This paper describes the method for improvement of surface quality by non-electrolysis wire electric discharge machining (Wire-EDM). In wire-EDM which generally employs low-conductivity water as dielectric, electrolytic current may flow via the dielectric and an electrolytic effect may cause change of properties over wide area of a workpiece. A non-electrolysis power supply developed to prevent electrolytic corrosion permits a full range of non-electrolytic machining from rough machining to finishing, achieving high-quality (surface) machining with high productivity. In life tests using actual dies, non-electrolytic machining produces few burrs on punched products and increases die life significantly.
