Study On Precision Forming Process Of Spiral Bevel Gear By Enlarging Die Corner

Driven spiral bevel gears are widely used in decelerating and heavy-duty driving devices.At present,the main processing method is still cutting,but there are many problems,such as insufficient gear performance,waste of materials and energy and low production efficiency.Although people have explored various precision forming methods for driven spiral bevel gear,including open die forging,closed die forging,open-close combined die forging,divided flow forming,rotary forging forming and other processes,which have been used in small-scale production,but there are difficulties in corner filling,excessive forming load and die life.In this paper,referring to the cavity expansion forming process of spur gears and straight / helical cylindrical internal gears and the theory that the die cavity and the blank metal do not fit together,a step-by-step expansion forming process is proposed to realize the precise forming of driven spiral bevel gear.The step-by-step expansion forming process includes two stages: pre-forming and final forming.During the pre-forming,the tooth die cavity reduces the tooth height and increases the transition fillet.At the same time,an expansion space is set at the small end of the tooth cavity,which is convenient for comparison.The multimetal flows close to the small end to obtain a preform with sufficient small end blank volume but less regular shape;in the final forming,not only the tooth height is increased,the transmission fillet is reduced,but the irregular small end is also reshaped.A precision formed part with a complete tooth profile is obtaind.This paper takes a driven spiral bevel gear with 25 teeth and 9 big end modulus(tooth wide L is 40mm)as the research object.With the help of DEFORM-3D software,the numerical simulation experiment is carried out.First,the traditional one-step forming process is studied.The simulation results show that the small end of the tooth is the most difficult to fill,so the small end is expanded.Then optimize the corner expansion length l and the corner expansion height h.Finally,it is concluded that when l=(13?17)mm and h=(3?4)mm are more reasonable,the filling effect of the corner is approaching optimal,and the forming load smaller.Take the expansion space parameters of the pre-formed tooth die as l=14mm,h=3mm,and analyze the metal filling,forming load,effective stress,effective strain and die ware in the forming process.The results show that the new process can significantly improve the filling of the gear corners,and the forming load is reduced by 14.3% compared with the traditional one-step forming process,and the wear of the die is reduced.The physical simulation test of the step-by-step expansion forming process of the driven spiral bevel gear with lead blanks shows that the test results are basically consistent with the simulation results.The tooth profile is intact and has no defects,and the corners are formed well.This further verifies the feasibility and feasibility of the new process and he accuracy of the simulation results.This study verifies that the corner expansion process can be applied to forgings where the angle between the action / motion of the die and the deformed metal surface is large or approximately orthogonal.The corner expansion process takes into account both the corner filling effect and the reduction of the forming load which are seemingly contradictory aspects.This new process has greater practical and academic value.