Irregular drawing at the printing blank, how to solve the best effect?
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The random drawing of the printing blank appears as an irregular ink path that is sometimes absent, short in duration, and usually relatively thick. The causes and solutions are as follows.
1. Scraper blade or foreign matter sticking under the knife
The squeegee can be moved back and forth, up and down during the printing process, and the stuck foreign objects can be removed or removed directly on the squeegee blade with a bamboo stick (must be done by a skilled operator to avoid unnecessary loss due to improper operation) If necessary, stop the squeegee thoroughly.
2, the ink cycle is not enough
Part of the ink in the dead space position in the ink tank, due to the lack of good circulation, the resin is precipitated, forming crystals and agglomerates of different sizes, or excessive drying causes the surface to form ink skin (summerly easy to produce ink skin in summer, due to temperature in spring and autumn) The effect of the ink crystallization and agglomeration is more). As the ink circulates, a part of the ink crystal or the ink sheet is brought to the blade by the rotating plate cylinder, and the doctor blade breaks it to form a random wire drawing. Therefore, it is necessary to improve from both the circulation and filtration of the ink.
(1) Cycle improvement. Method one, tilting the ink tank to the left and right to ensure that the ink can be injected from a slightly higher end, flowing out from the lower end to form a good cycle; Method 2, the ink tank is laid flat, but the ink must be injected simultaneously from both ends, The intermediate reflow can also form a good cycle, and it is not possible to inject ink from one side.
(2) Filter improvement. The ink must be filtered for the first time before use. Even if it is new ink, it should be filtered. Generally, a filter of 140 mesh/inch is used. The filtration of the ink circulating in the ink tank is more important. It can filter out the resin crystals and foreign impurities formed during the use of the ink. The selected mesh should be finer. The method is to set a stocking under the ink fountain. , forming a filter sleeve, after filtering for a period of time, if the filter is blocked, the ink is not smooth, you can insert some small holes in the top of the bucket with bamboo sticks to increase the ink guiding effect, and the bottom of the bucket can also To the effect of good deposition of impurities, as shown in Figure 3. Some large printing houses in Shanghai and Guangdong use this method to control the intermittent drawing of ink.
3, ink fatigue
This situation often occurs when the printing area of the printing plate is relatively small. During the printing process, the resin in the ink is continuously consumed. If the solvent is continuously added without adding new ink, the resin is not replenished, and the proportion of the components of the ink changes, thereby causing ink fatigue and affecting normal use. Solve the problem by adding new inks as appropriate.