Adjustment method of ink scraper of the hottest gr

Adjustment method of gravure machine ink scraper

with the continuous progress of social development, people have higher and higher requirements for external packaging. The main advantage of gravure printing is that the image is rich in color and tone. The main advantage of gravure printing determines that exquisite outer packaging generally requires gravure printing. However, there are many factors that affect the quality of gravure printing, such as the impact of the environment, the technical level of operators, the quality of ink, the quality of equipment and so on. The influence of ink scraper on the quality of gravure printing is particularly important. The adjustment of ink scraper not only directly affects the quality of printing, but also has a great impact on the service life of ink scraper

in order to facilitate the adjustment of the doctor blade and ensure the quality of the certified products of baoxinlun composite material, which will become the largest lithium battery aluminum-plastic film production factory in China, so that the ink on the plate roller can be scraped clean without knife wire or plate fog defects, the doctor blade mechanism is divided into several functional devices. Its functional components mainly include the driving device of the doctor blade moving left and right, the doctor blade clutch pressure device, the doctor blade lifting device, the doctor blade angle adjustment device and the doctor blade clamping device. The doctor blade moves left and right, some are driven by a separate motor, some are driven by the main drive through the worm gear deceleration; The clutch pressure of the doctor blade is realized by the air cylinder through the manual reversing valve, and its function is to make the doctor blade contact or separate from the plate roller; The lifting device of the doctor blade is realized by the gear rack, which can adjust the pressure; The angle adjustment of the doctor blade is realized by the worm gear, and the appropriate angle is very important; The scraper clamping device is composed of an upper clamping plate, a lower clamping plate, a scraper backing plate and a scraper blade, which can easily adjust the extension of its scraper

1 doctor blade clamping device 2 doctor blade lifting device 3 doctor blade clutch pressure device 4 doctor blade angle adjustment device 5 doctor blade driving device

Figure 1 doctor blade mechanism of gravure printing machine

functional components of each part of the doctor blade mechanism affect the quality of prints from different aspects. Therefore, the adjustment of the doctor blade is very important. In the long-term production practice, it is found that as long as the functional devices of the doctor blade mechanism are properly adjusted before printing, the defects that affect the print quality can be avoided. The following is some experience of the adjustment of the doctor blade:

1. The left-right movement of the doctor blade is realized by the rotation of the eccentric shaft. There is a sudden change in speed from the left limit to the right limit, so the ratio of the number of reciprocating movements of the doctor blade per minute to the speed of the master roll per minute is an infinite decimal. Generally, 1/7 or 1/9 is selected, which can change the trajectory of the doctor blade on the master roll, and the impurities on the doctor blade can be carried down through the left-right movement, Reduce the knife line to make the ink scraping effect better. Rotate the eccentric shaft to the left limit, adjust the thread of the joint bearing, so that the compression spring inside the left support receives the maximum compression

2. The overall rigidity of the doctor blade mechanism is also a major factor affecting the printing quality, especially the high-speed gravure printing machine. When the plate roller rotates, the plate roller brings the ink under the scraper. The ink has a force effect on the scraper, which makes the scraper turn outward. The cylinder overcomes this trend, and there is a pressure on the plate roller, forcing the ink outside the plate roller pit to scrape off. If the rigidity of the scraper is too poor, in order to scrape the ink outside the pit, the air pressure of the cylinder must be increased, thereby increasing the pressure of the scraper on the plate roller. In this way, the scraper blade and the plate roller are easy to wear, Cause relatively large waste. Of course, the best working condition is to use the minimum scraper pressure to scrape the ink outside the version roller pit, so as to save the scraper blade, and the version roller is not easy to wear. The adjustment of scraper pressure is generally 0.2 ~ 0.3MPa

3. The installation accuracy of the doctor blade mechanism is also a major factor affecting the printing quality. When installing the doctor blade mechanism, it is necessary to ensure the level of the doctor blade bottom plate. If the horizontal accuracy of the doctor blade bottom plate is too poor, the left and right height of the doctor blade bottom plate will be inconsistent, resulting in the inconsistency of the left and right height of the scraper planetary gear reducer, cycloidal needle reducer, worm reducer, planetary friction mechanical stepless speed reducer, etc, This will cause the pressure on the left and right of the doctor blade to be inconsistent, thus affecting the quality of the print. In the printing process, if you find that the left and right coloring depths are different, you need to find out whether the horizontal accuracy of the doctor blade base plate meets the requirements

