Development of a process for the two-stage production of gears

冷锻已应用于工业齿轮生产多年。为了生产直齿轮和斜齿轮，侧向挤压是一种常用的冷锻制造工艺。通常侧向挤压工艺需要很高的工艺力来填充齿形模具轮廓。这导致了主动模具表面的高弹性变形和从模具弹出后工件的巨大弹性回弹。因此，侧向挤压与没有修正的模具轮廓不能达到所需的精度的齿轮。通过多级成形或采用增量成形工艺，可以提高模具填充精度和齿轮传动精度，降低加工力。另一种提高充型力同时降低工艺力和刀具负荷的方法，可以通过已建立的分流法原理来实现。新发现的侧向空腔填充效应基于与分流法相同的原理，并已在实验和数值上得到验证，作为拟议研究项目的初步研究的一部分。以制造外啮合齿轮的两阶段侧向挤压工艺为例，进行了仿真，说明了侧向空腔填充的积极作用。通过应用这种创新的方法，一个相当大的减少超过40%的冲孔力是实现了目标材料沿独立工件表面在齿侧流动的结果。在应用研究项目中，将通过数值和实验研究来研究利用侧向挤压制造齿轮的创新技术方法。齿的成形过程是利用上述侧向腔填充效应在第二成形阶段进行的，以达到减小成形力和相应的刀具负荷的目的。通过在第一成形阶段系统的材料预分布和在第二成形阶段预成形件的特定不对称定位，以最小的模具表面接触形成齿廓。这种创新的成形工艺在模具填充过程中显著降低了压力和工具负荷，因此，与使用横向挤压的传统单级齿压机相比，提高了齿精度。

Cold forging has been applied since numerous years in industrial gear production. To produce straight and helical spur gears, lateral extrusion is a commonly used cold forging manufacturing process. Usually lateral extrusion processes require high process forces to fill a toothed die contour. These results in a high elastic deformation of the active die surface and a huge elastic springback in the workpiece after the ejection from the die. Therefore, lateral extrusion with without corrected die profile does not achieve the required accuracy of gears. An improvement of mould filling and gearing precision as well as a reduction of process forces can be achieved by multi-stage forming or the utilization of incremental forming processes. Another method to improve mould filling while simultaneously reducing process forces and tool loading can be achieved by the established principle of the divided flow method. The newly discovered effect of lateral cavity filling is based on the same principle as the divided flow method, and has been demonstrated experimentally and numerically as part of the preliminary studies for the proposed research project. Simulations have been performed to illustrate the positive effect of lateral cavity filling with the example of a two-staged lateral extrusion process to manufacture an external gearing. By applying this innovative method, a considerable reduction of punch forces of over 40 % was achieved as a result of the targeted material flow along the freestanding workpiece surfaces in the tooth flanks.In the applied research project an innovative technological approach for manufacturing gears using lateral extrusion by means of numerical and experimental investigations will be examined. The forming process of the teeth occurs in the second forming stage using the above-mentioned effect of lateral cavity filling in order to achieve a reduced forming force and correspondingly tool load. By systematic material pre-distribution in the first forming stage and a specific asymmetrical positioning of the preform in the second forming stage, the tooth profile is formed with a minimised die surface contact. This innovative forming process results in a significantly reduced pressing force and tool load during mould filling and, consequently, improves tooth accuracy compared with conventional, single-stage toothing presses using lateral extrusion.