Problems and difficulties in map printing 0

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Problems and difficulties in the process of full open map printing as a special case of sheet fed offset printing, the printing process of full open map has its inherent characteristics: (1) as a whole, its printing format is relatively large; (2) It generally has no continuous point change, but has a large area of flat; (3) Nesting is a key point of full open map printing; (4) There are many spot colors or designated composite colors (Geological Maps sometimes have as many as a dozen colors); (5) The number of prints of most kinds of pictures is less (more than - twothousand, less than one or two hundred); (6) There are many kinds of printing paper (sometimes the same picture needs to be printed with offset paper, coated paper, silk cloth, teweiqiang, etc.)

(7) there are more block printed drawings (at least two full open, and at most l-inch full open). Due to the above characteristics, full open map is prone to problems that are not common in folio printing, or problems that are easy to solve in folio printing but difficult to deal with in full open printing. Over the past decade, we have printed thousands of full open maps, both single and multiple; Both monochrome printing and multicolor printing; There are offset paper, coated paper, silk cloth and teweiqiang; There are both civilian map products and military map products. The following is my experience based on my years of participation in the production and printing of various full open map prints

first, large areas of uneven or uneven points

the use of large areas of flat is the most common in full open maps, such as blue common dyeing in the sea and regional common dyeing in zoning, and the flat area is usually more than 30%. Due to the large area of lithography, uneven and uneven dots often occur, mainly including:

(I) uneven dots of copied film: due to the uneven light source of the copier, loose air extraction and poor development, it is often difficult to ensure the dot uniformity of full open film, especially at points above 50%, at this time, only by adjusting the copier to copy again. With the emergence of computer mapping, such problems will gradually disappear

(II) uneven light source or loose air extraction during printing: due to the large area of the full open map, the influence of light source and air extraction around the full open layout is particularly serious. Therefore, the aged light source should be replaced in time, and the extraction pressure should be compared. Therefore, the design adopts the most advanced combination seal plate in the world, and there should be no foreign matter on the rubber of the plate printer

(III) uneven coating of PS plate or horseshoe print on the plate: the quality of PS plate should be relatively stable now, but due to different manufacturers, especially the quality of Daquan open plate is not ideal from time to time. Because of the large area, the plates we have purchased in recent years have horseshoe prints (generally produced in the process of handling). The stupid way is to use a rubber hammer to solve it

(IV) rubber aging or uneven pad: the pad is slightly uneven or the rubber is slightly aged so as to prolong its service life, which generally does not seriously affect the printing quality or is difficult to detect by the naked eye. However, in full open map printing, especially for large-area dot printing, it is particularly prominent (black or other dark spots are particularly obvious). In this case, the pad should be re padded or the rubber should be renewed

II. Inaccurate nesting

in full open map printing, due to its large format, when there are more printing colors, more collages and more types of paper, affected by factors such as printing cycle, temperature and humidity of printing workshop, paper adaptability, printing equipment, etc., the nesting synthesis between various color plates

is the difficulty and key point in full open map printing, mainly including:

(I) the nesting between colors of multi-color machine unit is not good: uneven thickness of printing plate The printing plate pad paper is not uniform or uneven, and the rubber pad is not uniform or uneven, which will lead to the incorrect combination between the first group and the second group (our department uses the Hamada Da full open two-color machine in Japan). At this time, it can be solved through corresponding adjustment. Another factor that is not easy to find that affects the nesting is the printing adaptability of paper. This usually occurs when special paper or offset paper is not dried, but coated paper will also produce similar problems, such as the 128 g coated paper (maybe fake?) of Hong wonpaper we used in 1997, After several days of multi-party investigation, change to another crystal 3.3 experimental fixture, the moving speed should meet the specified requirements, and the nesting problem between the first group and the second group naturally disappears

