Offset preparation work that the offset captain must do
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Offset printing machine setting and maintenance
1. Setting and adjustment of water roller and ink roller pressure
The product is printed with UV ink. After using the water roller and the ink roller for a period of time, different degrees of expansion will occur, which will cause problems such as water bars and ink sticks in the printing process. In this regard, we should always check the use status of the rubber roller, and adjust the pressure of the water roller and the ink roller according to the actual use condition of the water roller and the ink roller in the printing color group.
2. Lubrication of each transmission bearing of offset printing machine
In the offset printing process, the paper is conveyed between the printing color groups through the imprinted tooth row and the paper transfer tooth. If the transmission bearing is not lubricated, the open bearing will wear and affect the paper in each printing color group. The transfer time during the transfer, which leads to inaccurate product overprinting, especially when printing thin paper products, such phenomena often occur, and the consequences are more serious. In this regard, we should do a good job in the lubrication of the transmission bearings of the offset press.
Correct use of printed materials
1. Paper
(1) Plain paper. Before printing, you must first measure the exact thickness of the paper with a micrometer, then enter the corresponding value in the offset press console, and then fine-tune the pressure of each printing color group according to the ink color of the actual printing.
(2) Position the paper. Some cigarette packages, such as "Taishan (Huagui)" boxes, small boxes, etc., have been designed with paper in the early stage. In the printing production, the offset captain must register these patterns. Due to the limitations of the previous production process, the positions of these patterns are likely to be inconsistent, which puts high demands on printing production. The correct way is: before the paper is put, first classify the paper according to the rules, select the paper with the same rules to print first, and adjust the paper with different rules before the front and side gauges are adjusted, so that it can effectively reduce the frequent Bad prints resulting from adjustments to the rules.
2. Ink
In order to prevent the problem of a large amount of spot color ink being wasted due to the discontinuation of the cigarette factory brand, many spot color inks are prepared by using the original ink before going on the machine. Therefore, in the offset printing of offset color inks, it is necessary to accurately record the composition and ratio of each spot color ink. Before mass production, the ink adjuster determines the correctness of the spot color ink ratio, and estimates the ink dosage to avoid repeated times. The deployment causes the occurrence of chromatic aberration, waste ink, and the like.
3. Run solution
The pH of the dampening solution required by our company is 4.8-5.5. Other data are: temperature 10～12°C, conductivity 800～1200μs/cm, alcohol concentration 12%～15%, and must be measured regularly and confirmed dampening Whether the pH value of the liquid is within the standard range.
4. Blanket lining
The thickness of the blanket lining of each printing color group must be consistent, otherwise it will affect the overprinting accuracy of the product, especially when printing some products with high precision of overprinting. However, even if the quality is better, there will be inconsistencies in thickness. Therefore, before using the lining, it is best to use a micrometer to measure the thickness of the lining.
Plate confirmation
1. Whether the color area is added to the area other than the finished product on the printing plate
When producing a box-package product with a large color area, such as “Taishan (Hongtu), “Red Golden Dragon”, etc., because the color difference between the middle part and the two ends is large, it is easy to produce “ghost shadow” in offset printing. It is difficult to control the uniformity of the color. For this, prepress personnel usually add color blocks to the area other than the finished product on the printing plate before the plate making to reduce the difference between the color area of the middle part and the two ends. Can effectively reduce the occurrence of "ghosting" phenomenon.
2. The deformation of the plate
The plate may be deformed after being baked at a high temperature, which may result in inaccurate overprinting of the printed products, especially those products with fine lines overprinting, such as the "Taishan (Hongtu)" small box of cigarette packets. Therefore, for some prints with high precision in overprinting, the baking time should be reduced.
3. The dot angle of the plate
When printing green products, you must pay great attention to the dot angle of the plate. The normal dot angle is usually 0 degrees yellow, 45 degrees magenta, 15 degrees green, 75 degrees black, and the main color of green products is yellow and blue. If the angle between the two colors is still 15 degrees, it is very easy to appear. "Bumping the net" phenomenon, so before production, it is best to confirm the dot angle of each plate.