Causes and solutions of calendering on white board paper

As a packaged product, the quality of the appearance of the calendered product directly affects the market image of the product. Therefore, in the process of calendering, in addition to requiring the gloss of the product to be high, the product should also have a good flatness. However, a whiteboard paper having a basis weight of 250 g or less tends to have curls, tight edges, and scalloped edges, resulting in a lack of good flatness on the paper surface. This paper is easy to wrinkle when it is calendered.

In addition, improper use and adjustment of the machine can also cause the product to crush and wrinkle.

First, the paper caused by the flatness of the product of light wrinkles and solutions

Because the whiteboard paper has strong water absorption, especially in the environment where the environment temperature and humidity change greatly, the paper surface is most prone to tight edge, curl and lotus leaf edge deformation phenomenon. This is because the exposed edge of the paper is dissipated or absorbs moisture as the temperature and humidity change. When the water on the edge of the paper is lost, the paper edge shrinkage produces a tight edge. When the paper edge absorbs more moisture, the edge of the paper is expanded and a lotus leaf edge is deformed. When one side of the paper edge easily absorbs moisture, the paper edge curls toward the water absorption side due to the expansion of the paper edge. In this way, when the paper lacks a good flatness, the printed sheets enter the calender belt and are pressed by the pressure roller, and when the uneven slackening of the paper surface is concentrated on a certain part due to the pressing, wrinkling occurs. And, the direction of wrinkling tends to wrinkle laterally toward the fibers of the paper. Because the lateral FIBER structure of the paper is soft and the stiffness is poor, deformation is likely to occur. The solution to this problem is:

1, do a good job of keeping the original paper. Keeping the good flatness of the paperboard is the basic condition for preventing the light from wrinkling. Therefore, the whiteboard paper that is stored in the warehouse is not immediately put into use. Do not open the outer packing so as to prevent the edge water from being lost or absorbed and deformed.

2. The warehouse and production workshop should be equipped with a hygrometer so as to adopt simple methods for control, such as the recording of temperature and humidity differences, covering the doors and windows or covering the semi-finished products, and watering the ground to achieve the purpose of controlling humidity. There are no major differences in the temperature and humidity between warehouses, printing shops, and coating and calendering shops.

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

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

(2) Appropriately reduce the speed of the glazing because the sheets are easily wrinkled during high speed rolling.

(3) To dry the paper surface, it can be used from the calender receiving table, and each time the quantitative semi-finished product is placed on the steel belt, so that it can be transported to the paper feeding table along with the rotation of the steel belt, thereby drying The role. It not only reduces the deformation of the paper surface, but also improves the stiffness of the paper surface to a certain extent so as to prevent the light from wrinkling.

Second, due to poor machine factors or improper operation of the product caused by light wrinkles and solutions

In addition to the unevenness of the paper, it is easy to cause wrinkling when the product is calendered. The machine has unfavorable factors as well as improper operation. It is also likely to cause calendering and wrinkling. In daily production, the wrinkling failure caused by such causes is mainly manifested in:

1. There is a problem with the rubber roller. The rubber roller plays a role of pressing on the calender, and whether the front side of the printed sheet can maintain a uniform and moderate pressure with the steel strip depends on whether the rubber roller is in a normal state. In the case of uneven paper, if the rubber roller is slightly abnormal, it is very likely to cause calendering and wrinkling. Such as the surface of the rubber roller uneven or foreign body adhesion; rubber roller surface aging sticky, and adhesion to the printed material on the steel to produce the tensile force; rubber roller used for a long time, there is eccentric deformation, resulting in uneven contact pressure, Inconsistent; roller and steel belt is not parallel, that is, the phenomenon of high side and low side; other adverse factors exist or one side of the roller bearing damage and jam resistance, so that when the drum rotates a certain resistance. The solution is: if the surface of the rubber roller is uneven or there is obvious eccentricity, a new rubber roller should be replaced. If the surface of the roller is covered with shredded paper or other foreign materials, it should be cleaned; the surface of the rubber roller that is sticky to aging should be cleaned. , Talc talcum powder to reduce viscosity; check rubber roller shaft and track whether there is stuck phenomenon, check the oil pump pipeline to see if there is a blockage, oil leakage, in order to take appropriate measures to exclude; check the roller bearing is damaged, If it is damaged, it should be replaced to maintain a proper and even contact pressure between the rubber roller and the steel belt, and to achieve synchronous, uniform, free and flexible rotation, so as to better reduce or avoid calendering and wrinkling.

2, the pressure is heavier. In the case of a flat paper surface, the pressure should be heavier to make the gloss of the printed product stronger, but the stress of the biased, for paper with high moisture content and lack of good strength and toughness of the fibrous structure, is Not suitable. Because the paper is soft, the wrinkling phenomenon may occur due to the deformation caused by the extrusion during rolling. Therefore, the pressure of light pressure must be taken into account to ensure that the oil on the surface of the paper is laminated and bright, while taking into account the ability of the paper to withstand pressure.

3. There is foreign matter adhesion, deformation, cracks or inconsistent tension on both sides of the strip. When the steel strip has foreign matter adhesion (such as shredded paper, etc.), deformation, cracks or inconsistent tension on both sides, it is also easy to cause calendering and wrinkling faults occur, this should take appropriate measures to deal with.

4, the position or direction of the paper is not correct. When the surface of the rubber roller is worn or deformed due to the large difference in contact pressure, wrinkling is likely to occur if the paper is fed from a certain position, and wrinkling may be avoided if a position is changed to feed paper; The transverse direction of the paper is perpendicular to the drum, and the wrinkling phenomenon occurs, and the paper can be conveyed horizontally in parallel with the drum. In this way, the stiffness varies due to the different fiber orientations of the paper, and wrinkles are less likely to occur during rolling. For some paper with tight edges or flounces, it is also possible to feed paper diagonally, that is, one of the corners is fed into the drum first to prevent the light from wrinkling.

In summary, correctly understanding and understanding the fault conditions and causes of calendering and wrinkling of printed products, and adopting corresponding measures for prevention and control through process technology and operation, can not only effectively reduce or avoid the occurrence of faults, but also Greatly improve production efficiency.

Source: Dalian Packaging Network

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