How to properly adjust the squeegee in gravure printing
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The pressure, sharpness, and contact position of the blade in gravure printing have an effect on the print quality. According to actual needs, reasonable adjustment of these factors can solve many problems in printing.
1. Pressure
The factors affecting the pressure of the doctor blade are the size of the cylinder pressure, the difference between the hard and soft blades, the angle at which the doctor blade intersects the plate, etc., the greater the slope, the greater the pressure. Excessive pressure will reduce the transfer rate of the ink, and the printing plate and the blade will wear more. If the pressure is too small, the dirty plate may occur or the doctor blade line may appear.
2. Knife sharpness
The sharpness of the knife depends on whether the new knife, the angle of the blade when sharpening the knife, and the type of sandpaper (oilstone) used. The sharpness of the knife should be such that it effectively scrapes the ink without generating a knife. Too sharp scrapers tend to produce traces of the knife while wearing the plate.
3. The distance the doctor blade contacts the plate
The reduction of the distance between the blade and the printing plate is beneficial to increase the ink transfer rate, but it is easy to produce a dirty plate; otherwise, it can effectively solve the dirty plate and avoid some small line marks, but it will reduce the ink transfer rate.
4. Knife flatness
The flatness and warpage of the knife depends mainly on the method of installation. Of course, it may also be related to the sticking of foreign matter on the blade or the lining. When the flatness of the knife is poor, some water-like impressions appear on the edge of the printed surface, or some intermittent line marks appear from time to time. Some people think that the ink is rough and the ink flow is not good enough to produce the above phenomenon. In fact, the knife is not flat and this situation will occur.
5. Squeegee movement
The left and right movement of the squeegee knife plays an important role in reducing the scraper line, improving the utilization of the squeegee and reducing the wear on the plate. If the squeegee does not move properly, you should find a way to improve it.
When there is a line mark in printing, one is causing a plate injury, and the other is that the blade is not sharp. However, another reason is that foreign matter sticks behind the blade. The solution is to move the squeegee up and down to remove the adhesive. If it can't be smashed, it can only stop the squeegee.
Another problem is related to the scraper, and many people misunderstood it as caused by ink. This refers to dozens of irregular line marks that sometimes appear irregular. It looks like ink is piled up. It is different from the scraper line. It is not continuous, but sometimes it is not. This is actually a scraper. The pressure is too small or the scraper is not sharp enough.
Several indicators of the above scraper have different and similar aspects. When solving a specific problem, one of them can be used, and sometimes it needs to be comprehensively applied to completely solve the problem. For example, when some intermittent ink lines appear, it can increase the pressure solution or solve the problem by sharpening the knife; when there is a serious dirty version, it needs to be combined in several aspects; one must use a sharp blade, two To increase the pressure, the third is to increase the distance between the scraper and the contact surface.
When the scraper wear is serious and cannot be repaired with sandpaper or oilstone, it can be repaired by a special sharpener so that it can be reused several times, which greatly reduces the cost of the scraper.