Abstract: Low forming accuracy is an important defect of sheet metal incremental forming process. Aiming at the evaluation of incremental forming accuracy, an evaluation method based on displacement error is proposed, i.e. the forming accuracy is measured by determining the deformation displacement along the measuring direction. Forming accuracy of a set of cone type formed parts is studied by using the displacement error method, and the important influencing factors of the forming accuracy are springback of sheet metal and stiffness of forming tool system, were advanced in this investigation. During the forming process, constant forming angle causes constant springback, varied forming angle causes varied springback, and there is a nonlinear relationship between the forming angle and springback. Based on this, forming accuray improvement methods of the formed parts are indicated: (1) compensating the error size caused by the springback of sheet metal and insufficient stiffness of the forming tool system, (2) increasing the stiffness of the forming tool system. Experiments prove that both (1) and (2) can greatly improve the incremental forming accuracy of parts.

Key words: Displacement error, Forming accuary, Incremental forming, Spingback, Stiffness of forming tool system