too flexible or slender to support the cutting or grinding forces. The shape of the part is complex , such as internal and external profiles, or small diameter holes. Surface finish or tolerance better than those obtainable conventional process. Conventional machining involves the direct contact of tool and work-piece , whereas unconventional machining does not require the direct contact of tool and work piece. Need for the development of Nontraditional Machining Turbine Blade with cooling Holes

11. Based on the principle form of energy nontraditional manufacturing process can be classified in to following groups . Classification of Nontraditional Machining Processes Non Traditional Machining Processes Mechani c al Processes Electro c hemi c a l Processes Electrical Processes Chemical Pro c e s s e s Thermal Process

12. 16 Mechanical Based Processes Working principles Equipment used Process parameters MRR Variation in techniques used Applications AJM WJM A W JM USM Erosion of work material by a high velocity stream of abrasives and/or fluid .

13. 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

14. Principle and working : This process consists of directing a stream of fine abrasive grains, mixed with compressed air or some other gas at high pressure through nozzle on to the surface of the work piece to be machined. These particles impinge on the work surface at high speed and the erosion caused by their impact enables the removal of metal. The metal removal rate depends up on the flow rate and size of abrasive particles. ABRASIVE JET MACHINING ( AJM )

15. Important Characteristics of AJM: Process Parameters : Abrasive flow rate and velocity, nozzle tip distance, abrasive grain size. Material Removal : By impinging abrasive grains at high speed. ABRASIVE JET MACHINING ( AJM )

16. Advantages : Low capital investment required. Brittle materials of thin sections may be easily machined. Intricate cavities and holes of any shape can be machined in materials of any hardness. There is no direct contract between the tool and the work piece. Normally inaccessible portions can be machined with fairly good accuracy. ABRASIVE JET MACHINING ( AJM )

17. AJM Applications To machine hard and brittle materials Fine drilling and micro welding Machining of semiconductors Machining of intricate profiles Surface etching Surface preparation Cleaning and polishing of plastics, nylon and teflon

18. Abrasive Jet Machining Processes

19. AJM Disadvantages MRR is slow Soft material cannot be machined Machining accuracy is poor Nozzle wear rate is high Abrasive powder once used can never be used again Requires some kind of dust collection system Cleaning is essential after the operation

20. 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 i nducing 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. Used to cut paper boards, plastics, wood, fiber glass, leather

21. Schematic Representation of WJM

22. WJM Process parameters Material removal rate Geometry and surface finish of work material Wear rate of nozzle

23. WJM Characteristics Work material Soft and non-metallic materials Tool Water or water with additives Additives Glycerin, polyethylene oxide Pressure of water 100 to 1000 Mpa Mass flow rate 8 lit/min Power 45 KW MRR 0.6 Cu.m /S Feed rate 1 to 4 mm/s Nozzle material Tungsten Carbide, synthetic sapphire Stand off distance 2 to 50 mm

24. WJM Advantages Water is used as energy medium and hence it is cheap, non-toxic and easy to dispose Low operating cost Low maintenance cost Work area remains clean and dust free Easily automated No thermal damage to work

25. WJM Disadvantages Initial cost is high Noisy operation Difficult to machine hard material

26. Applications Of WJM Process

27. Abrasive Water Jet Machining Principle : In the Abrasive Water Jet Machining (AWJM) process, a high-velocity stream of abrasive particles is mixed with pressurized water and directed through a nozzle onto the workpiece . This jet is used to cut, shape, and remove material from various types of materials, including hard metals, ceramics, and composites. The process involves high-pressure water being forced through a nozzle where abrasive particles, such as garnet or aluminum oxide, are introduced. This high-velocity abrasive water jet then strikes the workpiece , eroding material through mechanical action to create precise, burr-free, and intricate cuts without generating significant heat . 

28. Schematic Representation

29. Abrasive Water Jet Machining Processes

30. Advantages of Abrasive water jet cutting No heat-affected zone (HAZ): As it is a cold cutting process, there is no thermal distortion or change in material properties. Can cut any material: Suitable for metals, ceramics, glass, composites, and even reflective or heat-sensitive materials. High precision and accuracy: Provides smooth, burr-free edges with minimal finishing required. Environmentally friendly: Uses water and natural abrasives, producing minimal hazardous waste. No tool wear: Since there is no physical contact between tool and workpiece , tool wear is eliminated. Minimal material wastage: The narrow kerf width results in efficient use of material. Capability for complex shapes: Can easily cut intricate profiles and patterns.

31. Disadvantages of Abrasive water jet cutting High operating cost: Abrasives and maintenance of high-pressure pumps are expensive. Slow cutting speed: Slower compared to processes like laser or plasma cutting for some materials. Noisy operation: The process generates high noise levels during cutting. Abrasive disposal issues: Used abrasives and sludge require proper disposal. Limited thickness: Efficiency decreases for very thick materials. Surface roughness: The surface finish may vary with cutting speed and abrasive flow rate .

