Study And Application Of New Technology Of Crankshaft Machining Quality Centering

As a key part of high-speed rotation in the engine,the crankshaft requires high dynamic balance accuracy,which is mainly guaranteed by the final dynamic balance process.The center holes pre-drilled at both ends of the crankshaft blank are the positioning benchmarks for machining.Currently,there are two main methods for center hole positioning: geometric centering and quality centering.The geometric centering is based on the geometric center of the main shaft journal of the blank.The advantages are simple processing equipment and good uniformity of the machining allowance of the journal.However,if the blank size tolerance and shape tolerance are large,the dynamic balancing process is used.The weight position and weight removal quality will fluctuate greatly,and even the dynamic balance will not be completed due to the incorrect weight removal direction,resulting in product scrapping;quality centering The center hole of the blank quality measured by the special equipment is punched into the center hole and the journal The uniformity of the machining allowance is relatively poor,which will affect the machining quality of the journal,and because there are non-machined surfaces on the crankshaft,the center of mass of the blank and the finished part does not coincide,so the quality centering exists in the dynamic balancing process The problem that the deduplication position and deduplication quality cannot be predicted and controlled.In view of the defects of the above two centering methods,this paper proposes a new centering method of punching a center hole on the blank with the virtual center of quality of the finished part,so that the weight-removal position and weight-removal quality of the dynamic balancing process can be predicted in advance Control and study the distribution law of the center of mass of the blank.The research results of this paper have good theoretical significance and practical value for ensuring the quality of crankshaft processing.The main research contents are as follows:(1)The solution method of the mass center line of the crankshaft blank scanning model is studied.The inverse model of crankshaft forgings is analyzed,the analytical center of the crankshaft blank mass centerline is established based on spatial coordinate transformation,the mass centerline of the forging scan model is calculated,and a unified benchmark is formed with the mass centering machine.The center-of-mass coordinate optimization model studies the influence of machining allowance on dynamic unbalance.(2)Proposed a virtual machining method of blanks aimed at the center of quality of finished crankshaft parts.An iterative method is used to establish a solution model for the deviation of the center of mass between the crankshaft finished part and the blank part,to ensure that the blank center and the finished part quality center line coincide,reducing the unbalanced amount of the finished part,thereby improving the crankshaft final balance processing efficiency,and verified by examples.(3)A mathematical statistical model of batch-based optimal machining center based on forging error is established.The forging error of the crankshaft blank is analyzed.At the same time,the theoretical calculation and discrete analysis of the mass center offset of the same batch are carried out.The optimal offset of the batch is obtained by numerical analysis and the sample imbalance is calculated;The forging sampling method uses the mathematical statistics theory to calculate the confidence interval of the unbalance of the finished part on the premise of reliability.(4)Combined with the UG secondary development technology,the crankshaft dynamic balance analysis software of the above research results is compiled to realize the functions of crankshaft imbalance calculation,blank mass centerline adjustment coordinate calculation,and blank mass center and finished product mass center offset calculation.