微放電高深寬比圓孔加工策略

Abstract

放電加工是一種適用於應用熱熔融金屬之加工方式，由於其加工程序簡單不繁雜，因此常使用於微小孔的加工，但其加工中會產生渣粒，使得微孔加工過程到達一定的加工深度時，加工液進入極間和放電渣排出都有難度，進而限制微細孔徑之加工深度。本研究以噴流位置與螺旋角差異，改善加工液體流通，得到上噴流方式深寬比較下噴流方式大；而螺旋角小對加工深圓孔效果好。研究繼續探討螺旋角應用於傾斜式進給方式配合震動輔助加工高深寬比圓孔之差異，此傾斜進給方式因微孔放電之進給速度低，而使得在接近水平的傾斜加工時，垂直方向幾乎僅為進給速度的十分之一速度，而且幾乎所有三軸機台皆受到此限制，導致其加工後之圓孔呈現長橢圓型。為解決傾斜式進給加工時圓孔呈現拉長型橢圓，其橢圓度達50%以上之孔不圓問題，本研究提出修正軌跡策略，成功以改變進給角度方向，使進給加工時，確實在設定軌跡內進給加工，如此使得圓孔橢圓度可維持在10%以內，但本方式會略為降低深寬比。最終在搭配傾斜式改良策略下，以傾斜向下10度，成功以圓柱電極，在6061鋁合金成功加工出橢圓度0.2%，深寬比16之圓孔；成功以正轉式螺旋角17度電極，在6061鋁合金上加工出橢圓度8%，深寬比20.5之圓孔；並成功以圓柱電極，在304不鏽鋼成功加工出橢圓度10%，深寬比20之圓孔。

Micro-EDM is a simple way of machining which is commonly used in conductive metal materials and widely employed in micro-hole drilling. However, when drilling to a certain depth, some difficulties pertaining to dielectric fluid entering the discharge gap and the remove of debris will arouse. Therefore the depth of micro holes is limited. In order to solve the difficulties confronted when dielectric fluid entering the discharge gap and the remove of debris, this study proposed a method of micro-hole drilling process based on micro electro-discharge machines with dielectric jet position and helix angle. A deeper micro hole can be achieved when above dielectric jet posi-tion drilling process and smaller helix angle electrode can achieve deeper and more circular hole. While machining micro holes with inclined-feeding and vibra-tion-assisted components in 10-degree-downward, vertical-feeding is almost tenth of inclined-feeding, causing the machined holes with ovality 50% on almost all three-axis platform. In order to solve the problem, this study proposed a method of a feeding-angle modified imputation Strategy. The ovality of a 10-degree-downward inclined feeding can be reduced to 8% and aspect ratio of 16 with cylinder electrode, and the ovality can be reduced to 0.2% and aspect ratio of 20.5 with 17-degree helix angle electrode.