Experimental investigation into tool wear behaviour of line-array tool electrode during the electrochemical discharge micromilling process

Abstract

A tool-workpiece gap during the electrochemical discharge machining (ECDM) process is a critical parameter for successfully fabricating microchannels using line-array tool electrodes. Tool wear during the ECDM process increases the tool-workpiece gap and result in non-uniform array microchannel depths or intermittent machining due to reduced heat flux transferred into the workpiece. Hence, proper selection of a tool material that results in uniform tool-tips height/tool-workpiece gap for a longer machining time is essential, especially for the line-array tool electrodes. In this article, the tool wear behaviour of four different materials, i.e., brass, SS304, molybdenum, and tungsten, during fabrication of longer (>15 mm) and deeper (>200 μm) array microchannels using multi-pass ECDM process is reported. The tool wear behaviour at varying machining time/pass numbers was investigated, keeping all other process parameters constant. The experimental results found that the brass electrode's wear rate was relatively faster, and the line-array tool electrode becomes unusable for the ECDM process after 15 min of total machining time. The wear behaviour of molybdenum and tungsten tool materials was similar and resulted in intermittent or no microchannels formation after 35 min of machining time. At the electrolyte-air interface, necking of the tips and subsequent breaking at different machining times was observed for the brass, molybdenum, and tungsten tool materials. Comparatively uniform tips height, microchannel depths, and negligible necking were observed for the SS304 tool electrode after 65 min of machining time. Therefore, SS304 is a suitable tool material for fabricating longer and deeper array microchannels using the multi-pass ECDM process. Moreover, the fabrication of a dual serpentine flow field was demonstrated in the glass workpiece using customized SS304 line-array tool electrodes.