Seal Information - Laminators Explained

FAQ Laminators

1. How does a laminator work?

2. Why do you need heated rollers?

3. How important is speed?

4. How important is pressure?

5. Why do you need pull rollers?

6. How to avoid waves/wrinkles while using a laminator?

7. How to determine the width of your laminator?

8. Why do SEAL laminators have crowned rollers?

1. How does a laminator work?

A laminator uses a pair of rollers to apply a film on a printed media. The film(s) and media are joined together by using pressure together with temperature if required. This can be done single sided, but most often it’s done double sided in order to completely protect the image. The film is fed to the rollers from an unwind shaft while the media is fed into the nip by hand.


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2. Why do you need heated rollers?

Heated rollers are needed when you use films that require heat in order to activate the adhesive. For instance if you want to encapsulate a print. However, a little heat can also be used when applying pressure sensitive films in order to make the adhesive spread out a little better. This means less chance of silvering (very small air bubbles).


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3. How important is speed?

Speed is important when working with heat activated materials. The film only has a short time to heat up (when touching the roller). In this time it needs to be heated to the activation temperature of the adhesive. When running too fast the adhesive will not be activated and as a result the film will not stick. When running too slow the film can become too hot causing it to stretch and cause waves and wrinkles. As you can see the speed also depends on the temperature of the roller. In theory you could just increase the temperature in order to go faster, this however does not work in practice. There is a balance to be found which depends from machine to machine and from film to film. For pressure sensitive films speed is less relevant and it’s more up to the experience of the user.


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4. How important is pressure?

Pressure is used to ‘push’ the laminate(s) onto the media. When using heat activated materials only a small amount of pressure is necessary. However, as the name suggests with pressure sensitive film, pressure is the more important factor. By ‘pushing’ the adhesive is activated. A simple test shows how it works. If you take a piece of sticky tape and lay it on a piece of paper you can take it off again without real damage. If you however lay the tape on the piece of paper and then push on it while rubbing you will not be able to take it off without damaging the paper.


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5. Why do you need pull rollers?

Pull rollers are needed when heat activated materials are used. They create a high film tension to overcome the deceleration effect, always present between two rubber coated laminating rollers. This effect starts at the centerline of the footprint (nip), and increases towards its rear border. The deceleration effect causes small lateral ripples over the entire film output. The high tension in the film is realized by using a clutch. It also cools down, and if necessary, flattens the web.



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6. How to avoid waves/wrinkles while using a laminator?

For any kind of laminator the following counts:

Waves will occur if the speed of the film within the nip is not exactly equal across the width of the roller.

Differences in film speed will occur when:

- The pressure, applied between the rollers, is too high (the footprint is smaller in the middle)

- The pressure, applied between the rollers, is too low (the footprint is wider in the middle)

(See also Question 8)

- There is a difference in thickness in the laminates and/or paper, going through the roller nip. For instance a 75mic film on the top with a 250mic film on the bottom. The same goes for a very thin/thick media with a very thin/thick film they will all contract at different rates.

- The width of the lamination film should not be much greater than the media as very large borders at the sides can cause “boat waking”.

Tensions counts: Too much tension will over stretch the film. Too little tension will create waves before the film enters the nip.

- The unwind tension is too low

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7. How to determine the width of your laminator?

The choice you make on what width largely depends on the printer you have and on the jobs you want to do. Normally we say buy a laminator that can handle the width of your printer. So if you have a 36” printer buy a laminator slightly bigger, for instance a 42” laminator. That way you can laminate whatever comes out of your printer. But please also consider the future, since buying a laminator slightly bigger is more cost effective then buying a new one 2 years later.


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8. Why do SEAL laminators have crowned rollers?

To overcome the “bending” effect of the top roller. When a roller is pulled or pushed down by it’s ends it will go banana shaped. This effect increases equal to the amount of pressure you put on the roller. This effect can be overcome by either using some very expensive, big diameter rollers, which would make the laminator twice as expensive, or using rollers which are slightly bigger in diameter in the middle (crowned). This way the pressure (and thus the speed) is the same in the entire nip, which is crucial for wave free laminating.


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