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This article mainly discusses quality accidents such as boat wrinkle film, transverse corrugation, printed product warping, poor adhesion and blistering, and solutions. Purely personal point of view, for reference only.
Boat wrinkle film
Boat wrinkle film refers to the distortion of the film after the film is covered, just like the traces produced by a boat passing over a calm lake. Goetter said that because the film is forced to stretch under the action of the laminator, whether it is using thermal or pressure-sensitive, it is possible to produce film distortion.
There are three types of boat wrinkle film accidents: away from the point of action, point to the point of action, and line-type stretch. Regardless of the type, it is because of the excessive pressure exerted on the film.
Solution
How will you deal with the structural sequence of the functional components of the film coating equipment? Goetter recommends not ignoring the chill roll, he said. "I don't claim to wind the product directly after lamination. Cooling rollers and cooling fans are the best way to avoid wrinkle film." When the printed product passes through the front portion of the hot press roller and the rear portion of the press roller, the magnitude of the applied pressure and the pressure of the press roller in the printed matter have a great relationship, and the larger the external force is, the more easily the film is twisted.
According to Goetter, using a cooling device on the back pressure roller or clutch is easier than using countless adjustment devices. If the laminator does not have a chill roll or cooling fan, try the following steps. For boat wrinkles away from the point of action, the pressure on the rear pressure roller can be reduced. For boat wrinkles pointing to the point of action, the pressure on the pressure roller can be increased. If the pressure applied to the film is too high, the film will stretch, resulting in long lines. At this time, the pressure applied to the rear pressure roller by the clutch should be reduced.
Horizontal ripple
Lateral corrugation, that is, after the film is covered with the film, forms a small strip of bubbles, typically due to the excessive pressure exerted on the pressure roller. In order to explain this problem, Goetter suggested using the thumb and index finger to make an "OK" shape. The connection between the two fingers can be described as pinching. The more you grip the two fingers, the larger the area between the two fingers. This is like the upper roller and the lower roller of the laminator. The greater the pressure applied, the greater the area of ​​contact. If the contact area varies with width, the print will pass through the laminator at different speeds. The bent prints come in contact with the adhesive, and then the air that is carried over the uncovered area causes the formation of small bubbles.
According to Goetter, if the contact area varies with width, it is easy to cause non-parallel. If excessive pressure is applied, deflection of the roller will result. That is to say, the bending of the roller is caused, so that the pressure on the left and right ends of the roller is too large, and the pressure in the middle is too small, resulting in widening of the indentation and narrowing in the middle. This uneven indentation causes cross-ripple quality accidents when the print passes through a machine with a non-uniform speed.
Solution
Many laminators use roller drums to compensate for the curvature of the roller. Between the front and rear rollers, there is a window-like area. The general practice is to use a window to determine if the impression on the print is even. Maybe you have to ask, how magical it is that the magic is that you can see the indentation on the front few inches of film. The correct indentation should be parallel. If the indentation is wide at both ends and narrow in the middle, the pressure should be reduced; if the indentation is narrow at the middle and wide, the pressure should be increased.
Printing products
The typical cause of print curling is the tension of the film, the path of the device, and improper adhesion. Goetter said many operators try to adjust the tension brake to prevent the print from curling. This is an error that can easily be made. When the tension brake is adjusted immediately, the operator usually sees a reduction in the degree of hair curling, but this is not a good solution. Excessive brake adjustment will cause more prints and other issues. It is best to slow down so that the film is fully exposed to heat.
Solution
Goetter thinks it's best not to let the film go directly from the front main roller to the back part of the film. The state of the film can be changed by changing the distribution of the device. The equipment distribution consists of passing the film through the upper side of the first cooling roller and the lower side of the second cooling roller, or the lower side of one cooling roller and the upper side of the second cooling roller, or both. The optimal setting is a function of the bonding force of the film, and it is usually best to slightly reduce the tension of the film.
If you still have problems after you have adjusted the tension brake and the equipment path, consider the problem with the film itself. Goetter recommends three considerations: the type of adhesive, the properties of the adhesive, and the suitability of the film. For example, high-gloss films can create problems under certain lighting conditions.
Poor adhesion
When air enters the film layer of the film, poor adhesion occurs. There are three main causes of poor adhesion: low pressure leads to poor contact between the adhesive and the printed material, improper roller temperature and speed, and a small amount of adhesive.
Solution
Increasing the pressure will solve some problems, but it cannot increase too much to avoid wrinkling. Estimate the temperature of the film. The adhesive should be flexible before entering the roller nip. Goetter said “Moisturizing the adhesive is critical to achieving a good flow rate. Ultimately, the adhesive flow rate determines the contact between the print surface and the adhesive is better than the press deviceâ€. Thicker films require more processing time than thinner ones.
Finally, consider the construction of the film. The heat sensitive film is divided into three parts: the base layer, the film itself, and the adhesive layer. Goetter said "Mylar film has three-and-a-half-thousandths of an inch of polyester and two-thousandths of an inch of adhesive. On the surface of the film to be coated, the amount of adhesive is insufficient to fill the surface, resulting in poor adhesion of air." .
Cold film (pressure sensitive) may already have air in it. According to Goetter, air is difficult to flow under the film and on the surface of the prints. He suggested adding a small amount of heat to change the viscosity of the adhesive.
Foaming
When the print is on the front roller of the laminator, hot areas can cause bubbles. Goetter concludes that fever, "In the time the roller stops, the increase in the heat of the top roller creates a hot spot. The temperature of the roller will increase by 30 degrees.
Solution
Do not put the device route in a grid. Ultimately, the print media determines the best temperature.
Source: Chinese and foreign printing and packaging network
Wide-width film coating of common problems and solutions
Goetter, who was a screen printing and digital printing technician, developed a wet electrostatic transfer printing method and assisted in the design of a laminating machine.