Comparative study of wire-EDM and hobbing for manufacturing high-quality miniature gears

With increasing emphasis on miniaturization, the demand for manufacturing the high-quality fine-pitched miniature gears is growing continuously. Inability of the conventional processes to manufacture high-quality miniature gears compels the need to explore a process which can economically manufacture precise and accurate gears required by the various miniature products used for different scientific, industrial, and domestic applications. This article reports on exploring and subsequently establishing wire electric discharge machining (WEDM) process as a superior, economical, and viable alternative for manufacturing the high-quality miniature gears through a comparative evaluation of process capabilities of WEDM and gear hobbing which is the most commonly used conventional process. The evaluation concentrated on those capabilities of these two processes which affect functional performance and service life of the miniature gears. This included microgeometry parameters (i.e., profile error and pitch error) and surface integrity aspects (i.e., surface topography, surface roughness, microhardness, and microstructure). The miniature gears manufactured by WEDM were found to be of superior quality (of DIN standard 5) and surface integrity than the hobbed gears (of DIN standard 10).