Troubleshooting of stacking in the most popular pa

Troubleshooting of stacking in the process of paper offset printing

during the offset printing process, due to the sizing pore structure, smoothness, absorption, viscoelasticity, etc., the filler, sizing, and pigment particles of the paper are rough in the papermaking process, and the appearance quality of the paper is poor in terms of dust, spots, fiber clusters, sand particles, etc., which often leads to stacking failures. There are many reasons for stacking. This article mainly talks about: paper depilation, paper depilation, pile of paper wool and paper ash on blanket. The reasons for paper stacking are different, and the solutions are also different

1 paper depilation and stacking

the failure of paper wool stacking during offset printing is mainly caused by paper depilation caused by the loose fiber structure on the surface of the paper. This phenomenon is mainly caused by the paper with poor printing quality. Its failure is manifested in the phenomenon that the surface of the imprinted ink is white like messy paper scraps, and the surface of the printing plate and blanket is covered with paper wool due to the fall of paper wool. In serious cases, the printing plate and rubber need to be wiped once for every 1000 sheets printed, Thus causing printing quality problems and delaying production progress and delivery time

depilation of front and back sides of paper is a technical problem in papermaking raw materials and papermaking process. Offset printing is a printing process that uses the intermediate elastomer rubber cylinder for indirect printing. 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 impression cylinder. In the offset printing process, 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, These 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 sticks to the printing plate text, and then the ink is applied by the ink roller. At this time, the wetted paper wool has oil resistance. Use a square level with a precision of 0.05/1000 to align it respectively. Although the ink cannot be absorbed after being inked by four inking rollers, it will appear graying when transferred to blanket stamping

solution:

(1) master the balance of water and ink during offset printing, and reduce the water content of the layout and the pressure of the water roller on the printing plate and fix the layout with the paper locking wheel on the premise of not dirty version. 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 close 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 when it passes through the ink roller for ink, transfer it to the ink roller, and mainly accumulate on the ink roller

in addition, adjust the printability of the ink, add ink mixing 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 honeycombed stars, which is caused by the falling off of countless fillers, glues, pigments and auxiliary materials, which seriously affects the quality of printing products. The printing plate needs to be scrubbed once when printing about 1000 sheets. The reason is similar to the formation of paper wool stacking, 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, appropriately add thinner ink mixing 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 paper under the printing plate to increase the printing pressure

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

is mainly due to the manufacturing process of the paper. During the printing process, the paper may be powdered and piled up on the blanket. SEBS thermoplastic elastomer is a new high-content sub material between rubber and resin, which affects the correct transmission of dots and graphics of the imprinted ink color. The paper ash and paper powder on the paper will pass through the rubber and plate cylinder, It is transferred to the ink bucket trough through the ink roller, which affects the ink path and is equipped with the corresponding pendulum transmission. When encountering the paper with serious paper powder loss, the ink bucket is full of paper ash, paper wool and paper powder until the end of printing. At this time, the ink volume is turned to the maximum, and the imprinted ink color also appears light and exposed. When 1000 pieces of paper are printed, it is white and adheres to the blanket, so it is necessary to scrub the blanket

solution

(1) wash and wipe the blanket frequently

(2) before the paper is officially printed, overprint a layer of white oil and water to make up for the lack of paper de powdering 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., and is mainly used for priming with white oil to reduce paper de powdering and galling)

(3) add a small amount of adhesive remover to the ink. Do not add coated paper with good flatness and smoothness, do not overdo it, and 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: Wang Xincheng, printing quality and standardization