Analysis on the control points of film covering qu

2022-08-03
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Analysis on the control points of book cover lamination quality

after laminating on the surface of printed matter such as book cover, the products often appear not bright, blistering and wrinkling. Now let's talk about the handling of common problems in operation

1. Temperature control

in rainy days or plum rain seasons, if the temperature adjustment is not appropriate, the coated products will not be bright. There is obvious water vapor on the silicone drum, which is caused by the paper absorbing a large amount of water. At this time, the temperature of the hot pressing drum can be adjusted to 40 ℃. If the temperature is too high, it will blister. Some hydrosol coating machines do not have heating devices, so it is necessary to add drying lamps before pressing according to the connection sequence and proportion of ether bond, ketone group and benzene ring in the molecular chain, so as to dry the adhesive layer and reduce foaming

2. Pressure control

the pressure shall be adjusted according to the thickness of the paper when laminating, generally at 5pa. If the pressure is too large, film wrinkle and paper deformation will occur

3. Gluing control

the glue amount control is controlled by the gap between the homogenizing roller and the gluing roller. In some cases, film scraping is added. The action stroke of high-speed scraping is longer than that of low-speed scraping, so the film pressure is light and the glue amount is large, and the pressure is heavy and the glue amount is small. The amount of glue should be well controlled, so that it can be covered firmly and evenly without crystal point. If the amount of glue is too large, the product will have no luster. Pay attention to prevent small particles and impurities from remaining in the glue tray after the glue solidifies. If it is stuck on the scraping film, a white offset will be produced, causing linear blistering. Before starting the machine, clean the upper rubber roller and rubber bucket with alcohol. If the upper rubber roller is not cleaned, it will cause needle eye blisters. The glue containing impurities can be diluted with water. After the impurities are precipitated, it can be used as diluent to reduce the waste of glue

4. Roller cleaning

when the paper is separated, the glue will directly roll on the silicone roller, causing accumulation, which is easy to wrinkle the product or affect the brightness of the product. The roller should be cleaned frequently to keep clean. The drum itself will wrinkle when it is not normal, so it needs to be replaced

5. Control of temperature and humidity

the ambient temperature and humidity change greatly, the paper absorbs moisture and produces ruffles. The paper is easy to wrinkle during film covering, so the balance of temperature and humidity should be maintained. If the temperature of the heating drum is too high, the tight edge of the paper will wrinkle. It is necessary to control the temperature as required

6. Paper feeding control

skew paper feeding will wrinkle the paper. Be careful during operation to make the paper feeding flat and the pressure on both sides consistent. During paper feeding, try to stack each paper for 3mm, and control the glue amount to prevent glue overflow. This can reduce the mutual adhesion of products after coating. If the joint is wrinkled or cavitating, properly increase the pressure under the condition of maintaining the balance of temperature and humidity to make the adhesion smooth and reduce foaming

7. Film roll control

to prevent wrinkling caused by inconsistent tightness on both sides of the film roll. First, select the film with the same tightness on both sides, and then adjust the tension on both sides of the film to make it balanced and prevent wrinkling. When covering the film, try to use the film with the size of the rough book plus the width of the opening material. For example, for a large 16 folio book, try to use the film with the width of 440mm instead of the film with the width of 460mm, which can save 4% of the cost. When using 780mm wide film for 16 folio, trim the edges as much as possible to reduce the amount of glue and save glue

8. Do not use additives in printing, and control the powder spraying amount

try not to use additives in the printing process, because the clamping device should not be fully locked, not easy to dry, and easy to blister after coating. It is also necessary to control the use of powder. Before laminating, special personnel shall be arranged to wipe off the dusting on the cover, so as to reduce the phenomenon of laminating flowers or bubbles and make the product bright

9. Machine speed control

during the film coating process, do not change the speed of the main machine at will. What are the maintenance skills of the universal material testing machine if the speed is too fast and the glue cannot meet the requirements? Let's take a look. When the acceleration is slightly increased, the glue amount is too large. If the speed is adjusted too low, the gluing amount will be reduced and it is easy to blister. In order to ensure that the glue quantity is basically the same, the speed of the laminating machine can be limited by 60% of the highest speed, so that each shift can run at the specified speed, and data management can be implemented to reduce unnecessary losses

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