How to check the PS version before printing on the machine
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We often encounter in our daily work, the PS version that has been printed on the machine has found quality problems, and then we have to re-save the PS version on the press, re-print the plate, and repeat the process of the plate. Since this process includes the printing time of the printing plate and the repeated printing time, this has an effect on the production efficiency. At the same time, there will always be mutual responsibilities in both 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 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, timely replenishment, avoid the situation of downtime and other versions.
Below we will discuss how to judge the quality of the printing plate.
·Check the appearance quality of the plate
It refers to the external performance state of the printing plate. The basic requirement is that the layout is smooth, clean, uniform in rubbing, no broken edges, no creases, no scratches, no dirt and ink spots.
· Layout specifications check
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 graphic and correct, not skewed.
·Check the content of the graphic
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, no film release, multi-color set, the color version 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 corner line are the standards for cutting the paper edge printing products, so it is necessary to ensure that the required rule lines should be complete and complete; The position of the rule line, the angle line and the tip line ensure that the size of the product on the 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.
·Check the quality of outlets
The dots in the printing plate should be full, complete, smooth, no damage, no scratches, no hollows, and less burrs. 5% of the small dots, 50% of the dots and 95% of the dots are 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 are compared. If the dot size of the high-light tone part, the middle tone part, and the shadow part are basically the same as the print sample, the depth of the plate is in accordance with the requirements of the machine. If the dot is enlarged, the tone is too deep, and the dot becomes smaller, 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, 98% of the 2% dark adjustment of highlights should be well reproduced.
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 has fog, unclear and so on.
·The difference between the color of the offset printing plate and the 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. The printing plates with texts, lines and graphics are easier to distinguish the specific colors of the plates according to the color drafts. For those printing plates with four colors, it is difficult to identify the colors. This requires us to do the printing. When you make imposition, you must 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 color. English words can be used to distinguish colors. In short, offset printing, trademarks, four-color overprinting, book covers, etc., where there are two or more overprinting products, mark the color block mark to avoid mistakes in color. In addition, there are often other alternative symbols on the printing plate to indicate the color. The operator should also have a certain understanding, and strictly avoid the phenomenon of the wrong printing plate. See the attached table below:
·The inspection of the graphic part and the blank part of the offset printing plate
The blank portion of the offset plate is required to be clean, tidy and flawless. It should be carefully checked to see if the layout is dirty or scratched, oxidized and dried, and there is a leaky photosensitive film. For the dirty place on the plate, you can use the PS version of the repair paste to remove the dirty treatment. 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 not dirty due to exposure and development, you can use a diluted developer to rub, so that the plate meets the printing requirements Rescuing as much as possible, reducing the consumption of raw materials and increasing the printing durability of the printing plate.
If the comprehensive analysis, the right medicine, it is very beneficial to reduce the consumption of finished products and improve the benefits.
In order to ensure the quality of the offset printing plate is stable and reliable, the operators and quality inspectors of the plate making process must carefully check the printing plates to make the plate quality problems before the large-volume formal printing, and correct them in a timely and effective manner. The quality of printed products, the purpose of the connection between the two aspects of plate making and offset printing.