Improving EDM performance by adapting gap servo-voltage to machining state

•Proved arcing ratio is the index used in the control system to compromise machining rate and machining stability.•Came up with a theorem for improving MRR with consideration of machining stability: forcing arcing ratios to follow an arcing ratio expectation.•Proposed a control strategy for the adaptive gap servo-voltage control system.•Achieved a machined depth 3 times deeper than conventional EDM and 2.2 times deeper than the same Tool assisted by another adaptive electrode-discharge-time.•Achieved a much higher MRR than the other two.