The Generation Of The Forming Path With The Springback Compensation In The CNC Incremental Forming

The NC incremental forming technology as a flexible technology is gradually developed for rapid manufacturing of complex sheet metal parts.However,the developments also bring some problems,such as forming precision.Springback is the key problem influencing forming precision of the sheet metal parts,the traditional method to solve springback is experimental method,then compensate the sheet according to the measured amount of springback.However,only one time compensation can't meet the required precision due to the complexity of many factors causing springback,many experiments are a waste of time and material resources,therefore a method of predicting springback and generating the forming path with springback compensation was proposed based on the explicit and implicit finite element analysis of the numerical simulations in the paper,and a special software system of forming path was developed.The springback of the sheet metal parts was divided into two processes.One was the springback in forming process,the other was the springback in unloading process.First,the first forming path was generated according to the sheet metal part to be formed,then the cutter location points of the forming path was used to do the explicit finite element analysis which was used to simulate the springback in forming process.The result of the explicit finite element analysis was used to do the implicit finite element analysis which was used to simulate the springback in unloading process.Secondly,the surface of the sheet metal part was reconstructed with the coordinates of all nodes obtained from the result of the implicit finite element analysis,then the reconstructed model was compared with the theory model for calculating normal deviation values.Third,the theory model was offset with unequal distance based on the springback deviation values to generate compensation facet and forming path,the finite element analysis was carried out again with the forming path points.Repeating above process until the compensation effect met the required precision set by user.Forth,the compensation iteration algorithm and smoothing algorithm were proposed respectively aiming at the problem of different compensation distance and rough compensation facet in the multi-compensation process.At the same time,a software system was developed based on VC++6.0,MFC class and OPenGL visualization platform,which can accomplish the generation of contour tool-path,surface reconstruction,the calculation of springback deviation values,the generation of compensation forming path and so on.Finally,the conclusion was drawn from the finite element analysis that three times compensation can meet the required forming precision.Then the forming path of the theory model and that of the compensated model after three times compensation were used for forming experiments.The forming experiment results show that the method of the prediction of springback and the generation of forming path with the springback compensation based on the explicit and implicit element analysis is available,which can improve the forming precision of the sheet metal part.