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UNIT-I INTRODUCTION AND ULTRASONIC MACHINING

UNIT-I INTRODUCTION AND ULTRASONIC MACHINING. Subject : Non-Traditional Machining (ME 635) N.RAM KUMAR M.E., ASSISTANT PROFESSOR DEPARTMENT OF MECHANICAL ENGINEERING CHRIST UNIVERSITY FACULTY OF ENGINEERING BANGALORE. SYLLABUS.

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UNIT-I INTRODUCTION AND ULTRASONIC MACHINING

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  1. UNIT-IINTRODUCTION AND ULTRASONIC MACHINING Subject : Non-Traditional Machining (ME 635) N.RAM KUMAR M.E., ASSISTANT PROFESSOR DEPARTMENT OF MECHANICAL ENGINEERING CHRIST UNIVERSITY FACULTY OF ENGINEERING BANGALORE N.Ram Kumar, Assistant Professor, CUFE.

  2. SYLLABUS UNIT – 1 13 Hours INTRODUCTION: History, Classification, comparison between conventional and Nonconventional machining process selection. ULTRASONIC MACHINING (USM): Introduction, equipment, tool materials & tool size, abrasive slurry, cutting tool system design:- Effect of parameter: Effect of amplitude and frequency and vibration, Effect of abrasive grain diameter, effect of applied static load, effect of slurry, tool & work material, USM process characteristics: Material removal rate, tool wear, Accuracy, surface finish, applications, advantages & Disadvantages of USM. UNIT – 2 11 Hours ABRASIVE JET MACHINING (AJM): Introduction, Equipment, Variables in AJM: Carrier Gas, Type of abrasive, size of abrasive grain, velocity of the abrasive jet, mean number. Abrasive particles per unit volume of the carrier gas, work material, stand off distance (SOD), nozzle design, shape of cut. Process characteristics-Material removal rate, Nozzle wear, Accuracy & surface finish. Applications, advantages & Disadvantages of AJM. Water Jet Machining: Principle, Equipment, Operation, Application, Advantages and limitations of water Jet machinery N.Ram Kumar, Assistant Professor, CUFE.

  3. SYLLABUS UNIT – 3 12 Hours ELECTROCHEMICAL MACHINING (ECM): Introduction, study of ECM machine, Elements of ECM process : Cathode tool, Anode work piece, source of DC power, Electrolyte, Chemistry of the process, ECM Process characteristics – Material removal rate, Accuracy, surface finish, ECM Tooling: ECM tooling technique & example, Tool & insulation materials, Tool size Electrolyte flow arrangement, Handling of slug, Economics of ECM, Applications such as Electrochemical turning, Electrochemical Grinding, Electrochemical Honing, deburring, Advantages, Limitations. CHEMICAL MACHINING (CHM): Introduction, elements of process : Preparation of work piece, preparation of masters, masking with photo resists, etching for blanking, accuracy of chemical blanking, applications of chemical blanking, chemical milling (contour machining): process steps – masking, Etching, Process characteristics of CHM: material removal rate, accuracy, surface finish, Hydrogen embrittlement, advantages & application of CHM. N.Ram Kumar, Assistant Professor, CUFE.

  4. SYLLABUS UNIT - 4 11 Hours ELECTRICAL DISCHARGE MACHINING (EDM): Introduction, mechanism of metal removal, dielectric fluid, spark generator, EDM tools (electrodes) Electrode feed control, Electrode manufacture, Electrode wear, EDM tool design, choice of machining operation, electrode material selection, under sizing and length of electrode, machining time. Flushing; pressure flushing, suction flushing, side flushing, pulsed flushing synchronized with electrode movement, EDM process characteristics: metal removal rate, accuracy, surface finish, Heat Affected Zone. Machine tool selection, Application, EDM accessories / applications, electrical discharge grinding, Traveling wire EDM. UNIT – 5 13 Hours PLASMA ARC MACHINING (PAM): Introduction, equipment, non-thermal generation of plasma, selection of gas, Mechanism of metal removal, PAM parameters, process characteristics. Safety precautions, Applications, Advantages and limitations. LASER BEAM MACHINING (LBM): Introduction, equipment of LBM mechanism of metal removal, LBM parameters, Process characteristics, Applications, Advantages & limitations. ELECTRON BEAM MACHINING (EBM): Principles, equipment, operations, applications, advantages and limitation of EBM. N.Ram Kumar, Assistant Professor, CUFE.

  5. INTRODUCTION • What is Engineering? • Engineering (from Latiningenium, meaning "cleverness" and ingeniare, meaning "to contrive, devise") is the application of scientific, economic, social, and practical knowledge in order to invent, design, build, maintain, and improve structures, machines, devices, systems, materials and processes. • Engineering is the Study of Design and working of any system. N.Ram Kumar, Assistant Professor, CUFE.

