Experimental investigation to improve the efficiency and surface integrity of deep micro-hole machined by micro-EDM

Micro-EDM is an important method to manufacture deep micro-hole, which has been widely used in aerospace and industrial fields. However, the presence of discharge debris reduces the machining efficiency and stability in the drilling process. In the study, the machining strategy was explored to meet the requirements of high efficiency and quality. Firstly, the process parameters are optimized using the Taguchi method in response to the machining efficiency. On this basis, a machining strategy of electrode jump motion combined with planetary motion is proposed, and the electrode motion parameters are optimized. The effects of electrode motion parameters, including eccentric radius of planetary motion (R), jump height (H), jump interval (I), and the starting position of electrode jump (L), were assessed through analysis of variance. To improve the quality of the deep micro-hole, an in situ grinding method was used. The results showed that L and R are significant parameters for machining efficiency. Furthermore, the influencing mechanism of electrode motion parameters on machining efficiency was discussed, and the optimal parameter combinations were obtained by signal-to-noise ratio analysis. Through in situ grinding, the quality of micro-hole entrance was significantly improved, the inner surface defects were considerably reduced, and the average surface roughness was reduced from 0.25 to 0.16 mu m.