Investigations and modelling of flank modifications of spur gears by pulsed electrolytic dissolution process

Abstract

Gears find wide applications in automobiles, aviation, railroad drives, marine transmissions, machine tools, construction equipment, agricultural machines, computer peripherals, helicopters, etc. Service life, functional performance, transmission efficiency, load-carrying capacity, and wear resistance of gear can be improved, its running noise and vibrations can be reduced, and the adverse effect of shaft misalignment can be mitigated by providing different flank modifications i.e., tip relief, root relief, end relief, profile crowning, and lead crowning to its flank surfaces. The intricate design of gears makes providing the above-mentioned flank modifications a challenging task. Researchers used conventional contact type processes such as gear hobbing, gear honing, gear grinding, gear skiving, and gear shaving to provide different gear flank modifications. In the present research, an innovative apparatus and five cathode gears were conceptualized and developed for non-contact flank modifications of anodic workpiece gear by the Pulsed Electrolytic Dissolution (PED) process and describe their imparting mechanisms. Continuous rotary motion was provided to the cathode gears. Constant reciprocating velocity was provided to anodic workpiece gear for its profile crowning, tip relieving, and root relieving, whereas lead crowning needed variable reciprocating velocity. No reciprocating velocity is required for end relieving. The intended functioning of the developed cathode gears was confirmed through experimental investigation. It revealed that the developed cathode gears not only provided the intended flank modification but also reduced flank surface roughness and completely removed the hob cutter marks and cracks from the flank surfaces of the modified spur gear. Imparted flank modifications are found to increase with voltage and modification duration. Root relieving required 20 minutes as modification duration, which is more than other flank modifications, which is 12 minutes. Analytical models for different flank modifications are developed and required to develop relation for the volume of material removed using Faraday’s law of electrolysis, and some common assumptions were made in the development of analytical models. The developed analytical models for tip relief, root relief, end relief, and lead crowning were validated by conducting 12 experiments for each model (i.e., a total of 48 experiments) by varying applied voltage, pulse-on time, and pulse-off time at four levels each according to OFAT approach and 12 experiments to study effects of pulse-on time, pulse-off time, and applied voltage for profile crowning (PC) using OFAT approach were performed.