Thermo-mechanical analysis of metallized stereolithography EDM electrodes

Abstract

EDM is widely accepted in tool and die industries for its versatility in machining hardened steels. Its ability to machine heat treated hardened steels eliminates the conventional method of heat treatment after machining which results in distortions. However one draw back of the EDM process, which makes its uses limited, is the high cost and time for the electrode manufacture. The die sinking EDM process employs complex shaped electrodes which require specialized machining operation and often results in high lead times. Solid free form fabrication is found to be an excellent alternative for the conventional all metal electrodes for EDM. Rapid prototyping of the electrode models and electroforming with copper is a fervently studied method of producing cost effective electrodes. However most of the studies have reported premature failure of the electroformed electrodes, limiting its commercial use on a large scale. This study attempts to analyze the failure mechanism of electroformed stereo-lithography electrodes by conducting a finite element analysis of the electrode model using LSDYNA- 970. It has been shown that high temperatures and coefficient of thermal expansion mismatch are the primary reasons for the premature failures experienced in these types of electrodes. The study also proposes some design modifications to improve the electrode performance during repeated thermal loading. The modified electrodes showed significantly improved performance in analysis studies.