Dieless blanking using micropunches fabricated by EDM

Blanking is widely employed in industry owing to its high productivity and machining accuracy for small-aspect-ratio holes. Piercing microholes by blanking requires a small-sized micropunch, which in turn demands the precise machining of high-hardness, fracture-tough punch materials. Electrical discharge machining, a non-mechanical, thermal process well-suited to this requirement, was therefore employed to fabricate cemented tungsten carbide micropunches in this study on the dieless blanking of stainless steel sheets. In prior studies on dieless blanking, adhesive tape served as the backing material supporting the workpiece underside. In this study, however, a sticky note was chosen instead to avoid the risk of workpiece damage during removal caused by the tape’s strong adhesion. When blanking a 5-µm-thick sheet using a punch with an approximate diameter of 20 µm, it was found that hole piercing could be achieved, similar to the results obtained with adhesive tape. Additionally, a stepped punch with a shortened straight section was used to enhance punch breakage resistance. As a result, a 20-µm-thick sheet was successfully blanked using a punch with an approximate diameter of 20 µm, which had been difficult with previously used punches that featured a longer straight section. Furthermore, a hole with an entrance diameter of 3.8 µm was pierced in a 2-µm-thick sheet using a 4-µm-diameter punch.