Improving Machining Localization in Abrasive-Assisted Electrochemical Jet Machining of SiCp/Al Composites using Large Standoff Distance

The electrochemical jet machining usually applies a very small standoff distance (SOD) between nozzle and workpiece in order to achieve a high anode dissolution rate. However, this small machining gap can cause intensive stray corrosion and secondary dissolution during the process, and consequently result in worse machining localization. This study investigated machining localization in abrasive-assisted electrochemical jet machining of SiCp/Al composites using large SOD. The analysis shows that using large SOD is expected to reduce stray corrosion of the matrix in the initial phase of the machining, and thereafter avoid secondary dissolution due to preventing the nozzle from re-contacting with reflected jet flow in the further phases. The experimental results agreed well with the analysis in processing 20%-SiCp/Al and 45%-SiCp/Al composites using the SOD ranged between 2 and 8 mm. It was found that the achieved entrance size significantly reduced with increases of the SOD, regardless of electrolyte type, processing time and abrasive concentration. The achieved aspect ratio due to relatively larger SOD will exceed that due to smaller SOD after a longer processing time. The investigation suggests that better machining localization can be obtained using relatively larger SOD and longer processing time compared to using usual narrow SOD.