Method for controlling a hydraulic rotary and feed drive for a cold pilger rolling mill

A method of controlling a hydraulic rotary and feed drive for rotating and feeding a rolling stock in a cold pilger rolling mill that produces the rolling stock, the cold pilger rolling mill having a rolling stand which moves back and forth in the rolling direction via a crank drive with a crank shaft, the rolls of the rolling stand being of a tapered design and rolling over a portion of the rolling stock with an alternating sense of rotation as the rolling stand moves back and forth, the roll stand intermittently releasing the rolling stock for rotating and feeding the rolling stock to a new position via the hydraulic rotary and feed drive as a function of the position of the crankshaft of the rolling stand, the rotary and feed drive having hydraulic motors which are actuated by a pressure medium for rotating and feeding the rolling stock and assigned to drive members acting on the tube, the method comprising the steps of:

• retrieving a stored time interval from a memory, the stored time interval corresponding to an actuation time required for rotating and feeding the rolling stock to the new position;
• controlling a feed of the pressure medium to the hydraulic motors of the hydraulic rotary and feed drive by opening a proportional valve for the stored time interval and thereby actuating the hydraulic motors for rotating and feeding the rolling stock to the new position;
• and
• measuring the actual movement effected by actuation of the hydraulic motors and comparing the measured actual movement with a stored desired value and determining differences therebetween, and determining a change in the stored time interval required to correct the differences between the measured actual movement and the stored desired value.