粉末放電加工(Powder-Mixed Dielectric EDM)可有效改善一般放電加工的表面粗糙度且可同時進行加工表面的改質,為一具有高度發展潛力的加工技術,然而其加工機制尚未解明,以致無法掌握其加工特性,限制了該技術的發展。本研究探討介電液中不同粉末材料的相異運動行為,以及粉末運動行為對於放電加工的影響,希望藉由粉末的運動行為解明添加不同材料粉末其加工特性形成的機制。研究首先觀察不同材料的粉末在平行電場中的狀態,發現不同粉末材料會有不同的運動行為與聚集型態,在分析多種粉末材料的運動行為特性後建立一套有系統的粉末運動行為分類,然後探討在施加電場的環境下,電源電壓、粉末濃度與電極間隙對於粉末運動行為的影響,以及粉末運動行為對於放電現象如放電間隙與放電火花發生位置的影響,然後實際進行放電加工實驗驗證粉末運動行為差異對於放電加工特性的影響,最後提出粉末放電加工可能之加工機制。 研究結果顯示,粉末的運動行為受到材料種類、粉末濃度、電源電壓與電極間隙的影響,若粉末的運動行為以聚集成鍊狀為主,放電火花發生於兩極表面的機率較高,若以聚集成團狀為主則放電火花發生於兩極表面的機率較低,而不同粉末濃度鋁粉、鈦粉與鎳粉放電火花發生於兩極表面的機率也會改變。研究中利用上述現象解明添加不同粉末材料進行粉末放電加工時,電極間隙、粉末材料與濃度影響表面粗糙度與材料移除率的機制。
Electrical discharge machining (EDM) are generally employed in the die machining field. But the surfaces produced by EDM usually have craters and a matt appearance. Powder-Mixed Dielectric EDM (PMD-EDM) has been found to not only produce very fine finish surfaces but also reduces significant machining time for fine finishing. However the mechanism was not fully understood yet, which makes the development of this technology become restricted. In this study, the relationship between powder activities and characteristics of PMD-EDM has been reveled. We found the surface roughness and material removal rate are both higher when metal powder gathered as a chain than clustered together. The reason is considered that sparks happen more probably on electrode surfaces for chained together than for cluster together. By the way, the concentration of powder and strength of electric field will influence the activities of powders. When the powder concentration getting higher, the particles tend to cluster together. And powder particles will chained together easier while stronger electric field.