Research on shaping of burr less gear by cold extrusion through reducing after expansion workpiece diameter

当挤压齿轮时，限制了工件的外径，尽管压力(载荷)很低，但成形件的端面仍会出现毛刺状的不规则性。在挤压齿轮的同时扩大了工件的内径，端面的不规则性变小了，但载荷变大了。为了充分利用上述两种方法各自的优点，本研究采用膨化后挤压的方法进行了成形实验。其目的是以低载荷获得具有小毛刺状不规则性的成形，并最终仅使用压力线来制造齿轮。首先，发现使用上述方法可以成形齿轮。确定了获得有利齿轮所需的截面积压缩下限。冲头、心轴和模具所需的压力远远低于冲头、心轴和模具材料的强度。端面毛刺状的不规则性与两步挤压法相比可以减小，但不能完全消除。由于尺寸的减小，这种不规则性可以用压力机来纠正

When extruding a gear while confining the outer diameter of the workpiece, burr-like irregularities occur on the end surface of the shaped form although the pressure(load) is low. When extruding a gear while expanding the inner diameter of the workpiece, the irregularities on the end surface become smaller but the load becomes greater. A shaping experiment was conducted in this study to take the respective advantages of the above two approaches by adopting a procedure of extrusion after expansion. The intention was to obtain a shaped form having small burr-like irregularities with a low load, and eventually produce gears using only a press lineFirst, it was found possible to form gears using the above method. The lower limit of cross sectional reduction in area to obtain a favorable gear was determined. The needed pressure of the punch, mandrel, and die is far below the strength of the punch, mandrel, and die materials. The burr-like irregularities on the end surface could be reduced in size compared with the two-step extrusion method, which has been proposed for gear shaping, but could not be eliminated completelyIt was found that the irregularities could be rectified with a press machine because of their reduced size