Research On Through-type Cold Extrusion Forming Method Of Helical Cylindrical Internal Gear

The helical cylindrical internal gear,referred to as the internal helical gear,is one of the most basic parts for transmitting motion and power.Due to its high meshing efficiency,low noise and large transmission load,it is widely used in industrial fields.At present,the internal helical gears are mainly processed by gear shaping and broaching,which have complicated processing technology,low production efficiency,so it is not suitable for mass production.The use of a cold extrusion process saves raw materials,increases production efficiency and reduces production costs.For the internal helical gear,it has a certain helix angle.If the conventional extrusion process is used,the internal helical gear has excessive forming force,the toothed corner is difficult to fill,and the precision of the tooth shape part is difficult to guarantee during cold extrusion forming.It is technically difficult to ensure the difficulty of demolding the extrusion parts,which has become a technical bottleneck restricting the near net shape application of the internal helical gear.In this paper,the helical internal gear is taken as the research object.According to the structural characteristics of the parts,the through-type process scheme is proposed to study the cold extrusion and demoulding,and the flow of the material in the cold extrusion process is studied.The principle of internal helical gear forming separately explores the influence of the inner diameter of the blank,the half angle of the mold,the length of the sizing belt and the friction coefficient on the load and quality of the cold extrusion forming;the main experimental parameters affecting the cold extrusion of the internal helical gear were optimized by orthogonal experiment and finite element method,and the optimal process parameters were determined;based on the elastoplastic theory,the influence of the elastic expansion of the lower punch and the elastic recovery of the extrusion on the gear precision is obtained.The anti-compensation method is used to modify the shape of the mold to improve the tooth profile accuracy and tooth accuracy.According to the results of numerical simulation combined with the optimized process parameters,the mold is designed and processed,and the internal helical gear cold extrusion forming process test is carried out.The process test results show that the process scheme using through-type process scheme can squeeze out the quality and precision to meet the requirements of the internal helical teeth.