  6. INTRODUCTION • What is Mechanical Engineering? Mechanical Engineering is one of the major activities in the engineering profession and its principles are involved in the design, study, development and construction of nearly all of the physical devices and systems. N.Ram Kumar, Assistant Professor, CUFE.

  7. INTRODUCTION N.Ram Kumar, Assistant Professor, CUFE.

  8. INTRODUCTION • What is Manufacturing? N.Ram Kumar, Assistant Professor, CUFE.

  9. INTRODUCTION Types of Manufacturing Processes: • Manufacturing processes can be broadly divided into two groups • Primary manufacturing processes • Secondary manufacturing processes. • The Primary manufacturing process provides basic shape and size to the material as per designer’s requirement. For example: Casting, forming, powder metallurgy processes provide the basic shape and size. • The Secondary manufacturing processes provide the final shape and size with tighter control on dimension, surface characteristics etc. Most of Material removal processes are mainly the secondary manufacturing processes. N.Ram Kumar, Assistant Professor, CUFE.

  10. INTRODUCTION Material removal processes can be further divided into mainly two groups 1. Conventional Machining Processes 2. Non-Traditional Manufacturing Processes Examples of conventional machining processes are turning, boring, milling, shaping, broaching, slotting, grinding etc. Examples of non conventional ( or also called non traditional or unconventional) are • Abrasive Jet Machining (AJM), • Ultrasonic Machining (USM), • Water Jet and Abrasive Water Jet Machining (WJM and AWJM), • Electro-discharge Machining (EDM) , • Electro Chemical Machining (ECM). N.Ram Kumar, Assistant Professor, CUFE.

  11. CONVENTIONAL MACHINING PROCESS • Generally macroscopic chip formation by shear deformation • Material removal takes place due to application of cutting forces – energy domain can be classified as mechanical • Cutting tool is harder than work piece at room temperature as well as under machining conditions N.Ram Kumar, Assistant Professor, CUFE.

  12. CONVENTIONAL MACHINING PROCESS N.Ram Kumar, Assistant Professor, CUFE.

  13. COMPARISON N.Ram Kumar, Assistant Professor, CUFE.

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  18. ULTRASONIC MACHINING • Introduction. • Equipment. • Tool Materials and Tool Size and Abrasive Slurry. • Cutting tool system design • Effect of parameter: Effect of amplitude and frequency and vibration. • Effect of abrasive grain diameter. • Effect of applied static load. • Effect of slurry, tool and work material. • USM process characteristics: Material removal rate, tool wear, Accuracy, surface finish, applications, • Advantages & Disadvantages of USM. N.Ram Kumar, Assistant Professor, CUFE.

  19. INTRODUCTION • What is the Difference between Frequency, Wavelength and Amplitude? • Frequency tells us how many waves pass through a point at a second. • Wavelength tells us the length of those waves. • Amplitude tells us how big the wave is. • In USM, abrasives contained in a slurry are driven against the work by a tool oscillating at low amplitude (25-100 microns) and high frequency (15-30 kHz). N.Ram Kumar, Assistant Professor, CUFE.

  20. PRINCIPLE • The machining zone (between the tool and the work piece) is flooded with hard abrasive particles generally in the form of water based slurry. • As the tool vibrates over the work piece, abrasive particles acts as indenter and indent both work and tool material . • Abrasive particles , as they indent , the work material would remove the material from both tool and work piece. • In Ultrasonic machining material removal is due to crack initiation, propagation and brittle fracture of material. N.Ram Kumar, Assistant Professor, CUFE.

  21. EQUIPMENT N.Ram Kumar, Assistant Professor, CUFE.

  22. EQUIPMENT • Ultrasonic Machining consists of : • High Power sine wave generator. • Magneto-strictive Transducer. • Tool Holder. • Tool. N.Ram Kumar, Assistant Professor, CUFE.

  23. N.Ram Kumar, Assistant Professor, CUFE.

  24. High Power Sine Wave Generator • This unit converts low frequency (50 Hz) electrical power to high frequency (20kHz) electrical power. N.Ram Kumar, Assistant Professor, CUFE.

  25. TRANSDUCER • The high frequency electrical signal is transmitted to traducer which converts it into high frequency low amplitude vibration. • Essentially transducer converts electrical energy to mechanical vibration. There are two types of transducer used 1. Piezo electric transducer 2. Magneto-stricitvetransducer. N.Ram Kumar, Assistant Professor, CUFE.

