Rigidity Coordination And Assembling Deviation Control Method Research Of The Bodysied-main Fixture System

The manufacturing quality of the BIW directly affects the performance of the car and the perceived quality of the user.What's more,the main work position is the key link in the vehicle manufacturing.The main work position is the position of welding and assembling the parts of the lower body assembly and the bodyside by the main fixture.The lower body includes front body,the front floor and rear car body,bodyside usually includes a bodyside inner plate,side plate and a column welded part,etc.At present,the production requirements of automobiles tend to be flexible production of multi-type vehicle.The main fixture of main work position reduces the stiffness to meet the needs of rapid production and tooling switching.On the other hand,because the BIW is welded by many thin-walled parts with complex shape,the error accumulation of manufacturing is always easy to happen when it comes to the main work position,which results in the assembly force,which means that the stiffness of the main fixture system of the main work position is relatively high.Therefore,the study of the stiffness characteristics of the main fixture system is of great significance to ensure the quality of the assembly.In this paper,a domestic brand automobile of the main work position was analyzed,and the bodyside-main fixture system has a deformation in the assembly due to contact problem by using the method of analysis of flexible assembly quality deviation on the contact constraint conditions.Ensure the optimal tolerance of process capability under control.The finite element method is used to do the assembly simulation analysis,and the deformation of the bodyside-main fixture system is obtained,and the stiffness is analyzed,which provides guidance for improving the manufacturing capacity of the main work position and the assembly quality of the BIW.The main research content of this article is divided into four parts:(1)Mechanical modeling of the assembly of the bodyside-main fixture systemAccording to the assembly form of the bodyside-main fixture system,the bodyside and main fixture were simplified.Considered the influence of deformation in bodyside-main fixture system which caused by the assembly.A simplified beam element is used for mechanical analysis of the possible contact problems in the assembly.The contact force is calculated by Lagrange multiplier method,and the influence of the deviation of the contact surface on the final deformation is obtained.(2)The bodyside flexible deviation analysis considering contact effectAccording to the contact constraint conditions are given,it analyzed the simulation and deviation of the assembly.By using 3DCS software to simulate the effect of deformation difference of main clamp positioning pin for final assembly quality,then,it used the orthogonal experimental method to optimize fixture positioning deviation.Finally,the location tolerance combination under the process capability was calculated.(3)Stiffness analysis of bodyside-main fixture system based on finite elementAiming at the contact problems in assembly,the assembly simulation is carried out in the finite element software ABAQUS.The deformation of the bodyside-main fixture system under the condition of ultimate contact deviation is obtained,and the stiffness of the system is evaluated for giving guidance.(4)The application of contact example of bodyside-main fixture systemSet the assembly contact problems arise in a domestic brand car manufacturing as an example.Obtained in the assembly quality of bodyside under contact constraint of critical control points by flexible assembly deviation analysis,then positioning deviation on the main clamp was optimized that calculate the positioning deviation control value to meet production.It used the finite element simulation to analyze the deformation of bodyside-main fixture system with limit deviation of contact,and proposed optimization scheme aiming at the insufficient rigidity of the bodyside-main fixture system.Finally compares the optimized simulation results and actual production results show the correctness of the method and model.