Causes and solutions for calendering failure
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The calendered print is used as a kind of packaging, and its appearance quality directly affects the market image of the product. Therefore, in the calendering process, in addition to the high gloss of the product, the product should have a good flatness. Whiteboard paper is one of the raw materials for packaging and decoration printing. Carton boxes, packaging boxes and handbags are generally printed on whiteboard paper, and then processed by polishing oil and calendering to form a bright protection on the surface of the product. The layer also makes the surface of the product waterproof, antifouling, abrasion resistant, beautiful and durable. However, white paper with a basis weight of less than 2 50 grams is prone to curling, tight edges and ruffle deformation during production, which makes the paper surface lack good flatness. When this paper is used for calendering, it is prone to wrinkle failure. . In addition, improper use and adjustment of the machine can easily cause wrinkling of the product. When the factory calendered the beer box paper (semi-finished product printed with 2 50 grams of white paper), the pressure wrinkling failure occurred from time to time, which affected the quality of the product. For the analysis of the causes of the failure phenomenon and solutions, we have the following experience:
1. Reasons and solutions for sticking steel strips when stamping is pressed
The phenomenon of sticking steel strip on the stamping of the printed product means that the printed product cannot be separated from the steel strip naturally after entering the calendering belt after being heated and pressurized, and it is necessary to remove the strip by hand, and even some of the stripping by hand is very If it is difficult to peel off, there may be cases where the surface of the printed product is peeled off. When we calendered pre-printed beer box paper, we had this problem. The printing was very expensive and the production efficiency was greatly affected. After careful analysis and discussion, the following problems were found to be the cause of the white-rolled paper-bonded steel strip: the thickness of the whiteboard paper was uneven; the surface of the whiteboard paper was rough and the oil absorption was too large; the polishing oil (paint) was too thin; the oiling roller Deformation of the eccentric core; dirty or poor gloss of the steel strip; insufficient calendering temperature and excessive pressure during calendering, etc., are all likely to cause the printed steel strip. The solution is as follows: Try to choose a whiteboard paper with a uniform thickness and a good paper coating quality and a relatively smooth surface for calendering; for whiteboard paper with a large oil absorption on the paper surface, the method of using the oil twice can be used. To overcome the problem of printed steel strips; if the eccentric deformation of the oiling roller causes unevenness in the oil on the printed product, it should be inspected and corrected to ensure uniform and sufficient oiling; dirt or surface gloss The steel strip with poor degree is cleaned and polished; calendering is carried out at a temperature of 1 30 °C; the pressure of the calendering is appropriately reduced, and by such control, the problem of the adhesive strip of the printed product can be better avoided.
2. Causes and solutions for streaks, wrinkles or blistering on the film surface when the printed product is calendered
The problem of streaks or wrinkles on the surface of the stamped film of the printed product is a common phenomenon of quality failure of the calendered product, and the reasons are various. In the case of glazing coatings with high viscosity values or poor wettability, the coating should be applied with a suitable amount of thinner or a wettable coating. If the coating amount is too large, the amount of polishing oil applied to the surface of the printed product should be appropriately reduced. If the process conditions are not compatible with the suitability of the coating, other types of glazing coatings should be used or the process conditions should be changed to match the performance of the coating. In addition, there is a problem of foaming on the surface of the printed film, which is related to excessive pressure during calendering and excessive temperature of the calendered steel strip, which causes softening of the coating layer locally. The pressure of the calender and the temperature of the machine should be appropriately reduced. . If the parameters of the glazing coating and the calendering process are not suitable, after the coating layer of the printing surface is cooled, and the peeling force of the calendering steel strip is poor, the process parameters should be considered, and the speed of the calender should be appropriately reduced to make the printing The coating layer can achieve a light peeling force with the calendered steel strip, so that the stamped surface of the printed product is not damaged by the adhesion of the steel strip.
3. Reasons and solutions for poor gloss of surface film after calendering of printed products
If the paper surface is too rough, the oil absorption is too strong; the calendering pressure is not enough or uneven; the calendering temperature is low; the surface of the calendered steel strip is dirty or rough; the quality of the calendering coating is poor or the concentration is insufficient; the glazing roll is eccentric and the coating is uneven When there is a problem such as excessive glazing speed, it is easy to make the surface film layer have poor gloss and lack brightness after calendering. In this regard, the solution is: For the paper surface is too strong oil absorption, the last two oil measures can be used to increase the brightness of the printed surface; appropriately increase the pressure of the calender and the pressure roller (rubber roller) The pressure is adjusted to balance, so that the pressure on both sides of the calendering is uniform; the temperature of the high-pressure light is properly adjusted; the dirt on the surface of the steel strip is cleaned, cleaned, and the surface of the rough strip is polished; the gloss is high Polishing coating or appropriately increasing the proportion of glazing coating; rounding the rubber roller which is out of roundness of the glazing roller or repairing the eccentric roller head portion of the glazing roller; varnishing the cardboard with large surface absorption When the oil is applied at a low speed, the effect of improving the calendering brightness can be achieved.
4. The reason and solution for the paper surface to be easily cracked after the stamp is calendered
If the calendering temperature is turned high, then the printed product will lose too much moisture in the calendering, and the water content of the paperboard will be significantly reduced, so that the paper fibers are easily brittle, and the cardboard is folded. When molding, it is prone to cracking. In this regard, consideration should be given to appropriately reducing the operating temperature in the calendering, so that the printed product retains a certain moisture content after calendering. In addition, if the pressure is too heavy during calendering to reduce the plasticity of the printed matter, then the toughness of the printed matter may be lowered, and the paperboard may be easily broken. The solution is: by reducing the pressure of the calendering, The fibrous structure of the paperboard is not damaged to maintain its desired toughness.
