After the offset press is installed, it must be checked and accepted. As an offset press operator, it is mainly to check its printing pressure and overprint conditions. Acceptance is a very meticulous job. You must not act sloppyly to avoid future troubles.
Trial printing and adjustment of Yiping screen
The requirements of the trial printing flat screen printing film: 175 lines of 50% flat screen (50%). Before printing, first use a density meter to measure the density of the three points of the gripper, middle and trailing edge of the film to confirm the density difference of the film itself After printing the plate, use a density meter to measure the density of the three dots on the mouth, middle and trailing edge of the PS plate, and finally measure the density of the dots on the debugging sample. The difference of the dot density on the same page is controlled within 0.08. Prerequisites for measuring, observing, and calculating the dot expansion value; the field density must reach 1.5-1.6 (blue ink), because under the same conditions, the thinner the ink layer, the smaller the dot expansion value, and the thicker the ink layer, the more the dot expansion value Big.
Printing flat screens generally use red ink or blue ink. Under the same flatness, red ink is more dazzling, but it is easy to reflect the problem. The requirements for flat screen testing: no streaks (black streaks, white streaks), The dots are smooth, strong, and clear. The expansion value of the dots is controlled within 12%, the density difference of the same page is controlled within 0.08, and solid bars are added in the middle of the flat screen to measure the solid density. See Figure 10-3.
(Figure 10-3 Schematic diagram of flat screen)
Before the flat screen trial printing, first adjust the center distance of the three rollers and the liner to the standard state according to the requirements of the operating instructions, and then adjust the water and ink rollers to the standard state (prompted on the ink road map), otherwise it is difficult to print Ideal test sample.
Second field trial printing
The center distance of the three cylinders and the adjustment requirements of the water and ink rollers are the same as those of the printing flat screen. The printing site requires three sides to leave white edges and drop the water roller for printing. The blue ink is used for printing. The advantages of blue ink are not dazzling, and the density requirement is 1.5- Between 1.6, the quality requires no white streaks and black streaks, and the density difference on the same page is within 0.08.
Three different speed overprint inspection and adjustment
The purpose of different speed overprinting is to check the working stability of the positioning system. For high-speed offset presses, the first printing speed is 7000 sheets / hour, and then 9000 sheets / hour, 11000 sheets / hour, and 13,000 sheets / hour respectively. Overprinting at vehicle speed, overprinting content: use full-millimeter grid, because in the all-speed printing, regardless of the direction of the size or the direction, there is a slight inaccuracy, the density value immediately rises to form a local dim, no need to use a magnifying glass, the naked eye Can also distinguish. See Figure 10-4.
(Figure 10-4 mm grid)
Inspection and requirements of four-color trial printing
There are many kinds of color trial printing plates, which are not consistent among different factories, but the test content generally includes the following aspects: field density, exposure of the printing plate, ghosting of the dots, gray balance, etc. Quality requirements for color trial printing:
(1) The four-color solid density value cannot be lower than the standard value.
(2) Ghosting phenomenon cannot appear in the ghosting test section of the signal bar, because when testing flat screens or on the ground, they are all monochrome printing, there is no transfer ghosting problem, and the color test printing is a four-color group Or the units with more than four color groups are pressed together for printing. The precision of the gripping cylinder and transfer cylinder of each unit is slightly poor, and the ghost phenomenon will appear on the imprint. Therefore, a signal bar must be placed on the trailing part of the trial printing plate .
(3) Place a circle of millimeter grids (four colors) on the edge of the graphic of the trial printing plate, the purpose is to check the accuracy of the four-color overprint, and at the same time check whether the machine has fan tail phenomenon.
(4) Compare the printed test sample with the original, and observe the contrast, that is, the deep place should be deep, the light place should be light, and the contrast must be pulled apart.
(5) Trial printing a batch of products, the quality requirements must reach the high-quality products, the entire commissioning work is considered to be over.
Product categories of College Backpack, we are professional China manufacturer of all kinds of Bags, High School Backpack, College Student Backpack for college students. This college backpack is great for casual day use and perfect for students going to high school & college, with more space and pockets that can hold books, folders, snacks, and school supplies. So, it is a perfect college high school student backpack for boys, girls, teens, and the college backpack is much lighter than other backpack, breathable, adjustable and wide shoulder straps added extra comfort to this college backbag. We have cooperated with many famous brands allover the world. We can do OEM or ODM for our customers. We have the perfect after-sales service and technical support. Contact us today to establishing new and goods business relationship.
College Backpack
College Backpack,College Laptop Backpack Bag,Classic College Backpack,Custom College Backpack
Panway Industries Co., Ltd. , https://www.panwaybags.com