On-line Gravimetric Feeding and Gauging Control, 1990 Polymers, Laminations & Coatings Conference Proceedings

Gravimetric mass-throughput overcame the first years of practical test. During this time two different systems were developed for extrusion. While the discontinuously working weigher can be calibrated absolute exactly and simply, the continuous weigher showed a dependency on the operation point and not on linearitary. With the development of material decoupling, by which the material in the weigher and the feed zone of the extruder is decoupled, absolute values and a very linear behaviour was achieved by modification of the continuous weigher. This is the prerequisite for extremely exact controlling of haul-off speed or dosing of material components. During extrusion the average layer-thicknesses of the film can be extruded over, for instance, the screw speed of the extruder.

The capacitive calculation of film thickness is a very accurate method at a favorable price.

By combination of the gravimetric mass-throughput recording and capacitive film thickness calculation, the relative thickness values can be calibrated to absolute thickness values. This is done inline and without manual interferences. This leads to an excellent measuring system which can be used for display and documentation of thickness measured values on the screen mask and can be considered as a basic value for controlling interventions in the overall process of film production.