How to solve the problem of improper receipt of the offset paper receiving machine
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In the offset printing process, the paper-cutting mechanism of the offset printing machine, the paper-retaining baffle, the paper-feeding teeth, the improper adjustment of the paper brake, the moisture of the printing plate, and the printing product graphic Large area, thin paper, flatness, poor uniformity, etc., easily lead to the problem of improper receipt of the paper receiving table of the offset press, even the paper is folded, the printed matter is folded out of the crease, affecting the quality of the product, and giving the printed sheet The binding, finishing, and statistics are in trouble.
The quality requirements for the delivery of the offset press receiving table are: loose, flat, flat, no folding, crushing loss and oily debris, especially for printing semi-finished products, requiring tipping and biting, front and back positions Can not be reversed, try to avoid the receipt of paper is not neat, chaotic. There are many reasons for the unfinished offset printing. The specific offset printing operation should be comprehensively checked and comprehensively analyzed to solve the problem in a targeted manner.
1. The paper is curled and misaligned during offset printing, mainly due to improper control of the moisture on 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 due to the large amount of paper. 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 large. 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. Other methods can also be effective for 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. In this case, 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 and rear 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 result in misfeeding. 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 slams up when it enters the delivery tray, 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 likely 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. 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 the dry weather in winter, the water content of the paper is too small, and it is easy to generate static electricity, so that the papers are stuck with 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 necessary, 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.