Toolpath Planning and Generation for Multi-Stage Incremental Forming Based on Stretching Angle.

To solve the problems that exist in the multi-stage forming of the straight wall parts, such as the sheet fracture, uneven thickness distribution, and the stepped feature sinking, a new forming toolpath planning and generation method for the multi-stage incremental forming was proposed based on the stretching angle. In this method, the parallel planes that were used for forming toolpath generation were constructed by using the stretching angle so that the distances between the parallel planes and the forming angles were gradually reduced. This makes the sheet material flow become changed and the thickness thinning is relieved. The software system for the toolpath generation was developed by using C++, VC++, and OpenGL library. In order to verify the feasibility of the proposed method, numerical simulation and forming experiments were carried out for the single stage forming, the traditional multi-stage forming, and multi-stage forming based on the proposed forming toolpath, using 1060 aluminum sheets. The comparative analysis of the thickness distribution, profile curve, strain curve, and sheet material flow shows that the proposed method is feasible, and the profile dimension accuracy is better, the thickness distribution is more uniform, and the sinking and bulging are significantly reduced. The formed sheet part with the stretching angle of 15° has higher dimensional accuracy, smaller bottom subsidence, and larger thickness than that of the stretching angle 5°.