Thermal-mechanical Coupling Error Analysis And Compensation Research Of Crankshaft Rotor-bearing System In Multi-link High-speed Precision Press

As a machine tool with high efficiency and less cutting,the press is mainly used to produce metal parts closer to the actual shape.It is one of the widely used forging and pressing equipment in the field of metal forming.The high speed precision press has the characteristics of continuous high speed stamping and quick backstroke,which greatly improves the processing efficiency and is the most commonly used processing equipment in all walks of life.With the increase of stamping elements and forming times and the improvement of quality requirements of stamping parts,the dynamic precision of dead point under high-speed precision press is required to be higher.The dynamic characteristics of the crankshaft rotor-bearing system of the press have a direct influence on the error of the bottom dead point.Therefore,it is of great significance to study the dynamic characteristics of the crankshaft rotor-bearing system of a press machine,to model the crankshaft system with thermal-force coupling and to model the compensation of thermal error.This thesis mainly carries out specific research on the following contents:1.According to the structural symmetry characteristics of the multi-link high-speed precision press,the right half of the mechanism is selected for kinematic analysis to obtain the displacement,velocity and acceleration response of each component.On this basis,the dynamic analysis of the multi-link mechanism is carried out to obtain the loads of the interaction between the crankshaft and the connecting rod.2.According to the dynamic model of the press mechanism,the thermal boundary conditions of the crankshaft system finite element analysis are calculated,the contact thermal resistance of the bearing joint surface is determined,the temperature field of the crankshaft system is analyzed by finite element method,and the thermodynamic model of the crankshaft rotor system is established.3.The three-dimensional model of the crankshaft rotor bearing system of the press is divided into three parts:the rigid disk element,the elastic shaft segment element and the bearing element.The dynamic analysis and simulation of the crankshaft rotor bearing system are carried out to obtain the displacement variation and the axial run out of each node of the crankshaft.4.The thermal boundary condition of the crankshaft system and the force load of the mechanism dynamics analysis are applied to the crankshaft system,and the thermal force coupling analysis model of the crankshaft system is established.The bearing running stiffness is taken as the support stiffness,and the influence of the interaction of the force load and the thermal load on the dynamic characteristics of the crankshaft is analyzed.5.The dynamic characteristics of the crankshaft system directly affect the dynamic accuracy of the lower dead point of the press.Based on the three thermal error models and the physical characteristics of the multi link press,a set of adjustment mechanism for the lower dead point of the press is designed.On this basis,an algorithm based on the thermal error model to compensate the bottom dead point offset is proposed to compensate the bottom dead point thermal error of the press on-line and in real time.