Dynamic Accuracy Analysis Of Multi-link High-Speed Precision Mechanical Press

In this paper,effects of several technological factors on the accuracy of a high speed precision mechanical press are investigated.These factors include the choice of bearing's tolerance and fit,elastic deformation of motion components,and thermal deformation of mechanism.Theories including kinematics,rigid body dynamics with clearance,elastic dynamics,and thermal dynamics are used during the investigation.On the basis of theoretical analysis,the closed multi-link high speed precision mechanical press is developed.And the result of performance test after assembling shows that the performance of the press reaches the stand of design.Furthermore,the validity of the theoretical analysis is proved.The main research in this dissertation includes the following content.In view of the punching process requirements,the principle institution of multi-link high-speed precision mechanical press is proposed.Based on the elastic dynamic analysis method,an elasto-dynamic finite element model without elastic properties of joints is built for the principle mechanism by transforming the mechanism components into finite beam elements.On this basis,a more complicated model with elastic properties of joints is built by transforming the rotantion joints into finite bar elements.By the theory of superosition of vibrational modes,the elastic vibration responses are obtained.The change values of slider bottom dead center(BDC)position caused by the elastic deformation are obtained respectively under different conditions.According to the structure characteristics of the mechanism,the lubrication and cooling system is designed,and its flow field analysis model is established.The distribution of temperature of cooling oil and moving components under different stamping speed are calculated by Fluent.Then,the thermal deformation of moving components under different temperature conditions is solved by Workbench.Based on the mechanism kinematics analysis theory,the error of slider BDC position caused by thermal deformation under different stamping speed is obtained.The rigid body dynamics model with clearance joints is established.The influence of kinematic and dynamic characteristics with different clearances is analyzed.It provides a reasonable theoretical basis for the choice of bearing's fit and the assurance of dynamic accuracy.According to the results of thermal deformation analysis of motion pair,the changes of bearing's tolerance and fit under different temperature field are obtained.Based on these results,bearing's tolerance and fit is designed.Finally,the multi-factor coupling dynamics analysis model of the mechanism considering elastic characteristics of motion pair,elastic deformation of movement components and thermal deformation is established.The change value of the slider BDC positon under the action of various affecting factors is obtained.According to the drift characteristics of slider's BDC position,the dynamic accuracy compensation mechanism of the BDC is designed,so the dynamic accuracy of slider's BDC can be further improved.After the completion of manufacturing and assembly of the press,the static accuracy of the mechanism such as slider's parallelism and verticality,and total clearance of the mechanism is tested firstly.Then the tests of lubrication flow,temperature of the joints,elastic deformation of movement bar,and dynamic accuracy of slider's BDC are done in the process of working.The corresponding part of the theoretical analysis results are compared with test results.The conclusion is consistent,so it verifies the correctness of the theoretical model.The design index of the press is completed finally.