4. Examples
4.1. Forming load reduction in pulley upsetting process
The motivation of this example is to reduce the forming load in the upsetting process of the CVT pulley product.
The final upsetting stage of the CVT forging process usually requires a higher forming load when compared to the
preceding forging stages. To reduce the forming load, this process is usually performed under hot or warm forging
conditions, which often leads to additional processing time and increased energy costs associated with the heating
and cooling processes.
In this study, we have investigated a simple upsetting process, similar to the final upsetting process of the CVT
pulley, for the press motion pattern shown in Fig. 4. Just before contacting the upper side of the billet, the speed of
the upper die was reduced to 5 mm/s in order to prevent the tool damage caused by the strong impact between the
tool and workpiece. After the initial contact, the tool speed was suddenly raised to 200 mm/s in order to reduce the
cycle time and to increase the workpiece temperature due to the heat generated from the plastic deformation
process. The die speed becomes slower around the final stroke, so as to utilize the effect of flow stress reduction
associated with the lower strain rate under the high temperature condition of the workpiece. Fig. 5 shows the