Simulation of Die-Sinking EDM by Discharge Location Searching Algorithm

本研究采用一种新开发的模拟算法来模拟凹模电火花加工侵蚀的工件几何形状，以逼真地模拟间隙中发生的实际现象。该算法是对以下步骤的简单重复：1.确定介电击穿强度最低的下一个放电位置；2.移除刀具和工件电极；3.分布碎屑颗粒；4.送入工具电极。模拟考虑了工具电极磨损、间隙宽度分布、工具电极的曲率和倾角、磨屑颗粒浓度等多种影响因素，所有这些因素都以非常复杂的方式相互影响。加工后刀具电极和工件的几何形状以及间隙宽度分布的仿真结果与平面和正方形表面加工的实验结果吻合较好。本研究的另一个目的是开发一种求解反问题的仿真方法，在该反问题中可以得到刀具电极的形状，从而获得最终的工件形状。在该反向模拟中，考虑到工件和工具电极的初始形状与其在正向模拟中的最终形状相同，使用与上述正向模拟中所使用的相同的算法。此外，以相反方向向工具电极馈送工作件，并且彼此交换关于分别属于工具电极和工作件的每脉冲放电的去除量的数据。作为反向模拟的结果，在正向模拟中，工具电极和工件的形状被恢复到初始形状。

This research deals with simulation of workpiece geometry eroded by a die-sinking EDM using a newly developed simulation algorithm for faithful imitation of the actual phenomena which are occurring in the gap. The algorithm is a simple repetition of the procedure which is comprised of : 1. determining the next discharge location where the dielectric breakdown strength is lowest, 2. removing the tool and workpiece electrodes, 3. distributing the debris particles, and 4. feeding the tool electrode. The simulation takes into account a variety of influential factors such as tool electrode wear, gap width distribution, curvature and inclination of the tool electrode, and debris particle concentration, all of which affect each other in a very complex manner. The simulation results for the geometries of the tool electrode and the workpiece after machining and for the gap width distribution agree well with the experimental results for machining of a flat and square surface.Another aim of this research is to develop a simulation method to solve the inverse problem in which the tool elctrode shape to achieve the final shape of the workpiece can be obtained. In this inverse simulation, the same algotithm as used in the forward simulation which is described above is used considering the initial shapes of the workpiece and tool electrode as equal to their final shapes in the forward simulation. Moreover, the workpiece is fed in the opposite direction toward the tool electrode, and the data concerning the removal volumes per pulse discharge pertaining to the tool electrode and workpiece, respectively, are exchanged each other. As result of the inverse simulation, the shapes of the tool electrode and workpiece were restored to the initial shapes in the forward simulation.