Servo control optimization of micro discharge gap and its reasonable matching with scanning speed in servo scanning 3D micro EDM based on threshold control method

3D scanning (or milling) micro electrical discharge machining (EDM) can machine 3D microstructures with free-form surfaces on metal/alloy materials. The novel process of servo scanning 3D micro EDM (SS-3D micro EDM) provides a practical solution for the real-time online compensation of micro tool-electrode wear. However, the key parameters of servo scanning are difficult to be optimized by a large number of trial-and-error experiments. This causes the unstable and destructive process of frequent short circuit, less cutting, and collision of tool electrode and workpiece because the optimization still lacks theoretical basis. In this research, considering the actual influence of delay response time of a machining system, we analyzed the process of servo control of machining gap according to threshold control method and the matching effect with scanning speed. Boundary models were established for providing the theoretical basis of the servo control speed and its reasonable matching with the scanning speed. Furthermore, the optimization procedures with the proposed boundary models for the reasonable matching of these parameters were proposed and verified by machining experiments.