Solution to the bulging problem in the open-die cold extrusion of a spline shaft and relevant photoplastic theoretical study

Compared with other forming methods, the cold extrusion of a spline shaft has many advantages. However, the problem of bulging at the die entrance, which is not yet solved, resists the wide application of this net (or near net) shape technology. To solve the bulging problem, the method of adding a guiding length upon the die entrance in the die designing is put forward in this paper. On the basis of photoplastic experiments, a theoretical analysis model of the solution is found, and the calculating method for the guiding length is also submitted. The appropriate processing parameters are chosen based on the calculated results, and a satisfactory effect has been obtained in the actual processing.