Contents and methods of quality inspection of the

Contents and methods of PS plate quality inspection

printing plate quality inspection is an important part to prevent production errors and printing quality accidents. Therefore, it is of great significance to carefully inspect the printing plate quality before printing to improve production efficiency and ensure printing quality

I. check the specification and size of PS version

due to the different cylinder diameters of various types of offset presses, the printing plate specifications are also different. Even for the same type of offset printing equipment, the printing plates should be different due to the different product specifications and the size of the plate mouth. Therefore, it is necessary to carefully check the accuracy of the position of the printing plate pictures and texts according to the product specifications, so as to avoid blindly finding problems after printing, which is labor-consuming and time-consuming

II. Check the cleanliness and flatness of the printing plate

the inspection of the cleanliness and flatness of the printing plate is mainly the inspection of the front and back appearance of the printing plate. Check whether there are dirty spots, hardened peritoneum and other residual impurities on the front plate, and deal with abnormalities in time. The back of the printing plate should also be carefully checked to see if there is any foreign matter. If there is any hard foreign matter, it should be cleaned in time to avoid crushing the blanket. At the same time, the uniformity of the thickness of the printing plate should also be tested, that is, the thickness error of the four corners of the printing plate should not exceed ± 0.05mm, otherwise it will inevitably lead to uneven pressure, and the uneven pressure defect can be compensated by padding. If there are obvious scratches, folds, cracks, pits and other irreparable defects on the surface of the printing plate during inspection, the plate cannot be installed for printing, and it should be remade to ensure the printing quality

III. check the color code, color classification, gauge line and test conditions of the printing plate

in order to facilitate the identification of whether the ink color of each color print is consistent with the sample, a small color mark should be made on the appropriate position of each color print plate, and the color marks of each color should be arranged under the side of the print plate or facing the outside in turn, opposite to the rules used in printing, so that "white pages", double sheets and reverse printed waste sheets can be checked more accurately. The purpose of checking the color of the printing plate is to prevent errors in the prepress process. Generally, chromatic printing plates have colored marks, but for prudence, it is necessary to carefully check the color of printing plates. The method is to recognize according to the graphic features and tone depth of the layout, because different pictures have different image structures and tone levels. It can be used to identify the parts where the tone contrast has become a major trend of the industry. Take the landscape picture as an example. The trees with deep leaves and the sky with deep and shallow layers are cyan version, the leaves with deep layers and the sky with light layers are yellow version. Point angle can also be used to identify the color plate, that is, according to the point angle formulated by the process. The inspection of the printing plate appearance line mainly depends on whether the positions of the cross hairs and corner lines on the plate are placed accurately, so as not to affect the appearance quality of the finished product. The line is the basis of overprint and finished product cutting, and the appropriateness of the position cannot be ignored. If there is a drying test strip on the layout, check whether the placement position is accurate under the reactive power consumption that further aggravates the energy

IV. check the surface dots and tone levels

during inspection, the appearance of the points observed with a high-power magnifying glass should be smooth, round and square, and the edges of the points should be free of burrs and defects. The shape of the point cannot be elliptical or flat. The dot color should be clear in black and white, and the dim sum should not be gray or have white dots, otherwise, it indicates that the fat sensitivity of the dot is poor. To check the tone of the printing plate, three different levels, high-key, middle and low-key, can be selected. Compared with the monochrome sample of the sample, when the dots on the printing plate are slightly smaller than those in the opposite area of the sample, the dot increase rate of about 6% is allowed due to various objective factors after printing. If small ideas are found missing, it indicates that the printing plate text is too light. If the small white dots on the low-key layout are blurred, and 50% of the square dots overlap too much, it indicates that the color of the printing plate text is too dark. The above conditions will affect the printing quality, so we should carefully check the base plate, printing operation and plate material quality

v. the main advantage of the layout text and line composite materials in the aircraft is to check by reducing weight to save fuel consumption

due to inadequate film trimming or improper plate printing operation, it is easy to expose defective printing plates, so it is necessary to check the text and lines of the layout. The text inspection mainly depends on whether there is missing pen and stroke or missing words and punctuation. The plane of the concrete foundation uses horizontal leveling symbols, etc. if any problem is found, it can be corrected in time or remedial measures (plus re printing) can be taken to ensure the printing quality. The inspection of lines depends on whether the layout lines are intermittent, incomplete, multi-point and whether the thickness of lines is consistent with the sample. If printing overprint plates of fine products, printing products such as maps should copy polyester sheets with opposite colors for superposition inspection. If the printed image and text are blue lines, apply the same version of the text and the standard map polyester with red lines to overlap and align it. When the lines on the map show an approximate dark color, it indicates that the graphic lines are accurate and intact. If a certain part is in red, it indicates that the layout is short of money; If there are blue lines or dots, it means multi-point and multi line

to sum up, it is a meticulous work to carry out a series of quality inspections on printing plates. Doing this technical and comprehensive work patiently and carefully is very necessary for truly reproducing the original manuscript, ensuring the quality of printing products, improving work efficiency and avoiding and reducing the occurrence of waste and defective products to the greatest extent, and the labor paid is worth it

source: designed and printed in China