2016 Volume 57 Issue 670 Pages 1077-1082
The fold-forging method, by which a stepped plate is folded into a crank throw shape, is one of the forming process of the built-up crank throw. In the bending process by the fold-forging method, surface defects occur occasionally. When these defects occur, they must be removed. Therefore, extra machining allowance is needed for clearing the surface defects, resulting in low material utilization. In order to prevent surface defects in the bending process, it is important to understand the generation behavior of surface defects, and thus, it was investigated. As a result of the bending test, it was confirmed that surface defects are generated by material overlap. In addition, it was clarified that the overlap originated from a minor surface defect near the bending point. In order to prevent the overlap, the actual bending process was improved. As a result, the surface defect dose not occur and material utilization is improved.
