Analysis and Solution of the Causes of Calendering of Whiteboard Paper Prints

Packaging products such as cartons, packaging boxes and handbags are generally printed on whiteboard paper, and then processed by calendering to form a bright protective layer on the surface of the product. At the same time, the surface of the product is waterproof, stain-proof and wear-resistant. And beautiful, durable features. As a packaged product, the quality of the appearance of the calendered product directly affects the market image of the product. Therefore, in the calendering process, in addition to requiring the gloss of the product to be high, the product should also have a good flatness. However, papers with a basis weight of 250 g or less are subject to curling, tight edges, and scalloped deformation, which results in a lack of good flatness. When the paper is calendered, improper use and adjustment of the paper can easily cause product pressure. Light wrinkles. For example, in the case of calendered paper box (a semifinished product printed with 250 g of whiteboard paper), there is no lack of calendering and wrinkling, which affects the quality of the product. The causes and solutions of wrinkling are summarized below.

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

Because the whiteboard paper has strong water absorption, especially in the environment where the temperature and humidity change greatly, the paper surface is most prone to tight edges, curls, and scallops. This is because the exposed edges of the paper follow the temperature. When the humidity changes, it loses or absorbs moisture. When the water on the edge of the paper is dissipated more severely, the paper edge shrinkage produces a tight edge phenomenon. When the paper edge absorbs more moisture, the paper edge swells to generate a scalloped edge; when one side of the paper edge easily absorbs moisture, the paper edge curls toward the less absorbent side due to the swell of the paper edge. In this way, when the paper lacks a good flatness, the printed sheet enters the calender belt and is pressed by the pressure roller, and when it is pressed, the uneven slackness of the paper surface is concentrated on a certain part, and a wrinkle appears. Phenomenon, and the direction of the wrinkles is often wrinkled laterally towards the paper fibers. Because the transverse fibrous 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. Warehouses and production workshops should be equipped with temperature and hygrometers so that they can be controlled in a simple way. For example, according to the recorded differences in temperature and humidity, the doors and windows can be switched or the semi-finished products can be covered, and the ground can be watered to control the humidity. The purpose is to make the temperature and humidity of warehouses, printing shops, and coating and calendering workshops not different.

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 glazing because the printed sheets are prone to wrinkling during high speed rolling;

(3) To dry the paper surface, we use the part of the calender receiving table, and take three or five sheets of semi-finished products each time on the steel belt to convey the parts to the paper feed table so as to play the role of drying. The degree of deformation of the paper surface is reduced, and the stiffness of the paper surface is increased to a certain extent, so that the purpose of preventing the light from wrinkling is achieved.

Second, the machine has a bad factor or improper operation caused by the product of light and wrinkling problems and solutions

In addition to the unevenness of the paper, which can easily cause the wrinkles to appear when the product is calendered, the presence of undesirable factors in the machine and improper operation can also cause calendering and wrinkling problems. In daily production, wrinkling problems caused by this type of cause are mainly manifested in:

1, rubber roller problems

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. ,Tapping talcum powder to reduce viscosity; Check the rubber roller shaft and track whether there is stuck phenomenon, and check the oil pump pipeline to see if there is a blockage, oil leakage, in order to take appropriate measures to exclude; Check whether the roller bearing is damaged If it is damaged, it should be replaced so that the rubber roller and the steel strip can maintain a moderate and uniform contact pressure, and synchronous, uniform, and free and flexible rotation can be achieved, so as to better reduce or avoid the occurrence of calendering and wrinkling problems. opportunity.

2, stressed

In the case of a flat paper surface, the pressure is appropriate to make the gloss of the printed product a little stronger, but the stress of the biased, for the paper with high moisture content and lack of good strength and toughness of the fibrous tissue is Not suitable. Because, in the process of soft rolling of paper, it is easy to cause wrinkling due to extrusion. 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, foreign material adhesion, deformation, crack or uneven tension on both sides

When the steel strip has foreign matter adhesion (such as shredding, etc.), deformation, cracks or inconsistent tension on both sides, it is also easy to cause calendering and wrinkling problems, which should be taken 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, if the paper is fed from a certain position, it is easy to wrinkle, and changing a position to feed paper can avoid wrinkling; The paper is fed horizontally in a vertical direction with the drum, and wrinkling occurs. 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 the paper diagonally, that is, one of the corners is fed into the drum first, so as to prevent the calendering and wrinkling problem from occurring.

In summary, the correct understanding and understanding of the causes of calendering and wrinkling in whiteboard paper products and the corresponding countermeasures for prevention and control in terms of process technology and operation technology can not only effectively reduce or avoid the occurrence of problems, but also The earth improves production efficiency.