Using ultra thin electrodes to produce micro-parts with wire-EDM

Small-sized tools and parts are gaining importance and share of the total product range ]. An appropriate manufacturing process to cover the growing need for accurate small tools is electro-discharge-machining with thin wires (W-EDM). Until now only a few scientific works have been dealing with cutting by W-EDM using wires with a diameter below 50 μm. The results of the experiments with ultra thin wires are presented in this paper. The materials of the wires are tungsten with high tensile strength and melting temperature and brass-coated steel wire. Typical ultra thin wire diameters are 20, 25, 30 and 50 μm. The process forces—until now often neglected—are becoming significant because of the small tension forces on the wire and the low wire weight ]. A special set-up to use 20 and 25 μm wires with an existing machine which can run wires up to 30 μm was designed and constructed. Different wire types and diameters as well as electrical parameters were tested in several series of experiments. The process forces on the thin wires were measured with a special measuring device. The measuring sensor was positioned at the place where the discharges take place and was electrically isolated in order to prevent measuring interference. The single discharge craters were investigated on the workpiece surface. An electrical circuit was adapted onto the machine in order to allow just one single discharge to occur. The craters were located on the pre-ground workpiece surface and their dimensions were measured with an optical microscope.