  26. MAGNETOSTRICTIVE TRANSDUCER • These transducer are made of nickel , nickel alloy sheets. • Their conversion efficiency is about 20-30%. • Such transducers are available up to 2000 Watts. • The maximum change in length can be achieved is about 25 microns. N.Ram Kumar, Assistant Professor, CUFE.

  27. TOOL HOLDER OR HORN • The tool holder holds and connects the tool to the transducer. It virtually transmits the energy and in some cases, amplifies the amplitude of vibration. • Material of tool should have good acoustic properties, high resistance to fatigue cracking. • Due measures should be taken to avoid ultrasonic welding between transducer and tool holder. • Commonly used tool holders are Monel, titanium, stainless steel. • Tool holders are more expensive, demand higher operating cost. N.Ram Kumar, Assistant Professor, CUFE.

  28. TOOL • Tools are made of relatively ductile materials like Brass, Stainless steel or Mild steel so that Tool wear rate (TWR) can be minimized. • The value of ratio of TWR and MRR depends on kind of abrasive, work material and tool materials. N.Ram Kumar, Assistant Professor, CUFE.

  29. Mechanism of Material Removal N.Ram Kumar, Assistant Professor, CUFE.

  30. Material Removal Models in USM The following are the Material Removal Models used in USM 1. Throwing of abrasive grains. 2. Hammering of abrasive grains. 3. Cavitations in the fluid medium arising out of ultrasonic vibration of tool. 4. Chemical erosion due to micro –agitations. N.Ram Kumar, Assistant Professor, CUFE.

  31. N.Ram Kumar, Assistant Professor, CUFE.

  32. N.Ram Kumar, Assistant Professor, CUFE.

  33. Effect of Slurry, Tool and Work Material • MRR increases with slurry concentration. • Slurry saturation occurs at 30 to 40% abrasive/water mixture. • Material Removal rate drops with increasing viscosity. • The pressure with which the slurry is fed into the cutting zone affects MRR . • In some cases MRR can be increased even ten times by supplying the slurry at increased pressure. • The shape of the tool affects the MRR. Narrower rectangular tool gives more MRR compared to square cross section. N.Ram Kumar, Assistant Professor, CUFE.

  34. Conical tool gives twice MRR compared to cylindrical tool. • The brittle behavior of material is important in determining the MRR. • Brittle material can be cut at higher rates than ductile materials. N.Ram Kumar, Assistant Professor, CUFE.

  35. APPLICATIONS • Machining of cavities in electrically non-conductive ceramics • Used to machine fragile components in which otherwise the scrap rate is high • Used for multistep processing for fabricating silicon nitride (Si3N4) turbine blades • Large number of holes of small diameter could be machined. 930 holes with 0.32mm has been reported ( Benedict, 1973) using hypodermic needles • Used for machining hard, brittle metallic alloys, semiconductors, glass, ceramics, carbides etc. N.Ram Kumar, Assistant Professor, CUFE.

  36. Used for machining round, square, irregular shaped holes and surface impressions. • Used in machining of dies for wire drawing, punching and blanking operations • USM can perform machining operations like drilling, grinding and milling operations on all materials which can be treated suitably with abrasives. • USM has been used for piercing of dies and for parting off and blanking operations. • USM enables a dentist to drill a hole of any shape on teeth without any pain N.Ram Kumar, Assistant Professor, CUFE.

  37. Ferrites and steel parts , precision mineral stones can be machined using USM • USM can be used to cut industrial diamonds • USM is used for grinding Quartz, Glass, ceramics • Cutting holes with curved or spiral centre lines and cutting threads in glass and mineral or metallo-ceramics. N.Ram Kumar, Assistant Professor, CUFE.

  38. ADVANTAGES • It can be used machine hard, brittle, fragile and non conductive material • No heat is generated in work, therefore no significant changes in physical structure of work material • Non-metal (because of the poor electrical conductivity) that cannot be machined by EDM and ECM can very well be machined by USM. • It is burr less and distortion less processes. • It can be adopted in conjunction with other new technologies like EDM,ECG,ECM. N.Ram Kumar, Assistant Professor, CUFE.

  39. DISADVANTAGES • Low Metal removal rate. • It is difficult to drill deep holes, as slurry movement is restricted. • Tool wear rate is high due to abrasive particles. Tools made from brass, tungsten carbide, MS or tool steel will wear from the action of abrasive grit with a ratio that ranges from 1:1 to 200:1. • USM can be used only when the hardness of work is more than 45 HRC. N.Ram Kumar, Assistant Professor, CUFE.

  40. BEST OF LUCK N.Ram Kumar, Assistant Professor, CUFE.

  41. THANK YOU N.Ram Kumar, Assistant Professor, CUFE.

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