1. Check the printed sheets
Diligent inspection of printed sheets refers to the constant checking of the quality of the products during the printing process. In the process of lithographic offset printing, various conditions may occur that affect the quality of the product, resulting in a large number of defective products or even waste products. Therefore, inspecting printed sheets is indispensable during the printing job.
Diligent inspection of printed sheets includes the following: checking whether the overprint is accurate, checking the ink color, checking the quality of the dot, checking for dirty spots, white spots, pasting plates, and flower patterns.
2, stirring the ink fountain
Stirring the ink fountain means that the ink in the ink fountain is stirred at a certain time during the printing process. Mixing ink fountains in order to ensure continuous underground ink is the premise to ensure uniform and consistent ink before and after printing.
Ink is a plastic fluid with thixotropy that gradually changes in fluidity with external forces. That is, under the condition that the temperature of the ink is kept constant, after a certain external force is applied to the stationary ink, the ink gradually becomes thinner and softer, and the rheology becomes better. When the external force stops stirring, the ink gradually becomes thick and hard, and the fluidity changes. difference. If the ink fountain is not stirred for a long time, the fluidity of the ink is deteriorated, and the ink under the ink fountain is poor, resulting in the phenomenon of blocking ink or not, the ink roller is difficult to transfer ink and evenly ink, and the printing plate ink is insufficient, and it is difficult to achieve The ink breaks in the middle to make the remaining ink layer protect the layout and cause offboarding.
An ink stirrer can be installed in the ink fountain to uniformly stir the ink and increase the fluidity of the ink. It is also possible to stir the ink in the fountain with a knife.
3, diligently check the layout moisture
Diligently checking the surface moisture refers to constantly checking the size of the water in the printing plate during the printing process.
In the course of printing operations, it is important to correctly grasp and control the moisture in the layout, achieve the ink-water balance in the printing process, and properly identify the layout moisture. Identification method for the size of water in the production process:
1 visual test. In daily production, visual inspection is generally based on the operator's experience. The method is to illuminate the screen obliquely with the illumination lamp to determine the size of the water in the layout according to the brightness of the reflection; the thicker the water film, the stronger the light reflection and the thinner the water film reflection. The weaker the light.
2 Judgment according to the phenomenon of printing faults. If there are stencils or dirty prints, you should be aware of whether the water on the print surface is too small. If the prints are dull, patterned, curled, or the like, the water on the surface may be too large.