Research On Automatic Establishment And Its Application Of Kinematic Model Of Body In White Welding Fixture

White fixture is the Automobile welding jig is the guarantee of diversified and personalized automobile high-precision production and manufacturing.The efficient design of jig and the effective reuse of jig cases are the necessary conditions for the transformation of automobile production line and the increase of production line.With the maturity of CAD technology,the research of fixture motion model can promote the development of flexible fixture design.Fixture ontology classification,fixture parametric design and parametric model optimization based on the motion model of welding fixture are effective ways to improve the reuse rate of fixture,which can reduce the fixture design cost,improve the fixture design efficiency,and thus shorten the fixture research and development cycle.In this paper,the existing automobile welding fixture model is taken as the object to realize the reuse of fixture case design.This paper proposes an algorithm from the feature recognition of circular hole and cylinder to the automatic extraction of fixture motion model,which realizes the automatic reading,judgment,motion pair positioning,model element drawing and the automatic establishment of motion model of fixture,and meanwhile calculates the main parameters of fixture according to the motion model,and realizes the parametric design of fixture case.Firstly,the kinematics and mechanism theory of the motion model of welding jig are summarized.According to the relationship between fixture functional domain and physical structural domain,the hierarchical division method is used to extract and classify fixture functional modules.According to the different motion structure,the fixture ontology is classified,the motion mechanism is extracted and defined,and the basic motion model is constructed.In order to realize the automatic establishment of fixture motion model,this paper analyzes the automatic identification method of motion pair and the research on the establishment of motion model of plane mechanism,and systematically studies the connection mode of fixture assembly.This paper presents an automatic motion model establishment algorithm based on the characteristics of connecting holes of fixture assemblies,and presents the rules of progressive relation of algorithm steps,automatic identification of moving pairs and automatic identification of components.The motion model of typical automobile welding jig is extracted and the motion model is established automatically.In the aspect of parametric design of fixture based on the moving model,the motion model of typical welding fixture is parameterized,and the parametric method of fixture parts is studied,and the reuse of parametric design of fixture ontology based on the moving model is discussed.The jig motion model automatic establishment system is carried out on the NX10.0 working platform.With VS2012 as the programming tool,the program is compiled to realize the automatic establishment of the jig motion model of automobile welding.The feasibility of automatic motion model extraction algorithm and automatic model establishment system is verified by the example of one-link Mechanism and hinge-toggle Mechanism fixture,which makes the research on automatic motion model establishment and application of automobile welding fixture have engineering application and practical significance.