Auto-body Surface Model Sewing In CAD Data Exchange

With the development of globalization,the global cooperation of design and production in manufacturing has been formed,especially for the automobile industry.In such a cooperation mode,the data exchange of CAD models is inevitable in the process of car design.However,existing data exchange methods cannot avoid the data loss in exchanging of CAD models,such as the auto-body surface model.Therefore,a large number of surface defects will be generated due to the loss of data,the differences in the architecture and precision of heterogeneous CAD system in the data exchange.Due to the complex body structure and the curved surface of the body parts with thousands of facets,the number of surface defects will also be very large after data exchange.Defects are generally referred to 0verlapping surfaces,gaps,deficiency in smoothness,degeneration surfaces,self-intersection,etc.,which will give rise to problems that the surface suture operation can't be completed or suture can't meet the needs of the follow-up finite element meshing and the design of NC path generation,etc.At present,the repair and stitching of the body surface defects are mostly done manually by the designer.Therefore,the complexity of repairing lead to the entire process costly and time consuming.With regard to the above issues,this project,based on the actual demand of the engineering applications in automotive field,is committed to the development of a set of curved surface suture tools for the automotive industry.More specifically,for the surface defects caused by the data exchange of the car body surface CAD model,it tries to solve the representative problems of several types of defects that are widely existed in the automotive industry.This study fully considers the relevant standards and requirements of the automotive industry.It conducts a study on the programmed suturing method by simulating the manual repairing process of engineers and evaluates the final suture results complying with the automotive industry standard.This paper mainly proposes the design schemes for the marking and repair of overlapping surfaces,the marking of degenerated surfaces,the stitching of non-smooth surfaces,and the repair and stitching of curved surfaces.This paper,based on the knowledge fusion technology and integrated various modules,intends to embed the formulated product parameters,design experience and relevant standards,etc.into the CAD model,thus realizing parameterization of automatic repairs and stitching.It finally submits parametric surface stitching results for the follow-up modification.For surface defects that are not yet resolved by the automation program,the user can adjust the model parameters through the interactive interface to solve the problems.Compared to the traditional repairs,the optimal combination of the automatic surface suturing tool and the flexible user interface greatly improves the efficiency of stitching surfaces.