Optimization of material removal rate in wire electric discharge grinding for micro machining of tungsten electrodes

摘要

Manufacture of micro cylindrical electrodes has been proposed using the CNC wire electric discharge machine by attaching a rotary spindle. The work material tungsten is chosen due to its wide spread uses in aerospace, electronics and health care areas. In this work, tungsten work-piece of empty set2.0 mm is machined to empty set0.4 mm by WEDG by considering the factors such as spindle speed, peak current, pulse off time and wire speed. The full factorial experimental design has been used to find out the effect of process parameters. The results are further analyzed through analysis of variance (ANOVA) and surface plots for confirmation. It was found that spindle speed, pulse off time and wire speed has higher influence on material removal rate from this study. At low pulse off time and low wire speed more thermal energy is transferred to the work-piece which results in higher material removal of the material. The optimal process parameters for higher MRR are peak current of 5 A, pulse off time 1 mu s, wire speed of 5 m/min and spindle speed of 700 rpm. The SEM images of machined work-pieces confirm the results obtained. The confirmation tests have been done and found that the variation is within 1.5%. From the study electrodes of empty set400 mu m has been machined to a length of 10 mm (aspect ratio l/d of 25) which is otherwise a challenge by the conventional machining processes.