With the continuous development of social development, people's requirements for external packaging are also increasing. The main advantage of gravure printing is that the image is rich in color and thick in color. The main advantage of gravure printing determines that the fine outer packaging generally requires gravure printing. However, there are many factors that affect the quality of gravure printing products, such as: the impact of the environment, the technical level of the operator, the quality of the ink, the quality of the equipment, and so on. The effect of the ink scraper on the quality of gravure printing is particularly important. The quality of the squeegee adjustment not only directly affects the quality of the printed product, but also has a great influence on the life of the squeegee.
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. The left and right squeegee of the squeegee is realized by the rotation of the eccentric shaft. There is a sudden change of the 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 infinitely small. , Generally choose 1/7 or 1/9, this can change the track of the squeegee on the plate roller, and it can bring the impurities on the blade to go down through the left and right squeezing to 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 rigidity of the squeegee mechanism is also a major factor affecting the print quality, especially high-speed gravure printing presses. 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 left and right height of the squeegee base plate will be achieved. Inconsistent, resulting in inconsistent blade height, resulting in inconsistent pressure around the squeegee, thus affecting the quality of printed products. 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 machining accuracy of the upper and lower clamps in the doctor blade also affects the quality of the print. If the flatness of the upper and lower clamps of the doctor blade is poor, then the upper and lower clamps will scrape and scrape When installed together, the flatness of the doctor blade will be affected and become a microscopic wave type. In order to eliminate this microscopic wavy form, the pressure of the squeegee is increased by scraping off the ink outside the plate roller net. As a result, the blade and the plate roller 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.
5. The adjustment of the squeegee angle is also very important. The angle is the size of the contact angle α between the squeegee and the platen roller (the angle between the tangent line at the contact point of the blade and the platen roller) (see Figure 3). 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.
6. The adjustment of the squeegee pressure is also one of the key elements of the quality of the printed product. The squeegee pressure refers to the pressure applied by the squeegee blade to the platen roller. There are two main functions of the squeegee pressure: the first is to scrape the ink outside the image area and not only the outside of the pit; the second is to resist the ink. The impact force prevents the ink from flowing out of the knife edge. Squeegee pressure is too small, easy to produce non-graphic area fog or knife line, when the printing speed increases, the plate roller speed increases, the roller line with the ink line speed increases, the impact of the ink on the squeegee The increase in force will make it easier to lift the squeegee and seriously affect the quality of the printed product. Squeegee pressure is too high, will reduce the transfer rate of the ink, the wear of the plate roller and the blade is very large. The size of the squeegee pressure is determined by its effect, ie: P=P1+P2
P is the pressure required by the doctor
P1 is the pressure required to clean the ink outside the pits in the non-graphic area
P2 is the pressure required to resist the impact of ink
The pressure P2 required to resist the impact force of the ink is related to the blade pressure angle and the linear velocity V of the ink. That is: P2âˆCOSαV2
Therefore, the larger the blade pressure angle, the smaller the P2, the smaller the pressure P required for the squeegee; the lower the printing speed, the smaller the linear velocity V of the ink, and the smaller the P2, the required pressure of the squeegee P. The smaller the value is, the smaller the value is; the smaller the blade pressure angle is, the larger the P2 is, the larger the pressure P required by the squeegee is. The higher the printing speed is, the larger the linear velocity V of the ink is. The larger P2 is, the larger the squeegee blade is. The greater the pressure P required.
In actual work, adjusting the squeegee according to the above method can ensure the quality of the corresponding print product. After a certain period of use, the printing press may cause the accuracy of the relevant important parts to decrease due to various reasons such as wear and tear, as well as the same print quality problems. This requires further analysis and judgment. In order to eliminate the impact of the squeegee on the print quality in a timely manner, the scrap rate is reduced, the finished product rate is increased, and the production efficiency is increased.
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. The left and right squeegee of the squeegee is realized by the rotation of the eccentric shaft. There is a sudden change of the 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 infinitely small. , Generally choose 1/7 or 1/9, this can change the track of the squeegee on the plate roller, and it can bring the impurities on the blade to go down through the left and right squeezing to 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 rigidity of the squeegee mechanism is also a major factor affecting the print quality, especially high-speed gravure printing presses. 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 left and right height of the squeegee base plate will be achieved. Inconsistent, resulting in inconsistent blade height, resulting in inconsistent pressure around the squeegee, thus affecting the quality of printed products. 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 machining accuracy of the upper and lower clamps in the doctor blade also affects the quality of the print. If the flatness of the upper and lower clamps of the doctor blade is poor, then the upper and lower clamps will scrape and scrape When installed together, the flatness of the doctor blade will be affected and become a microscopic wave type. In order to eliminate this microscopic wavy form, the pressure of the squeegee is increased by scraping off the ink outside the plate roller net. As a result, the blade and the plate roller 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.
5. The adjustment of the squeegee angle is also very important. The angle is the size of the contact angle α between the squeegee and the platen roller (the angle between the tangent line at the contact point of the blade and the platen roller) (see Figure 3). 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.
6. The adjustment of the squeegee pressure is also one of the key elements of the quality of the printed product. The squeegee pressure refers to the pressure applied by the squeegee blade to the platen roller. There are two main functions of the squeegee pressure: the first is to scrape the ink outside the image area and not only the outside of the pit; the second is to resist the ink. The impact force prevents the ink from flowing out of the knife edge. Squeegee pressure is too small, easy to produce non-graphic area fog or knife line, when the printing speed increases, the plate roller speed increases, the roller line with the ink line speed increases, the impact of the ink on the squeegee The increase in force will make it easier to lift the squeegee and seriously affect the quality of the printed product. Squeegee pressure is too high, will reduce the transfer rate of the ink, the wear of the plate roller and the blade is very large. The size of the squeegee pressure is determined by its effect, ie: P=P1+P2
P is the pressure required by the doctor
P1 is the pressure required to clean the ink outside the pits in the non-graphic area
P2 is the pressure required to resist the impact of ink
The pressure P2 required to resist the impact force of the ink is related to the blade pressure angle and the linear velocity V of the ink. That is: P2âˆCOSαV2
Therefore, the larger the blade pressure angle, the smaller the P2, the smaller the pressure P required for the squeegee; the lower the printing speed, the smaller the linear velocity V of the ink, and the smaller the P2, the required pressure of the squeegee P. The smaller the value is, the smaller the value is; the smaller the blade pressure angle is, the larger the P2 is, the larger the pressure P required by the squeegee is. The higher the printing speed is, the larger the linear velocity V of the ink is. The larger P2 is, the larger the squeegee blade is. The greater the pressure P required.
In actual work, adjusting the squeegee according to the above method can ensure the quality of the corresponding print product. After a certain period of use, the printing press may cause the accuracy of the relevant important parts to decrease due to various reasons such as wear and tear, as well as the same print quality problems. This requires further analysis and judgment. In order to eliminate the impact of the squeegee on the print quality in a timely manner, the scrap rate is reduced, the finished product rate is increased, and the production efficiency is increased.
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