How to deal with base paper of different materials

2022-08-21
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How to deal with the base paper of different materials in carton printing

the common base paper varieties used for corrugated paper are: carton board, face paper, kraft paperboard, tea board, whiteboard and single-sided Coated Whiteboard. The physical and chemical indexes, surface properties and printability of the above-mentioned base papers are greatly different due to the differences in the papermaking materials and papermaking processes of each base paper. Next, we will discuss the problems brought by the above paper products to the starting process of corrugated board ink printing

I. problems caused by low gram base paper

when using low gram base paper as corrugated board surface paper, there will be problems of showing corrugated marks on the surface of corrugated board. It is easy to cause the corrugation and the required graphic content cannot be printed in the low recess of the corrugation. In view of the uneven surface of the corrugated board caused by the exposed corrugation, the flexible resin plate with good resilience should be selected as the printing plate to overcome the defects of unclear printing and bottom leakage. In particular, type a corrugated board produced from low gram paper will suffer great damage to the flat pressing strength of corrugated board after printing by the printing machine. In addition, the edge pressing strength of corrugated board will also suffer great damage after passing through the printing roller and the embossing roller

if there is too much difference between the grams of paper on the surface and inside of the corrugated board, it is also easy to cause the corrugated board produced by the corrugated board line to warp. Warped paperboard will cause overprint inaccuracy and printing slotting, so warped paperboard should be reprinted after flattening, or reverse flattening at the rocking line. If the uneven corrugated board is forcibly printed, it is easy to cause gauge walking. It will also cause the thickness of corrugated board to decrease

second, problems caused by different surface roughness of base paper

printing on paper with rough surface and loose structure, its ink permeability is large, and the drying speed of printing ink is fast, while printing on paper with high surface smoothness and dense and tough fiber is slow. Therefore, on the coarser paper, the ink application amount should be increased, and on the paper with smooth surface, the ink application amount should be reduced. Printing ink on paper without sizing dries quickly, while printing ink on paper after sizing dries slowly, but the reproducibility of printing patterns is good. For example, the ink absorption of Coated Whiteboard is smaller than that of carton board and tea board, the ink drying is slow, and the smoothness is higher than that of carton board, face paper and tea board. Therefore, the resolution of printing fine dots on it is also high, and the reproducibility of its pattern is better than that of face paper, carton board and tea board

III. problems caused by the absorption difference of base paper

due to the difference of papermaking raw materials and the difference of base paper sizing, calendering and coating, the absorption performance is different. For example, when overprinting on single-sided coated white board paper and cow pickup truck, due to the small absorption performance, the drying speed of ink is slower, so we should reduce the viscosity of the previous ink specifications and improve the viscosity of the subsequent overprint ink. And put the lines, words and small patterns in the first color for printing, and put the full page on the last color for printing, which can improve the overprint effect. In addition, put the dark color on the front for printing, and the light color on the back for printing, which can cover the overprint error, because the dark color coverage is strong, which is conducive to the overprint accuracy, while the light color coverage is weak, which is not easy to observe even if there is a deviation from the specification in the back printing

different sizing conditions on the surface of base paper will also affect the absorption of ink. The paper with small sizing amount absorbs more ink, while the paper with large sizing amount absorbs less ink. Therefore, the clearance of each ink roller should be adjusted according to the sizing state of the paper, that is, the clearance of each ink roller should be reduced to control the inking amount of the printing plate. It can be seen that when the base paper enters the factory, the absorption performance of the base paper should be tested, and a base paper absorption performance parameter should be given to the printing slotting machine and ink distribution personnel to facilitate their ink distribution and equipment adjustment. And adjust the viscosity and pH value of ink according to the absorption state of different base paper

IV. problems caused by the difference in the surface color of the base paper

the color difference of carton board, face paper, tea board and whiteboard is large. Even after the same batch of whiteboard or single-sided Coated Whiteboard is processed by the corrugated board line, due to the different speed of the production machine and the different heat condition of the whiteboard, its whiteness will also change, and whiteness will decrease or become gray and dark; As a result, the whiteness of the same batch of products is different, and the whiteness of the white board printed by the offset press and pasted on the surface is still good. Therefore, when the corrugated board processed by the white board through the corrugated board line is printed on the ink machine, the selected ink is better than that of the offset press, which can improve the contrast of the printing pattern and have bright colors. In addition; That is, using the same variety of the same enterprise but different batches of base paper products, there may also be different hue differences, such as the whiteness of general whiteboard is more than 75%, and the whiteness of Coated Whiteboard is more than 75%. However, different batches of whiteboard will appear some blue and some yellow. In order to ensure the color consistency of the same batch of products, try to use the same batch of base paper to print the same batch of products. However, when the quantity of base paper in the same batch is not enough, even if different batches of base paper are used, the color difference of base paper between batches should also be considered, and the products printed from different batches of base paper should be marked to show differentiation, so as to ensure that the color of formed products is consistent

