Electric Parameters Optimization And The Affected Layer Research In Cr12MoV WEDM

Wire electric discharge machining which has been developing from the1960’s hasbeen widely applied in the modern industry, especially in mould processing field. Qualityof the mould processing is one of the main influence factors for the die life. Thus themechanism of WEDM should be studied to guarantee the die life. It’s complicated andchangeable, having many influence factors, so the objective law is difficult to control.According to this situation, we have done some work about the affected layer and theinfluence law of the electric parameters on the technical index.First, taking the view that mould processing is one critical influence factor on dielife as the entry point, operational conditions and characteristics of machine tools areunderstood through onsite inspection in the mould enterprise. On the base of reading lotsof literature about mechanisms of WEDM, we are familiar with the current researchstatus in this field.Second, through analyzing and summarizing the literature information, and basedon the study, confirm the main electric parameters affect the processing effect need to becontrolled: current peak, pulse width, pulse intervals and servo voltage. Design anorthogonal experiment including four factors that each one has three levels, consideringfour processing index: processing speed, surface roughness, dimensional accuracy andwhite layer thickness. The result of the extreme difference and variance analysis showsthe influence law of all the electric parameters on each processing index, the order ofimportance of each factor and the optimized electric parameters combination. Thecomprehensive balance method is used to choose a best parameters combinationcomprehensively considering the four processing index.Finally, due to the affected layer produced in WEDM has an important influence onthe die life, we observe the micro morphology and microstructure, and measure residualstresses on the surface. The difference between WEDM and other processingtechnologies concretely concentrates on the affected layer produced in WEDM. Thesurface is covered with pockmarks, shallow craters, voids and micro cracks. The contentof austenite on the surface reaches as high as70%~80%, residual tensile stress is1000MPa or so, the white layer thickness is about20μm. Through the analysis of experimentdata, it is found that the surface residual stress and the white layer thickness are related.And try some methods to improve the stress state on WEDM surface.