Offset fault handling collection

Fifth, how to identify the size of water

To identify the major moisture, we must first look at the layout of moisture. This depends on the operator's experience. In general, the moisture content is large, and the amount of reflected light on the plate is strong, and the side view is bright. On the contrary, the amount of reflected light on the plate is weak and the side view is dark. If the water is too large, it can be observed from the following points:

(1) Scoop the ink on the ink roller with a paper jam. Small water drops will remain on the paper.
(2) Small water droplets on the string water roller, deinking or water droplets in the ink roller group;
(3) After the water is turned off or the machine has been shut down for a long time, the water in the layout still has not dried up;
(4) The imprinted dots are empty and the ink is dull and dull;
(5) There are shadows or drops of water on the tail end of the blanket cylinder.

Six, control the water balance

Ink and water are not absolutely incompatible. In the actual printing process, the ink and water are squeezed by the rubber roller and the rubber roller, and they fuse together to emulsify the ink. There are two types of ink emulsification: when the water is large in ink, the formation of "oil in water"; when the water is small in ink, the formation of "oil in water". In the offset printing process, the mastery of the ink-moisture balance has a close relationship with the normal transfer of imprinting, the depth of ink, the accuracy of color registration, and the drying and stickiness of the printed matter. In general, the water is large, the ink is emulsified, and the ink is light; the water is small, and the blank part of the layout will adhere to the ink and cause a stain. Therefore, it is the key to printing that offset control is a good balance between ink and water.

Seven, control the ink balance

To control the balance of ink and water, it is generally necessary to grasp the principle of less ink and thicker water. Less water means the premise that the blank part of the layout is not sticky; ink thick refers to the increase in the amount of ink that is built on the basis of less water. In the printing process, the most taboo is the big ink. When considering the amount of water, the area size and distribution of the layout, the thickness of the ink layer, the properties of the printing paper, the performance of the ink, the speed of the machine, the temperature and humidity of the workshop, the pH of the fountain solution, and the amount of ink added Supplements and other circumstances.

Eight, cleaning blanket, change the ink roller must be clean

After printing for a period of time, there will be paper, paper powder, ink and other dirt on the blanket, which will reduce the quality of the printed matter. Therefore, the blanket must be cleaned in time, especially when printing paper with low strength. The accumulation of paper powder is even more severe. Therefore, if the ink roller set is not cleaned when the color is changed frequently, the purity of the new ink color will be affected, especially when changing from dark ink to light ink. If black ink is replaced by yellow ink, if black ink is not cleaned, yellow ink will be black, which will affect the quality of printed matter. Therefore, the ink roller set must be cleaned when changing colors.

9. The main factors of overprinting

Before and after overprinting is not allowed:

(1) Printing press

a. The heavenly adjusting plate locking screw is not fixed, or the M5 hexagonal screw on the feed rocker arm is tightly fixed;
b. Push paper seat copper sleeve is worn out;
c. Paper feed wear;
d. Printing pressure is too small;
e. gear wear;
f. The blanket is too loose and tight.

(2) Paper

a. Paper cutting accuracy is not high;
b. The amount of water during printing is too large and the paper is stretched.

(3) Others

a. There is a problem with the plate or manuscript itself;
b. The stack of paper jams is too high or the pressure of the platen is too heavy, causing paper jams.

Left and right sets are not allowed:

a. The left and right baffles are too tight or the left and right baffle screws are fixed;
b. The length of cardboard is different;
c. The drum moves around;

Source: Guangdong Printing