Problems in the second overprint of the rewinding

2022-07-22
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Problems in the secondary overprinting of the rewinding of the commercial form rotary printer

for the high-speed rotary commercial form printer, the more complete the color number of the printing equipment and the printing cylinder, the better the quality and quantity of the printing equipment can meet the customer's requirements in the shortest time. 2. The cross beam operation inspection of the waterproof coiled material tensile testing machine. However, in special cases, if the customer's product color number exceeds the number of color groups of the equipment, or for the computer continuous bill, When the roller is not complete, the second overprint will be required, that is, part of the color number will be printed first, and then the second printing will be carried out after rewinding to complete the whole printing process

the most important problem in the second overprint is the registration problem in the first and second printing. Generally, the repetition of the pre printed signal block on the first printing page is determined by the photoelectric detector. On the second printing page, if the position of the signal block on the second printing page deviates, the equipment will automatically detect it and remind the operator to adjust it in time, In this way, the position of the signal block must be repeated continuously during the first printing, otherwise the rules need to be adjusted many times during the second printing, which will bring great waste

in the first printing, in principle, the content is less, and the overprint position requires a more tolerant color, so that even if there is a slight inaccuracy in the second overprint, it will not have a decisive impact on the quality of the whole product, especially for computer continuous bills

the following is the problem encountered in the production of our factory. Try to discuss the aspects that should be paid attention to in the secondary overprint

this is a triplicate carbon free copy computer continuous bill. The second copy has three colors, but we only have two sets of rollers to match, so we must carry out secondary overprint. Two of the three colors are the main content. Finally, it is determined that the seal should be printed first for the first printing, because its printing plate is small and the position requirements are slightly more tolerant than the other two colors. Seals and signal blocks are printed with resin plates for the following reasons:

1 Because the resin plate belongs to relief printing, the seal printed is clear, solid, three-dimensional and beautiful

2. The ink balance of resin printing is not strict, which is easy to control

3. Resin printing ink is not easy to emulsify

4. In the rotary printing press, the printing with resin plate group is usually pressed, and it is also pressed when it needs to be stopped for various reasons. In this way, the signal strip or block for detection is always in the print, that is, it repeats at an equal distance all the time. As long as the paper strip is clamped at the machine stop and the scrap is torn off during the second overprint, there is no need to readjust the rules. If PS printing is used, the signal block cannot be printed when the machine is off press after shutdown. During the second overprint, the rules need to be readjusted in this section, which will increase the consumption and cause waste

after the first printing, for various reasons, the rewinding printed matter was placed for a period of time before we began overprinting. However, during the second overprinting, we found that in addition to the red seal on the printing, there was a blue seal on the printed matter, which alternated irregularly with the red seal. At first, we thought that the blue ink of the previous printing on the resin plate imprinting cylinder was not cleaned, and the imprint was dirty after pressing, But after checking the inside of the roll, it was found that the blue seal continued to the inside of the roll. This means that it will not be caused by dirt. After careful inspection, it is found that the blue seal is always located at the same position of the inner paper of the red seal, just like the outer red seal is printed on the inner paper. Originally, for the carbon free copy paper, the microcapsule technology is used. The upper paper is coated with microcapsules containing couplers on the back of the base paper, the middle paper is coated with couplers on the front and microcapsules containing couplers on the back, and the lower paper is coated with microcapsules containing couplers on the front of the base paper, When in use, the microcapsule is damaged due to pressure or impact, and the colorless coupler flows out and is absorbed by the developer. At the same time, a chemical reaction is generated to form color. In recent years, the main business of plastic modification materials of the company has an obvious feature. In high-speed rotary printing, the web paper delivery will have an impact on the rules, which is generally tight, so the paper tension is large. Because the resin version is letterpress printing, the pressure is too high during the printing process, resulting in slight bulge on the back of the printed product, and the embossing process itself has damaged some of the developer and coupler capsules, In addition, after receiving the paper, the two layers of medium paper are actually stacked together. Under the action of large paper tension, the inward convex part of the outer paper will exert pressure on the inward unfolding medium paper, causing the microcapsule to damage and develop color. After being placed for a period of time, this pressure also continues to damage the capsule, making the seal slowly and clearly appear. This is the reason for the problem

rotate on commercial forms Martin said: "I believe that our research will open a new frontier in the research of materials science. In the second overprint of the rewinding machine, the author thinks that the following problems should be paid attention to in the first printing:

1. the signal bar or block should be printed with resin plate for the first printing. The reason is as mentioned above, which can make the overprint rules have continuity;

2. if the color of the first printing is printed with resin plate, on the premise of ensuring the printing quality, 2. If The equipment adopts the handover mode, and the pressure should be as small as possible

3. The paper take-up roll should not be too large. If it is too large, the tension will increase, and the pressure between the inner and outer layers of paper will also increase

4. For the first time, resin plate printing shall be adopted. The rewound paper roll shall not be placed for too long. The second overprint shall be completed continuously to reduce the damage of microcapsules

5. PS plate printing is adopted to avoid the recurrence of similar situations

source: Book Printing

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