Computer Aided Design Of Automotive Connecting-rod Precise Plastic Rolling Process

Connecting-rod is an important safety component widely used in automotive.It endures intensive impact load and alternate stress in its working time, hence it'sseverely required in its strength, ductility, dimensional accuracy and weighttolerance. It's very strict in every aspect of the automotive connecting-rodforming and manufacturing process. Nowadays, there are three main formingprocesses in automotive connecting-rod, casting, forging and powder forging, inwhich forged connecting-rod holds over 80 percentage of automotiveconnecting-rod market share. So it's very important to enhance forgedconnecting-rod market competition by renovating connecting-rod forging process.The traditional forging process of automotive connecting-rod includes stockpreparation, heating, preforming, preforging, final forging, flash trimming andshaping etc. Roll forging machine and cross wedge rolling mill are widely usedin preforming procedure. Hammer and press are usually used in preforging andfinal forging procedures. There are some intrinsic limitations in the process andequipment used by preforming and forging operations. It brings relevant problemsin the connecting-rod forging process, such as expensive equipment investment,poor flexibility in production line, short die life-span, considerable energyconsumption, low material utilization and poor forming precision etc. Theselimitations confine the development of automotive connecting-rod forgingprocess.To solve the above problems in the traditional forging process of automotiveconnecting-rod, my tutor professor Song has put forward a plan to solve theequipment problems as first step. He has devised plate precise cross wedge rollingmachine and precise plastic rolling machine innovation. These creative ideas caneffectively conquer slipping forward and backward in roll forging process, poorstiffness of plate cross wedge rolling machine and low accuracy in CWR processby using cross wedge rolling mill. Based on these solutions on equipments, he hascreatively put them into automotive connecting-rod precise plastic forming anddevised a new process named as automotive connecting-rod precise plastic rollingprocess. This process can efficiently solve a series of problems in the traditionalconnecting-rod forging process.This thesis is an important part of my tutor-professor Song's research fieldon automotive connecting-rod precise plastic rolling process. Based on advanceddesign works on the core equipments of the process, it has studied on materialdistribution of every rolling pass and the design method and scheme of the rolledparts in the connecting-rod rolling process, strictly according to the patentautomotive connecting-rod precise plastic rolling process and equipment. Becausethis process is technology innovation, its design method and scheme can't copythe traditional connecting-rod forging process. Work in this thesis is onlyelementary R&D on the design scheme and method. It needs a lot of profound andsuccessive work to be done in order to put this process into practice.Based on profound comprehension about the traditional forging process ofautomotive connecting-rod, strictly according to the patent idea of automotiveconnecting-rod precise plastic rolling process, the thesis takes an existingconnecting-rod forging as study object. By studying the precise plastic rollingprocess of this connecting-rod forging, it concludes the proper design scheme andmethod suit to this forming process. Main work in this thesis is listed as following.At first, build up 3D model of the connecting-rod by using Pro/Engineer. Thenacquire cross section area data of the connecting-rod 3D model by using theslicing function in Rapid Prototyping System and construct mass distributiondiagram of the connecting-rod forging in Origin by using acquired cross sectionarea data. Referring to the design experience in connecting-rod preforming byusing roll forging and cross wedge rolling, design the start billet for theconnecting-rod precise plastic rolling process. Based on the designed start billet,design the cross wedge rolled part model (double billet in once CWR process) andcompute material distributing condition in the preforming process. Compare thefinal connecting-rod forging with the start billet, establish precise rolling project,including preforming small end of the start billet, turn 90 degrees about the axisand flattening big end of part â… , broadening big end of the partâ…¡and finalforming four rolling passes. According to the rolling project, design the rolled part,upper and bottom molds and middle cavities of every rolling pass. And thensimulate the four rolling passes of the connecting-rod by using CAE softwareDeform-3D. Simulation results act as reference of revising the design of therolling process. After revising, simulate again. Just like this procedure, undergonemany times CAD and CAE iteration, optimize every pass of the connecting-rodrolling process. According to the whole rolling process simulation results,optimize the start billet of the connecting-rod forging for enhancing materialutilization further.Based on all above CAD and CAE work to the precise plastic rolling processof the existing connecting-rod forging, we can get the following conclusions.Three dimensional CAD technology and rigid plastic numerical simulationtechnology are the proper solution for precise plastic rolling process design ofautomotive connecting-rod forging. The four designed rolling passes for theexisting connecting-rod forging are suitable. In the process of putting automotiveconnecting-rod precise plastic rolling process into practice, the scheme andmethod in this thesis are valuable reference.