Micro EDM Milling with Electrochemical Fabrication of Ultra-thin Microtools and Mapping of Electrical Microdischarges

摘要

The aim of this paper is to describe some possibilities allowed by a micro EDM milling machine, which has been entirely developed in our laboratory. Among other features, this machine does not make use of WEDG for fabricating the microtools. Instead of this, a compact low cost electrochemical reactor allows automated etching of tungsten microtools with a diameter ranging from 1 to 30 μm and very high aspect ratio (50-100). Thus, fragile microtools are obtained and regenerated without any intervention by the operator. Micro EDM milling is performed with such microtools thanks to a specially designed electronics based on a parallel architecture with 3 microcontrollers. The electrical signals of the micro discharges are continuously characterized which allow mapping of micro electrical discharges and contacts. It is demonstrated that the spatial distributions of discharges and contacts give valuable information on the micro EDM milling process. During the machining of microchannels in stainless steel, it is reported that the positions of contacts match with a low number of discharges. So, high tool wear and low part removal rate are related to a high number of contacts. Heterogeneous machining along the vertical Z axis and the horizontal XY axis can be also characterized.