Influence of discharge gap on material removal and melt pool movement in EDM discharge process

• DOI: 10.1007/s00170-021-08577-z
• Publication Date: 2022-01-28T00:04:01Z
• Authors: Xiaoming Yue; Ji Fan; Qi Li; Xiaodong Yang; Zuoke Xu; Zhiyuan Chen
• Keywords: 0209 industrial biotechnology; 0203 mechanical engineering; 02 engineering and technology

Abstract In electrical discharge machining (EDM), gap control is the key to stable processing; the discharge gap plays a significant role in EDM. To determine the influence of the discharge gap on material removal and melt pool movement, which are two fundamental issues in EDM, high-speed photography and molecular dynamics (MD) simulations were used to study the discharge process. Research results demonstrate that the discharge gap has a significant influence on material removal during the discharge process. A smaller gap width produces more and larger removed materials. The influence mechanism of the gap width on material removal is explained as follows. A smaller gap width produces discharge plasma with a smaller diameter and greater heat flux. Discharge with a greater heat flux generates more material removed during the discharge process. In addition, a smaller gap width and greater heat flux produce a stronger interaction of metal vapor jets, generating a stronger shear force acting on the melt pool. The discharge gap also influences the movement of the melt pool and the final topography of the discharge crater through external pressure acting on the melt pool. Smaller gap width produces greater external pressure acting on the melt pool, generating a bowl-shaped melt pool and a discharge crater with a depression in the center and a bulge around the edge. A larger gap width produces less external pressure acting on the melt pool, generating a flat melt pool and a discharge crater with swelling in the center and a depression around the edge.