(II) composite materials can't be used to replace metal during the second and third paper runs: map products have quite strict requirements for printing fits, especially for the double-line chromatic printing of traffic maps. It is more difficult to master the line type and text chromatic fits produced by computer graphics and plate making. When the water runs improperly, the temperature and humidity in the workshop are unstable, the climate changes suddenly, and the printing cycle is long, it will lead to inaccurate paper runs for the second and third times. Therefore, in addition to the normal control of ink balance and workshop temperature and humidity, we should also fully consider the weather conditions and the determination of the printing cycle during multi panel printing. When there is a nesting problem that is difficult to correct, you can also consider printing the map in pieces and times. Because a certain printing color of the map product is generally discontinuous, when a certain color cannot be nested, you can print the color left and right or up and down twice or even three times to ensure the nesting accuracy

third, the difficulties of multi panel printing

when users need a large-scale map and the area is large, it is often difficult to accommodate a full sheet of paper, such as urban maps and planning maps. At this time, they are usually divided into two, four, nine, etc. because these maps are generally special maps (wall charts), the number of prints is relatively small, and the printing color is usually large, in order to ensure the overall effect of the printed mosaic map, Attention should be paid to when printing:

(I) determine the number of pieces printed at the same time: from the perspective of printing, multi block maps are of course printed at the same time, which can better reflect the ink color of each piece of map, and maintain its accuracy and consistency. However, when there are a large number of pieces, such as eight pieces and nine pieces of jigsaw puzzle, it is necessary to ensure that the printing color is accurate and consistent, and that the nesting is accurate. At the same time, the impact of temperature and humidity, printing cycle and so on on on the printing quality should be considered. Four or five prints can be printed at the same time in stable seasons, and two or three prints can be considered at the same time in rainy seasons and other volatile times. When there is no sunlight source in the workshop, in order to make the ink color consistent, the printing should be arranged in the daytime, so the number of printing sheets must be reduced accordingly

(II) arrangement of printing color sequence: because there is no continuous tone change in map printing and the requirements for color restoration are not particularly high, it is not necessary to follow the color sequence of image printing. When the air humidity is small, the main color printing can be arranged first, so that the paper can generally be restored to its original state when the paper is transported for the second time; When the air humidity is high, a secondary color printing with relatively low nesting requirements can be arranged first, so that the map quality will not be seriously affected even if the paper cannot be restored to the original state during the second paper feeding

four. The difficulties of special paper printing

Silk Map and teweiqiang map have the characteristics of waterproof, wear-resistant and folding resistance, which make them popular in some fields. However, the silk cloth can only be printed after being pasted, and it is curly and deformed greatly; Teweiqiang has light texture and poor adaptability. In addition, their printing cost is high and the number of prints is small. Full open printing is even more difficult to master

(I) printing of Silk Map: Silk map is generally mounted on offset paper above ioog, which is heavy and thick. According to the crimping characteristics of silk cloth, it is necessary to press and empty it once before printing to ensure the stability of paper feeding during formal printing. When feeding paper, the air blowing and suction volume should be increased, the double sheet control height should be increased, and the printing pressure should be appropriately increased. As silk fabric is easy to penetrate ink, the ink output should be appropriately increased during printing to avoid too light map ink after paper stripping

(II) printing of teweiqiang map: because teweiqiang is a chemical fiber product made of high-density polyethylene by blowing and hot pressing, 70% of its volume is air, so it should be pressurized and emptied once before formal printing, otherwise, the first color and other colors cannot be combined (actually caused by pressure deformation). During paper feeding, the air blowing and suction volume should be reduced, and at the same time, the water delivery volume should be reduced to prevent deformation caused by water absorption and expansion, so as to ensure the nesting accuracy

full open map printing is similar to ordinary printing in terms of printing equipment and printing technology. However, everything has its particularity except commonness, and full open map printing is no exception. Therefore, in full open map printing, we should grasp its characteristics, adjust the printing process methods, solve the problems in the printing process, and constantly grasp its internal laws, so that the printed full open map products can meet various requirements

source: PRINT world Tu Chunhua

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