Several points of quality check of PS plate

The PS version is the main plate of lithographic printing and is the source of printing quality. The quality of its production directly affects the printing efficiency and printing quality. Therefore, a series of serious inspections of the printing plate in the prepress process is of great significance in effectively preventing production errors and printing quality accidents, and improving printing production efficiency and product printing quality.

According to the author's quality management experience, the PS version should mainly carry out the following aspects of quality inspection:

1. Check the specifications of the PS version.

Since the diameters of the cylinders of various types of offset presses are not the same, the specifications of the plates are also different. In addition, the same type of offset printing equipment, due to the printed product specifications and layout size, the printing plate is also different. Therefore, we must carefully check the position of the printing plate graphic and text according to the product specifications, check whether it meets the requirements of the printing positioning, binding process and trim size, so as to avoid problems after blind plate printing, causing unnecessary waste of time and labor. .

2. Check the plate layout cleanliness and flatness.

The examination of the cleanliness and flatness of the printing plate is mainly about the appearance of the front and back of the printing plate. See if there are dirty spots, hardened films and other residual impurities on the front plate. The back of the plate should also be carefully checked for foreign matter. If there are hard foreign materials, it should be cleaned in time to avoid rolling the bad blanket. In addition, the uniformity of the thickness of the printing plate should also be inspected. That is, the thickness error of the four corners of the printing plate should not exceed ±0.05 mm. Otherwise, pressure non-uniformity will inevitably occur. This should be compensated for by the pad plate. If, during the inspection, noticeable scratch marks, creases, cracks, and jagged marks on the surface of the plate are found to be unrecoverable, this type of plate cannot be printed on the machine, and the plate should be remastered to ensure the quality of the product.

3. Inspect the plate color, color, gauge, and test strips.

In order to make it easy to identify whether the ink color of each color printing product is consistent with the sample draft, there is a drying color standard block in the appropriate position of each color printing plate, and each color color mark is arranged on the lower side or the upper side of the printing plate in order to enable comparison. Accurately check out the "white pages", double sheets, reverse printing, and scrap sheets that are inaccurate. The inspection of the printing plate color can prevent the mistakes in the prepress process and the quality problems and troubles caused by the printing. In the inspection, the author once encountered such a plate-making quality problem: the color plates of the blue plate and the yellow plate of the film are mutually exclusive. Confusely, it was found out that the color was not correct (the pattern is not the same). Therefore, changing the printing plate to reload the school version was very troublesome. Therefore, for the sake of prudence, it is very necessary to carefully check whether the printing plate color is in conformity with the graphic in the prepress process. The method is: According to the characteristics of the layout text and shades of the color to identify, because different images, its image structure and tone levels are not the same. It can be used to identify areas where the hue contrast is relatively large. For example, in the case of landscape images, the leaves of the trees are deeper and the sky is darker than the cyan version. The leaves are darker and the sky is lighter than the yellow version. The inspection of the printing plate guideline is mainly to see whether the position of the crosshair and the corner line on the plate surface is accurately placed, so as not to affect the appearance quality of the post-processing and the finished product. The guideline is the basis for the overprinting of products and the cutting of finished products. The appropriateness of the position cannot be ignored. If the layout has a solar test strip, check its position.

Fourth, check layout and tone levels.

During the inspection, the appearance of the dots observed with the high magnification magnifier should be bright and clean, the circle can be clearly distinguished, and the edges of the dots do not have burrs and defects. The dots of the dots cannot be oval or flat. The black and white color of the outlets should be clearly defined, and dim sums should not be grayed out or have white spots. Otherwise, the sensory performance of the outlets is poor, and when printing, the ideas appear to be false. For the check of the tone in the printing plate hierarchy, the three different levels of high-profile, mid-tone and low-key can be selected. Compared with the monochromatic proofs of the sample, the dots on the plate are slightly smaller than the dots in the relative area of ​​the sample, after printing. With the influence of various objective factors, the increase in outlets is a normal phenomenon. If you find that the tiny point is missing, it means that the plate image is too light. If the white spots on the low-profile layout are murky, and if 50% of the squares are overlaid, then the plate is too dark. The above conditions will affect the quality of printing, so it is necessary to seriously check the film, printing operation, and the quality of the plate. Unqualified printing plates cannot be printed on the machine and should be re-plated.

V. Check the layout text and lines.

As the film trimming is not in place or improper printing operation, drying out of the printing plate are prone to quality defects, so it is necessary to check the layout of the text and lines, can better avoid print quality failures, improve printing production efficiency. Text inspection mainly depends on whether there are missing pen strokes, missing letters, or missing punctuation marks. If problems are found, they can be corrected or remedial measures (such as reprinting) can be made to ensure the printing quality. The inspection of the line depends on whether the layout lines are broken, incomplete, multiple points, and the line thickness is consistent with the sample draft. If the overprint version of the printed fine products, such as maps and other printed products should be copied to the opposite polyester polyester laminate inspection, if the printed text is a blue line, the same pattern lines, red lines standard map The polyester sheet is superimposed on it, and the line on the map shows a blackish color, indicating that the lines of the picture and text are accurate and intact. If a part is in a red state, it indicates that the layout has a missing line; if there is a blue line or a small dot, it indicates a multi-point, multi-line.

To sum up, to do a good job in quality inspection of the plates can not only detect and deal with quality problems in a timely manner, avoid the printing quality problems that appear in the printing, ensure the printing quality of the products, and effectively improve the production efficiency.