PS version of the machine before the quality check
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It is often encountered in our daily work. The PS version that has been printed on the machine has found quality problems, and then the PS version has to be removed from the press, re-printed, and the process of repeating the version. Since this process includes the drying time of the printing plate and the repeated printing time, this has an impact on production efficiency. At the same time, there will often be a phenomenon of shirking responsibility between the two departments of plate making and printing. For example, due to insufficient exposure of the printing plate or improper development, a small amount of photosensitive film remains on the plate surface, causing the blank portion to become dirty. The best way is to make a reasonable and correct judgment on the quality of the PS version before the printing plate is printed on the machine. If there is a quality problem in the printing plate, it should be replenished in time to avoid the situation of downtime. . Below we will discuss how to judge the quality of the printing plate.
1, the appearance quality check of the printing plate
It refers to the external performance state of the printing plate. The basic requirements are that the layout is smooth, clean, uniform, no damage, no creases, no scratches, no dirt and ink spots.
2, the inspection of the layout specifications
Check the layout size, graphic size, mouth size, folding size, folding relationship, etc. To achieve a layout size error of less than 0.3mm, the color version must be straightforward and not skewed.
3. Inspection of graphic content
The basic content is correct text, no missing words, no swear words, the corresponding content of the plate and the text is the same, the direction is correct, the PS version of the photosensitive film is firm, not imaginary, not stripped off the plate, and the multi-color set is complete. The rule line is the basis and benchmark for offset four-color overprinting. It is required to be fine and black. At the same time, the rule line and the angle line are the standards for cutting the paper edge printing products, so it is necessary to ensure that the required rule lines are complete and complete; The position of the line, the angle line and the tow line ensure that the size of the product on the printing plate is larger than the size of the finished product after cutting, avoiding the cutting of the angle line and the rule line, and it is unsightly attached to the printed product.
4, check the quality of outlets
The dots in the printing plate should be full, complete, smooth, solid, no damage, no scratches, no hollows, and less burrs. 5% of the small dots, 50% of the dots, and 95% of the dots were observed and analyzed with a magnifying glass of 5 to 10 times, and the dots of the corresponding color of the offset printing plate and the proofing sample were compared. If the dot size of the high-light tone part, the middle tone part, and the dark tone part is basically consistent with the sample, it indicates that the plate depth meets the requirements of the machine. If the dot is enlarged, the tone is too deep, and the dot is too small, indicating that the tone is too shallow. If the dot reduction occurs, the high-light small dot is lost, etc., indicating that the color of the graphic is light, if there is a dot enlargement, the white dot is darkly changed, indicating that the color of the graphic is dark. In general, 2% of highlights and 98% of darkness should reproduce well.
By checking the depth of the plate's tone level, you can observe the PS version of the plate, the electric level adjustment level, whether there is a problem with the dot finish, whether the film is foggy or unclear.
5, the difference between the offset printing plate color and inspection
After the offset printing of the PS version, it is necessary to check the color of the printing plate according to the color proof of the proofing to see if it meets the needs of overprinting. Printing plates with text, lines, and graphics are relatively easy to distinguish the specific colors of each plate according to the color draft; for those printing plates with four colors, there are certain difficulties in identifying colors, which requires us to make plates, When spelling, be sure to color the edges of the plate, such as: yellow (Y), magenta (M), cyan (C), black (K), so when you print on the machine, just look at the English and Chinese characters. You can distinguish the colors. In short, the logo of offset printing, four-color overprinting, coloring pages, etc., where there are two or more overprinting products, the color blocks should be marked to avoid mistakes in color. In addition, there are often other alternative symbols on the plate to indicate the color, the operator should also have a certain understanding, strictly avoid the phenomenon of the wrong version.
6. Inspection of the graphic part and blank part of the offset printing plate
The blank portion of the offset plate is required to be clean, tidy and free of dirt. It should be carefully checked to see if the layout has dirty spots or scratches, oxidized dryness, and whether there is a leaky photosensitive film. For dirty places on the plate, you can use the PS version of the repair paste to remove the dirty, the leaky photosensitive film can be corrected with the PS version of the patch. For some small layouts, with dirty spots and other patterns, there is no need to replace the printing plate, the layout is dirty due to exposure or development, can be rubbed with diluted developer, so that the plate meets the printing requirements Save as much as possible to reduce raw material consumption and increase plate durability.