Analysis And Optimization Of The Effects Of The Key Process Parameters On The Forming Quality Of QSn7-0.2 Connecting Rob Bushing Stagger Spinning

The connecting rod bushing is a key component that connects the small end of the engine connecting rod with the piston pin.In the engine working process,it is not only affected by the friction of the connecting rod and the piston pin,but also affected by the high temperature environment and the impact of alternating stress,which requires a high demand for its performance.The connecting rod bushing is generally manufactured by the stagger spinning technology which is an advanced surface plastic reinforced forming process that can make the fatigue strength,carrying capacity and other properties of the connecting rod bushing meet the requirements of its working environment.The main problem is that the inner diameter accuracy of the workpiece after spinning are not ideal enough to ensure that the machining allowance is sufficient to complete the subsequent finish turning process.Sometimes because of an unreasonable combination of process parameters or other reasons,there is a serious inner diameter expansion in the mouth of the workpiece which makes the size of the inner diameter can not meet the requirements of the subsequent finish turning allowance,resulting in a waste of human and material resources.At the same time,due to the existence of the shape error,the cutting depth in the subsequent finish turning process is different,which brings a big variation of the surface hardness,the metallographic structure,the residual stress,resulting in a greatly reduce of the product reliability.In this paper,numerical simulation method was used to establish the finite element simulation model of QSn7-0.2 connecting rob bushing stagger spinning.And the reliability of the model was verified by experiments.The effects of the reduction ratio,the feed rate,the first round reduction ratio,the axial offset,the spindle speed on the radial forces,the axial forces,the tangential forces,the square deviation of the radial forces during spining and the inner diameter precision,the roundness error and the straightness error after spinning were studied based on the single factor test design method.According to the single factor test results and the actual production situation,the orthogonal test design scheme which taked the feed force ratio,the first round reduction ratio,the axial offset as the experimental factors and the square deviation of the radial forces,the inner diameter tolerance and the outer surface roundness error as the optimization indicators was designed.The numerical simulations of different combinations of the factors in the orthogonal test scheme were carried out,and the square deviation of the radial forces,the inner diameter tolerance and the outer surface roundness error were obtained.Finally,the experimental results were analyzed based on the intuitive analysis of orthogonal experiment design and the comprehensive balance method,then the optimal combination of process parameters was obtained.