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The proper use of the gravure squeegee largely determines the quality of the printed matter. The following are some of the correct ways to use the gravure squeegee.
The selection and installation of the squeegee, the high-speed gravure printing machine, generally adopts the imported steel squeegee with high elasticity, and its thickness is 0.15~. When installing the squeegee, pay attention that the two sides of the squeegee should be 10 longer than the printing plate to prevent the ink of the printing plate from splashing on the rubber roller. The steps and key points are as follows:
1. The distance between the lining and the back of the blade is approx. The distance between the lining and the blade is 5~. However, according to the specific situation, the distance can also be appropriately increased (that is, a soft blade is installed), or the distance can be reduced (a hard blade is installed).
2. Put the new blade behind the lining, put it into the groove and tighten the screw on the back of the blade. It should be tightened from the middle of the blade first, and then gradually outward, and both sides should be tightened in turn. Here is a trick to avoid blade warping: when tightening the screw, it should be done two or three times, not in one step. While turning the screw, hold a rag to clamp the blade and the lining and pull it to one side, so that the assembled knife is flat. A flat blade can ensure that the ink volume of the printing plate is uniform.
3. Choose suitable sharpening tools and sharpening methods.
When sharpening knives with unrefined stones, if the whetstone is rough, it is not suitable for sharpening new knives. According to practical experience, it is more appropriate to use No. 1 emery paper to sharpen knives, which can not only sharpen new blades, but also sharpen old blades with large defects. If you use 0-gold steel sandpaper to sharpen a new knife, it is fine, but if it is used to wear an old blade with a slightly larger notch, it is difficult to sharpen it well. If you sometimes feel that grinding the blade with No. 1 emery paper is still rough, you can use No. 0 emery paper for a little finer grinding. There are generally two ways to sharpen the knife: one is to fold the sandpaper into a V shape, but you should pay attention to folding several layers of sandpaper to prevent the blade from cutting through the sandpaper and hurting your hands. This method is more efficient, and it is easier to control the angle of the cutting edge, but it is not safe; the other is to use two hands to pull the ends of the sandpaper to sharpen the knife, which is very safe, but the angle of the cutting edge is not very good control. Blades that are too dull and too sharp have a negative impact on print quality.
Reasonable adjustment of the squeegee, the pressure of the squeegee, the sharpness, the contact position with the plate, etc. all have an impact on the printing quality. According to actual needs, reasonable adjustment of these factors can solve many printing problems.
1. Stress
The factors that affect the pressure of the squeegee are the size of the cylinder pressure, the difference between hard and soft blades, the angle of the squeegee and the printing plate crossing, etc. The greater the slope, the greater the pressure. Excessive pressure will reduce the transfer rate of the ink, and will cause greater wear on the printing plate and blade; if the pressure is too small, dirty plates or scraper lines will occur easily.
2. The sharpness of the knife
The sharpness of the knife depends on whether the knife is new, the angle of the blade when sharpening the knife, the type of sandpaper (whitstone) used, etc. The appropriate sharpness of the knife should be able to effectively scrape the ink without producing filaments. Squeegees that are too sharp tend to produce filament marks and wear out the printing plate at the same time.
3. The distance between the squeegee and the printing plate
The reduction of the distance between the scraper and the printing plate is conducive to improving the ink transfer rate, but it is easy to produce dirty plates; on the contrary, it can effectively solve the dirty plates and avoid some small line marks, but it will reduce the ink transfer rate.
4. The flatness of the knife
The leveling and warping of the knife mainly depends on the installation method, of course, it may also be related to the foreign matter stuck in the groove of the knife holder or on the blade and lining.
