Fabrication of high-accuracy micro-holes in micro-EDM under tool electrode spiral motion feed mode combined with fixed reference axial compensation

The accumulation of debris between the inter-electrode gap caused by inefficient flushing during the micro-electrical discharge machining (micro-EDM) process leads to severe tool electrode wear and decreases the machining accuracy of micro-holes. In this study, a novel method using tool electrode spiral motion feed mode combined with fixed reference axial compensation (FRAC) is proposed to promote the debris evacuation and improve the machining accuracy of micro-holes. Different depths of micro-holes in titanium alloy were drilled using the tool electrode linear motion feed mode and spiral motion feed mode combined with FRAC and without compensation. The process parameters were optimized and determined by means of response-surface experiments to improve machining accuracy and machining efficiency. The results showed that the tool electrode spiral motion feed mode can improve the debris evacuation more effectively than the tool electrode linear motion feed mode. The micro-holes without cone at the bottom could be fabricated using the tool electrode spiral motion feed mode. The introduction of FRAC could improve the depth error of micro-holes furtherly. A high accuracy micro-hole with a depth error of only 0.21% could be fabricated efficiently under the condition of the optimal process parameters. The tool electrode spiral motion feed mode combined with FRAC has an obvious advantage in the fabrication of high accuracy micro-holes during the micro-EDM process.