1. Keep and store paper scientifically and reasonably. In view of the uniqueness of cardboard, in order to prevent the paperboard from dewetting or absorbing moisture and causing the paper to adapt to changes, in the transportation and storage of paper, the integrity of the product packaging should be paid attention to so as to prevent the packaging from being damaged due to improper transportation and operation. Storage should not only pay attention to ventilation, but also avoid light and wind, temperature control at 15-25 °C, relative humidity 40% -65%. The stacking of paper should be categorized according to the paper production date, product category, and production address. Paper use should be based on the order of the production date in order to provide paper as much as possible to provide the next process with a more stable paper humidity fitness.
2, effective control of paper humidity changes. If it is necessary to properly store and rationalize the use of the product before cutting, how should we take measures to prevent changes in the paper size caused by changes in temperature and humidity after cutting? First, we must be scientific and reasonable in production and direction, and we must strive to achieve With printing, it is best to be able to control the preparation of paper in an hour before printing. A large quantity cannot be opened or cut all at once. It must be cut in batches according to the printing speed and progress, and the best paper can be cut. It is more important to use a plastic cover with good sealing performance to minimize the time of direct contact with air, especially when multicolor products are printed on single and double color machines. Not only white paper but also every color must be processed in the same way to prevent multi-color overprinting caused by humidity changes caused by paper stretching, to ensure the quality of printed products.
Influence of moisture change on die-cutting precision of calendered paper
In order to increase the beauty of the product and increase the smoothness of the color box, 70%-80% of the carton packs are now subject to gloss and calendering. Polishing is that the prints are evenly coated with a layer of varnish on the surface of the prints by a glazing roller, and then the solvent is volatilized to form a bright layer by heat and dryness. The calendering is the reprocessing on the basis of the glazing of the printing products. With a high temperature of 100-130° C. and a pressure of about 138 kg/cm 2 , the bright layer formed on the surface of the printed matter is more dense and the brightness is higher.
Due to this special process, the water content of the paper itself is severely dehydrated in a short time, and the paper inevitably shrinks. The amount of shrinkage is related to the size of the paper structure and the initial humidity. Although its shrinkage has nothing to do with printing overprinting, it directly affects the precision of die cutting. For example, the input length of a product original document is X, and the width is Y. If there are 5 cross-cuts on a K-paper and 3 vertical prints, a product with a pattern size of 3Y×5X will be obtained after printing. After the shrinkage of the paper pattern size, in the transverse contraction △X, shrinkage in the longitudinal △Y, with the original size of the die-cutting die after die-cutting products will certainly die precision inaccurate, or even embossed, Bleeding, pattern is not centered around the phenomenon. If the customer is not satisfied, it will lead to partial or total scrapping of the product, causing undue losses to the company.
So how to avoid or reduce such errors in the specific production? A simpler method is to produce a die (dieboard) according to different paper and different shrinkage after finishing the calendering, but this often seriously delays the production cycle, and die-cutting The size of the molding will be smaller than the original size. For this purpose, we should gradually explore the humidity characteristics of various types of paper used in this unit and the horizontal and vertical shrinkage after calendering. Add this amount of shrinkage to the input size of the manuscript when printing, so that the final distance after contraction, The entire graphics size meets the standard requirements, which also allows the die-cut version to be produced in advance to ensure product quality and cycle time.
Effect of Varying Water on the Folding Resistance of Products after Polishing
Fold resistance refers to the paper crease property that occurs when the paper is folded, without cracks on the surface of the folding belt, peeling off of the slit coating, etc. It is usually used to indicate the toughness and surface strength of cardboard and board in the folded condition. . From the paper itself, the resistance to folding depends on the length, strength, flexibility of the fibers and the binding force between the fibers. A large part of China's papermaking raw materials are non-wood raw materials, of which more are grasses such as reeds, wheat straw, straw, and bagasse. Due to the influence of the properties of these raw materials, different toughness and brittleness will appear after paper is formed. The paper produced from raw materials such as hemp, hemp, and wood is better in toughness, but most grass materials have poor fiber length and a high content of heterocells.
The paper we are using now. Paper mills generally use grass fibers and wood fibers to properly match the toughness of paper. However, due to the different proportions of wood pulp, different filler properties, and different production processes, there is a big difference in the toughness of different papers, and calendering is a high-temperature, high-pressure dehumidification process for paper. By calendering, the paper itself is simple. The root fiber becomes brittle due to dewetting, the ability of the fiber to slip and disperse stress is greatly reduced, and the folding endurance performance is weakened, so that during the die cutting, gluing, and folding processes, the carton produces hairiness, peeling, and cracks. Fouling and other ills may even cause the entire batch to be scrapped. Therefore, in the specific production arrangements, customers choose paper, pay special attention to the performance of the paper and the effect of calendering on the folding resistance of the paper.
Under normal circumstances 250-380g white board white board, white cardboard, better folding resistance, can be considered calendering process; and gray-white paper, not suitable for calendering. Moreover, because of the inherent characteristics of paper fibers, the folding endurance in the longitudinal direction is significantly better than the folding endurance in the transverse direction. This factor should be fully taken into account in the calculation of the vertical and horizontal arrangement of the carton and the calculation of the open size.
Prior to die-cutting, before the die-cutting, firstly, the folded paper should be subjected to folding resistance test in the transverse and longitudinal directions. If it is found that the folding endurance is poor, the calendered product can be passed on the machine again from the reverse side of the paper. Water, if the cycle is available, can also be placed in a place where the humidity is relatively high and the humidity is naturally adjusted so that, after proper moisture absorption, the paper has enhanced fiber strength and flexibility, improved folding resistance, and reduced waste and loss.