Sustainable manufacturing of stainless steel elliptical gears and study of their tribological behavior

Elliptical gears are used effectively in automatic machines to generate variable gear ratios. Manufacturing of elliptical gears is difficult due to their complex tooth design and non-standard shapes. Wire spark erosion machining (WSEM) process has emerged as a sustainable alternative for gear manufacturing because it does not emit any toxic gases due to the use of deionized water as the dielectric (i.e., socially sustainable), consumes less power (i.e., environmentally sustainable), and incurs less cost of dielectric, tooling, and maintenance (i.e., economically sustainable). In this research, WSEM process has been used for net-shape manufacturing of elliptical gears from stainless steel 304 using 250 µm diameter diffused brass wire as the tool and deionized water as the dielectric fluid. Taguchi L9 orthogonal array approach has been used to identify the optimum combination of WSEM process parameters namely, pulse on-time, pulse off-time, wire tension, and wire feed rate as 2 µs; 40.5 µs; 420 g; and 2 m/minute respectively. Use of this combination yielded maximum and average surface roughness values, and manufacturing time as 11.73 µm, 1.67 µm, and 112 minutes respectively. Pulse-on time is found to be the most influencing parameter for manufacturing of the elliptical gears followed by pulse-off time, wire tension, and wire feed rate. The tribological behavior of the best quality elliptical gear manufactured by WSEM process has been studied by conducting linear reciprocating wear tests at an applied load of 20N, 30N, and 40N on its flank surfaces. A maximum reduction of 48.2% in coefficient of friction has been observed at the flank surfaces of WSEM manufactured best quality elliptical gear as compared to the gear blank surfaces. This research establishes the WSEM process as a sustainable alternative for manufacturing good-quality elliptical gears.