Method and device for forming a hollow body

摘要

The invention relates to a process and apparatus for the forming of a hollow body. The process includes providing a forming mold comprising an upper mold and a lower mold which form a mold cavity having a cross-sectional contour in a closed state of the forming mold. The upper mold includes a roller. The hollow body is placed between the upper mold and the lower mold in an area of the mold cavity. The hollow body is preprofiled by moving at least one of the upper mold and the lower mold into the closed state at which time the roller comes into frictional contact with a surface of the hollow body running at an acute angle with respect to a direction of the movement of the at least one upper mold and lower mold. The preprofiled hollow body is then formed into a final shape corresponding to the cross-sectional contour of the forming mold by applying a hydraulic internal pressure into the preprofiled hollow body and expanding the hollow body while the upper mild and the lower mold are in the closed state. By way of the present invention, a hollow body can be reliably formed while significantly reducing the stress on the hollow body.