Analysis Of The Workbench's Position Accuracy And Variation Propagation Of Multistage Machining Process In The Flexible Manufacturing System

With the development of processing and manufacturing industry,new ideas,new methods are emerging,the human society on the function and quality of the product requirements are getting higher and higher at the same time,began to high efficiency,high flexibility direction of development,so flexible manufacturing system came into being,become the focus of manufacturing industry.At present,the basic principles and system composition of flexible manufacturing system has been widely recognized in china,but the basic control theories for flexible manufacturing system have not been fully grasped,which is not conducive to playing the further application and effectiveness of the full play.On the one hand,the type of CNC machine tool is more,the number of worktable is large,making the establishment of the precision modeling very difficult;on the other hand,because the workpiece has complex structures,so it needs multistage machining process,and due to the variation accumulation and propagation,it becomes very difficult to predict.Based on the above problems,this paper takes the worktable positioning error and the error transmission between multistage machining process into consideration,to establish the error model,providing theory and method for flexible manufacturing system control.The main contents of this paper are as follows:(1)The basic theory of error modeling.Firstly,according to the characteristics of the flexible manufacturing system,the error source is classified and analyzed,and determine the influence of the worktable positioning error and the deviation propagation of multistage machining process.The theory of multi-body kinematics is introduced and deduced,which lays the theoretical foundation for the subsequent processing error modeling,and then the Monte Carlo simulation method is also deduced.(2)Analysis of the worktable positioning error.Firstly,the structure of the worktable is analyzed in detail,and the directed graph of the worktable is built by according to the constraint relation among the parts.The error accumulating path and the key tolerances are selected based on the graph.Then,the key tolerances are modeled with displacement torsors,and the error propagation between two features is analyzed by the homogeneous coordinate transformation method.Then,the key tolerances along the error accumulation path is connected to establish the worktable positioning error model.On this basis,through the Monte Carlo simulation method,analysis of the accuracy of the worktable positioning accuracy.(3)Analysis of machining accuracy of flexible manufacturing system.Firstly,the three-axis machine tool is used as an example,and the machining error model is established by using the homogeneous coordinate transformation method.On this basis,the tool nose error is transformed into the geometric tolerance of the workpiece.The tolerances and relative contribution of the tolerances of the workpiece are analyzed,and the tolerances with large influence are obtained,which provide the theoretical guidance for the flexible manufacturing system.Then,the influence of multi worktables on the overall processing quality is analyzed,and put forward the optimization design to ensure the accuracy of the design.When the machining accuracy is given,through the Monte Carlo stochastic simulation method,select the best combination of machine tools and worktable,to achieve flexible,high-quality processing.(4)Analysis of multistage process machining error propagation.Firstly,analysis of the multistage machining process phenomenon,and the error source and the transfer mode are put forward.On this basis,the error propagation model is established for the influence relationship between the stages.At last,give an example to validate the effectiveness of this model.