Q.: How can i eliminate silvering, or a myriad small bubbles of air caught between the image and the laminating film?
A.: Silvering may be caused by insufficient heat to fully melt the adhesive layer, but in digital imaging applications this problem is more likely to be caused by the excessive heat needed for a "high-melt" laminating film, or the heat built up when laminating too slowly. Ink jet output often needs to be laminated before it is fully dry, so heat can drive vapor out of the moisture in the ink. Use a "low-melt" laminating film. Keep the laminating speed up. One little known trick of the trade is to run the item image down (provided you are laminating 2 sides with the same film on top and bottom). This will get rid of that last bit of silvering which will typically show up on the dark areas of the image (where ink coverage is heaviest).
Silvering is often seen when laminating with cold films too. With many cold films, this silvering will go away by itself in a day or so as the adhesive penetrates and pushes the air through the back of the sheet. If silvering is extreme, the film may benefit from a heat assist. Cold laminating does not work well in a cold room, and most cold adhesives will flow better with a heat assist even in hot weather.
Q.: Does wrinkling of one side of the web or skewing of images as they are laminated indicate that the pressure on one side of the laminating or pull rollers is greater than on the other?
A.: Skewed, wrinkled laminated images are most often generated by skewed trimming or skewed feeding. If the leading edge of an image is not trimmed at right angles, the nip will catch one side before the other. Unless the paper is fairly heavy and stiff, the item will most likely be ruined. The same thing will happen if the operator feeds an item in with the leading edge not parallel to the nip. If trimming or feeding is not the problem, check to make sure the laminator's roll tension is balanced. Make sure both set of rollers are fully closed. If your laminator has a lock position for the laminating rollers, make sure they are locked. Consult your laminator vendor if the problem persists.
Q.: Laminating film gets wrapped around one of the laminating rollers (or pull rollers). How can I correct this?
A.: This problem is caused by allowing exposed adhesive to go onto the rollers. Adhesive may stick to the rollers, or it may build up on the rollers to cause a wrap-around later.
When laminating two sides, make sure:
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The top and bottom webs are the same width and lined up within 1/8 of an inch or so.
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Never allow one roll to run out before the other.
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Put matched rolls on the machine, and if you can't do that, stop laminating while there are still a few turns of film on the smaller roll.
When laminating one side:
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Keep your items wider than the film and keep them overlapping each other; or run a web of paper under the web of film.
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Sheets of scrap paper or plastic can be run under the web of film as you set up adjust the machine, and do your laminating.
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There should be an unbroken stream of material under the adhesive as it goes into the nip.
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If adhesive does get on the rollers, clean it off before continuing to work. Use a hard rubber eraser or a moistened white Scotchbrite pad to clean the adhesive off a warm roller. Then wipe the roller down with a clean cloth and some glass cleaner.
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NEVER try to clean the rollers while they are turning. Clean one section of the rollers at a time while the laminator is turned off.
Q.: Why do large bubbles appear intermittently, and only on one side when laminating items are being encapsulated?
A.: This generally indicates that the image is getting in contact with the adhesive before the nip.
Causes can include:
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Curled images
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Improper feeding, and
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Insufficient supply roll tension.
Make sure the leading edge of the image goes into the laminator straight and flat. Then pull back and to the sides on the trailing corners to keep the item flat as it goes in. Keep the item on the same plane as the feed tray.
Q.: What causes bubbles or wrinkles in the laminate?
A.: The presence of bubbles and/or wrinkles in a laminated film is caused by insufficient supply roll tension due to the film core slippage on the supply roll mandrel. Increasing the clutch tension doesn't help, because the roll is turning on the mandrel, instead of turning with the mandrel. Either the supply roll lock mechanism has failed, or it was put into the laminating film core backwards.
Q.: How can I eliminate tenting of the film on the image?
A.. This has nothing to do with the laminating film or the laminator. It's caused by various contaminates such as dust, dirt, grit, or lint on the surface of the image. Use cotton gloves, a tack rag, or a cleaner roller, as appropriate to clean your image just before it is laminated. If your lamination system is not in a fairly clean environment, close off the area and filter the air, or move the laminating system.
Q.: What causes laminated images to exhibit opposite corner curl?
