Layer Depth Constrained Servo Scanning EDM for 3D Microstructures

Abstract

Servo scanning 3D micro electro discharge machining (3D SSMEDM) method can automatically compensate the axial wear of micro rod-electrode in real time by preferably keeping a discharge gap. However, the depth errors of 3D SSMEDM were even to 10% due to the accumulation of layers’ thickness errors. In addition, the machining process with keeping the discharge gap must bring the initial errors of inclined or uneven workpiece-surfaces into dimensional errors, and also cause that 3D structures cannot be machined on the workpieces with a hollow area. In this study, a layer depth constrained algorithm (LDCA) is proposed to solve the above problems. LDCA strategy is to control an electrode-feed maximum at every scanning spot during 3D SSMEDM processes. By using LDCA, machining experiments were carried out on several typical micro cavities <1mm of rectangle, truncated cone and cross structure. The experimental results show: The accumulation errors of the layers’ thickness can be avoided, so the machined depth errors can be controlled <2μm. The designed 3D structures can be machined in the workpieces with unknown hollow areas.