Study On Blanking Mechanism And Design Method Of Hot Shearing Mechanism For Cross Wedge Rolling Without Stub Bar

Cross wedge rolling technology is an indispensable part of the near net forming process as an advanced forming process method for shaft parts.However,in the actual rolling forming,the metal of bar on the surface flows faster than in the center's,resulting in end concavity,whereas,the concave part must be cut off as the waste stub bar.This not only reduces material utilization,but also needs to specially configure the process of cutting stub bar,which raises the production cost.Therefore,carrying out the research on the cross wedge rolling process without stub bar has a great theoretical significance and engineering application value for improving material utilization,realizing accurate forming of parts and perfecting the near net forming process of cross wedge rolling.Changing the end shape of the bar is the most effective and versatile method to eliminate concavity of the end and to achieve rolling without stub bar,but there are problems of wasting materials and low production efficiency if traditional processes such as turning and forging are used to process the end shape of the bar.Based on it,this dissertation proposes hot shear blank forming without stub bar for cross wedge rolling and its realization mechanism,and conducts basic research on the application.In the process of hot shear blank forming without stub bar for cross wedge rolling,the heated bar is clamped by a special fixture(The blank is fixed circumferentially while the axial direction is free).The upper and lower tools rotate around the blank while advancing gradually along the radial.The bar in the shear zone will generate radial compression,axial extension and deformation,and finally become the final end shape which is desired.Different end shapes can be achieved by designing and adjusting the shape of the tool.In this dissertation,DEFROM-3D software was used to establish the finite element model of hot shear blank forming.The forming principle of the end of bar and the causes of end stacking during the hot shearing were studied.The method of orthogonal experiment was used for research on the influence of different technological parameters on the end stacking of the bar.Based on the orthogonal experiment,with the aim of minimizing the number of the end stacking,a set of optimal technological parameters was singled out under consideration of the processing efficiency,production cost and equipment energy consumption.In order to further control the defect of end stacking of the bar and obtain the blanks to meet the need of the actual processing in cross wedge rolling,the semi-cylindrical stop block with taper angle was added to the both ends of the bar from the perspective of mold innovation.The numerical simulation calculations were accomplished by DEFORM-3D software.The result shows that this method can effectively inhibit the end stacking.Furthermore,in order to optimize the energy performance of the tool in the process of heat shear blank forming,the force energy conditions of the tool under different radial motion laws were investigated.Finally,the radially modified constant velocity motion law(Speed is minimum at the period of constant speed)was selected,which can not only meet the quality requirement of the hot shear blank forming of the bar,but also can improve the energy performance of the tool.In order to achieve the above-mentioned--the tools rotating around the blank at a constant speed while advancing along the radial under the designed motion law;a combination transmission of a differential gear train mechanism,a denatured oval gear mechanism,and a conjugate cam mechanism,the hot shearing mechanism without stub bar for CWR was designed.Based on illustrating the working principle of the mechanism,its kinematic mathematical model was established.On the basis of the mathematical model,the MATLAB software was used to program “auxiliary analysis and optimization software of the hot shearing mechanism without stub bar for CWR” and get the structural parameters satisfying the requirements of the tool movement law as well as the conjugate cam transmission characteristic.And then,the three-dimensional modeling and component assembly of the hot shearing mechanism were carried out with UG software.The three-dimensional model was imported into ADAMS software to simulate the virtual prototype.Comparing the theoretical calculation results with the virtual prototype simulation results,their results are basically consistent,which verifies the correctness of the kinematics mathematical model,and provides technical support for the subsequent prototype processing of the hot shearing mechanism.