The reason why the offset printing machine can not afford paper
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1. Paper is curled and misaligned during offset printing
Mainly due to improper control of the moisture of the layout. In general, the paper moisture content should be in a flat state under normal conditions, and the paper fiber absorption capacity is strong. However, when the moisture content of the printing plate is too large and the water content of the paper exceeds the normal limit, the fibers will swell and swell, causing the paper to be deformed and curled, so that the paperboard of the delivery member cannot control the soft and weakly curled paper, resulting in uneven delivery. failure. Offset printing should strictly control the moisture of the layout. Under the premise of not being dirty, use the least amount of water; adjust the water supply according to the position of the layout of the printing plate to reduce the bending deformation of the paper and avoid paper misfeed.
2. The printed product has a large area of paper and the paper is not uniform.
When printing a printed product with a large area, the paper tends to curl downwards, especially when the mechanical strength of the paper is poor, and the viscosity of the ink is high, paper picking is likely to occur. The offset printing ink belongs to the oxidized conjunctiva type. Under the pressure of the printing plate and the rubber two rollers, the printed ink immediately after printing is not dried, which affects the flatness of the paper and causes the paper to be misaligned.
When printing the full version of the field, it is possible to adopt a method of appropriately reducing the printing speed and reducing the viscosity of the ink; for products with a large printed area, pay attention to adjusting the printing color sequence, and add rubber bands and gauze strips on the paper receiving board. The method can also be effective for the paper that is curled down, and the purpose of receiving the paper is neat.
3. The distance between the left and right or front and back paper baffles is large, which is not suitable for the size of the printed paper web, resulting in uneven delivery.
At this time, adjust the telescopic and position of the left and right or front and back paper guides so that they are the same size or slightly larger than the printed paper.
In addition, if the paper flapper swinging time of the front, rear, left, and right of the paper receiving table is not correct, the printing paper is hindered during the falling process, and cannot fall smoothly into the paper receiving table, which may cause the paper to be misaligned. The position of the control flap of the paper flapper should be adjusted so that its swing time is coordinated with the time of picking up the paper to ensure that the delivery is neat.
4. The printed paper moves up when entering the delivery table, causing the paper to be misaligned
This is due to the stress difference of the printed paper itself, and on the other hand, due to the failure of the suction wheel of the printed brake or the suction of the suction wheel is too small. After the suction wheel loses its function, the thing blocked by the small hole of the suction wheel wall can be pulled out, and the paper ash and dirt on the suction wheel can be cleaned and used. If the suction wheel is too small, it can be adjusted appropriately. Suction.
5. The pick-up in the chain-type paper conveyor is too early or too late to allow the printed paper to enter the delivery table accurately, and the problem of misfeeding is also prone to occur.
At this time, it is necessary to adjust the time of the teeth of the delivery paper to facilitate the timely entry of the paper into the delivery table.
6. When printing, if the paper is too thin, it is often easy to pick up the paper.
Since the offset printed paper web is usually large (over four sheets of paper) and the plate needs to be wetted with water, the paper is too thin. (35g/m228g/m2), after passing between the impression cylinder and the blanket cylinder, the water is transferred to the paper through the blanket, the paper will be soft and weak, and the delivery will be difficult to finish, so the offset paper is best protected. Above 52g/m2, to ensure that the delivery of the delivery desk is neat.
7. Paper quality problem
Due to paper quality reasons such as: flatness and poor uniformity, it often causes the paper to enter the delivery table, such as roll, upturn, bowing, wrinkling, ruffles, etc., causing misfeeds.
Before printing, the above-mentioned poor quality paper should be carefully hanged and conditioned, and placed in a warehouse or offset printing workshop for storage for a certain period of time. The paper slab is placed on the paper slab and pressed with heavy objects (large stones, Iron plate, etc.), to make it flat, the paper on the machine should be knocked in addition to the coated paper to increase the stress of the paper.
8. The relative humidity of the offset printing workshop is too low, especially in the winter when the climate is too dry. The water content of the paper is too small, and it is easy to generate static electricity, so that the papers are stuck to each other and the paper is not properly received.
In this case, static electricity can be used to eliminate static electricity, or to increase the relative humidity of the workshop, especially in the dry weather in winter. If conditions permit, the humidifier can be used to adjust the humidity in the workshop. Moreover, the offset printing workshop should open the window as little as possible, the glass window should be sealed, and the water can be sprinkled on the floor of the workshop to adjust the humidity.