Study Of Springback Of Single Point Incremental Forming For Sheet Metal

Single point incremental forming is a production technology with low production cost and high degree of flexibility.It has been widely used in automobile manufacturing,aerospace,medical equipment and other fields.However,serious springback defect problems occur in the parts formed by the technique,which often makes the shape and size of the parts not meet the accuracy requirements.Therefore,aiming at the springback defect,the influence of some technological parameters on the springback of forming parts was studied.The specific work of this thesis is as follows:(1)The relationship between the three process parameters and the springback of the formed parts was analyzed by numerical analysis,including different sheet thicknesses,different bottom areas and different support modes.The thickness of sheet metal is inversely proportional to the springback of the side wall and the bottom of the forming part.The bottom area of the forming part is inversely proportional to the negative springback of the side wall of the forming part.Compared with the way that the lower pressure plate does not extend out,the negative springback of the side wall in the way of the lower pressing plate extending is smaller.Then a formula for calculating the wall thickness of square cones is derived,and the correctness of the formula is verified.(2)The effect of sheet thickness and bottom area on the springback was verified by machine tool experiments.When the parts are processed in the way that the lower pressure plate is not extended,the accuracy of the parts is seriously reduced due to negative springback.Therefore,the relationship between four factors and negative springback was studied by orthogonal experiment,including forming temperature,layer feed,forming angle and forming height.The experimental results show that the forming angle is the main factor affecting the negative springback of the side wall,and the height of the forming part is thesecondary factor affecting the negative springback of the side wall.A parameter combination consists of a forming angle of 40 degrees,a forming temperature of250 degrees,a layer feed of 1.5 mm and a height of 25 mm.This combination is the best.(3)Experiments show that the springback of the formed parts can only be suppressed by changing the technological parameters.The springback of the formed parts can be effectively reduced by tool path compensation.Therefore,the positive and negative springback of 45 degree and 50 degree parts are compensated by tool path compensation method respectively.It is found that when the tool path compensation value is 0.5 mm,the average positive springback of 45 degree and 50 degree parts is 0.11 mm and 0.39 mm respectively,and the compensation effect is the best.The negative springback is also significantly reduced after tool compensation.(4)In order to effectively establish the corresponding relationship between the springback of the side wall and the parameters,springback prediction was carried out.The man-machine interface is designed in MATLAB,which simplifies the operation steps of BP neural network prediction.The structure of3-6-2 three-layer BP neural network is selected.The input layer includes three parameters: forming angle,forming temperature and layer feed.The output layer includes two parameters: side wall springback and bottom Springback.The prediction accuracy of the two algorithms is compared,including BP neural network and BP neural network optimized by particle swarm optimization.For the springbackof side wall,the absolute error of PSO-BP algorithm is ±0.07 mm,and that of BP algorithm is ±0.05 mm.The prediction accuracy of the two algorithms differs slightly.So these two algorithms can be used to predict springback of forming parts.