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| 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?
Lamination is a process of bonding materials together. Seal laminators accomplish this process by using a set of rollers with a precision ground silicone coating which presses and bonds the materials together.
The materials come with different adhesives attached to them. Some of these adhesives require heat to "activate the adhesive" prior to entering the "Nip", where the bonding process actually takes place. The laminator supplies this required heat by internally heating one or both of the silicone coated rollers. This type of laminator is generally described as a laminator with "heated rollers".
Laminators also bond films that come with pressure sensitive adhesives attached to the film. In this case the films adhesive system requires only pressure and no heat. This type of laminator is referred two as a "cold laminator."
The process starts of by loading rolls of materials (laminations films, and or mounting adhesives onto supply shafts. Those materials are then "webbed" or threaded threw the laminator. The main bottom roller is motor driven with variable speed set by the operator. Prints or images are then fed into the laminator either as cut sheet or on a roll depending on the type of laminator. The materials are then permanently bonded together forming a new product. That was not previously available as a single component.
Modern day laminators or "print converters" have high tech process controls and onboard computers. These "print converters" can process an endless array of material combinations. Allowing the operator to develop products for any type application.
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2. Why do you need heated rollers?
The main reason to opt for a laminator with heated rollers is profitability, as heat activated adhesives generally cost less than pressure sensitive films and adhesives. So by selecting a cold laminator that will not process thermal products could cost you more in producing your finished display products over a period of time.
Another consideration for heaving a laminator with heated rollers is that although pressure sensitive adhesives don't require heat - they do benefit substantially when some heat is applied. This is because pressure sensitive adhesives generally have poor adhesive flow prior to the point of contact of the two main rollers which often leads to silvering in the image. Another reason is that pressure sensitive materials increase their bond strength over time usually a 24 -72 hour period and by applying a small amount of heat you can reduce the waiting period before rolling and shipping.
For optimum productivity, workflow and cost savings, Seal Graphics recommends the purchase of a laminator with at least one heated roller.
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3. How important is speed?
Speed is important particularly 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.
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 varies 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 most 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.
One common mis-conception however is that "more pressure" is better. Too much pressure can deflect the main top roller causing it to bow this will create more pressure on the outer widths of the laminator and less in the middle. The results in an uneven pressure from the far left side of the laminator to the far right side which could cause an in-feed wave which will cause bubbles and even wrinkles.
You should consult your laminator owners manual for the proper roller pressure settings as they do vary depending on the model laminator you have.
Too little pressure can also cause problems like ‘silvering’ which is a defect that happens when very small ‘silvery’ air bubbles are trapped between the printed surface and the lamination adhesive.
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5. Why do you need pull rollers?
Pull rollers improve the quality of output when working with heat-activated materials particularly, thermal adhesives on polyester films.
Pull rollers keep the bonded layers of heat-activated materials taught when they exit the main nip. During this time the materials go from "soft and malleable" to rigid and roll able. By allowing the materials to cool down before exiting the laminator, thereby minimizing material distortion.
Pull rollers work closely with different types of film cooling systems such as "chill rollers" and "cooling fans." to ensure no material distortion such as "boat wakes".
Pull rollers on selected SEAL laminators also provide the ability to mount images from the back side of the laminator while the front rollers are still hot. These laminators are referred to a ‘bi-directional’.
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6. How to avoid waves/wrinkles while using a laminator?
Waves will occur if the speed of the film within the nip is not exactly equal across the width of the roller or the proper brake tension has not been applied on the film, as well as back tension on the printed media.
Waves in your finished print that run in the "web direction" are usually cased by stretching the materials you are laminating together. Classified as film distortion, these waves are more visible when you have a gloss finish. The direction they run will show you which machine adjustments need to be made. Start by reducing the clutch pull pressure. When you process films with thermal adhesives the films soften when subjected to heat. Too much clutch pull pressure can physically stretch your laminated films leaving distortion waves. If you do not have an adjustment for your pull rollers clutch, other items such as using your chill rollers, reducing break tension and lowering your temperature setting will help resolve this issue.
Waves across the web in the image before it enters the pressure rollers are caused by to much down pressure on the rollers. To resolve this reduce the downward (nip) pressure on the rollers.
Waves in the image in the web direction before it enters the pressure rollers can be caused when either a) the Media being encapsulated is very heat sensitive and is expanding, b)the back tension applied to the media is too great or c)the media being encapsulated is of poor quality.
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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 recommend buying 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.
If you are likely to invest in a wider width printer in the future - opt for a wider laminator than you currently need.
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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 its ends it will take on a ‘banana’ shape. 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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