The use of squeegee tips

In order to facilitate the adjustment of the squeegee and ensure the quality of the printed product, the ink on the plate roller can be scraped cleanly without the occurrence of knife wire or fog defects. Therefore, the squeegee mechanism is divided into several functional devices. The functional components mainly include a driving device for squeezing the blade left and right, a squeegee blade separating and pressing device, a squeegee blade lifting device, a squeegee blade angle adjusting device and a blade squeegee device. Some of the left and right squeegee blades are driven by a separate motor, and some are driven by the main drive and then decelerated by the worm gear. The clutch pressure of the squeegee is achieved through the air-to-air shutoff of the squeegee. Its function is mainly to make the squeegee contact or Off-print roller; squeegee blade lifting device is realized by rack and pinion, which can realize pressure adjustment; squeegee blade angle adjustment is realized by worm gear and worm, suitable angle is crucial; scraper plate clamp device consists of upper clamp plate , Lower splint, scraper pad and scraper blade make it easy to adjust the amount of blade extension.

The function parts of each part of the squeegee mechanism affect the quality of the printed product from different aspects. Therefore, the adjustment of the squeegee is very important. It has been found in long-term production practice that as long as the functional devices of the squeegee mechanism are properly adjusted before printing, the defects that affect the quality of the printed product can be avoided. The following are some lessons from squeegee adjustment:

1. Left and right squeegee squeegee is realized by eccentric shaft rotation. There is a sudden change in speed from the left limit to the right limit. Therefore, the ratio of the number of reciprocating movements per minute from the squeegee to the rpm of the platen roller is 1. Infinite decimal, generally choose 17 or 19, this can change the track of the squeegee on the plate roller, and can remove the impurities on the blade by swaying left and right, reduce the knife line, and make the squeegee effect better. Rotate the eccentric shaft to the left limit and adjust the thread of the joint bearing so that the compression spring inside the left bracket receives the maximum amount of compression.

2. The overall stiffness of the squeegee mechanism is also a major factor affecting the print quality, especially the high speed gravure printing press. When the platen roller rotates, the platen roller brings the ink under the doctor blade, the ink has a force effect on the doctor blade, so that the doctor blade from the tendency of turning outwards, the cylinder overcomes this tendency, and there is a pressure on the platen roller, forcing the platen roller The ink outside the pit is scraped off. If the rigidity of the scraper is too bad, in order to scrape the ink outside the pit, the air pressure of the cylinder will inevitably increase, thereby increasing the pressure of the blade against the plate roller. Thus, the blade and the plate roller Easy to wear, resulting in a relatively large waste. Of course, the best working condition is to scrape the ink outside the roller roll with a minimal squeegee pressure, which saves scraping and the roll is less prone to wear. Squeegee pressure adjustment is generally 0.2 ~ 0.3Mpa.

3. The installation accuracy of the squeegee mechanism is also a major factor affecting the printing quality. When the squeegee mechanism is installed, the level of the squeegee base plate must be ensured. If the horizontal accuracy of the squeegee base plate is too poor, the squeegee base plate will be made. The left and right heights are inconsistent, resulting in inconsistent blade heights. This results in inconsistent pressures on the squeegee blade and thus affects the quality of the printed product. In the printing process, if it is found that there are different shades of left and right, it is necessary to find out if the horizontal accuracy of the squeegee base plate meets the requirements.

4. The precision of the upper and lower splints in the doctor blade also affects the quality of the print. If the flatness of the upper and lower splices of the doctor blade is poor, then the upper and lower splints will scrape and scrape. When the pad is installed together, the flatness of the blade will be affected, becoming a microscopic wave type. In order to eliminate this microscopic wavy shape, the ink outside the plate roller net is scraped clean and the blade is enlarged. Pressure, which causes the blade and plate roller to wear. Squeegee blade installation and angle adjustment of the squeegee blade are also important factors affecting the quality of printed products. When squeegee blades are installed, the squeegee blade and blade plate are installed between the squeegee and the lower plate, and the length of the installation is adjusted. , Screw the upper and lower clamps tightly, so that the scraper plate and the scraper blade are clamped, the scraper installation is very particular, the scraper is too prominent, the scraper is easily deformed and wavy, and when printing, some places can scrape Clean, and some areas do not clean scratches, which affect the quality of printed products; blade out of too short, but also lack of flexibility, it must increase the pressure of the blade to scrape the ink outside the net pit, so easy to wear roller. Scraper pad is generally extended from the splint 20 ~ 30mm, scraper blade out of the blade pad 5 ~ 7mm. As shown in Figure 2 is a blade scraper blade device. The thickness of the squeegee pad is generally 0.3-0.5 mm, and the purpose of adding the blade is to enhance the rigidity of the blade. Generally, a high-quality steel sheet having a thickness of 0.1-0.15 mm is used for the scraping blade.

6. The adjustment of the squeegee angle is also very important, and the angle refers to the size of the contact angle α between the squeegee and the plate roller (the angle between the tangent line at the contact point of the blade and the platen roller). The larger the contact angle α, the better the squeegee effect, but the blade is easy to wear, the contact angle α is too small, the contact area of ​​the squeegee and the plate roller is increased, and the squeegee effect is poor, and it is easy to generate fog and wear. In general, the contact angle α is preferably 45°-65°, and the angle is determined according to the materials to be printed, the ink used, and the printing speed.

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