Refers to the external performance status of the printing plate. The basic requirement is that the plate is flat and clean, and the glue is even, no damage, no creases, no scratches, no dirt and ink spots, etc. 2. Inspection of layout specifications The plate layout size, graphic size, nip size, fold size, and fold relationship should be checked. To make the layout size error less than 0.3mm, the color printing plate must be correct and graphic, not skewed. 3. Inspection of graphic content The basic content is correct text, no missing words, no words, the corresponding content of the plate and the text is consistent, the direction is correct, the PS version of the photosensitive film is strong, does not produce virtual, does not strip off the version, multi-color sets when the sun is complete. The rules line is the basis and benchmark for four-color overprinting of offset printing. Fine and black are required. At the same time, the rules and corner lines are the cutting standards for paper-edge printing products. Therefore, it is necessary to ensure that the proper rule lines are complete and complete. Also, pay attention to the rules. The position of the line, the corner line and the trailing line ensure that the size of the product on the plate is larger than the size of the finished product after cutting. This avoids the cutting of the corner lines and the rule lines, and is not attached to the printed products. 4. Inspection of network quality The dots in the printing plate should be full, complete, smooth, real, no damage, no scratches, no hollow, and less burrs. With a magnifying glass of 5 to 10 times, 5% of small dots, 50% of dots, and 95% of dots were observed and analyzed, and the dots corresponding to the monochromatic color pattern of the offset printing plate and the proof sheet were compared with each other. If the mesh size of the high-light, mid-tone, and dark-tone portions is basically the same, it indicates that the depth of the printing plate meets the requirement of the machine. If the dot is enlarged, the tone is too deep, and the dot is too small to indicate that the tone is too light. If there is a phenomenon such as dot reduction, loss of high-gloss small dots, etc., it indicates that the graphic text is sun-dried. If there are dot gains, dark-spotting will cause the text to fade. In general, 2% of the highlights and 98% of the shadows should be reproduced well. By checking the depth of the tone level of the printing plate, we can observe whether the printing plate of the PS plate, the level of the electric gradation tone, the quality of the spot spot finish, and whether the film is fogged or unclear. 5. Differences and inspections of offset printing plates After offset printing of the PS version of offset printing, it is necessary to check the color difference of the printing plate according to the color sample of the proof to see if it meets the need for overprinting. The printing plates with texts, lines, and images are relatively easy to distinguish the specific colors of the printing plates according to the color drafts; for those overprinted four-color printing plates, there are certain difficulties in distinguishing the colors. This requires us to make plates, When imposition, be sure to color the edge of the plate, such as: yellow (Y), magenta (M), blue (C), and black (K). When you print on the machine, you only need to look at the words in Chinese and English. You can distinguish between colors. In short, the offset printing logo, electric four-color overprint, color pages, etc., where there are more than two colors of overprint products, should be marked with color blocks, so as not to mistake the color. In addition, there are often some other substitute symbols on the printing plate to indicate the color. The operator should also have a certain understanding, strictly avoid the phenomenon of mistakes. 6. Examination of graphic and blank parts of offset printing plates The blank part of offset printing plate requires clean, neat, and no dirt. It should be carefully examined to see if there are any spots or scratches on the plate surface, oxidize dry matter, and whether it has leaked the photosensitive film. For dirty areas on the plate, you can use the PS version of the paste to remove the dirt. The leaky film can be corrected with the PS version of the pen. For some fine layouts, with dirty spots and other patterns have problems, not necessarily non-renewal plate, layout due to exposure or lack of development with dirty, you can use diluted developer to wipe, so that the printing plate meet the printing requirements Save as much as possible to reduce the consumption of raw materials and improve the printing plate printing rate.
1. Plate appearance quality inspection
PS version quality inspection before printing on the machine
In our day-to-day work, we can often meet with the quality of the PS plate that has already started printing on the machine. Then we need to remove the PS plate from the printing press, reprint it, and repeat the printing process. Since the process includes the drying time of the printing plate and the repeated printing time, this has a certain effect on the production efficiency. At the same time, there are often shirking responsibilities between the two departments of platemaking and printing. For example: In the blank part, due to insufficient exposure of the printing plate or improper development, a trace amount of photosensitive film remains on the plate, causing the blank part to be dirty. The best method is to make a reasonable and correct judgment on the printing quality of the PS version before the printing plate has not been printed on the machine. If there is a problem with the quality of the printing plate, promptly make up the drying and avoid the situation of stopping the printing plate. . Below we will discuss how to determine the printing quality of printing plates.