32. Ultrasonic Machining Principle  In the Ultrasonic Machining process the material is removed by micro-chipping or erosion with abrasive particles . A slurry of small abrasive particles are forced against the work piece by means of a vibrating tool and it causes the removal of metal from the work piece in the form of extremely small chips Ultrasonic refers to high frequency – above 20khz

33. USM Construction and working

34. Working : The abrasive particle are driven into the work surface by a tool oscillating normal to the work surface at high frequency. The tool is made of soft material, oscillated at frequencies of order of 20 to 30 kHz with an amplitude of about 0.02mm .  It is pressed against the work piece with a load of a few kg and fed downwards continuously as the cavity is cut in the work. The tool is shaped as the approximate mirror image of the configuration of the cavity desired in the work. ULTRASONIC MACHINING ( USM )

35. Important Characteristics of USM : Tool Materials : Brass and Mild steel. Work piece material : hard and brittle materials like semiconductors, glass and ceramics. Process parameters : Frequency, amplitude, grain size, slurry concentration and feed force. Material Removal : Fracture of work material due to impact of grains. Abrasive : Aluminum oxide, silicon carbide and boron carbide. Grain size : 100- 800 mesh size. Gap : 0.2 to 0.5 mm. ULTRASONIC MACHINING ( USM )

36. Advantages : Noiseless operation. Low metal removal cost. Extremely hard and brittle materials can be easily machined. Operation of the equipment is quite safe. High accurate profiles and good surface finish can be easily obtained. The machined work pieces are free of stresses. ULTRASONIC MACHINING ( USM )

37. Disadvantages : High tooling cost. Low MRR. The size of the cavity can be machined is limited. High power consumption. The initial equipment cost is higher than the conventional machine tools. The process is unsuitable for heavy metal removal. It is difficult to machine softer materials. ULTRASONIC MACHINING ( USM )

38. Applications : Several machining operations like turning, threading, grinding, milling etc. Machining of hard to machine and brittle materials. Dentistry work – to drill fine holes of desired shape in teeth. Tool and die making, specially wire drawing and extrusion dies. ULTRASONIC MACHINING ( USM )

39. 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)

40. 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

41. 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.

42. Principle : This process involves controlled erosion of electrically conducting materials by the initiation of rapid and rupture electrical discharge between the tool (cathode) and the work piece (anode) separated by a dielectric fluid mechanism. ELECTRICAL DISCHARGE MACHINING( EDM )

43. Working: A suitable gap between the tool and the work piece is maintained to cause the spark discharge. The gap can be varied to match the machining conditions such as MRR. As soon as the voltage gradient set up between the tool and the work piece is sufficient enough to break down the dielectric medium. A conducting electrical path is developed for spark discharge owing to ionization of the fluid medium and thereby causes the current flow. ELECTRICAL DISCHARGE MACHINING( EDM )

44. The temperature of the spot hit by the spark may rise up to 10,000 C causing the work surface to melt and vaporize and ultimately to take the form of sphere as it is quenched by the surrounding fluid. If the tool is fed downwards, maintaining the predetermined gap, the tool shape profile will be reproduced on the work piece. The spark gap generally 0.01 to 0.1 mm. discharge Higher gap increases the energy but decrease the spark frequency. ELECTRICAL DISCHARGE MACHINING( EDM )

45. ELECTRICAL DISCHARGE MACHINING( EDM ) The servo control unit is provided to maintain the predetermined gap. It senses the gap voltage and compares it with the present value and the difference in voltage is then used to control the movement of servomotor to adjust the gap. Important Characteristics of EDM : Tool Material : Copper, Brass an Graphite. Work piece material : conducting materials and alloys. Process parameters : Voltage, Capacitance, Spark Gap, Melting Temperature of work. Material Removal : Melting and Vaporization.

46. Advantages : Machining time is less than the conventional machining process. Any completed shape that can be made on the tool can be reproduced on the work piece. The process can be employed for extremely hardened work pieces . The process can be applied to all electrically conducting metals and alloys irrespective of their melting points. Brittle and slender work pieces can be machined with out distortion. Considerably easier and more economical polishing can be done on the catering type surfaces developed by EDM. Fine hole can be easily drilled. Enables high accuracy on tools and dies, because they can be machined in as hard condition. ELECTRICAL DISCHARGE MACHINING( EDM )

47. Disadvantages : It can not be applied to non- conducting materials . Power required is very high compared to conventional machining processes. In some materials surface cracking may be takes place. Sharp corners can not be produced. Low MRR Surface tend to be rough for larger removal rates. ELECTRICAL DISCHARGE MACHINING( EDM )

48. Applications : Very useful in tool manufacturing due to ease with which hard metals and alloyed can be machined. Re- sharpening of cutting tools and broaches, trepanning of holes with straight or curved axes. Machining of cavities for dies and re- machining of die cavities without annealing. ELECTRICAL DISCHARGE MACHINING( EDM )

49. 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

50. Wire Cut Electrical Discharge Machining (WC-EDM) Principle Wire Cut Electrical Discharge Machining (WC-EDM) is  a non-conventional process that uses controlled electrical sparks to erode and cut electrically conductive materials along a programmed path . A thin, continuously moving wire acts as one electrode, and a series of sparks between the wire and the workpiece , submerged in a dielectric fluid, melt and vaporize the material. This process is highly precise, capable of creating complex shapes, and is often used for hard metals, tool steels, and advanced composites where conventional machining is difficult. 

51. Wire Cut Electrical Discharge Machining (WC-EDM)

52. WC EDM How it works Electrical Sparks:  A high-frequency voltage is pulsed between a thin wire electrode and a conductive work piece. Dielectric Fluid:  The wire and work piece are immersed in a dielectric fluid, typically deionized water, which acts as an insulator until the voltage reaches a critical point, creating a plasma channel and a spark. Material Removal:  The spark melts and vaporizes a tiny amount of the workpiece material. The fluid flushes away the molten particles (debris) as the spark gap is restored. Continuous Motion:  A CNC system guides the wire along a programmed path to cut the desired shape, while the wire itself is continuously fed from a spool to maintain its integrity. 

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

54. 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