Subject: Advanced Manufacturing Process
Unit 2: Part 1: Ultrasonic Machining
Definition of USM:
Ultrasonic machining (USM) is a machining or material removal process in which material is removed from the work- piece by brittle fracture caused by impact of abrasive grains due to tool vibration at very high frequency.
Construction of USM setup:
A typical USM setup consists of following essential elements:
a. Power Supply (AC)
b. Tool Feed Mechanism
c. Abrasive Slurry
d. Abrasive slurry supply & recirculation system
e. Working Tank or, Basin
• At first, the workpiece is assembled in the fixture inside the working tank & the tool is brought closer to it.
• Then the power supply is switched on & the tool starts to vibrate.
• An abrasive gun or nozzle supplies an abrasive slurry in the gap between the tool & the workpiece at a definite pressure.
• As the tool vibrates it produces impact force upon the abrasive particles & these particles cause brittle fracture upon the workpiece surface & it causes material removal.
• The tool feed mechanism, which is fitted with the tool, feeds the tool against the workpiece maintaining a constant gap between them, as the material removal progresses.
• The abrasive slurry carries away the wear out metal particles from the work area & gets collected at the bottom of the working tank.
• From the working tank it is then supplied to the slurry tank & from the slurry tank it is again supplied to the work area with the help of a slurry pump.
Process Parameters in USM
• Amplitude of tool vibration (a): 15 – 50 μm
• Frequency of tool vibration (f): 15 – 30 kHz
• Abrasive grit size: 15 μm – 150 μm
• Abrasive material: Al2O3, SiC, B4C, Diamond.
Advantages of USM
• Drilling circular & non-circular holes in very hard materials like carbides, ceramics etc.
• Best suited for hard & brittle materials.
• Glass can be machined by USM.
Disadvantages of USM
• Low material removal rate (MRR).
• Shorter tool life as tool wear is high.
• Depth of holes & cavities formed by USM are small.
Applications
• Ultrasonic machining is ideal for materials like ceramics, glass, and certain types of hardened metals, which are challenging to machine with traditional methods. Example: Ceramic substrates for electronic devices.
• The electronics industry requires extremely precise machining of brittle semiconductor materials, which USM can achieve without thermal or mechanical damage. Example: Shaping and cutting silicon wafers used in semiconductors.
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