Influence of extrusion tap parameters on the forming quality of internal thread cold extrusion

In the process of internal thread cold extrusion, the extrusion tap is an indispensable tool. Therefore, it is important to improve the service life of the extrusion tap and reduce the tool wear. In this paper, using Central Composite Design response surface test, the influence of the parameters (including the guide cone angle, backhoe capacity, guide cone length and working cone length) of the extrusion tap on the forming quality of internal cold extrusion are investigated, so as to obtain the minimum extrusion torque and the minimum extrusion temperature. A polynomial regression response model of the minimum extrusion torque and minimum extrusion temperature is obtained. Using the regression model, the objective function is optimized, and a group of optimal parameters is obtained (guide cone angle: 10°, backhoe capacity: 0.32, guide cone length: 4 mm, and working cone length: 13 mm). Numerical simulation of the optimal parameters is also carried out. The results show that the measured extrusion torque and extrusion temperature are close to the predicted values with errors of 2 and 2.55%, respectively, which are well fitted by the model.