Research On The Theory And Technology Of Intelligent Control For Profile Stretch-Bending

Profile stretch-bending is widely used in automobile and aerocraft industry. The most prominent problem in profile stretch-bending process is that it is difficult to control bending springback accurately, especially complex workpiece. There are many factors that effect the springback of stretch-bending. Even if for the same trademark,batch plate, the material performance and the technical condition variation can also cause comparatively big change of the springback. The current manufacturing industry trend to develop high accuracy, the multi-varieties, the small batch bending workpiece needed in market and the difference between raw material cost and the final product price reduces gradually. The competition in market is so drastic that more effective method is needed to reduce the production cost and to enhance the productivity. Using the intellectualization to realize accurate control of springback is one effective way to solve above problem.The intellectualization of profile stretch-bending regards each blank as individual with different performance identifies in real-time the performance parameter of each individual, consequently confirms the optimal craft parameter, and finally accomplishes the process of stretch-bending and unloading with the optimization craft parameter. In this way, high precision workpiece is obtained.The key technologies of intelligent stretch-bending are analyzed, and the relevant issues to the theoretic analysis, the identification of parameters, the prediction of optimal technological parameter are studied in this paper.Among the four basic elements required by intelligent stretch-bending of sheet metal, the establishment of the identification model of parameters and the prediction model of optical technological parameter is dependent upon the level of understanding of the forming rules of stretch-bending. Based on sheet metal plastic forming theory and according to the stretch-bending characteristics, the study is conducted on the stretch-bending process and springback mechanism of all profiles with minimal curvature in the loading condition that bending is carried out after stretching. The influence rule of the geometrical parameters and loading parameters on springback in the stretch-bending process is found. The theoretical basis of intelligent control of profile stretch-bending is established.The main factors having effect on stretch-bending of rectangular sheet metal and its springback after unloading have been analyzed by adopting theoretic analysis, finite element method simulation and experiments. The revision approach of theoretic prediction model and the criterion of property parameter of real-time identification are proposed.A portable DAQ system is established by applying virtual instrument control software LabVIEW,6062E card and other modules. Based on portable DAQ system, the signal acquisition and sensor calibration are developed, and the satisfied speed and precision to monitoring and control of signals is acquired. The intelligent control system of stretch-bending process is completed. The approach of controlling springback with the aid of regulating pre-load is proposed. The experimental stretch-bending devices are designed and manufactured. At the same time, the hydraulic system used for experiment is modified. The stretch-bending experiments of rectangular sheet metal and symmetricalПsection are conducted and the results obtained indicates that the theoretical prediction models established in this paper is reasonable and can be used in practice.