| Nowadays with the in-depth development of automotive welding equipment industry,intelligent automation and efficiency as well as flexibility has been leading the research direction of body-in-white welding manufacturing equipment due to the variety of automobiles in the market and manufacturing cost saving.The flexible assembly system is a core section in body automatic welding station which is part of one production line populated by multiple models.In addition,the development of domestic automated flexible assembly equipments started later also constrained by foreign technology.In response to this situation,this paper relies on one research and development project from an automobile manufacturing company to develop a fully automated flexible assembly system with high-density distribution of welding robots that can be compatible with the production of three vehicle models.First,the process of preliminary production of the general assembly station was analyzed.The welding production cycle,welding spot distribution,welding gun pre-selection,the two-dimensional layout of the station,equipment plan,distribution of body positioning and clamping information which were preliminary determined based on the production process and program.The process planning in the early stage is the primiliary analysis of the research work in the later stage of equipment design and digital virtual simulation verification.Then,based on the content of the preliminary process planning,the composition and working principle of the flexible assembly system are firstly beening explained.This paper uses NX comprehensive digital simulation design platform to apply top-down modeling method to design mechanical structure which contains welding fixture,fixture conveying system,and fixture assembly system.Analyze and judge the strength and rigidity of key parts in mechanical equipment by the means of statistics and multi-body dynamics combined with the finite element simulation method in the design process.However,it is still not known the 3D mechanical structure model based on this traditional design method whether would interfere with the welding process of the robot or not.Therefore,the 3D models of these equipments provide manufacturing resources for the subsequent virtual simulation verification of the digital factory.After that,the Tecnomatix digital factory simulation platform was used to simulate the welding manufacturing process on the basis of the pre-process and the 3D data of mechanical design.During the early stage of simulation,the reachable area and load capacity of KUKA KR210 R2700 robot were analyzed based on the theory that is robot's positive kinematics theory and the space inhomogeneous rigid body rotation inertia around any axis.It was concluded that the robot model meets the requirements for application.Import product data,welding spot information,and manufacturing resources into the process of simulation enviroment,then the planning of the robot welding trajectory,and the verification of the interference between the robot and the equipment during the movement.Also analyze the rationality of the robot welding posture and proposes optimization methods.After optimization,the robot welding production time is 49.65 seconds,which is in accordance with the beat of the previous process planning.Digital factory virtual simulation technology can uncover process planning problems and mechanical structure interference problems in a timely manner.The process planning coule be directly optimized while the mechanical structure interference problems not directly because Tecnomatix does not have a good modeling function.Finally,due to the Tecnomatix simulation platform cannot directly modify the design data,this paper uses the theory of similar transformation to analyze the process of rotation transformation of the working coordinate system which is relative to the absolute coordinate system.The corresponding transformation matrix is the core algorithm of the program and the design-side software NX was re-developed on the basis of C++.The robot welding trajectory data in Tecnomatix was successfully imported into the NX design modeling environment and interacted with the original 3D data model.Directly verified the reliability of the program and the model structure which was also optimized from the design-side software.In summary,the advanced design concept is adopted in the entire equipment system research process.Not only does utilize traditional mechanical design methods,but also combine industrial digital simulation technology.With design software secondary development,systematically verified and improved the process and equipment structure.It is of great significance to be the guidance of complex flexible automated equipment design thinking... |
PDF Full Text Request