Study On The Application Of Helical Cylindrical Gear Precision Forming With Two Steps

The precision forming of the helical cylindrical gear(hereinafter referred to as the helical gear) was few applied in factory production because of its special shape and demoulding difficulty. In order to achieve the precision forming of the helical gear in industrialization, my tutor studied and proposed a new technology about “half swelling- up and half grooving” two steps precision forming. Firstly, it was processed by the same height of the preliminary shallow profile back taper shape as target gear, and the same helix angle as the target gear. And then pushed the workpiece through the die from the large face to the small face to realized the final shape of the tooth and tooth socket of gear. Consequently, a complete tooth shape helical gear was acquired.This paper analyzed the common screw mechanisms, which was widespread applied in the industry. They could be divided into four types as followers: the nut screw mechanism, the ball screw mechanism, the cylindrical cam roller screw mechanism, and the mold work with the ball thrust bearing screw mechanism. And it was found that the one-way cylindrical cam roller screw mechanism and the die work with ball thrust bearing screw mechanism were suitable screw mechanism for the precision forming of the helical gear.In order to demonstrate the feasibility of demoulding, this paper had simulated the demoulding process of the helical gear with one step forming by Deform-3D software. The ways of demoulding including the cylindrical ejector direct demoulding, the cylindrical ejector spiral demoulding, the punch ejector spiral demoulding, the punch with a prismatic convex platform spiral demoulding and the punch ejector and die with the ball thrust bearing spiral demoulding 5 kinds. And compared to each demoulding methods, we found that the punch spiral demoulding was the best way of demoulding for helical gear. And we have applied it to this mold design.After consulted the method of the application of spur gear with two steps precision forming, this study chose the appropriate screw mechanism for the demoulding in pre- forming process and the splitting extrusion in final forming process, and designed two main molds of the new technology: the upsetting mold of pre-forming and the splitting extrusion forming mold. The pre-forming used the open die forging, the flash was set in the larger face of the workpiece, and used the punch which opened the spiral through slots, together with the fixing pins, to achieve the spiral demoulding. The final splitting extrusion forming mold used a guide pin together with the guide tube which was opened the spiral through slots and the ball thrust bearing which was mounted under the die, to achieve the screw extrusion of the punch and die, and achieve the final forming helical gear. And in order to achieve accurate positioning before splitting extrusion, this study has used the locating device mechanism, which had designed by my tutor.The paper was the first study on the application of helical gear “half swelling- up and half grooving” precision forming with two steps, and made the helical gears precision forming from theoretical research to industrial applications a step further.