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

冷锻在工业齿轮生产中的应用已有多年。为了生产直齿和斜齿圆柱齿轮，侧向挤压是一种常用的冷锻加工工艺。通常侧向挤压工艺需要很高的加工力来填充齿形模具轮廓。这导致活动模具表面的高弹性变形和从模具顶出后的工件产生巨大的弹性回弹。因此，没有修正模具型面的侧向挤压不能达到齿轮所要求的精度。通过多工步成形或采用渐进成形工艺，可以提高充模精度和齿轮传动精度，降低工艺作用力。通过建立分流法的原理，可以实现另一种在同时减少工艺力和刀具载荷的同时改善模具充填的方法。新发现的侧向空腔充填效果与分流方法基于相同的原理，并已作为拟议研究项目的初步研究的一部分进行了实验和数值验证。以双级侧向挤压制造外齿轮为例，对侧向充型的积极作用进行了模拟。通过应用这种创新的方法，由于沿齿面中独立的工件表面的定向材料流动，冲压力显著降低了40%以上。在应用研究项目中，将通过数值和实验研究的方法来检验利用侧向挤压制造齿轮的创新技术方法。齿的成形过程发生在第二成形阶段，利用上述侧腔填充效应，以实现减小成形力和相应的刀具载荷。通过在第一成形阶段进行系统的材料预分配和在第二成形阶段对预制件进行特定的不对称定位，以最小的模具表面接触来成形齿形。这种创新的成形工艺显著降低了充模过程中的压力和工具载荷，因此，与使用侧向挤压的传统单级齿形压力机相比，提高了齿形精度。

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.