Research On Cold Extrusion Forming Method Of Floating Positioning Sleeve For Gear Hollow Billet Of Truck

Hollow gears are important components in automotive transmission systems.In recent years,the demand of hollow gears are gradually increasing with the rapid development of the automotive industry,the manufacturing precision and cost of hollow gears are directly affected by the machining quality and efficiency of gear hollow billet.At present,gear hollow billets are mainly processed by traditional machining,which no longer meet the requirement of mass production.While cold extrusion forming technology is an advanced process method,which not only improve the production efficiency and meet the needs of mass production in the market,but also has high material utilization rate,which can reduce the gears manufacturing cost and improve the competitiveness of the products.So the cold extrusion forming method is gradually applied to machine hollow gear.At present,there are two technical problem to be solved in cold extrusion forming of gear hollow billet.One is product quality that the concentricity of the inner hole and the outer circle of extruded part is lower,which the Bending deformation of lower punch cause,and some extruded parts are distorted at the mouth,which the unevenness of blank end cause.The other is die strength that cracks or even fractures may occur in the transition region of lower punch due to stress concentration.Therefore,it is difficult to promote mass production of gear hollow billets because of above two problem.Aiming at above problems,the gear hollow billet of wheel-sided reducer of truck is taken as the research object in this paper.According to structural characteristics of gear hollow billet,through comparing three process scheme such as positive extrusion、reverse extrusion and compound extrusion,the positiveextrusion scheme is adopted and the finite element model is established.With the help of finite element software of Deform-2D,the quality of gear hollow billet and the strength of lower punch are analyzed,and then the method with floating positioning sleeve in cold extrusion forming is proposed.The numerical simulation results show that this method can solve the above technical problems that the concentricity of gear hollow billet is low and lower punch is easy to fracture.The individual and interaction influence of main process parameters,such as cone-apex angle、land length、circular radius in die transition zone、friction coefficient,are studied and optimized by the orthogonal experimental design.And the optimum process parameters are determined.According to above simulation result,cold-extrusion process experiments without and with a floating positioning sleeve are carried out.The experiment results with a floating positioning sleeve show that the concentricity of extrusion part is improved and lower punch don’t fracture after repeated extrusion.The experiment results is consistent to the simulation results,which verifies the feasibility of cold extrusion forming method of the floating positioning sleeve.