5. Reasons and solutions for product calendering wrinkles caused by poor paper surface roughness
Because the white paper has strong water absorption, especially in the case of large changes in ambient temperature and humidity, the paper surface is most prone to tight edges, curls and flakes. This is because the bare paper edge is warm. When the humidity changes, the water is scattered or absorbed. When the water at the edge of the paper is dissipated, the edge of the paper shrinks. When the paper edge absorbs more water, the edge of the paper expands to produce the deformation of the edge. When one side of the paper edge absorbs moisture easily, the paper edge curls toward the side with less water absorption due to the expansion of the paper edge. Thus, in the case where the paper surface lacks a good flatness, the printing sheet enters the calendering belt and is rolled by the pressure roller, and when the unevenness of the paper surface is concentrated to a certain portion by the pressing, wrinkles appear. Phenomenon, and, the wrinkle direction is often wrinkled transversely to the fibers of the paper, because the transverse fiber structure of the paper is soft, the stiffness is poor, and deformation is easy. In this regard, the solution 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, the whole whiteboard paper that is stored in the warehouse is not put into use immediately. Do not disassemble the outer packaging material, so as to avoid deformation or moisture absorption of the paper edge. .
2 The warehouse and production workshop should be equipped with a temperature and humidity meter for easy control. For example, according to the recorded temperature and humidity differences, the door and window switches or semi-finished products can be covered, and the ground can be splashed for easy control. The temperature and humidity of the warehouse, the printing workshop and the upper and the calendering workshops are not subject to large differences in temperature and humidity.
3 When the printed semi-finished product has been deformed on the edge of the paper, the following measures can be taken when the calendering is wrinkled.
Appropriately reduce the pressure during calendering to reduce the chance of wrinkling; properly reduce the speed of glazing, because the sheet is prone to wrinkle during high-speed rolling; for drying the paper, we have used calendering At the delivery table of the machine, three or five pieces of semi-finished products are placed on the steel belt each time, so that it is transported to the feeding table with the rotation of the steel belt, thereby drying the paper, thereby reducing the degree of deformation of the paper surface. Moreover, the stiffness of the paper surface is improved to a certain extent, and the purpose of preventing curling and wrinkling is achieved.
6. Causes and solutions for product calendering wrinkles caused by bad factors or improper operation
In addition to the unevenness of the paper surface, it is easy to cause wrinkles when the product is calendered. If the machine has bad factors and improper operation, it will easily cause the occurrence of calendering wrinkles. In daily production, the wrinkle failure caused by such reasons is mainly manifested in:
1 There is a problem with the rubber roller. The rubber roller acts as a pressurizer on the calender, and whether the front side of the sheet can maintain a uniform and moderate pressure with the steel strip depends on whether the rubber cylinder is in a normal state. In the case of uneven paper, if the rubber roller is slightly abnormal, it is easy to cause wrinkling. For example, the surface of the rubber roller is uneven or has foreign matter adhered; the surface of the rubber roller is aging and sticky, and the printing force adhered to the steel strip produces a twisting force; the rubber roller is used for a long time, and eccentric deformation occurs, resulting in uneven contact pressure. Inconsistent; the drum and the steel strip are not parallel, that is, there is a phenomenon that one side is high and the other side is low; other bad factors exist or one side of the roller bearing is damaged and jam occurs, which causes a certain resistance when the drum rotates. 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 stuck with paper or other foreign matter, it should be cleaned; the surface of the rubber roller that is sticky to the aging Sweat the talcum powder to reduce the viscosity; check the rubber roller shaft head and the track for jamming, and check the oil pump pipeline to see if there is any blockage or oil leakage, so as to take corresponding measures to eliminate it; check whether the roller bearing is damaged. If it is damaged, it should be replaced, so that the rubber roller and the steel belt maintain a moderate and uniform contact pressure, and achieve synchronous, uniform speed, free and flexible rotation, so as to better reduce or avoid the occurrence of calendering wrinkles. opportunity.
2 The pressure is heavy. In the case of a flat paper, the pressure is more moderate, so that the gloss of the printed product is stronger, but the heavy pressure is high for papers with high water content and lack of strength and toughness in fiber structure. Unsuitable, because the paper softness is easy to wrinkle due to the deformation caused by the extrusion during the rolling process. Therefore, the pressure of calendering should be considered in order to make the oil on the paper surface laminated, and to take into account the ability of the paper to withstand pressure.
3 The steel strip has foreign matter adhesion, deformation, crack or inconsistent tension on both sides. When the steel strip has foreign matter adhesion (such as paper shatter), deformation, cracks or inconsistencies in the tension between the two sides, it is also easy to cause the occurrence of calendering wrinkles. In this regard, corresponding measures should be taken to deal with them.
4 The paper feeding position or orientation is incorrect. When the surface of the rubber roller is worn or deformed due to the difference in contact pressure, if the paper is fed from one position, wrinkles are likely to occur, and when the paper is fed in another position, wrinkles can be avoided; The lateral direction of the side is perpendicular to the drum to carry the paper, and the wrinkling phenomenon occurs, and the transverse direction of the paper can be conveyed in parallel with the drum. Thus, the stiffness changes due to the different fiber directions of the paper, and it is not easy to roll when rolled. Wrinkles appear; for some tight or ruffled papers, oblique feeding can also be used, that is, one corner is first input into the drum to prevent the occurrence of calendering wrinkles.
In summary, the causes of quality failures in the calendering process of printed matter are various, caused by a kind of undesirable factors, and there are also several undesirable phenomena. As long as we are in the production process, we pay attention to earnest production. Process technology and operation technology are closed, and corresponding measures are taken to prevent and control the links that are prone to quality failures, which not only can effectively reduce or avoid the occurrence of faults, but also greatly improve production efficiency.