Application knowledge of ink scraper in gravure pr

2022-08-18
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The use of ink scraper in gravure printing at this time, customers often don't know how to choose

the selection, installation and adjustment of ink scraper in gravure printing have an important impact on the quality of prints. Here are some views on the application of doctor blade in gravure printing and some problems involved

I. selection and installation of ink scraper in gravure printing

high speed gravure printing machines generally use imported steel scraper with high elasticity, and its thickness is 0.15~0.2mm. When installing the doctor blade, pay attention that both sides of the doctor blade should be 10 ~ 20mm longer than the printing plate to prevent the printing plate ink from splashing on the rubber roller. The steps and key points of gaining market favor are as follows:

1 The distance between the lining and the knife back is about 10m, but the profit is higher M. The distance between the lining and the blade is 5 ~ 7mm. However, the distance can also be appropriately increased (that is, installed as a soft blade) or reduced (installed as a hard blade) according to the specific situation

2. Put the new blade behind the lining, install it into the knife slot, and tighten the back screw. First tighten it from the middle of the blade, then gradually outward, and tighten it on both sides in turn. Here is a trick to avoid blade warping: when tightening the screw, it should be completed twice or three times, and it cannot be achieved in one step. While screwing the screw, hold a piece of rag to clamp the blade and lining and pull it to one side with force, so that the installed knife is flat. A flat blade can ensure a uniform amount of printing plate ink

3. Choose suitable sharpening tools and methods. When sharpening a knife with a stone, if the oilstone is rough, it is not suitable for sharpening a new knife. According to practical experience, it is more appropriate to grind the knife with No. 1 emery paper, which can grind both new blades and old blades with large defects. It is OK to grind a new knife with 0 steel sandpaper, but it is difficult to grind an old knife with a slightly larger notch. If you sometimes feel that grinding the blade with No. 1 emery paper is rough, you can use No. 0 emery paper to grind it slightly. There are generally two ways to sharpen the knife: one is to fold the sandpaper into a V shape, but pay attention to folding several layers of sandpaper to avoid cutting through the sandpaper and hurting your hands. This method is more efficient and easy to control the angle of the cutting edge, but it is not very safe; The other is to grind the knife by pulling both ends of the sandpaper with two hands, which is very safe, but the angle of the blade is not easy to control. Too blunt and too sharp blades have a negative impact on the printing quality

II. Reasonably adjust the ink scraper in gravure printing

the pressure, sharpness and contact position with the plate of the scraper all have an impact on the printing quality. According to the actual needs, reasonable adjustment of these factors can solve many problems in printing

1. Pressure

the factors that affect the pressure of the doctor blade are the size of the cylinder pressure, the difference between the hard and soft blades, the angle of the doctor blade and the printing plate, etc. the greater the inclination, the greater the pressure. Excessive pressure will reduce the transfer rate of ink and cause greater wear to the printing plate and blade; Too little pressure is prone to dirty version or scraper line

2. Sharpness of the knife

the sharpness of the knife depends on whether it is new, the blade angle when sharpening, the model of sandpaper (oilstone) used, etc. The suitable sharpness of the knife should be that it can effectively scrape the ink without producing knife threads. Too sharp scrapers are often prone to produce traces of knife threads and wear plates at the same time

3. The distance between the doctor blade and the printing plate

the reduction of the distance between the doctor blade 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 version and avoid some small line marks, but it will reduce the ink transfer rate

4. The flatness of the knife

the flatness and warpage of the knife mainly depend on the installation method. Of course, it may also be related to the foreign matters stuck in the knife rest groove or on the blade and lining

when the flatness of the knife is poor, there will be some bead like marks on the edge of the printing surface, or some intermittent line marks from time to time. Some people think that the above phenomenon occurs only when the ink is rough and the ink fluidity is not good. In fact, this situation also occurs when the knife is uneven

5. The movement of the doctor blade

the left and right movement of the doctor blade plays an important role in reducing the scraper line, improving the utilization rate of the doctor blade, and reducing the wear of the plate. If the doctor blade moves abnormally, find a way to improve it

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