D81 Offset Printing Machine

With the rapid development of the printing industry, the requirements for exquisite and diversified quality of printed products are also increasing. Weifang Huaguang Precision Machinery Co., Ltd. produces the D81 series of small-scale offset printing presses that use the front gauge and side (push, pull) stipulated structure, which is more suitable for the printing of small-format, short-run color prints. Now I will introduce the experience of color printing production of D81 offset printing machine to readers and discuss it with you.
1. The front and side rules of the machine should be adjusted. Accurate rules are the exact guarantee of overprinting of printing products, and they are the most basic conditions for color printing production. Users can refer to the user's manual, high-speed machine time, affect the paper feeding time, open teeth time, push (pull) paper time and the upper and lower feed roller pressure, then try to print 10-20, continuous overprint 4-5 times , ensure that all rules are registered, and then tighten the adjusted bolts and nuts. Of course, in order to ensure the printing of high-quality fine prints, a lower print speed is generally preferred, and about 40 prints per minute is preferred because low speed printing will reduce and reduce the registration error caused by the sheets and the machine.
2, master the balance between water and ink. This machine uses the principle of water and ink immiscibility to achieve printing, so water and ink on the printing plate to maintain mutual balance constitute the basis for color printing production, this problem is easy to say, practical operation is difficult. Because only when there is a strict dividing line between the water film on the surface of the blank part of the printing plate and the ink sheet on the surface of the graphic part, the ink and ink do not infiltrate each other, ie, the ink and water balance is achieved. However, the ink fountain and the water roller, the ink roller transfer water and ink during the high speed rolling process, so the ideal static ink balance is difficult to achieve in the dynamic printing. There are many factors that affect the balance of ink and ink, such as the nature of paper, ink fountain solution, and the area of ​​printed graphics, so the size of the water is usually controlled according to the size of the ink. That is, under a certain printing speed and printing pressure, with the minimum amount of water supply to compete with the ink on the printing plate, it is generally said that under the premise of ensuring the printed product is clear and not dirty, the smaller the amount of water, the better. The specific situation should be treated specifically. If the distribution of printing plates is not symmetrical, ink consumption can be locally controlled by adjusting ink supply screws or adding a rubber wiper to the roller (a waste rubber blanket can also be used instead). Keep it balanced and stable.
3, pay attention to the color sequence. The so-called color sequence refers to the multi-color offset printing, the order of successive printing of various colors, usually color order is yellow, red, blue, black. The opaque black ink on the first color printing, on the one hand, will not affect the color synthesis of other inks due to the yellow ink transparency and the large light blocking rate; on the other hand, the large amount of yellow ink is not easy to dry, avoiding the crystallization of the ink. It facilitates overprinting of the second color ink. The black ink has the lowest transparency, and the ink plate is only used in the outline and shadow portion, and the amount is also the least. Therefore, the last color printing has little effect on the color of the ink overprint. From the perspective of the depth of the ink, the light color is overprinted with a dark color. If there are traces of misprints, it is not noticeable. On a dark color, the overprint is not allowed to be exposed. However, it should be noted that the yellow ink is light, and it is not easy to identify the amount of ink and the dot layer on the paper. Therefore, the depth of the printing plate should be checked before printing. The size of the printing plate and the size of the original plate can be identified by 25 magnifiers. Generally, it is allowed. Slightly smaller than the original outlets. With the continuous improvement of ink quality, the transparency of yellow ink is also increasing. For example, if we choose Tianyin brand quick-drying bright transparent medium yellow as the next color sequence (ie, red, yellow, blue, black or blue, red, yellow, black) in overprinting, the effect can also be achieved.
4, adjust the printing pressure, the pressure between the three rollers. Excessive or too little pressure can affect the quality of printed products. Printing pressure is too large, it is easy to distort the picture and text, the paper is brushed, the dot network is expanded, the level is unclear, and the printing plate and the blanket are worn out; if the printing pressure is too small, the transfer of the printing graphic is not perfect and the dot is not true. . Under normal circumstances, the pressure between the plate cylinder and the blanket cylinder is 0.15 mm, and the pressure between the blanket cylinder and the impression cylinder depends on the thickness of the paper. Generally, the dots of the printed product are not subject to deformation. It is worth noting that the pressure should be completed at a high speed, and no pressure adjustments should be made during printing.
In addition, in the printing of solid or large print area, in order to avoid the back of the dirty, you can reduce the height of the folded sheet to reduce the pressure on the paper, or in the ink to add the right amount of dry......