Laminating; Cold Spots; Curl - usi CRL 40 Instruction Manual

9.

LAMINATING

9.1

Cold Spots

Good laminating film resins activate at around 212 o F and to produce adequate bond, they need to be
laminated with hot nip rollers. The rubber nip rollers are heated by exposure to radiant heat from the
surrounding heat shoes. As the nip rollers gather less heat in their area of contact with each other,
roller rotation during the warm-up process is essential to ensure even heating. After the initial
warm-up a colder spot may be present at this point where the laminating rollers touch. This is
because the rubber rollers insulate themselves from the heat source at this contact point (See Fig
9.1). Symptoms of a cold spot are a thin, milky horizontal line repeating regularly on the laminated
item. The cold spot on the laminating rollers has insufficient heat to provide the same level of
adhesion as the hotter areas of the laminating rollers.
Fig 9.1 COLD SPOTS
Cold spots are usually a result of laminating before the full warm-up period procedure is finished.
To overcome cold spots allow a longer warm-up time and rotate the rollers more frequently.
A quick way to shorten the warm-up period and to eliminate cold spots is to run the machine with
just the film webs passing through the machine. The passage of hot film accelerates the heating of
the laminating rollers. While not recommended due to the loss of expensive film it may be useful in
urgent situations.
9.2

Curl

An imbalance in roll brake tensions is the cause of laminate curl. The solution is to identify which
roll of film has the higher brake tension. Cut a 200 mm strip of laminated film of the back of the
machine, and by holding it in a vertical position will clearly indicate even the slightest curl.
Upwards curl (as it exits the laminator) indicates higher tension on the top film roll, downwards curl
indicates higher tension on the bottom position.
To overcome the curl adjust the film tensions. Always try to release the brake on the film position
with the higher tension, providing the film passing over the second half of the heat shoe can be kept
wrinkle free. Alternatively slightly increase the tension on the other roll of film.
While most laminated items are generally flat the inherent tensions within film will not always allow
a perfectly flat result.
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