Process behaviour of segmented and actuated tool electrodes for variable shaping in sinking EDM

In sinking electrical discharge machining (S-EDM), many applications such as the manufacturing of injection moulds require numerous tool electrodes due to tool wear compensation. The manufacturing of tool electrodes causes a high cost and time expenditure in the entire process chain. This paper aims for a novel approach to a segmentation of the tool electrode in order to shape it variably. The shaping is realized by actuation of single tool electrode segments (STES) using miniaturized linear actuators. In the future, the roughing process in S-EDM could be carried out by segmenting and variably shaping of the tool electrode. To investigate the process behaviour of a segmented tool electrode in S-EDM, different geometry configurations of the tool electrodes are compared. Experimental results show a similar material removal rate for the different tool electrode configurations. The relative linear wear of a segmented tool electrode is only 7.7 % of the relative linear wear of a monolithic tool electrode. In order to dynamically position the STES, a miniaturized electrical linear drive is developed and constructed. The outer diameter of the actuator must not exceed the edge length of an STES. In the machine tool an actuated STES is tested and the material removal rate and the relative linear wear for different Z-axis lifting motions are analysed. The material removal rate could be increased by 37 % applying actuated Z-axis lifting motions compared to the process without Z-axis lifting motion. In this context the relative linear wear increased slightly. The results of this paper are used for the further development of the system to enable more efficient process chains in the EDM process.