Research On Double Sided Incremental Forming Trajectory Planning And Generation Based On STL Model

Double sided CNC(Computer numerical control)incremental forming is a incremental forming technology.In this paper,the generation of bidirectional convex feature trajectory,backing plate auxiliary forming strategy,point pressing forming method and simulation system development under the DSIF(double sided CNC incremental forming)method are studied.Firstly,a DSIF method for the forming of bidirectional convex feature sheet parts based on STL(Stereo Lithographic)triangular grid model was proposed.According to the convex direction and position relationship of the model is read into,the different types of features to be formed are classified.The main forming surface and supporting surface were determined by the forming features,and the squeezing and supporting tasks of the main and slave tool heads are assigned.The main tool and slave tool location are generated,and according to the forming sequence and forming methods of different forming features,the main tool and slave tool head trajectory are planned.Finally,a method of interference detection and correction between the tool and sheet part is proposed.Secondly,aiming at the problem of sheet parts deformation in unsupported suspension area in DSIF,a forming method of backing plate assisted DSIF are proposed.The DSIF strategy based on the backing plate for complex sheet parts,and the algorithm to automatically generate the required backplane CAD(Computer Aided Design)model for a given STL model are discussed.The STL model contour of the to be formed sheet parts according to their different types are extracted by the algorithm,and the backing plate CAD model was generated.Thirdly,aiming at the problem that the pre-set thickness of the plate is too small due to the improper control of the distance between the two tools in DSIF,the sheet deformation occurs due to an excessive force.The continuous extrusion of the tool head on the sheet surface is replaced by point pressing.The point pressing forming trajectory is generated by the traditional double sided forming continuous extrusion trajectory.Finally,in order to solve the problem of the forming trajectory which is complicated and prone to error because of the using of two tools in DSIF,a numerical simulation method of DSIF is proposed based on double lattice model.According to the characteristics of DSIF,the double lattice model is used to represent the upper and lower surfaces of the sheet plate,and the shape change of the forming sheet part is transformed into the displacement of the points of the lattice model.The model surface are reconstruction by the points after displacement transformation,and the simulation model was finally formed.A software system for continuous trajectory generation and detection applied to DSIF,point pressing and backing plate automatically generation based on VC ++ and OpenGL was developed.The feasibility of the algorithm is evaluated by the application software system.Finite element numerical simulation and experiments are carried out on the NC(numerical control)code of the main tool and slave tool generated by the developed software system.And the proposed scheme is verified.