There are several variables that can affect proper lamination conditions. Most of these variables are a result of laminator condition and adjustments. These problems can cause completely unsatisfactory laminations.
Roll Condition
Smooth, clean, parallel, properly adjusted pressure.
Don't: Good lamination must start with nip rolls in excellent condition and adjustment. The upper and lower rolls should be smooth, clean, parallel, and have left and right side pressure adjustability.
Concave, convex, or canted rolls will cause problems such as poor adhesion, adhesive picking, lifting, wrinkling, trapped air bubbles and web steering difficulty.
Feed - In & out
The in and out feed tables must be at the same level or plane and should be of adequate length to hold at least one sheet of substrate. There will normally be curl stresses if the out feed table is positioned as shown above.
Thread Up-Roll Wrap
It is also very important that the roll of laminating adhesive be threaded into the machine so that there is a good smooth wrap around the rubber roll. This will smooth the adhesive and liner and prepare it to be laid down on the substrate. A lesser degree of roll wrap will not accomplish this and wrinkling and bubbling may result.
Nip Pressure
Nip roll pressures can be controlled either manually by screw downs or air cylinders. The best design would be single control for simultaneous and uniform adjustment of both actuators.
The major problems of non-uniform pressure as shown (exaggerated) here, are wrinkling and steering of the web.
Contact Point
A common application problem is caused if the technique allows the laminating adhesive to contact the substrate prior to the nip pressure point. Air entrapment can only be minimized or eliminated by keeping the adhesive off the substrate until it enters the nip contact point. The diagram on the left shows how air can be trapped by premature non-pressure contact of the laminated materials. The air will then remain trapped in the laminate as it passes through the nip and trapped air results in adhesive picking during liner removal.
The following table is the summary of problems usually happened in lamination process and the solutions:-
| Problems | These problems can be solved by adjusting the following |
| Wrinkles, misalignment, poor bond, cross web curl | Roll condition, tension control |
| Internal laminate stresses, down web curl, edge lifting | In and Out Feed, tension control |
| Wrinkles, bubbles, alignment | Thread Up |
| Weak bond, adhesive ooze, steering trouble, wrinkles | Nip adjustment, tension control |
| Trapped air bubbles, wrinkles, adhesive picking | Contact Point |
If the adhesives has water or solvent we called it wet lamination process. Wet lamination can be divided into two processes: The first process is applying the adhesive by rolling head, spraying as mentioned before. The second process is to dry the water/solvent of the materials by the application of heat. Normally it is used a heating drum, oven or infrared heater. Due to the fact the solid contents of the water or solvent based adhesive is between 30-40% so that there is an important quantity of water or solvent to dry out.
Machine Operation Execise
Your job is to solve the problem and let the machine run smoothly.
(Please click on each case for solving the problem)
| Case 1 : Feeding Error |
| Case 2 : Nip Pressure Error |
| Case 3 : Up-Roll Wrap Error |