For U-shaped channel, a precise bent angle (no springback) is essential, and furthermore, most of the cases flatness of the bottom plate and sharp bent corner are required. To satisfy these requirements, an optimum combination of clamping force F1 and pushing-up forces F2 should be determined. In the case of bending without clamping force (F1= 0 kN) combined with bottom pushing-up force F2=10 kN, it was found that, springback angle