Influence of ECM pulse conditions on WC alloy micro-pin fabrication

Micro-pins with a large aspect ratio are required for micro tools and micro parts. We have proposed to use a neutral and less harmful electrolyte, NaNO3 aqueous solution to fabricate tungsten-carbide (WC) alloy micro-pins with ECM. The workpiece rotation and ultrasonic flushing were adopted during processing in order to obtain a higher machining accuracy and removal rate. However, it was found that oxidized substances adhered to the pin surface, which decreased the removal rate and machining accuracy. In order to reduce the oxidized substance adhesion to the WC alloy surface under the NaNO3 aqueous solution condition, bipolar pulses was then used, since it has been reported that a negative current has the effect to generate NaOH which can dissolve the oxide. Experiments were carried out by changing the pulse condition to investigate the influence of the positive and negative pulse width on the machining characteristics. The results show that a micro-pin with the diameter about 20 mu m was obtained in a very short time of 2.5 min. It is also found that using the bipolar pulse power supply is an effective way to reduce the adhesion of oxidized substances to the pin surface, and there exists an optimized pulse period for the micro-pin fabrication. (C) 2013 The Authors. Published by Elsevier B.V.