Study on the shaping of geard parts by two-step extrusion method

在传统的挤压成形齿轮的方法中，需要将工件面积减小25%以上才能形成完整的齿轮轮廓。相反，在两步挤压法中，在冲孔压力为460MPa时，成形完整齿轮的面积缩小最小值仅为7%。结果表明，两步挤压法对齿轮零件的成形十分有利。为了弄清这种优势产生的原因，采用有限元方法对挤压过程中的物料流动进行了研究。定量分析表明，两步法的周向物料流动抑制了径向向内的物料流动。从成形性角度考虑，提高模具第一步齿厚和减小半模角是降低成形压力的最佳选择。模拟这些影响的有限元分析表明，即使在较低的冲压压力下，该模具也能很好地产生完整的齿。这也表明有限元分析可以作为一种有用的工具来模拟齿轮插齿过程。有限元分析可以很好地模拟齿轮插齿实验，为确定最优的模具设计提供了有益的工具。虽然未来的研究需要明确的过程，更多的有限元分析将有助于轻松确定最佳的模具几何形状。

In conventional extrusion method for the formation of a gear, more than 25% reduction in area of the workpiece is needed to shape the complete gear profile. On the contrary, in two-step extrusion method, it is shown that the lowest value of the reduction in area to shape complete gear is only 7% and puntch pressure is 460MPa.These results shows that the two-step extrusion method is quite advantageous to shape geared parts. In order to clear out the reason of this advantage, the material flow during extrusion was investigated by the finaite element methods. This analysis showed quantitatively, that the circumfential material flow in two-step method restrained the material flow toward radialy inward direction. It is also found that from the shapability stand point of view, higher thickness of tooth in the first step of the die is preferable and smaller semidie angle is prefered to lower the shaping pressure. The finite element analysis simulating these effects is performed and is cleared that this die can well produce the complete tooth even with much lower punch pressure. This also shows that finite element analysis can be used as a useful tool to simulate the gear shaping process.Gear shaping experiments can be well simulated by the finaite element analysis and this analysis can be a useful tool to determine an optimal die design. Although future research is needed to clear the process, much more finite element analysis will help easy determination of optimal die geometry.