In contrast to the slow reaction of the feed back control the volume flow control reacts very fast to thickness changes because the negative influence of the strip transport time between the gap and the exit thickness gauge have no influence to the volume flow control response time. 

The basic principle of volume flow control is that, based on the measured entry thickness deviation, the target entry and exit thickness and the measured entry and exit strip speed, the exit thickness deviation is calculated. This calculated exit thickness deviation is in the same moment available in which the strip thickness can be affected in the roll gap. This means that it is possible to react immediately on thickness deviations. 

Due to measuring inaccuracies there is a very small deviation between the estimated and the target thickness. Therefore the measured exit thickness deviation is used to correct the estimated deviation and to ensure the target exit thickness of the strip. For volume flow control a proportional and integral (PI) controller is applied. The volume flow control calculates offsets to the position control taking the strip width dependent mill modulus and the material modulus into account.