Geometric prediction of conic tool in micro-EDM milling with fix-length compensation using simulation

• Cone angel forming mechanism is included in micro-ED milling with fix-length compensation.
• Cone angle and workpiece profile are precisely predicted for most real conditions.
• Relationship between cone angle and layer thickness is analyzed.

Micro-EDM milling is an effective machining process for three-dimensional micro-cavity of high hardness materials. However, tools wear sharply in micro-milling, thus several compensation methods are applied. The present study examines the fix-length compensation method, and the initial experiments show that a cone-shaped tool end is formed with this compensation method. Because the cone angle is of great importance in the determination of the fix-length compensation parameters in the machining procedure, a clear explanation of the forming mechanism and precise prediction are of great necessity. First, the tool and the workpiece were geometrically and mathematically modeled as two-dimensional matrices. Second, the machining process was divided into three parts including sparking, horizontal feeding and vertical feeding. Finally, a series of experiments were conducted in order to verify the accuracy of the simulation. The results show that the relative error of the simulation compared to the experimental data is within 4% under most machining conditions. The developed model can thus be used to predict the machined surface of the tool and the workpiece and can also provide a better understanding for the mechanism of the cone shaped tool end.