A NEW EXTRUSION PROCESS FOR HELICAL-GEARS - EXPERIMENTAL-STUDY

A new process design for the cold extrusion of helical-gears (a modified Samanta's gear-extrusion process) has been explored in this study. The process design involves the structure of the die, and the manufacture of the electro-discharge machining electrodes and the extrusion die and tooling. To design these electrodes, a computer software system was developed. The stress and elastic deformation of the dies during the extrusion process for both Samanta's and Choi's cold extrusion process were calculated using a commercial finite-element code. The accuracy of the extruded gears and of an extruded-shaved gear was measured. The results are summarized as follows: (1) gear electrodes were designed successfully using a CAD program. (2) The electrodes were machined with a standard or a shaving hob cutter by controlling the addendum modification factor or the shaving allowance. (3) The strength of the die teeth was improved remarkably using Choi's new process. (4) The accuracy of the gears was not affected greatly by elastic deformation of the die. (5) The tolerance of the gears from the Choi-process were closer than those from the Samanta-process. Therefore, the Choi-process can be used as an advanced technique to replace the conventional hobbing process for gears.