Small elements used in the meshing portion of metal zippers are formed by successive plastic deformations, i.e.,shearing of a preformed copper alloy wire, forging of a sheared piece, and bending of a forged piece, in a chain machine. These plastic deformations are carried out repeatedly and continuously at high speed to form a fastener chain. However, in a new design of zipper elements, owing to the difficulties in forming the designed structures by the deformation process, design and production must be repeated many times to reach an optimal solution. The purpose of this study is to clarify the shearing mechanism of round wire using a simple shape for the zipper element. As result, the shearing process was estimated as follows. In the first step, shearing is proceeded by a shearing force generated by a punch force. During the process, the cut material is compressed, and the height of contact with the punch increases owing to compressive deformation. In the final step, bending stress at the edge of the cutting line reaches the tensile strength of the material and divided from the wire. Then dimples are formed on the cut surface.
