Analysis and optimization of micro-geometry of miniature spur gears manufactured by wire electric discharge machining

• Study the effects of WEDM parameters on micro-geometry of miniature gears.
• Irregular shaped craters and wire-lag identified as main causes for geometric inaccuracy.
• Optimization of WEDM parameters to minimize deviations in the micro-geometry.
• Optimized parameters produced miniature gear of DIN 5 standard.
• Establish WEDM as alternative process for manufacturing high quality miniature gears.

This paper reports about the analysis and optimization of micro-geometry parameters (i.e. total profile deviation ‘Fa’ and accumulated pitch deviation ‘Fp’) of the wire electric discharge machined (WEDMed) fine-pitch miniature spur gears made of brass. Effects of four WEDM process parameters namely voltage, pulse-on time, pulse-off time and wire feed rate on the micro-geometry of the miniature gears were analyzed by conducting the experiments designed using Box–Behnken approach of response surface methodology (RSM). Analysis of variance study found all four input parameters significant. Larger deviations in profile and pitch were observed with higher values of the voltage and pulse-on time, and with lower values of wire feed rate and pulse-off time. Multi-performance optimization of WEDM parameters was done using the desirability analysis to minimize profile deviation and pitch deviation simultaneously. The values of Fa and Fp of the gear obtained by the confirmation experiment conducted at the optimized WEDM parameters were as 11.5 μm and 9.1 μm respectively. These values categorize the WEDMed gear having DIN quality number as 7 and 5 respectively for profile and pitch which are better than those obtained by the conventional miniature gear manufacturing processes.