|Achieving optimum machining accuracy in EDM die-sinking of particulate metal matrix composites
Machining -- Mathematical models
Hong Kong Polytechnic -- Dissertations
|Department of Mechanical and Marine Engineering
Department of Manufacturing Engineering
|[vi], 73,  leaves : ill. ; 30 cm
|An investigation has been made into the feasibility of using EDM die-sinking technique as an effective means of machining particulate metal matrix composites (MMC) with different silicon carbide content. An experimental design model, based on orthogonal arrays, is used to study a large number of control factors with a small number of experiments. Thus, the most economical process design can be accomplished at the smallest, affordable development cost. A practical way of developing the mathematical model leading to the finding of optimum parameter settings for producing the best possible precision machining results is presented. Verification experiments were also conducted to confirm the validity and predictive accuracy of the model. Electrical Discharge Machining, following a matrix experimental approach, was performed at a selected range of currents, pulse durations, pulse-off time and gap voltages with different combinations of tool materials and polarity. The measures of performance for the mathematical model are taken to be the relative wear rate, surface finish and metal removal rate. It is found that, in precision electrical discharge machining, copper electrodes perform better than graphite and tungsten-copper electrodes in terms of tool wear, and tools with positive polarity give higher material removal rate and lower tool wear ratio. The results of investigation also indicate that the higher the amount of silicon content in the MMC workpiece the more electrode wear will be induced.
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