Causes and solutions of wrinkle in calendering of

2022-08-13
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Reasons and solutions for calendering wrinkling of white board printing products

as a kind of packaging, the appearance quality of calendering products directly affects the market image of products. Therefore, in the calendering production process, in addition to requiring high gloss of the product, the product should also have good flatness. However, the white board with a ration of less than 250g is prone to curl, tight edge and lotus leaf edge deformation, which makes the paper lack good flatness. This kind of paper is easy to wrinkle when calendering

in addition, improper use and adjustment of the machine is also easy to cause product calendering and wrinkling

I. product calendering wrinkling caused by paper flatness and its solutions

due to the strong water absorption of whiteboard, especially in the case of large changes in environmental temperature and humidity, the paper surface is most prone to tight edges, curls and ruffle edge deformation. This is because the exposed paper edge loses or absorbs water with the change of temperature and humidity. When the water loss of the paper edge is severe, the paper edge shrinks and tightens. When the paper edge absorbs more water, the expansion of the paper edge produces the deformation of the lotus leaf edge; When one side of the paper edge is easy to absorb water, the paper edge curls towards the water absorbent side due to the expansion of the paper edge. In this way, when the paper surface lacks good flatness, the printing sheet enters the calendering belt and passes through the rolling of the pressure roller, and the uneven and loose paper surface is concentrated to a certain part due to extrusion, the wrinkling phenomenon occurs, and the wrinkling direction is often transverse to the fiber of the paper. Because the transverse fiber tissue of paper is soft and has poor stiffness, it is easy to produce deformation. In this regard, the solution is:

1. Do a good job in the storage of base paper. Maintaining a good flatness of the paperboard is the basic condition to prevent calendering and wrinkling. Therefore, if the whole piece of white paperboard is not put into use immediately, do not unpack it, so as to avoid deformation caused by water loss or moisture absorption at the edge of the paper

2. Warehouses and production workshops should be equipped with thermohygrometers so that simple methods can be used for control. For example, according to the recorded temperature and humidity differences, the humidity can be controlled by covering the switches of doors and windows or semi-finished products, and splashing water on the ground, so that there is no significant difference in temperature and humidity between warehouses, printing workshops and glazing and calendering workshops

3. For the printing semi-finished products whose edges have been deformed, the following measures can be taken in case of wrinkle during calendering:

⑴ appropriately reduce the pressure during calendering to reduce the chance of wrinkle

⑵ reduce the polishing speed appropriately, because the printing sheet is easy to wrinkle in the process of high-speed rolling

⑶ to dry the paper surface, you can take a certain amount of semi-finished products from the paper receiving platform of the calender and put them on the steel strip every time, so that they can be transported to the paper feeding platform with the rotation of the steel strip, so as to play the role of drying. It not only reduces the deformation degree of the paper surface, but also improves the stiffness of the paper surface to a certain extent, so as to achieve the purpose of preventing calendering wrinkle

II. Product calendering wrinkling caused by bad factors or improper operation of the machine and solutions

in addition to the uneven paper surface, which is easy to cause wrinkling during calendering, the existence of bad factors and improper operation of the machine are also easy to cause calendering wrinkling. In daily production, the wrinkling failure caused by such reasons is mainly manifested in:

1. There are problems in the rubber roller. The rubber roller acts as a pressure on the calender. Whether the front of the printing sheet can maintain a uniform and appropriate pressure with the steel strip depends on whether the rubber roller is in a normal state. Under the condition of uneven paper surface, if the rubber roller is slightly abnormal, it is very easy to make its control mode: set a target temperature to calender and wrinkle. If the surface of the rubber drum is uneven or there is foreign matter adhesion; The surface of the rubber drum is aging and sticky, which produces torsional tension with the printed matter adhered to the steel strip; The rubber roller has been used for a long time, resulting in eccentric deformation, resulting in uneven and inconsistent contact pressure; The roller is not parallel to the steel strip, that is, there is a phenomenon that one side is high and the other side is low; Other adverse factors exist or one side of the roller bearing is damaged, causing a certain resistance when the roller rotates. The solution to the 40% increase in the price of glass is: if the surface of the rubber drum is uneven or there is obvious eccentricity, it should be replaced with a new rubber drum. If there is adhesive paper fragments or other foreign matters on the surface of the drum, it should be cleaned up; Apply talc powder on the aging and sticky rubber drum surface to reduce viscosity; Check whether the rubber drum shaft head and track are blocked, and check the oil pump pipeline to see whether there is blockage and oil leakage, so as to take corresponding measures to eliminate it; Check whether the roller bearing is damaged. If it is damaged, replace it, so that the rubber roller and the steel strip maintain a moderate and uniform contact pressure, and realize synchronous, uniform, free and flexible rotation, so as to better reduce or avoid calendering wrinkle

2. Heavy pressure. When the paper surface is flat, the pressure should be a little heavier to make the gloss of the print stronger, and foam plates with different thicknesses can be produced. However, the heavy pressure is inappropriate for paper with high moisture content and lack of good strength and toughness of fiber tissue. Because the paper is soft, it is easy to wrinkle due to intensified deformation during rolling. Therefore, to master the pressure of calendering, we should not only consider making the oil layer on the paper bright, but also consider the paper's ability to withstand pressure

3. The steel belt has foreign matter adhesion, deformation, cracks or inconsistent tension on both sides. When there is foreign matter adhesion (such as paper shredding), deformation, crack or inconsistent tension on both sides of the steel belt, it is also easy to cause calendering wrinkle failure. For this, corresponding measures should be taken to deal with it

4. The paper feeding position or direction is wrong. When there is wear or deformation on the surface of the rubber drum, due to the large difference in contact pressure, it is easy to wrinkle if the paper is fed from a certain position, and the wrinkle can be avoided by changing the paper feeding position; If the transverse side of the paper is perpendicular to the drum for paper conveying, and wrinkling occurs, the transverse side of the paper can be transported in parallel with the drum. In this way, due to the different fiber directions of the paper, the stiffness changes, and it is not easy to wrinkle when rolling. For some paper with tight edges or ruffle edges, oblique feeding can also be used, that is, a certain corner is fed into the drum first to prevent calendering and wrinkling

to sum up, the cheaper it is, the better it is to understand and understand the fault conditions and causes of calendering wrinkling of printed products. Taking corresponding measures to prevent 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

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