MICRO-HOLE PUNCHING USING MULTI-POINT PUNCH AND DIE MADE BY EDM

In this paper a multi-point micro punch and die were developed using tungsten and tool-steel as the punch material. The process of electric discharge machining (EDM) was used to produce both the punch and die. The punches were machined from 5 mm diameter tungsten and 10 mm toolsteel rods by wire electric discharge machining (WEDM) and the die holes were made using the punch as the electrode. The punch and die were set on a micro die-set and the holes were machined on a newly developed desktop EDM machine. The die-set was then transferred to a micro-press and the punching process was conducted. Experiments to produce 50-69 μm square micro-holes on 50 μm thick aluminum, 30 μm thick copper and 20 μm thick stainless steel foils were conducted. The capabilities of multi-point punching were examined and tungsten was chosen as the best material for making the punch. After the EDM process it was discovered that the surfaces of the punch were rough and had to be flattened by reverse EDM. The effects of gold plating the micro-punches were examined as a means of reducing the discharge processing time and the roughening of the punch surface. The results indicate that gold plating the punch tool significantly reduces the discharge processing time and the surface roughness. Consequently the process of flattening after machining the die holes was not necessary. With the aid of a scanning electron microscope the holes produced appeared clean and the sheared surfaces smooth. The tools showed no signs of defect or deformation even after repeated punching