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Elements of Ultrasonic Machining by Himanshu Vaid
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- 2. PRINCIPLE • The machiningzone (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. 18-10-2016 AKHIL MANHAS
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- 4. EQUIPMENT • Ultrasonic Machiningconsists of : 1.High Power sine wave generator. 2.Magneto-strictive Transducer. 3.Tool Holder. 4.Tool. 18-10-2016 AKHIL MANHAS
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- 6. High Power SineWave Generator • This unit converts low frequency (50 Hz) electrical power to high frequency (20kHz) electrical power. 18-10-2016 AKHIL MANHAS
- 7. TRANSDUCER • The highfrequency 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-stricitve transducer. 18-10-2016 AKHIL MANHAS
- 8. MAGNETOSTRICTIVE TRANSDUCER • Thesetransducer 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. 18-10-2016 AKHIL MANHAS
- 9. TOOL HOLDER ORHORN • 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. 18-10-2016 AKHIL MANHAS
- 10. TOOL • Tools aremade 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. 18-10-2016 AKHIL MANHAS
- 11. Mechanism of MaterialRemoval 18-10-2016 AKHIL MANHAS
- 12. Material Removal Modelsin 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. 18-10-2016 AKHIL MANHAS
- 13. APPLICATIONS • Machining ofcavities 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. 18-10-2016 AKHIL MANHAS
- 14. • Used formachining 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 pain18-10-2016 AKHIL MANHAS
- 15. • Ferrites andsteel 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. 18-10-2016 AKHIL MANHAS
- 16. ADVANTAGES • It canbe 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. 18-10-2016 AKHIL MANHAS
- 17. DISADVANTAGES • Low Metalremoval 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. 11/19/16 N.Ram Kumar, Assistant Professor, CUFE.
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