Abstract: In accordance with the manufacturing of microstructure mold insert with high hardness, a kind of electrical discharge machining method by use of a six-station combination electrode is proposed. The mold insert for micro fluidic chip molding is selected as researched object, NAK80 as the material of mold insert, and copper-tungsten alloy (70%w) as the material of the electrode. The combination electrode with six narrow slits is designed according to the raised micro cross structure of the mold insert and the wear law of electrode during electrical discharge machining. The combination electrode is machined by precision wire-cut electrical discharge machining, using multiple cutting and constant feeding. The error of corner shape on the narrow slit is less than 5 μm; the width tolerance is about ±2 μm. Instead of changing electrodes traditionally, the method of transforming the electrode station is applied; the repeatability of positioning error can be avoided. The raised micro cross structure is formed by precision EDM with the combination electrode, followed by completion of the rough, semi-finishing and finish machining. The cross section of the microstructure is approximately trapezoid, and the surface roughness of the mold insert is Ra 0.208 μm, all this can be satisfied with the primary demand of micro fluidic chip molding.

Key words: Combination electrode, Electrical discharge machining, Microfluidic chip, Microstructure mold insert