For high-speed rotary commercial form printers, the more color numbers and printing cylinders of printing equipment are, the more they can meet the customer's requirements in the shortest time, but in special circumstances, if the customer's product color number exceeds The number of color sets for a device, or for a computer continuous ticket, in the case where the drum is not complete, will result in the need for secondary overprinting, that is, the number of partial colors printed first, and the secondary printing after rewinding to complete the entire Printing process.
The main problem in secondary overprinting is the registration problem in the previous and the next printing. The general situation is determined by the photoelectric detector, and the repetitive appearance of the signal blocks printed on the surface of the first printing is determined. On the second printing layout, if the position of the signal block on the second printing plate is deviated, the device will automatically detect and prompt the operator to make adjustments in time so that the position of the signal block must be as far as possible during the first printing. Repeatedly appearing, otherwise the rules need to be adjusted several times during the second printing, which will cause great waste.
In the first printing, in principle, there is less content to choose and the position of the overprinting requires a more tolerant color, so even a slight inaccuracy in the secondary overprinting will not affect the quality of the entire product, especially For computer continuous bills.
The following are some of the problems that we should pay attention to in the secondary printing process.
This is a triple carbon-free replication computer continuous ticket, in which the second line has three colors, but we only have two sets of rollers, so we must carry out two overprints, two colors in the three colors are the main content, and finally determine the first time The first printing seal is printed, because its printing layout is small and its position is slightly more tolerant than the other two colors. Seals and signal blocks are printed in resin format for the following reasons:
1. Because the resin plate is a relief printing, the printed seal is clear, solid, and strong in three-dimensional appearance;
2. Resin printing ink and ink balance requirements are not strict, easier to control;
3. It is not easy to emulsify with resin printing ink;
4. In the rotary printing press, printing with the resin printing plate set will not depress under normal circumstances, and shutting down due to various reasons will generally not leave the pressure. In this way, the signal strips or blocks for inspection are always in the prints, that is, they are repeated at equal distances. As long as the paper is clamped at the stop, the waste can be torn off at the time of the second overprint, and it is not necessary to re-rule the rules. Adjustment. If PS printing is used, after the machine is stopped, the machine will be separated from the pressure and the signal block will not be printed. During the second printing, the rules will need to be readjusted. This will increase consumption and waste.
After printing for the first time, we printed the rewinded product for a certain period of time because of various reasons. However, after the secondary printing, we found that in addition to the printed red seal, a blue print appeared. The color stamp and the position of the red stamp alternately appear irregularly. It was thought that the blue ink printed on the resin platen impression roller had not been wiped clean, and the ink was dirty after the pressure was pressed. However, after checking the inside of the printing plate, It was found that this blue seal continued into the paper roll. This shows that it will not be dirty. After careful inspection, it was found that the blue stamp was always located at the same position in the inner layer of the red stamp, as if the outer red stamp was printed on the inner layer of paper. For the carbonless copy paper, the microcapsule technology was used. The paper is coated on the back of the base paper with a microcapsule containing a coupler. The medium paper is coated with a color developer on the front side and microcapsules containing a coupler on the back side. The bottom paper is coated with a color developer microcapsule on the front side of the base paper. When the microcapsules are destroyed due to pressure or impact, the colorless coupler flows out and is absorbed by the color developing agent, and at the same time, a chemical reaction is formed. The high-speed rotary printing, web take-up situation will affect the rules, generally close, so that the paper tension is greater, due to the use of resin plate is relief printing, printing process pressure is too large, so that the back of the print product Micro convex, the imprinting process itself has destroyed part of the color and coupler capsules, plus the fact that after the delivery is actually two layers of paper stacked together, under the greater paper tension, the outer paper inward The micro convex places will exert pressure on the paper in the introvert, causing the micro capsule to break down and develop color. For some time, this pressure will continue to damage the capsule and make the seal appear clearly and clearly. This is the cause of the problem. .
In the secondary reprinting of commercial form rotary presses, I believe that the following issues should be noted in the first printing:
1. The signal bar or block is printed on the first printing, and the resin printing is applied. The reason is that the overprinting rules are continuous as described above.
2. If the color of the first printing is printed by resin printing, under the premise of guaranteeing the printing quality, the printing pressure should be as small as possible;
3. The receiving paper roll should not be too large. If the paper roll is too large, the tension will increase, and the pressure between the outer paper will increase;
4. The first use of resin printing, rewinding the paper roll should not be placed too long, the time should not be too long, the secondary overprint should be completed continuously, so that a smaller number of micro-capsule damage;
5. Use PS printing to avoid similar situations from happening again.
Problems in the secondary reprinting of commercial form rotary press
December 25 06:07:19, 2023
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