Fabrication of high accuracy micro-hole by micro-EDM under tool electrode spiral motion feed mode aided with fixed reference axial compensation

Abstract

The accumulation of debris in 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 of tool electrode spiral motion feed mode combined with fixed reference axial compensation (FRAC) is proposed to promote the evacuation of debris and improve the machining accuracy of micro-holes. Different depths of micro-holes in titanium alloy are drilled using the tool electrode linear feed mode and tool electrode spiral motion feed mode combined with FRAC and without compensation. The process parameters are optimized and determined by means of response-surface experiments. The results show that the tool electrode spiral motion feed mode can improve the debris evacuation more effectively than the tool electrode linear feed mode. The micro-hole without a cone at the bottom can be fabricated using the tool electrode spiral motion feed mode. The introduction of FRAC method can improve the depth error of micro-holes further. A high accuracy micro-hole with a depth error of only 0.21% can be fabricated efficiently under 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.