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|Study on the Influence of Process Parameters of WEDM on the Machinability of D2 Steel
|WEDM;MRSN;D2 steel;ANOVA;mechanical engineering;med;production engineering
|Wire Electrical Discharge Machining process has significantly improved with the latest requirements in the industry. Wide capabilities of WEDM have allowed it to be used in production of aerospace and automotive industries. WEDM is a process in which a thin wire as electrode is used to transforms electrical energy to thermal energy which melts and removes the material. This process can be used to machine high strength alloy steels, conductive ceramics and aerospace materials. The literature survey reveals that little research has been conducted on the comparison of wires to machine alloys having high hardness. Most of the research has been conducted with plain brass wire. It is well known fact that high material removal rate and high surface finish could not be obtained simultaneously. Brass wires produce high MRR but give poor surface finishing. So, the purpose of this dissertation is to optimize the process parameters of WEDM using two different wires; plain brass and zinc coated brass, of same diameter and D2 steel (hardened) is used as workpiece material due to its high hardness and wide use in mechanical industry. Pilot investigation is performed to find out significant factors and their levels by varying one factor at a time (OFAT approach). Taguchi‟s methodology is used to perform main investigation. S/N ratio and ANOVA techniques are used to examine results. L18 mixed OA is used with one factor at six levels and three factors at three levels. Peak current is varied at six levels. Factors for experiments are chosen by performing pilot study on maximum factors available and subsequently significant factors are considered. The four factors; Pulse on Time, Pulse off Time, Peak Current and Spark Gap Set Voltage are considered to examine their effect on performance characteristics that are material removal rate, kerf width and surface roughness. The size of the specimen machined is 10 mm* 10mm* 10mm. Two trials are taken for each experiment and total number of specimen machined is 72. The results were analyzed for single response optimization using Taguchi‟s delta statistic utility to find the optimum levels of four parameters for high material removal rate, low surface roughness and low kerf width. Multi response optimization is performed using multiple response signal noise (MRSN) technique. As per industrial machining requirement, both material removal rate and surface roughness are equally important. In this technique, equal weightage is given to material removal rate and surface roughness, so that optimum levels of parameters can be obtained for high MRR and low surface roughness simultaneously. The result data for material removal rate, kerf width and surface roughness obtained from the machining with both wires i.e. plain brass wire and zinc coated brass wire, is compared to examine parametric effect of both wires. The comparative study reveals that zinc coated wire is more superior in case of material removal rate and surface roughness as compared to plain brass wire. The surface topography is examined on SEM to find out the thickness of recast layer obtained when machined with both wires and results are also compared for lesser recast layer. The SEM images and the EDX spectroscopy reveals the addition of different materials to the workpiece surface from wire surface during machining which in turn reveals the underlying mechanism of the formation of craters, debris and material deposited in the machined surface.
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