Preliminary Study On Precision Forming Of Helical Cylindrical Gear With Two Steps

There are a series of problems include filling corner fully difficultly, large forceto form, mold with complex structure to manufacture difficultly, demouldingdifficultly, etc on helical cylindrical gear (hereafter referred to as helical gear)precision forming. This paper proposed a new process of precision forming of helicalgear with two steps, which involved pre-forming with open die forging and finalforming with splitting extrusion after comprehensively referencing existing formingmethods, especially a new way of gear precision forming which tutor invented.Taking a kind of helical gear with No. of tooth z of12, normal modulus mnof4, helixangle β of14°as the research object, numerical simulation, experiment mold design,and physical simulation research was finished, and obtained qualified lead workpiece.Referring to existing research results of splitting extrusion forming, This papermainly research deeply around aspects of mold design, preform optimization, andmetal flow discipline in forming process.Final forming mold includes two parts of forming structure and guidingmechanism. Forming structure consists of punch and integral die. Splitting angle αand splitting edge range angle β of splitting knife of die are defined all of60°. Toguarantee both sides face each other, angle of two working surface with neutralsurface are of27.8°and32.2°; to guarantee both sides work with equal length ofworking tape, die of the lower end is with a shape of "lotus leaf". Guiding mechanismconsists of guide plate with helical groove, guide pins and thrust ball bearing.Determine the preform with characteristics of being with shallow teeth shape incircular fringe whose trend is toward with teeth of target gear and reserving metal insome height in the split-in end, whose radial dimension longer than end. The performis with parameters of undulate height△R of4mm, reserving height△B of6.5mm,addendum and dedendum circle diameter D1and d1of55.6mm and47.6mm in thesplit-in end,addendum and dedendum circle diameter D2and d2of51.6mm and43.6mm in the end. Pre-forming die is with a combinatorial construction to ensuremanufacture. In the process of pre-forming, the whole cylindrical billet moves down in axialdirection and expansion outward in radial direction, whose cylindrical sidetransferring to undulating side with shape of half-ridge slot; in the process of finalforming, tooth groove is formed as surface metal of groove bottom transferring; toothis formed as metal of groove radial filling with helix angle β.The results show that: Per-forming is with good manufacturability as using opendie forging; action of final forming equipment is simple, without complex institutionlike floating die, forming force is small and demoulding easily; the workpiece is withclear tooth profile and full surface.This study implements helical gear precision forming according to the way of"half ridge-slotting" for the first time. A series of process parameters by analyzingdeformation process can provide reference for production mold and process design.