Experimental and numerical investigation into material removal mechanism of fast ED-milling

Abstract

Fast electrical discharge milling (Fast ED-milling) has become a promising technology in the manufacturing industry for machining complex structures such as diffuser-shaped lm cooling holes. However, the mechanism of the e cient removal of materials in this technology is not yet fully understood. To gain a further insight into this matter, an experimental investigation on the morphology of discharge craters including the absolute material removal volume per discharge, material residual volume per discharge, and directionality, is rstly carried out. The obtained results imply that a high-pressure inner ushing can signi cantly promote the expelling of molten material from a molten pool and is a fundamental reason why fast ED-milling can be of higher machining e ciency than regular ED-milling.To explore the mechanism behind, a novel thermal-uid coupling model is developed to simulate the evolution process of the molten material under the effect of a ow eld. The results of numerical simulation show that during a discharging, the molten material moves along the workpiece surface towards the outlet of a gap channel and solidi es at the side of a crater that is away from the electrode center. Another interesting nding is that an inappropriately high ushing pressure can result in a low machining e ciency because the severe heat convection will consume a large part of the heat generated by a discharge. This well explains the phenomenon that occurred during the experimental investigation.