Variation Analysis And Control Considering Assembly Processes

With the rapid development of manufacturing,mechanical products are becoming more and more complicated.Making high-precision products is a challenging and demanding job in a manufacturing firm.The traditional assembly accuracy prediction is based on tolerance analysis,and less consideration of the deviation factors introduced in the assembly process,which leads to the inaccurate prediction of the final assembly accuracy.There are many kinds of deviation factors introduced in the assembly process.In addition to manufacturing errors,the rigid body assembly variation is mainly affected by the process error at fixture locators.The compliant body assembly variation is more affected by the deformation factors.In order to study the variation propagation,a universal mathematical formula for deviation factor needs to be given.The welding deformation is most common problem in the compliant body assembly.For reducing time and improving efficiency of finite element method,method of influence coefficients is introduced.An integrated influence coefficient model is established considering fixture error and welding gun error.This paper deeply analyses the deviation factors in assembly process and discusses how they transform into assembly variation.A datum flow chain of an assembly model is built,allocating assembly variation to each feature coordinate system.The distribution of assembly total variation is calculated by Monte Carlo simulation.To help the designers choose the most influential deviation factor to modify,the paper analyses the sensitivity and contribution of all deviation factors associated with the assembly variation.Finally,on the method proposed in this paper,a prototype system for assembly variation calculation is developed via C++ programing and embedded in Creo Parametric environment.Through the running of an armored vehicle body assembly,the validity and practicability of the theoretical methods get testified.