New Model 8000 gauging system for multilayer blown film from NDC, Irwindale, Calif., can quickly determine both the profile shape and average thickness of both the total web and critical barrier layers. A MiniTrak-O scanner is installed after the collapsing frame to measure the double layflat film thickness using an FG710S infrared sensor. This sensor provides coextrusion thickness measurement for up to four components, such as nylon and EVOH barrier layers.
The system measures the double layflat film and then processes this data through a special algorithm called DLSA that mathematically separates the two layflat layers to provide a continuous, full-circumference, single-layflat thickness profile.
The algorithm includes accumulator and die-rotation modeling that accurately maps the film against die position. The algorithm calculates die or nip oscillation/rotation speed and direction, bubble twist and melt-slip modeling, and diebolt/air-ring mapping. The result is a 360° profile of total thickness and barrier components within thee to four scans, taking 1 minute or less.
Automatic profile control supervises the diebolt positions based on the DLSA profile measurement. The control also includes a “smart” pulse alignment profile map. Profile control to less than ±2% has been achieved.