Causes and solutions of stacking plate failure cau

Causes and solutions of stacking failure caused by paper in offset printing

in the process of offset printing, due to the sizing pore structure, smoothness, absorption, viscoelasticity, etc. of the paper, 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 dust, spots, fiber clusters, sand particles, etc., which often leads to stacking failure. The main reasons for stacking are: paper depilation, paper depilation, pile of paper wool and paper ash on the blanket. The reasons for paper stacking are different, and the solutions are also different

I. paper unhairing and stacking

the failure of paper unhairing and stacking during offset printing is mainly caused by the paper unhairing caused by the loose fiber structure on the paper surface, This phenomenon is mainly ink "> for paper with poor printing quality, the fault surface is imprinted ink, and the surface is a messy white phenomenon like scraps of paper. The falling off of paper wool causes the surface of printing plate and blanket to be covered with paper wool. In serious cases, the printing plate and rubber need to be wiped once for every 1000 sheets printed, resulting in 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, and offset printing uses intermediate elasticity For indirect printing with 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 impression 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, These paper wool will adhere to the imprinted surface of the printing plate, thus affecting the quality of the printed matter

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 being wetted and pressurized by the water roller, most of the paper wool sticks to the printing plate text, and then is inked by the ink roller. At this time, the wetted paper wool has oil resistance. Although it cannot absorb the ink after being inked by four inking rollers, it will appear graying when transferred to the blanket impression

solution:

(1) master the balance of ink and water during offset printing. On the premise of dirty cloth, reduce the water content of the page and reduce the great impact on China's POM industry. Lighten the pressure of the water roller on the 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 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 printing adaptability 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

II. Paper degumming and stacking:

the stacking caused by paper surface degumming presents honeycomb 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 cause is similar to that 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 of the ink, increase the ink storage on the ink roller, and deepen the imprinted ink color. In addition, increase the thickness of the pad paper under the printing plate to increase the printing pressure

III. pile paper wool on the blanket

paper ash is mainly caused by the manufacturing process of petroleum paper: during the printing process, the paper may be powdered and roughened, and accumulated on the blanket, which will affect the correct transmission of the 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, and then pass through the ink roller to the ink bucket trough, thus affecting the transmission of the ink path, In case of paper with serious powder loss, the ink bucket can be used as the prepreg of the car wheel cover 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. If 1000 pieces of paper are printed and adhered to the blanket, the blanket needs to be scrubbed

2. Technical parameters

solutions:

(1) wash 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 loss (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, and do not overdo it. The dosage should not exceed 3%

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