Experimental study on debris evacuation during slot EDMing

Manufacturing high aspect ratio slots in low machinability aeronautical materials using conventional machining methods is an arduous work. Electrical discharge machining has become an appropriate solution to carry out this task due to the independence of this process from material properties such as hardness or machinability. Former works show that process parameters have influence on material removal rate (and in consequence on machining time) and on electrode wear. However, the influence of flushing has not been considered yet. During slot erosion, there is a depth in which erosion destabilizes and process time starts to grow. Although the depth in which this instability appears varies slightly with process parameters, this effect is unavoidable because it occurs due to debris accumulation in the erosion zone. The described problem has motivated an experimental study of the debris movements inside slots using different flushing methods. Tests have been carried out using a high speed camera to record and analyze how particles move inside the slot. Trials with no flushing, intermittent flushing applied with a nozzle and continuous flushing have been made. In addition, different electrode jump heights have been programmed. Result show that best debris evacuation is achieved with the highest electrode jump and applying continuous flushing. Besides, the feasibility of the use of numerical simulation in order to analyze alternative flushing methods has been studied. Commercial CFD-Computational Fluid Dynamics-software has been used to simulate a simple problem using no flushing and moving the electrode only. Numerical and experimental results have been compared. Comparison shows that numerical simulation is a good tool for further research on alternative flushing methods. (C) 2016 The Authors. Published by Elsevier B.V.