Micro-EDM of micro-stepped hole based on the wear of micro-bit

Applying different micro-bits with different sizes to carry out step-by-step drilling is a common technique to obtain micro-stepped holes. However, the possibility of repeated misalignments in the clamping of micro-bits will affect the machining accuracy of the micro-stepped holes. Furthermore, for difficult processing materials such as die steel and cemented carbide, it is difficult to obtain ideal machining results through drilling. Under this background, micro-stepped hole was processed on die steel based on the electrical discharge machining (EDM) wear of micro-bits. Firstly, a high-speed rotating micro-bit was used to perform micro-EDM on die steel to obtain a basic micro-hole. During the micro-EDM process, the micro-bit was worn and thus its length was reduced. Secondly, the worn micro-bit shook along a defined axis to carry out micro-EDM on the die steel workpiece, thus machining micro-stepped hole on the basic micro-hole. This method avoided the clamping error of micro-bit found in other techniques and improved machining accuracy of micro-stepped hole. Through the analysis of variance (ANOVA) of processing parameters and the establishment of surface response model, the appropriate processing parameters were selected. Finally, under the action of appropriate processing parameters, micro-stepped hole was obtained by the proposed method.