Hydraulic screwdown control system for mandrel mill

A hydraulic screwdown control system for the mandrel mill was successfully installed at Wakayama Steel Works of Sumitomo Metal Industries, Ltd., in April, 1989. The purpose of the control is to shape the tube ends in a thin tapered form. By applying this screwdown control, it is possible to eliminate end thickening in the reducer and to reduce the length of crop losses. This screwdown control system must respond rapidly without position offset error. Therefore, the following functions of the screwdown servo control were applied: (1) velocity feedforward compensation, (2) position offset compensation, (3) hydraulic pressure feedback compensation, (4) adaptive function of screwdown start time, and (5) application of an expert system.<>