Local bending effect and its controlling methods in multi-point forming

摘要

In multi-point forming (MPF), the dislocation in the direction of forces from the upper and lower punches generate a local bend moment (LBM), thus reducing the forming precision. This phenomenon is called local bending effect (LBE). The force instability of the edge area magnifies LBE and increases the shape error significantly. Numerical simulations were carried out to analyze LBE and its controlling methods. Results show that the increase of the effective forming area (EFA) can convert the edge instability into a relatively balanced state and greatly improve the forming precision of the edge area. But it has little effect on the central zone. The use of swing units can increase the contact area between plate and punches and diminish the dislocation of force directions, so that the forming errors can be reduced among the whole plate. Parts of high forming precision can be obtained under the combination of the two methods. Experimental tests proved the effectiveness and realistic feasibility of the amendment by increasing EFA of MPF.