Investigations on surface quality improvement of straight bevel gears by electrochemical honing process

Abstract

Electrochemical honing is a hybrid finishing process combining advantages and simultaneously overcoming the individual limitations of electrochemical machining and mechanical honing. Finishing of conical gears by electrochemical honing is very complicated due their complex geometry. This article reports on the development of an innovative experimental setup and investigations on improving surface finish of straight bevel gears by electrochemical honing and its process productivity. A novel idea of using twin-complementary cathode gears was envisaged to ensure simultaneous fine finishing of all the teeth of straight bevel gear made of 20MnCr5 alloy steel. Effects of five important electrochemical honing parameters, namely, concentration, temperature and flow rate of electrolyte, rotary speed of workpiece gear, voltage on surface finish and material removal rate of the bevel gear were investigated. Improvement in the microstructure of electrochemical honing finished gear was studied using scanning electron microscopic images. To prove importance of hybridization in improving finishing capabilities of electrochemical honing, a comparative study of surface quality of a bevel gear finished by mechanical honing, electrochemical machining and electrochemical honing was done. The results revealed considerable improvements in the surface quality of the bevel gears finished by electrochemical honing. Electrolyte concentration of 7.5%, temperature of 32 °C, flow rate of 30 L/min, 8 V as voltage and speed of 40 r/min of the workpiece gear yielded the best combination of percentage improvements in average surface roughness (i.e. 58.5%), maximum surface roughness (i.e. 44.4%) and volumetric material removal rate (0.21 mm3/s). This work helps to establish electrochemical honing as a viable alternative bevel gear finishing process which has potential to overcome the limitations of conventional bevel gear finishing processes.