Effect of Wire Electrode Materials on Performance Characteristics for Wire Electrical Discharge Machining of Metal Matrix Composite Material

Composite materials are the advanced materials which are widely used in manufacturing industries. The most commonly used composite materials are metal matrix composites. Due to the presence of abrasive reinforcing particles, traditional machining of these causes severe tool wear and hence reduces the life of cutting tool. Wire electrical discharge machining (WEDM) is quite successful for machining of metal matrix composites. Wire Electrical Discharge machining is a specialized thermal machining process capable of accurately machining parts of hard materials with complex shapes. The selection of process parameters in WEDM to obtain greater accuracy or cutting efficiency is still not fully solved due to the complicated stochastic process mechanisms with the most recent CNC wire cut EDM. One of the main research fields in WEDM is related to the improvement of the process productivity by avoiding wire breakage. The different factors viz., decrease in flushing pressure, inefficient removal of erosion debris and some other types of stochastic phenomena that occur during the machining process can lead to the breakage of wire electrode. In such cases, the wire has to be looped again by stopping the machining process, which leads to an undesired time waste. Before wire breaks, wire breakage has to be predict by diagnosing in advance low quality cutting regimes in order to perform an on line readjustment of the machine parameters. Worn electrode state dramatically affects the texture of the machined surface. Wire electrical discharge machining has been found to be a promising machining technique for obtaining desired dimensional accuracy and surface finish on hard and tough materials. Wire electrodes used in WEDM are the core of the system. WEDM is extensively used in machining of conductive material. In this study the effect of different wire electrode materials on dimensional accuracy and surface finish for wire electrical discharge machining of metal matrix composite material were investigated. The experiments were conducted under the following process parameters viz., pulse on-time, pulse off-time, current and wire feed speed. For the experiment the aluminium 6061 alloy with 0%, 5%, and 10 % of silicon carbide (SiC) reinforcement material was used. To conduct the experiment CNC wire EDM machine with two different wires viz., molybdenum and brass wire was used. L9 Taguchi orthogonal array technique was used to design the experiment. Experimental results indicate that for better surface finish and dimensional accuracy of Al6061 alloy, the brass wire is more suitable. Good surface finish and dimensional accuracy can be obtained with molybdenum wire in Al-SiC composite material. Increasing percentage of silicon carbide in aluminium 6061 alloy increases the variation in surface finish and dimensional accuracy. Wire wear rate of both brass and molybdenum wire is increased with increase in percentage of silicon carbide.