UNIT I.pptx
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The document discusses various unconventional machining processes including abrasive jet machining (AJM), water jet machining (WJM), abrasive water jet machining (AWJM), and ultrasonic machining (USM). It provides an overview of the working principles, equipment used, process parameters, material removal rate, and applications of each process. Specifically, it explains that AJM uses a high-speed stream of abrasive particles to remove material, WJM uses a high-velocity water jet, AWJM adds abrasive particles to the water jet, and USM removes material using abrasive particles oscillated at ultrasonic frequencies. The document also discusses factors for selecting among these unconventional machining processes.
UNIT I.pptx
- 1. UNIT I UNIT I INTRODUCTION AND MECHANICAL ENERGY BASED PROCESSES Unconventional machining Process – Need – classification – merits, demerits and applications. Abrasive Jet Machining – Water Jet Machining – Abrasive Water Jet Machining - Ultrasonic Machining. (AJM, WJM, AWJM and USM). Working Principles – equipment used – Process parameters – MRR- Applications.
- 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 1. Unconventional Machining process or Non Traditional Machining Process 2. Unconventional Forming process
- 7. Unconventional Manufacturing process 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 interval
- 8. Need 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. CLASSIFICATION
- 11. 12 Unconventional Machining Processes – Based on Energy
- 12. 13 Unconventional Machining Processes – Based Mechanism
- 13. 14 Unconventional Machining Processes – Based on Energy used for Removal
- 14. 15 Unconventional Machining Processes – Based on Transfer of Energy
- 15. 16 Mechanical Based Processes 1. Working principles 2. Equipment used 3. Process parameters 4. MRR 5. Variation in techniques used 6. Applications AJM WJM AWJM USM
- 16. 17 Electrical Based Processes 1. Working principle 2. Equipment used 3. Process parameters 4. Surface finish & MRR 5. Electrode/Tool 6. Power & Control circuits 7. Tool wear 8. Dielectric 9. Flushing 10. Applications Electrical EDM WEDM
- 17. 18 Chemical & Electrochemical Based Processes 1. Working principles 2. Etchants & Maskants 3. Techniques of applying maskants 4. Process parameters 5. Surface finish & MRR 6. Electrical circuits in case of ECM 7. Applications CHM ECM ECG ECH
- 18. 19 Thermal Based Processes 1. Working principles 2. Equipment used 3. Types 4. Beam control techniques 5. Applications LBM PAM EBM
- 19. Selection Process • Selection Process is based of following parameters – Physical Parameter – Shapes to be Machined – Process Capability – Economic consideration
- 20. Physical Parameter fluid Parameter ECM EDM EBM LBM PAM USM AJM Potential, V 5- 30 50-500 200 x 103 4.5 x 103 250 220 220 Current, A 40,000 15-500 0.001 2 600 12 1.0 Power, kW 100 2.70 0.15 20 220 2.4 0.22 Gap, mm 0.5 0.05 100 150 7.5 0.25 0.75 Medium Electrolyte Die electric Vacuum Air Argon Nitrogen Abrasive grains Work Material M/C diff Tungsten carbide All Mtl All Mtl All Mtl Tungsten HSS carbide
- 21. 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
- 22. Process Capability or Machining Characteristics Process MRR ( mm3/s ) Surface Finish (μm) Accuracy (μm) Power (kW/ cm3/ 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
- 23. Process Economy Process Capital Cost Tool & Fixtures Power Requirement 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 Convention al V. Low Low Low V. Low
- 24. Limitation • More Expensive • Slow Process • Commercial
- 26. 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.
- 27. 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
- 31. Typical AJM Parameters Abrasives used. Aluminum Oxide (Al o Silicon Carbide (Sic) 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)
- 32. 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
- 33. ADVANTAGES Low capital cost Less vibration No heat generated in the work piece Eco friendly Only one tool is required
- 34. DISADVANTAGES Low metal removal rate Abrasive powder can not be reused The machining accuracy is poor Nozzle wear rate is high
- 35. Water Jet Machining Principle In WJM, the high velocity of water jet comes out of the nozzle and strikes the material, its pressure energy is converted into kinetic 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.
- 38. 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
- 39. Advantages of water jet cutting There is no heat generated in water jet cutting; which is especially useful for cutting tool steel 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
- 40. 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.
- 41. 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.
- 42. 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.
- 45. 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
- 46. 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.
- 47. Disadvantages of Abrasive water jet cutting Cannot drill flat bottom Cannot cut materials that degrades quickly with moisture
- 48. 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.
- 49. 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).
- 52. 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 Frequency Actual M R R High amplitude Low frequency High frequency
- 53. CONTD… EFFECT `VELOCITY` MRR is Directly Proportional to the Particle Velocity M R R Feed force Mean grain diameter Surface rough
- 54. CONTD.. EFFECT OF STATIC LOADING OR FEED FORCE: - MRR increases with an increase in feed force. EFFECT OF GRAIN SIZE: - Grain size increases with an increase in MRR
- 55. 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.
- 56. USMApplications 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 Hard, brittle work materials such as ceramics, glass, and carbides.
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