Troubleshooting of stacking in the process of the

2022-08-07
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Handling of plate stacking in the process of paper offset printing

in the process of offset printing, due to the pore structure, smoothness, absorptivity, viscoelasticity, etc. of the paper, the particles of fillers, adhesives and pigments in the paper making process are rough, and the appearance quality of the paper is poor in terms of dust, spots, fiber clusters, sand particles, etc., which often lead to plate stacking. Therefore, there are more and more requirements for environmental simulation under extreme experimental conditions: ultra-high pressure, ultra-high temperature Ultra low temperature, ultra vacuum, ultra-high strength, ultra radiation, corrosion resistance and other barriers. There are many reasons for the stacking of plates. This article mainly talks about: the failure to mention the deformation index in the new regulations for paper removal will constitute a batch of independent intellectual property achievements with international advanced level. The absolute error requirements for wool, paper de dusting, stacking paper wool and paper ash on the blanket. The reasons for paper stacking are different, and the solutions are also different

1 paper depilation and stacking

during offset printing, the problem of paper pile stacking is mainly caused by the paper depilation caused by the loose fiber structure on the paper surface. This phenomenon is mainly caused by the paper with poor printing quality. The problem is that the surface of the imprinted ink is white like scraps of paper. The paper pile falling off causes the surface of the printing plate and the blanket to be covered with paper wool. In serious cases, the printing plate and the rubber need to be cleaned once every 1000 sheets are printed, Thus causing printing quality problems and delaying production progress and delivery time

The depilation of the front and back sides of paper is a technical problem in papermaking raw materials and papermaking process. Offset printing is an indirect printing process using an intermediate elastomer rubber cylinder. The printing plate transfers pictures and texts to the rubber cylinder, and the rubber cylinder transfers them to the printing paper under the action of the imprinting cylinder. During offset printing, the paper wool will be transferred from the surface of the blanket to the printing plate. With the increase of printing times, the paper wool remaining on the surface of the printing plate will accumulate more and more, resulting in the failure of paper wool stacking, The paper wool will adhere to the imprinted surface of the printing plate, thus affecting the quality of the printed products

the fiber paper wool and paper ash on the paper have both water absorption and oil absorption. When the paper wool is adsorbed on the printing plate text, with the transfer of the printing plate cylinder, it first touches the water roller to wet, and at the same time, the water roller has a certain pressure on the printing plate. After the water roller is wet and pressurized, most of the paper wool is attached to the printing plate text, and then the ink is applied by the ink roller. At this time, the wetted paper wool has the oil resistance of the verification method of the universal material testing machine of the testing machine series, for example. Although the ink cannot be absorbed after being inked by four inking rollers, it will appear gray when transferred to the blanket for stamping

solution:

(1) master the balance of ink and water during offset printing, and reduce the water content of the plate and the pressure of the water roller on the plate without dirty plate. The purpose is to minimize the wetting of the paper wool on the surface of the printing plate, so as to reduce the oil resistance of the paper wool and increase the ink force, and try not to make it cling to the plate

(2) increase the fluidity and viscosity of the ink, add a small amount of ink mixing oil, print the product with less ink, and correspondingly increase the pressure of the ink roller on the surface of the printing plate. The purpose is to pull out the paper wool on the printing plate and transfer it to the ink roller when the paper wool on the printing plate passes through the ink roller, mainly accumulating on the ink roller

in addition, adjust the printability of the ink, add ink blending oil and auxiliary materials, and mix them repeatedly. The problem can also be solved by appropriately increasing the ink volume of the ink bucket

2 paper degumming and stacking

the stacking caused by paper surface degumming presents honeycomb like stars, which is caused by the falling off of numerous fillers, glues, pigments and auxiliary materials, which seriously affects the quality of printing products. The printing plate needs to be scrubbed once to print about 1000 pieces. The reason is similar to the stacking of paper wool, but the solution is different. The proportion of paper wool and powder is different. The paper wool has a large area and light weight, and the powder is very fine and heavy

solution:

increase the fluidity of the ink, properly add thinner ink blending oil to the ink, increase the viscosity and ink delivery volume of the ink, increase the ink storage on the ink roller, and deepen the color of the imprinted ink. In addition, increase the thickness of the pad under the printing plate to increase the printing pressure

3 the pile of paper wool and paper dust on the blanket

is mainly due to the manufacturing process of the paper. During the printing process, the paper may be de powdered and piled up on the blanket, which will affect the correct transmission of the dots and graphics of the imprinted ink color. The paper ash and paper dust on the paper will be transferred to the ink bucket trough through the rubber and printing plate cylinder, thus affecting the transmission of the ink path, When the paper is seriously powdered, the ink bucket is full of paper dust, paper wool and paper powder at the end of printing. At this time, the ink volume is turned on to the maximum, and the imprinted ink also appears light and exposed. When 1000 pieces of paper are printed and adhered to the blanket, the blanket needs to be scrubbed

solution

(1) wash and wipe the blanket frequently

(2) before the paper is officially printed, a layer of white oil and water is overprinted to make up for the lack of paper de dusting and hair removal (white oil is a white translucent emulsion, which can dilute the ink color, reduce the viscosity of the ink, and match the color evenly. It is composed of magnesium carbonate, stearic acid, water, dry vegetable oil, etc. it is mainly used for priming with white oil to reduce paper de dusting and hair removal)

(3) add a small amount of adhesive remover to the ink. Do not add too much coated paper with good flatness and smoothness. The dosage shall not exceed 3%

(4) add 0.05mm thick backing paper in the rubber drum, or adjust the center distance to increase the printing pressure

reprinted from: Printing Technology

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