Abstract
In micro-electrical discharge machining (micro-EDM), it is crucial to maintain an optimal gap between tool electrode and workpiece for stable and continuous machining. Accurate and real-time state detection is a prerequisite for the implementation of gap servo control. A novel monopulse-recognition based state detection method for self-adjustable servo control is proposed. This detection method discriminates pulse types with high precision by utilizing unique monopulse characteristics. The detection circuit avoids capacitive filtering but integrates multi-level nanosecond comparators to overcome the trade-off between accuracy and real-time performance caused by improper time constant RC in conventional average voltage detection method. The self-adjustable servo control iteratively refines the servo speed to approach the optimal value, forming a macroscopic stair-stepping pattern complemented by microscopic fine-tuning self-adjustment. Orthogonal experiments of micro-hole machining demonstrate that it achieves a significant 42% improvement in machining efficiency with a 3% increase in the effective discharge ratio compared to conventional threshold servo control. Applying to micro 3D structure scanning, a precise and robust electrode wear model considering varying wear rates at different scanning positions is established, forming an effective-pulse based depth-constrained algorithm insensitive to scanning speed. It effectively suppresses the recurrence of crater and bump errors on the machined surface.