4. The processing accuracy of the upper and lower splints in the doctor blade splint also affects the print quality. If the flatness of the upper and lower splints of the doctor blade is very poor, then when the upper and lower splints install the doctor blade and the doctor pad together, the flatness of the doctor blade will be affected and become a micro wave shape. In order to eliminate this micro wave shape, scrape the ink outside the plate roll pit, It will increase the pressure of the scraper, resulting in the wear of the scraper blade and the plate roller. The installation of doctor blade and the adjustment of doctor blade angle are also important factors affecting the quality of printing. When installing the doctor blade, install the doctor blade and the doctor pad between the upper and lower clamping plates of the doctor blade. After adjusting the installation length, tighten the upper and lower clamping plates with screws, so as to reduce the cumbersome clamping of the installation of the doctor pad and the doctor blade. The installation of the doctor blade is very particular. The installation of the doctor blade is too prominent, and the doctor blade is easy to deform and appear wavy, When printing, some places can be scraped clean, and some places can't be scraped clean, which affects the quality of prints; The scraper extends too short and lacks elasticity, so the pressure of the scraper must be increased to scrape the ink out of the pit, which is easy to wear the version roller. Generally, the scraper base plate extends 20 ~ 30mm out of the splint, and the scraper blade extends 5 ~ 7mm out of the scraper base plate As shown in Figure 2, the doctor blade clamping device. Among them, the thickness of the doctor blade pad that allows this industry to quickly slide into the trough is generally 0 5mm. The purpose of adding scraper backing plate is to strengthen the rigidity of the scraper. The thickness of the scraper blade is generally 0 15mm high-quality steel sheet

1 upper splint 2 lower splint 3 doctor blade pad 4 doctor blade

Figure 2 doctor blade splint device

6. The adjustment of doctor blade angle is also very important, which refers to the contact angle between the doctor blade and the plate roll α (the included angle between the blade and the tangent at the contact point of the master roll) (see Figure 3). contact angle α The larger the size, the better the ink scraping effect, but the blade is easy to wear, and the contact angle α Too small, so that the contact area between the doctor blade and the plate roller is increased, the scraping effect is poor, and it is easy to produce version fog and wear. In general, contact angle α 45 ° -65 ° is appropriate, and the angle is determined according to the material to be printed, the ink used and the printing speed

Figure 3 contact angle of doctor blade

7. The adjustment of doctor blade pressure is also one of the key elements for print quality. The pressure of the doctor blade refers to the pressure exerted by the doctor blade on the cylinder of the plate roller. The main functions of the pressure of the doctor blade are two: first, scrape the ink outside the pit in the non graphic area; The second is to resist the impact of ink and prevent ink from flowing out of the knife edge. The pressure of the scraper is too small, which is easy to cause version fog or knife line in the non graphic area. When the printing speed increases, the rotation speed of the version roller increases, the ink line speed brought by the version roller increases, and the impact of the ink on the scraper increases. In this way, it is easy to lift the scraper, which seriously affects the quality of the print. Too much pressure on the scraper will reduce the ink transfer rate and cause great wear on the plate roller and scraper blade. The pressure of the doctor blade is determined by its function, that is:

p=p1+p2

P is the pressure required by the doctor blade

P1 is the pressure required to scrape the ink outside the pit in the non graphic area

P2 is the pressure required to resist the impact of the ink

and the pressure P2 required to resist the impact of the ink is related to the pressure angle of the doctor blade and the linear speed V of the ink. Namely: P2 ∝ cos α V2

therefore, the larger the pressure angle of the scraper, the smaller P2, and the smaller the pressure P required by the scraper; The lower the printing speed, the smaller the linear speed V of the ink, the smaller P2, and the smaller the pressure P required by the doctor blade; On the contrary, the smaller the pressure angle of the doctor blade, the larger P2, and the greater the pressure P required by the doctor blade; The higher the printing speed, the greater the linear speed V of the ink, and the greater the P2, the greater the pressure P required by the doctor blade

in practical work, adjusting the doctor blade according to the above method can ensure the corresponding print quality. After the printing machine has been used for a period of time, due to wear and other reasons, the accuracy of relevant important parts may be reduced, and the same printing quality problems will also occur. This requires further analysis and judgment. So as to eliminate the impact of the doctor blade on the printing quality in time, reduce the scrap rate, improve the yield and improve the production efficiency. (end)