Cheol-Soo Lee

A Method of Hole Pass-Through Evaluation for EDM Drilling

The Electric discharge machining (EDM) process is used to minimize the difference between designed feature and machined feature while the most workpiece is removed through the cutting processes. The tiny-deep hole machining and perpendicular wall machining in mold and die are good applications of EDM. Among EDM equipment, the super drill uses the hollowed electrode to eliminate the debris which causes the second discharge with the electrode and degrades the machining quality. Through the hollow, the high pressured discharge oil is supplied to remove the debris together with the spindle rotation. The thin-hollow electrode tends to easily wear out compared to the sold die-sinking electrode and its wear rate is might not allowed to monitor in real time during discharging. Up to now, the wear amount is measured by off line method, which leads machining time to increase because the hole pass-through moment can be check by visual (manually) with the extra tool path. Therefore, this study suggests the attractive method to evaluate the hole pass-through moment in which the gap voltage and z-axis encoder pulse are monitored to predict the moment. The commercial super drill is used to validate the proposed method and the experiment is carried out.

Discharge Parameters for Pass-Through Holes in EDM-Drilling

Electrical discharge machining (EDM) drill is a kind of EDM processes to machine deep, micro sized holes of hard machining material. Since it works regardless of materials strength or stiffness, it is known that EDM drilling is effective than conventional drilling for the micro-drilling. The accuracy of a machined surface is determined by electric discharge parameters. Thus, in this study a EDM-drilling plan with the experiment of design (DOE) is set up to analyze the characteristics of Pass-Through Holes in EDM-drill and then the relationship between the four major discharge parameters and machined hole accuracy is addressed in terms of hole diameter and surface roughness. Finally, the tendency in each parameters of EDM-drilling is studied with average response value (ARV).

Electrode Wear Estimation and Compensation for EDM Drilling

Electric discharge machining (EDM) is commonly used to machine precise and tiny parts when conventional cutting methods face difficulty in meeting productivity and tolerance requirements. Die-sinking EDM works well to machine micro-parts and perpendicular walls of die and molds, whereas EDM drilling is excellent for machining deep and narrow holes regardless of material hardness and location. However, EDM electrode wear is rapid compared to conventional cutting and makes it difficult to control the electrode feed and machine precisely. This paper presents an efficient method to estimate electrode wear through a hole pass-through experiment while a stochastic method is adopted to compensate the estimation model. To validate the proposed method, a commercial EDM drilling machine was used. The experimental results show that the electrode wear amount can be predicted acceptably.

A Study of Electrode Wear Estimation and Compensation for EDM Drill

Electric discharging machining (EDM) is commonly adopted to machine the precise and tiny part when it is difficult to meet the productivity and the tolerance by the conventional cutting method. The die-sinking EDM method works well to machine the micro-parts and the perpendicular wall of die and mould, whereas EDM drilling, called super drill, is excellent to machine the deep and narrow hole regardless the material hardness and the hole location. However, the electrode wear is rapid compared to the conventional cutting tool and makes it difficult to control the electrode feeding and to machine precisely. This paper presents an efficient method to estimate the electrode wear using hole pass-through experiment while the stochastic method is used to compensate for the estimation model. To validate the proposed method, the commercial EDM drill machine is used. The experiment result shows that the electrode wear amount can be predicted very precisely.