Sometimes problems occur during lamination, the below mentioned are common problems and suggested solutions. If there are some problem which you can’t find here, you may contact us Megabond for additonal technical support for lamination.
1. Accurate and reliable web tension control: the tension of substrate from unwind to rewind should be precisely regulated to avoid formation of creases, wrinkles, curl, etc. and obtain a good finished roll of laminated material. The winding pressure must also work uniformly over the whole web width as otherwise there will be risk of telescoping.
2. Regular and uniform adhesive application: in the solvent process, the speed differential, temp determines the adesive quantity. And gap between the coating rolls. These variable should be monitored and controlled accurately as this will not only affect the overall properties of the final laminate but also affect the economies of the process.
3. Nip pressure and temperature control: the adhesive coated web is combined to the corona treated secondary web at 50℃ to 70℃, by heating the nip roller. The nip pressure must be worked evenly over the web. If the pressure is too low the air will get entrapped. If pressure is too high it will lead to squeeze.
4. Corona Treatment: While some films may be treated to the proper level, other films may need additional treatment on the laminator to promote adhesion. Poly principally has to be treated above 38 dyne/cm. In case of additional treatment in the machine i.e. online corona treatment on the backside must be avoided (sealing weakness).
5. Roll Stage: The rolls are stored in hot room (480C) to accelerate curing which result in better bond strength and visual characteristics. To avoid the rolls taking a set during the curing process, they should be suspended horizontally and the store in a track.
6. Speckling: This occurs when there are spots in the laminate at various positions. This is due to incorrect gsm of adhesive used in the process of lamination.
7. Delamination: This is the problem where the two webs which were laminated together are somehow not adhered properly. This problem arises whenever lamination machine is to be stopped for any defect or some other reason and this then has to be removed while slitting.
8. Blocking in the Laminate: The problem of blocking in the laminate results if the adhesive application is such that some portion of adhesive is not entirely in between the two webs due to which one web tends to stick over the other one which during storage over a period of time, with the pressure of rolled laminate tends to block the laminate.
9. Lamination Wrinkles: Two different forms of wrinkles can occur: those which form in the lamination nip, and those which appear some time after lamination (also known as post-lamination wrinkles). Both of these wrinkles are closely associated with the polyester base film which supports the photopolymer layer but are caused by factors independent of the base film.
10. Adhesive Line: Foreign particles like dust, dirt and some unwanted matter may stick to the engraved cylinder which makes a continuous line in the laminate .this problem arises time to time hence it is important to clean the cylinder within specified time to eliminate the problem.
11. Curling: The cause of curling during drying is two sidedness and therefore non uniform dimensional changes when exposed to temp and humidity. Due to this shrinkage takes place in the coating side and curling occurred.
12. Tunnelling: Web tension of the two substrates should be proper otherwise this problem can come. Second reason may be the ratio of the adhesive can be different or some different grade of adhesives.
13. Blister and Speckling: It may formed during drying, like entrapment of liquids under the adhesive layer, it evaporates when exposed to a higher temp, or Introduction of air trapping.
