Development of Multi-Point Micro-Punch: The Effects of Gold Plating on Discharge Time and Punch Surface

The continued demand for micro-hole and slots is one of the driving forces behind this research. Coupled with this are successes gained in developing a single-point micro-punching unit. 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 the punch and die. The punches were machined from tungsten and tool-steel 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 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 round 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 rounding of the punch surface. With the aid of microscopes the holes produced were confirmed as clean and the sheared surfaces smooth. The holes produced by the gold plated punches were much cleaner than those produced by the non-gold plated punches. Consequently, the process of flattening after machining the die holes was eliminated and processing time was significantly reduced. The punch tools showed no signs of defect or deformation even after repeated punching.