EXPERIMENTAL INVESTIGATION AND PERFORMANCE OPTIMIZATION OF HELICAL GEARS BY PULSE ELECTROCHEMICAL HONING (PECK PROCESS

Abstract

This thesis reports the experimental investigations and performance optimization on precision finishing of helical gears by pulse-electrochemical honing (PECH) process. Gears which run at high speed and transmit large forces may be subjected to additional dynamic forces due to errors in tooth profile. Therefore, the gear teeth must be smooth and error free. These errors may be reduced significantly by finishing the tooth profiles. Several types of conventional gear finishing processes are available to improve the quality of gears. But the finishing that can be obtained and productivity of these conventional processes is low which led to the evolution of advanced finishing process of gears like electrochemical honing (ECH). ECH is a hybrid electrolytic micro finishing technology characterized by a distinct coupling of electrochemical machining (ECM) and conventional honing processes to provide controlled functional surface generation capability of honing and fast material removal capability of ECM in a single operation. It can produce surface roughness as low as 0.05 μm while material removal rate is 2-8 times higher than conventional processes. It is proposed to utilize pulse DC supply further improve the finishing capabilities and process performances of electrochemical honing (ECH) of external gears. In the present work, existing experimental setup for PECH of spur gears has been modified for the PECH of helical gears by designing and fabricating a tooling system. The experimental investigations involved studying the effects of four key input parameters namely current, pulse-on time, pulse-off time, and rotating speed, on the measure of PECH process performances namely percentage improvement in average surface roughness (PIRa) and percentage improvement in maximum surface roughness (PIRA). The Experimentation consists of three-phases: pilot experimentation, main experimentation, and confirmation experimentation. Pilot experiments were conducted to study the time dependent behaviour of PECH to fix the finishing time by varying one parameter at a time. Based upon the pilot experiment results, 24 minutes as finishing time was fixed for the main experimentation. Main experimentation was designed using Box-Behnken approach of Response Surface Methodology (RSM) in which DC pulsed current, pulse-on time, pulse-off time and rotating speed of the workpiece were varied in the ranges of 10-30 A, 1-2 ms, 3-7 μs and 50 - 80 respectively...