As a kind of packaging, calendered products have a direct impact on the market image of the product. Therefore, in the calendering production process, in addition to the high gloss of the product, the product should also have good flatness. However, whiteboard paper with a base weight of less than 250GSM is prone to curl and deformation, which makes the paper surface lack good flatness. This kind of paper is easy to wrinkle when calendered.

Due to the strong water absorption of whiteboard paper, especially in the case of significant changes in ambient humidity and temperature, the paper surface is most likely to curl and deform. This is because the exposed paper edge loses or absorbs water with the change in temperature and humidity. When the water loss of the paper edge is severe, the paper edge shrinks and produces a tight edge phenomenon. When the paper edge absorbs more water, the paper edge expands and deforms; when one side of the paper edge absorbs water quickly, the paper edge curls toward the water-absorbing side due to the paper edge expansion. In this way, when the paper surface lacks good flatness, when the printed sheet enters the calender belt and is rolled by the pressure roller when the uneven and loose paper surface is concentrated on a certain part due to extrusion, wrinkling occurs. , and, the wrinkling direction tends to be towards the transverse direction of paper fibers. Because the transverse fibrous structure of the paper is soft and the stiffness is poor, it is prone to deformation. The workaround for this is:

1. Do a good job of keeping the original paper. Keeping the good flatness of the cardboard is the basic condition to prevent calendering and wrinkling. Therefore, if the whole piece of whiteboard paper is not put into use immediately, do not disassemble the outer package, so as not to cause the paper edge to lose moisture or deform due to moisture absorption.

2. Warehouses and production workshops should be equipped with thermometers and hygrometers in order to take simple methods for control, such as according to the recorded temperature and humidity differences, by switching doors and windows or covering semi-finished products, and splashing water on the ground to control humidity The purpose is to make the humidity and temperature of the warehouse, printing workshop and glazing and calendering workshop not have a big difference.

3. For the printed semi-finished products that have been deformed on the paper edge, when the calendering appears wrinkled, the following measures can be taken:

(1) Appropriately reduce the pressure during calendering to reduce the chance of wrinkling.

(2) Properly reduce the speed of glazing, because the printed sheet is easy to wrinkle during the high-speed rolling process.

(3) To dry the paper surface, you can use the winding part of the calendar to take a certain amount of semi-finished products and put them on the steel belt each time so that they can be transported to the paper feeding table with the rotation of the steel belt, so as to play a role in drying. dry effect. It not only reduces the degree of deformation of the paper surface, but also improves the stiffness of the paper surface to a certain extent, and achieves the purpose of preventing wrinkling by calendering.

Calendering and wrinkling of products caused by machine defects or improper operation and solutions

In addition to the unevenness of the paper surface that may easily cause calendering and wrinkling, in daily production, the wrinkling failures caused by such reasons are mainly manifested in:

1. There is a problem with the roller. The roller plays the role of pressure on the calendar. Whether the front of the printed sheet can maintain a uniform and moderate pressure on the steel belt depends on whether the roller is in a normal state. In the case of uneven paper surfaces, if the roller is slightly abnormal, it is very easy to cause calendering and wrinkling. If the surface of the rubber roller is uneven or foreign matter adheres, the surface of the roller is aging and sticky, and it will produce torsional tension with the printed matter attached to the steel belt. The roller has been used for a long time, and eccentric deformation occurs, resulting in uneven and inconsistent contact pressure. If the drum is not parallel to the steel belt, one side will be higher and the other side will be lower. Other unfavorable factors exist or the bearing of one side of the drum is damaged and jamming occurs, which will cause a certain resistance when the drum rotates. The solution is: if the surface of the rubber roller is severely uneven or has obvious eccentricity, a new roller should be replaced. If there is shredded paper or other foreign matter on the surface of the roller, it should be cleaned. For the aging and sticky roller surface, pave Use talcum powder to reduce viscosity, check the roller shaft head and track for jamming, check the oil pump pipeline to see if there is any blockage, and take corresponding measures to eliminate: Check whether the roller bearing is damaged, and if there is any damage, it should be repaired. Replacement, so that the roller and the steel belt maintain a moderate and uniform contact pressure, and realize synchronous, uniform, free, and flexible rotation, so as to better reduce or avoid calendering wrinkles.

2. The pressure is heavy. When the paper surface is relatively flat, the pressure should be a little heavier to make the gloss of the printed product stronger. However, for the paper with high moisture content and lack of good strength and toughness in the fibrous structure, it is the best pressure. Very inappropriate. Because the paper is soft, it is easy to wrinkle due to extrusion and deformation during the rolling process. Therefore, the control of calendering pressure should not only make the oil layer on the paper surface bright but also take into account the ability of the paper to withstand pressure.

To sum up, a correct understanding and understanding of the faults and causes of calendering and wrinkling of whiteboard paper, and taking corresponding measures to prevent and control them through process technology and operation can not only effectively reduce or avoid the occurrence of faults, but also Can greatly improve production efficiency.