CHARACTERISTICS OF A HYBRID PROCESS OF EDM IN GAS COMBINED WITH ULTRASONIC VIBRATION AND

AJM

PRESENTED BY - SAYAN MALLICK ROLL NO - 16ME61R14

M.TECH (1st YEAR)MANUFACTURING SCIENCE

IIT KHARAGPUR

Contents• Objective• Introduction• Process description• Experimental Method• Results & Discussion• Conclusion• References

Objective• To describe a new Non conventional

machining process , which is a combination of developed hybrid EDM in gas combined with AJM and USV, and studying its advantages.

• To discuss the AJM and EDM process in detail so as to compare it with above process.

continued• Advantages of using compressed dielectric

media over the conventional dielectric used in EDM.

• To show that material removal rate and surface roughness is much better than general EDM and AJM process.

Principle of ELECTRO DISCHARGE MACHINING

EDM is a controlled metal-removal process that is used to remove metal by means of electric spark erosion.

Spark is produced between the shortest distance of tool & workpiece. Dielectric media like kerosene reveals prominent machining performance . A pre shaped or formed electrode (tool),usually made from graphite or copper, is

shaped to the form of the cavity it is to reproduce.

Principles of AJM process Abrasive Jet Machining is an abrasive blasting machining process that

uses abrasives propelled by a high velocity gas to erode material from the work piece.

High pressure air or gas is supplied to the mixing chamber containing fine abrasive particles.

This mixture is passed through the small nozzle and the erosion caused by it’s impact at high speed.

The combined hybrid machining of EDM With USV and AJM

Working process A die-sinking EDM machine with transistor controlled circuit integrated

with a fixture of specific USV is used. Fixture is made of fiber glass reinforced plastic. The main purpose was to explore the effects of main input variables on

machining characteristics of the hybrid process of EDM combined with USV and AJM for SKD 61 tool steel.

Dimension of tool is 15 mm × 5 mm. The dielectric media were adjusted by a regular pressure valve. The molten material is removed as fast as possible by high speed air

jet.

Experimental Method

Experimental Results

Continued

Continued

Why MRR is increased? The MRR obtained by the hybrid EDM process was higher than that by EDM in gas. The mechanism of AJM & USV incorporated into the machining gap would improve the molten material and machining debris expelling from the machined surface and preventing the secondary sparks during the machining. O2 gained the highest MRR because of the violent oxidation induced by O2. And Ar got the lowest due to the suppressing feature of inert gas.

Relationship of pick current with MRR and EWR

• As discussed previously, ultrasonic vibration of workpiece creates cavitation and intensive micro ejecting micro-streams, can be acting as a pump, causing better flushing in the spark gap, preventing the carbon and graphite debris deposition on the machined surface.

CONCLUSION• The machining characteristics such as MRR , EWR, and SR obtained by the process

were compared with that obtained by process of EDM by gas.• The machining characteristics i.e. MRR , EWR, and SR increased with an increase

of peak current.• Oxygen , the dielectric media generated the highest MRR and Argon produced the

lower.• The morphology caused by the EDM in gas combined AJM illustrates obvious micro

pores on the machined surface.• The thickness of the recast layer obtained by the EDM in gas incorporated with

AJM was thicker than that obtained by the developed hybrid EDM process.

References• A. Ghosh and A.K. Mallik, Manufacturing Science. p.

366. Ellis Horwood, Chichester (1986).• Lin YC, Chen YF, Lin CT, Tzeng HJ. EDM

characteristics associated with electrical discharge energy of cemented tungsten carbide.

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