Research On Machining Mechanism Of Difficult-to-conductive Hard And Brittle Materials By Electrochemical Discharge Machining

With the rapid development of science and technology, difficult-to-conductive hard and brittlematerials such as single crystal silicon, optical glass and Al2O3ceramic play a more and moreimportant role in electron, photics aerospace and other modern high technology industries. There aremany problems by machining methods, because the high brittleness and low fracture toughness ofdifficult-to-conductive hard and brittle materials. Electric discharge machining relies on electricalenergy and thermal energy to achieve the purpose of material removal, but the conductivity is verypoor even non-conductive, so it can’t be an electrode directly, spark discharge machining can beachieved through electrolysis. Specified to great energy loss, low machining efficiency and highgrinding wheel cost which brought by traditional electrochemical discharge machining, a new methodnamed mist-jetting electrochemical discharge machining with slotted metal wheel as an electrode andconductive sheet metal which pressed to workpieces surface as another electrode is proposed, themainly research contents are as follows:(1) Physical process of electrochemical discharge machining is analyzed, and the heat transferphysical model is constructed, then energy distribution relationship and thermal distribution areanalyzed, and a series of measures and methods such as atomization of electrolyte, optimal structuredesigning of slotted metal wheel, optimization of size and position for conductive sheetmetal, androtation speed optimization of slotted metal wheel are proposed.(2) Three kinds of difficult-to-conductive hard and brittle materials such as single crystal silicon,optical glass and Al2O3ceramic are researched with the method of mist-jetting electrochemicaldischarge, the machining principle is expounded, machining discharge waveforms and surfacemicrostructures are analyzed, and the machining mechanism is researched.(3) Electrochemical discharge machining equivalent circuit model was set up by resistors, diodeand switch, and then the correctness is verified through the analysis of average current characteristics.(4) Average current-voltage curve and relation curve between rotation speed of slotted metalwheel and average current of single crystal silicon and Al2O3ceramic are analyzed, suitableprocessing range are confirmed which include: machining voltage should be selected in the stablespark discharge stage, it should be greater than200V when the workpieces are semiconductormaterials, and greater than220V when the workpieces are insulation materials; the rotation speed of slotted metal wheel should be selected in the spark discharge role stage which is usually controlled inthe range of1200～1800rpm.(5) The effects of parameters such as peak voltage, pulse width, pulse interval, electrolyteconcentration and rotation speed of slotted metal wheel on material removal rate and surfaceroughness of single crystal silicon, optical glass and Al2O3ceramic are researched in detail, then thenarrow slot entities are machined.