Light in front of the whole automatic production line are the highest tensile machine, the entire production line tension is followed by the process of the tension in the medium range, and the light machine tension somewhere in between, and designed a tension roller, 4 will pull back, steel belt light overall tension in the section on the basis of improved technology, namely light overall tension tension roll process period of tension and 4, the sum of its size by adjusting the tension roller 4 current to achieve. Light used in most cases the appliance pressure mode, then 4 tension roller is a model. Also sometimes use elongation model, then 4 tension roll into elongation model.