(1) Check whether the norms of 4 color films are consistent (whether the 4 color films are the same set).
(2) Check whether the graphics are complete against the sample sheet.
(3) Balance the moisture and ink volume to ensure the consistency of ink color in the same batch of prints.
(4) Close the machine less or clean the blanket after closing less.
What operators should focus on when printing are as follows:
(1) Look at the operation of the metal offset printing machine, the sample ink color and registration, and dot quality.
(2) Listen to the offset printing equipment sound to check whether there is noise in the vibration-sensitive area.
(3) Touch the machine parts which are easy to heat up due to wear and tear, and check whether there is a significant temperature change.
(4) Smell if there is no electrical burning and other abnormal strange smells. (when UV ink printing, you should pay more attention to the power cord of the UV coating machine).
(5) Check the print quality and the offset printing equipment, solve problems in time.
Ink and water are compatible. In the printing process, ink and water through the extrusion of rubber rollers will be fused and emulsify the ink. There are two states of ink emulsification: when the water is more than ink, the oil will cover water; when the water is less than ink, water will cover ink. In the offset printing process, the command of ink and water balance is closely related to the normal transfer of the print, the depth of the ink color, the accuracy of the color set, the dryness of the print, and sticky dirt. Generally speaking, when the water is more, the ink is emulsified, making ink color shallow; when water is little, the blank part of the layout will adhere to the ink, producing dirty stains. Therefore, the key to printing is the water-ink balance of the printing press offset printing.
The principle to control water-ink balance is less water and more ink. Less water refers to the blank part of the page that is not sticky and dirty; more ink refers to the appropriate increase of ink volume based on less water. In the printing process, the big volume of water and ink is wrong. When it comes to the amount of water, it should depend on the size and distribution of the layout graphics area, the thickness of the ink layer of the print, the nature of the printing paper, ink performance, offset machine operating speed, shop temperature, and humidity, the PH value of the fountain solution and the auxiliary agents added in the ink.
Ink rollers must be washed completely while color-changing. After a period of printing, the blanket will accumulate paper hairs, paper powder, ink, and other dirt, reducing the quality of the print. So the offset press blanket should be cleaned on time, especially when printing low strength paper, paper hairs, and paper powder accumulation get more serious. Therefore clean frequently, especially from a dark ink to light ink. If the ink roller group is not clean enough when changing colors, it will affect the purity of the new ink color. During the transformation from black ink to yellow ink, black ink, if not clean, will pollute yellow ink, which will affect the quality of the print. Therefore, when changing colors, the ink roller set must be clean.