The Roll-setting Method of Automatic Control of Gauge in Hot and Cold Rolling Mills

When strip is rolled at a constant speed, errors in the finished thickness occur owing to changes in width, hardness, and thickness of the incoming material, in tensions applied to it, and to variations in friction in the roll gap. The gauge of strip may also vary when the mill speed is changed. A closed-loop regulator had been constructed to demonstrate, on a pilot-plant scale, a method of automatically controlling the gauge of sheet and strip rolled in hot and cold mills. A measure of the departure from gauge is obtained from simultaneous measurements of roll-load and the roll-setting, and correction is made by varying the position of the rolls. The controller is described together with experiments which demonstrate that the method is capable of consistent rolling to close tolerances in gauge.