A.: Opposite corner curl comes from stretching the laminating film too much. See the two previously discussed laminating problem solutions. Reduce supply roll tension on both top and bottom.
Q.: How do I keep laminated images from curling up or down?
A.: Make sure lamination temperature and supply roll pressure are the same on top and bottom. Curling up indicates too much tension on the top web, curling down indicates too much on the bottom. The same problem can happen in cold laminating. Excessive supply roll tension causes the laminated image to curl up. The curl can be strong enough to prevent the item from hanging straight. It can even pull a mounted image off the substrate. Don't try to use different thickness films on top and bottom, until you become a finishing expert. A finishing expert is someone who makes the same mistakes as a beginner, but knows how he made them.
Q.: What is necking in a laminated film?
A.: Necking describes a problem where the laminating film becomes narrower as it is exposed to heat before it goes into the nip. To solve this problem, decrease the laminating film supply roll tension and/or decrease the heat. There is a tendency to believe that if 220¼ F is good for laminating, 280¼ F is better. If two turns of tension are goodfor laminating, four turns must be twice as good. Even laminating and finishing professionals tend to use too much heat and too much unwind tension. Use the least amount of supply roll tension that will do the job, the job being to keep wrinkles out of the finished web.
Use the least heat that will yield a good bond.
Q.: What causes warping or waviness over the entire surface of a laminated film or print?
A.: This generally indicates that a coated paper or plastic substitute is reacting to heat. The answer is not to reduce the lamination temperature, but to increase the speed. There seems to be a tendency for people to run their laminators much too slowly. We generally run our 5-mil film at five or six feet per minute. Thinner films, where they are appropriate, can be run faster.
Q.: How can I eliminate fading of a digital image even though it has been laminated with a uv film?
A.: The only solutions I know are:
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Develop better inks
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Lose our preoccupation with the images that will last outdoors for years.
The thought process that drives people to buy digital imaging services goes something like this:
* I can get it now.
* I can get it the way I want it.
* I can replace it when my market/promotion/price/goal changes.
* I can afford it even for a single, brief event (it doesn't have to last forever).
Here are some facts that will put the issue of color fastness in perspective.
* Off the shelf films (without added UV screening agents) already keep out most of the UV spectrum. The base, or adhesive layers, of hot or cold films only allow a fraction of the UV light through.
* The entire visible spectrum causes fading. We can't screen that without hiding the image.
* Adding the UV screening agents adds little to the image life and a lot to the price of the film. You choose.
* Depending on many film and environmental variables, lamination will generally add about 20 to 80 percent to the color life of an image. That can be valuable if the ink has a long enough inherent life.
* Color enhancement and protection of the image from handling, moisture dirt, abrasion, and other immediate environmental hazards are far more important benefits than added resistance to fading.
Q.: What film thickness should I use for laminating?
A.: Information about polyester content has to come from your film supplier, and is expressed as a ratio. For example, a combination that is ideal for a wide range of digital imaging applications is a 3-2 film or 32 film. The first number 3, represents the mil of polyester. The second number 2, is the thickness in mil (millimeters) of the polyethylene.
We have found that:
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Novice laminator operators who use a good 3-2 film have a very few problems and few rejects.
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The use of a 3-mil film greatly increases the reject rate during the learning curve.
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There is also a 1-4 combination 5-mil film. If you have any 1-4 film in your shop, do yourself a favor and don't use it in a digital imaging application.
Q.: Should I use vinyl laminating film or polyester film?
A.: Polyester is too stiff to be used over vinyl for applications where vinyl was chosen for its flexibility.
Most films are two part films, for example a film may have as an outside layer, polyester, and as an inside layer, polyethylene.
The polyester is very important because it is the layer of the film that ends up on the outside of the finished item. It is the part which does not melt, and which has to hold the polyethylene adhesive together while it is in a liquid state at the operating temperature of the laminator.
High polyester films are more expensive, because polyester is more costly than polyethylene. Using the wrong film for finishing applications for graphics will ruin the image, create additional work, and delay your production. It's just too expensive to buy cheap film. Some films may contain agents and primers in conjunction with the polyethylene to make it bond to the polyester, adhere to the graphic, or to make it melt at a lower temperature. These are additives known as co-polymers, which offer three significant benefits:
* They allow the polyethylene to melt at a lower temperature.
