The pre punching process is to prepare for the punching process and reserve the punching skin thickness for the punching process. After the upsetting process is completed, click to enter the forming module of the pre-processing, select the last step of the upsetting process, add the work step and delete the geometric model of the upper and lower cutting blocks, input the geometric data of the upper and lower dies of the pre punching through the edit geometry table, and complete the parameter setting of the pre punching. Deform will save the blank grid and shape of the previous process, so the blank shape and grid do not need to be input and divided. The two-dimensional drawings of upper and lower dies for pre punching of spiral bevel gear blank are shown in Figure 1 (a) and 1 (b) respectively. Since the thickness of the reserved connecting skin for punching is 5mm, the pre punching depth of the upper and lower dies of the pre punching of the spiral bevel gear blank is (81-5) / 2 = 38mm, that is, the stroke of the pre punching die of the spiral bevel gear blank is 76mm. The initial drawing and completion drawing of pre punching process of spiral bevel gear blank are shown in 2 (a) and 2 (b) respectively.
(b) 2D drawing of pre punching lower die
According to the design drawing of pre punching die for spiral bevel gear blank, the upper and lower die angles of pre punching for spiral bevel gear blank are 45 °, which leaves a large horn hole for ring rolling blank, which makes the initial wall thickness of rolling blank larger and the rolling stroke longer, so as to ensure the distribution of blank metal after rolling and less upper and lower flash. In the future design process of the plastic forming die of the ring blank, the pre punching die of the same kind of ring blank similar to the driven spiral bevel gear blank can also refer to the design of a larger horn hole, which can reduce the metal flash of the blank after rolling. At the same time, in the pre punching process of spiral bevel gear blank, a small punching skin thickness is reserved for the next step, which is generally about 5mm. The punching belongs to thin-walled punching, with small fracture surface and less damage to the formed blank.
(b) Completion drawing of pre punching process