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

在用于形成齿轮的传统挤压方法中，需要工件的面积减少25%以上以形成完整的齿轮轮廓。而两步挤压法成形完整齿轮的断面收缩率最低仅为7%，冲裁压力为460 MPa，表明两步挤压法成形齿轮零件是十分有利的。为了弄清这一优势的原因，采用有限元方法对挤压过程中的材料流动进行了研究。定量分析表明，两步法中的周向物质流抑制了径向向内的物质流。从成形性的角度考虑，模具第一步齿厚越大，半模角越小，成形压力越小。通过有限元分析，模拟了这些影响因素，结果表明，该模具在较低的冲裁压力下也能很好地生产出完整的齿形。有限元分析可以很好地模拟插齿实验，并为确定最佳模具设计提供了一种有效的工具。虽然需要进一步的研究来明确这一过程，但更多的有限元分析将有助于轻松确定最佳模具几何形状。

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.