* They make the polyethylene more adhesive.
* They make the polyethylene clearer (when a film lacks clarity, it's usually because the polyethylene is cloudy).
Other agents may be added to make the adhesive bond better to particular kinds of graphic surfaces. Primers are used to make the adhesive layer stick better to the base layer.
Q.: Do I Use Hot Or Cold Lamination?
A.: The vast majority of graphic and digital image laminating is done hot. Hot lamination tends to be much more permanent and tolerant of rolling or folding. Hot laminating generally uses inexpensive films. Thermal laminators can apply film to both sides. Hot lamination can offer true encapsulation of an image, while cold lamination generally cannot.
Cold laminating film has to be used with papers or inks which cannot tolerate heat. Cold laminating film is several times more costly than hot film. Cold films tend to offer more choices as to base film (i.e. polyester, vinyl) and type of adhesive (i.e. permanent, repositionable). Cold lamination is typically a one-sided process. Some cold lamination can tunnel if rolled or folded. Cold laminator equipment is usually less costly than hot laminators.
Cold lamination is often preferred over vinyl because a vinyl over-lamination maintains the "hand," or flexibility of vinyl.
Q.: In thermal laminating, how can i eliminate wrinkling, silvering, waviness, stretch marks, and delamination?
A.: Typically, these laminating film problems are caused by using the wrong laminating film for the job.
Digital imaging finishing applications; whether ink jet or electrostatic, require laminating films of the highest quality. Many common graphics finishing jobs benefit from higher quality laminating film.
What constitutes high quality? In short, high polyester content, low melt temperature, clarity, and more aggressive adhesives constitute quality.
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Clarity can be observed in the finished output and should be close to "water-clear." You do not have to accept output that has a milky appearance.
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Information about polyester content has to come from your film supplier, and is expressed as a ratio. For example, a combination that is ideal for a wide range of digital imaging applications is a 3-2 film or 32 film. The first number 3, represents the mil of polyester. The second number 2, is the thickness in mil (millimeters) of the polyethylene.
Q.: Hot or Cold Laminating
A:. Should I mount laminated products hot or cold?
Printed graphics can be laminated and mounted either hot or cold. When coated papers are mounted to coated substrates, cold mounting is more reliable.
In digital imaging applications, Pressure-Sensitive Adhesives (PSA) is used more often than dry mount adhesives. PSA's run a lot faster, and permit relatively high speed simultaneous mounting and laminating.
Conventional dry-mount adhesives often do not do a good job of holding coated ink jet papers to coated mounting materials such as foam board. While some new heat activated adhesives have been developed especially for coated papers and mounting boards, many imaging businesses still use cold pressure-sensitive adhesives for mounting.
Q.: What about roller flat spots
A.: Flat spots mainly occur on soft sponge rollers as a result of the machine not being operated over a long period of time. Pressure on the rollers causes the soft rubber to compress, which can leave a repeating mark across the width of a laminated item
How do I prevent flat spots from occurring?
If the machine is not in use for over a month, back off the roller pressure springs, taking note of their current settings. When the machine is back in use, tighten the roller pressure springs.
My rollers have flat spots, what can I do?
Firstly, ensure that this is your problem. A flat spot is visible on a roller, and can be felt by hand, remembering to never feel the rollers while they are turning. The mark left by flat spots is a narrow strip across the width of the lamination, which repeats regularly. To remove a flat spot, remove film from the machine and run the laminator at medium speed. It may take around half a day of running to remove the flat spots. If you are unable to solve your problem, please contact your supplier for more information.
Q.: How to position mandrel core adapters
A.: Care should be taken to make sure that core adapters are spaced evenly over the width of the mandrel. This prevents the core from moving or buckling, which can result in poor quality lamination. The quantity of adapters supplied differs between machine widths, but the adapters should always be positioned with one at each end of the film core, and the remaining adapters spaced evenly between these two.
Q.: What is proper positioning of a thermal laminator
A.: Thermal laminators should be kept out of draughty areas, such as near open windows, air conditioning vents and electric fans. This is to prevent unwanted cooling of the heater bars which can cause problems with laminating. Draughts can also carry dust, which is a problem for both thermal and pressure sensitive laminators.
