Advantages of the PlanetCalender® for the production of transparent film and sheet
Markus Berndt, Dipl.-Ing. (FH), Sales Manager Thermoforming Film and Sheet Extrusion Lines, Berstorff GmbH (Germany)
The patented PlanetCalender® is the ideal smoothing roll unit for the manufacture of transparent film and sheet in PMMA, PC, PET, PS and SAN. Of the three rolls, only the central one is fixed whilst the other two can be arranged with complete flexibility, thus enabling cooling to be controlled over the entire roll contact area. For different polymers and different film and sheet thicknesses, the cooling down can be optimally adjusted during the process. By adjustment of the first roll, the melt entry angle can be controlled to suit the weight and elongation of the melt. Wrapping angles from 90 to 240 degrees can be realized. For thicker sheets, the necessary cooling conveyor is connected to the third roll to have a tangential transfer of the sheet from the third roll to the cooling conveyor. A software system is provided to calculate the cooling down process. The different parameters, like processes, outputs, polymers or thicknesses, are shown in the presentation. The basis for the calculation is to define different phases which characterize the cooling process. Phase 1 describes the first contact of the melt on the first cooling roll. Phase 2 shows the first, phase 3 the second roll gap. Phase 4 describes the point when the sheet leaves the third roll. Finally, phase 5 represents the end of the cooling conveyor. The sheet is then separated into different layers showing the following results: 0% represents the surface of the sheet which has first contact to the centre roll. 100% represents the opposite side of the sheet. 50% is the centre of the produced sheet.