Study on precision forging process of spur gear in parking brake

Facing the complex structure feature of spur gear in parking brake, a novel combined hot-cold forging process plan which includes cutting, upsetting, pre-forging, extrusion, piercing, end surface turning and cold sizing was proposed. A finite element model which could simulate the multi-stage forging process was created, and the hot multi stage forging processes which include upsetting, pre forging and extrusion were simulated successfully. The detailed information of temperature, equivalent strain and velocity distribution were discussed, and the changing rule of load in each hot forming step was also analyzed. According to the process design and simulation results, corresponding experimental work of the hot multi-stage forging processes was performed on a 6.3MN high energy screw press, and a good agreement could be found compared with the simulation results. To decrease the cold forging load and improve the die stress condition, three useful measures which include hole-relief divided flow method, combined punch structure and back pressure mechanism were applied in the final cold sizing process. After cold sizing, the qualified forging part of the spur gear in parking brake was obtained.