Abstract
In the first experiment, steel sheets with a high tensile strength of approximately 1,000 MPa were trimmed. For a steel sheet with a free end, a highly precise trimmed surface was obtained by shearing even at a small tool clearance of 5-10%t (t: steel sheet thickness), whereas for a steel sheet with both ends fixed, a highly precise trimmed surface was obtained by shearing when the tool clearance was increased to approximately 15%t. Next, bent formed products were trimmed. As the angle of the side wall of the steel sheet with respect to the tool end surface increases, the quality of the trimmed surface deteriorates because of the friction between sheared surfaces and other factors. The poor quality is caused by the difference in the timing of separation from the tool depending on the position of the steel sheet. Therefore, we developed a new punch with a shape that enables simultaneous separation over the entire steel sheet. It was experimentally demonstrated that defects related to the cut surface are prevented and high-precision sheared surfaces are obtained by trimming using the punch developed.