Q: What are some tips for successful lamination of large batches?
A.: When laminating, try to prevent items which are exiting the laminator from falling to the floor whenever possible, for the following reasons.
* Static electricity which builds up during the laminating process can cause dust to stick to the film.
* Scratches can be caused by rough flooring surfaces
* In long runs, the collective weight of other items can cause crushing and creasing damage to items
Preventing items from falling to the floor can be achieved by having an assistant hold the laminated item as it exits the machine, by using a smooth table or bench behind the machine, or by winding the items onto the Rewind / backing paper rewind system available on some models of laminator.
Q.: Advice for proper care of laminated items?
A.: Once an item has been laminated, it is important to handle it properly to ensure that it is not damaged. Laminated items are best when wound into a tube, and should never be allowed to crease. It is also important to never allow a laminated item to touch the heater bar of a machine, as this will permanently mark the item.
Q: How should I prevent marks on laminated items
A.: Wearing a pair of lint free cotton gloves can prevent marks on items being laminated, as oils in the skin can cause marking on items. Heat from thermal laminators, or hot weather can cause sweat to build up on hands, which in turn can cause marks on laminated goods.
Application Tips for all Professional Image Laminating Films
* If possible, store laminates 24 hours prior to use in the same or similar environment as the finishing department. Radical changes in temperature or humidity can create problems.
* Store all laminates upright or make sure they are suspended. Laying laminates on their side, especially pressure-sensitive materials, will create flat spots.
* Before laminating, be sure that the print is clean.
* When applying a laminating film to a print, laminator operators should start with as little tension as possible, adding more tension as it is required.
* Remember that with any laminating film, inadequate pressure can cause silvering which will be particularly visible on darker colors.
* When laminating a print, try to laminate the entire print without stopping. Stopping in the middle of an image can create "hot spots" and/or flat spots. Removing a release liner from a laminate in a "jerky" or stop-and-go fashion (especially clear polyester liners) can create lines in the adhesive, which can then be transferred to your image.
Application Tips for Pressure Sensitive Laminating Films
* Applying a little heat (see specific product specifications) to cold laminating films will reduce silvering and curing time.
* Adjust the take-up shaft in such a way that the release liner is removed just prior to the laminate entering the nip rollers. By reducing the adhesive's exposure to the air, there is less chance of picking up dust particles.
* When laminating on 1 side only, save your release liners and web the liner on the bottom roller of the laminator. As the print is laminated, the release liner will protect the bottom roller from adhesive build-up when your print is smaller that the width of the lamination roll.
Application Tips for Adhesive Films
* If you experience problems when mounting you might not be spending enough time preparing your substrate before coating. This can be the most important step when mounting a print for display, though it is often overlooked.
The surface of Foamboards (GatorFoam(tm), Foam-Cor(tm) etc..) is porous and often contains particles that can spoil an otherwise perfect mount. To prepare clay- and veneer-coated foam boards, the surface should be scraped. After scraping the board, wipe the surface with a lint free cloth to remove dust particles.
* Always run your laminator with the least amount of tension possible on the supply shaft. Excessive tension may cause your adhesive to lift or curl your board.
* Do not wipe your substrates with alcohol as they are entering your laminator as you will risk losing adhesion if alcohol gets trapped between the adhesive and the board. You should always allow time for the alcohol to evaporate prior to applying your adhesive
* Draw guidelines on the in-feed table of your laminator. This can become an important reference when mounting to larger substrates. The adhesive material may run off the board at the end if it is not lined up correctly
* Maintain your equipment. Dirt or debris on your rollers can result in surface imperfections, ruining your prints. Also, adhesive residue left on your rollers can cause uneven hardness across the roller creating more problems for you in the future
* Some foam boards absorb moisture and have a propensity to warp. If, however, you also coat the backside of the board with a suitable laminating film and provide the proper tension, the board should remain flat. Most "bowing" and warping occur as heat exits the board. The heat exits boards at a greater speed through the back of the board causing it to bow towards the back of the board. This film coated on the back of the board helps the heat to escape evenly
Michael
Brunstedt michael@stikesco.com 1452
W. 110th
Cleveland , OH 44102 Phones:
216.227.8521 & 216.458.0604
