Unwind tensions should be set to a minimum. You only need enough tension to ensure the film tracks through the web guide and over the rolls without creasing. Rewind core should be clean and free of old web or debris. Nip rollers, lay on rolls application rolls for film lamination should also be cleaned and completely free of dried adhesive or debris.
Curl of the laminated web should be confirmed before beginning to laminate by cutting a x in the center of laminated film with glue.
If the film curls towards the sealant in the machine direction, you should decrease the secondary web tension, or if aleady low, increase the primary web tension. If the laminate curls towards the primary layer, generally an inextensible web, decreasing the primary layer tension or increasing the secondary web tension may help or there may be in roll tension from the supplier or drag somewhere in the machine creating excess tension under load. The lay on roll should be used on all laminations. This roll ensures air is squeezed out between the film wraps. The ensuing roll pressure as you build the roll diameter will squeeze any unwanted air from between the laminated film layers. Ensure tension reduction as the roll builds and to ensure enough roll pressure during the run.
Coat weight for flexible packaging lamination is determined by manually measuring the amount of adhesive applied across the laminated web.
Coat weight should be confirmed in three areas minimum, each side and the center of the web. Depending on the width, you may need to measure more than one area in the center, spaced evenly. Measure coat weight with PU adhesive for laminate at the desired temperature and at machine line speed. If there are no clear areas, use clear film or foil sheet to set up your machine and make adjustment to the application roll speed or gap to adjust the desired coat weight. Coat weight should be confirmed at the beginning of each run.
