Polymer Film Production: Modeling and Control of the Forward Draw

Many industrial processes involve the transportation of a continuous web of material over a series of rollers to obtain a finished product. The manufacture of polymer film is one such web transport process, which utilizes a series of rotating elements that act to manipulate the film. This paper develops a dynamic mathematical model of the "forward draw" in a polymer film production process. The model is capable of being implemented in real-time for control purposes, yet includes significant physical phenomena such as material damping. Experimental results from a pilot production plant are used to validate the model under steady-state and transient conditions. The model is then used as a basis for a feed-forward control scheme, which reduces speed variations in the forward draw by a factor of 8 and therefore improves considerably the film quality.