v. problems caused by different moisture content of base paper

different moisture content of base paper will affect the flatness and dimensional accuracy of corrugated board. Therefore, when producing corrugated board on the corrugated board line, it is necessary to adjust the envelope area of the base paper on each preheater and the production machine speed of the board line according to the moisture content of the base paper. It is best to control the moisture content of the produced corrugated board at 9% to ensure that the produced corrugated board is flat, the hardness of the corrugated board is large and the stiffness is good. Otherwise, after the corrugated board is printed by the slotting machine of the linear rotary combination friction and wear tester, Its strength will be damaged greatly. However, the corrugated board is too dry, and it is easy to crush the inner paper when it is pressed by the paper guide roller and the line pressing wheel on the printing machine, so the moisture content of the corrugated board should be strictly controlled

VI. problems caused by poor debugging of ink printing slotting machine

when using low gram paper to make corrugated board surface paper and carton inner paper, if the gap of the paper feed roller is adjusted too small, the corrugated will be crushed. When the grammage of the lining paper is low, the gap of the crimping wheel is adjusted too small, and it is particularly easy to crush the lining paper

if the pattern near the indentation line is missing during printing, the flap indentation line can be changed into a dark line (on the slitter of the corrugated board automatic line or on a single paper separation and pressing machine; only the indentation line of the paper in the carton is pressed, not the indentation line of the box surface)

VII. Problems caused by the damage of base paper fillers and sand to the tools

corrugated cardboard must be cut by various tools before printing. In order to ensure that the edge of the corrugated cardboard cutting edge is smooth and burr free, and if the machine is not used for a period of time, less paper ash, paper scraps, and impurities are stuck to the printing plate by ink and block the printing plate, resulting in the printed products not meeting the requirements. Therefore, all kinds of cutting tools for processing corrugated board are required to be peak profit. In particular, corrugated cardboard produced from ordinary carton board and low-grade tea board paper is easy to produce paper ash, paper scraps and impurities. Therefore, it is more required that the cutting tools for processing corrugated cardboard should not have sharp edges and gaps, and should be sharpened or replaced regularly. In addition, the sand particles and hard fillers in the base paper are also quite serious to the tool damage, so this pass should be strictly controlled when the base paper enters the factory, and the base paper with more sand particles should not enter the factory

VIII. Problems of different paper-making raw materials and paper-making processes on printing belt

for example, the soaking ability of ink on kraft cardboard is slower than that of carton board, and the absorption of ink on coated paper is less than that of carton board and tea board paper. The ink absorption of face paper is between kraft cardboard and tea board paper. The surface strength of tea board paper is poor, and it is easy to shed wool and dust, so the ink with low viscosity is better, which can reduce the paste version. In addition, when carton board and tea board are used as carton face paper, due to the large absorption performance of carton board and tea board, the viscosity of ink can be appropriately reduced to reduce the problem of powder and wool loss. However, the base paper with too large absorption performance will have another problem, that is, it will cause the printed color to fade and become not bright

IX. selection of printing plate

the thickness of printing plate is best selected according to the surface roughness of corrugated board and different thickness. If printing fine pictures of photos on corrugated box, it is best to choose coated white board and print on offset press with PS plate, so as to obtain better natural color reproduction effect. For printing on kraft cardboard, face paper, carton board and tea board with rough surface, flexible resin plates with large thickness, good resilience and strong wear resistance should be selected. For thin lines, small words and small patterns, the rubber version with high hardness can be selected, but the thickness of the printed version must be consistent, and the pressure can be appropriately increased during printing, so as to achieve the purpose of printing the printed content clearly on the corrugated paper. A flexible resin plate with low hardness and good elasticity should be selected for the printing plate used on the field

the printing plate should be firmly pasted on the polyester film, otherwise the ink will soak into the place where the double-sided adhesive tape is pasted, causing the printing plate to pop open. When the printing plate is running at high speed, it will be damaged or the printed products will appear undue wild ink

X. optimize the process

when printing the laminated ink, pay attention to the high viscosity of the post printing ink, otherwise the laminated ink will not print on the previous color ink, and there will be blooming and bottom color exposure. In addition, it should be noted that the ink contains volatile solvents such as alcohol and amine. Therefore, the ink roller of the printing machine should be kept in operation for a long time when the printing machine is shut down, so as to prevent the ink on the ink roller from thickening and pasting

printing should avoid printing hot corrugated board. Because the fiber of the hot corrugated board is relatively soft under the action of heat, and the shape of the corrugated board has not been completely finalized, it is necessary not to print hot corrugated board, otherwise the edge compression strength of the corrugated board will be greatly damaged, and in serious cases, the edge compression strength of the corrugated board will be reduced by more than 20%, and the thickness loss of the corrugated board will also be caused. So it's best not to heat corrugated board

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