People who are involved in flexographic printing know that the quantitative ink supply system is one of the important factors that affect the final print quality and print product performance. Many people compared the ceramic anilox roller, which is the main component of the quantitative ink supply system, to the “heart†of the flexographic printing press, and compared the Other important component of the squeegee that forms the quantitative ink supply system with the “valve†of the heart. The "valve" valve effectively controls the amount of ink entering the "heart." The role of the two in the ink supply system is clear, and the status and importance of the entire ink supply system in printing machines is self-evident.
Ink Supply System Development Overview 1. Two-Roll System Usually, the quantitative ink supply of a flexographic printing press is completed by two rollers, referred to as a two-roll system. After the anilox roll is inked from the ink plate, another rubber squeegee roller scrapes the ink, and then the anilox roller transfers the ink remaining in the mesh to the plate to complete the entire process of ink transfer. From this two-roll system, a quantitative procedural ink supply can be achieved. This structure is still widely used in middle and low flexo printing presses, coaters and carton printers. Such a structure is still very suitable for occasions where the printing and coating quality requirements are not high.
2. Forward squeegee system When the control of the amount of ink is more precise, this two-roll system will have problems. Particularly when the printer speed reaches or exceeds 100 m/min, the hydraulic pressure generated by the high-speed flow of the ink between the anilox roller and the doctor roller tends to increase the gap between the two rollers, eventually causing excessive ink transfer to the plate. And printing materials. Taking into account the above problems and the requirement of accurate ink supply, people first proposed a positive-squeegee-type quantitative ink supply system similar to a gravure printing system. In this system, the rubber inking roller transfers the ink ribbon in the ink tray to the anilox roller, and then the scraper removes the ink not deposited in the mesh from the surface of the anilox roller, and transfers the ink in the mesh hole to the printing plate. Above, the function of quantitative ink supply was realized.
The anilox roller can use metal anilox roller, but its life is short. The ink supply system combined with a doctor blade is preferably made of a ceramic anilox roll for use as a metering roll. Scrapers are often made of steel, with the backing against the metal pad lining the pressure plate, and after being fitted to the metal frame, the bracket provides the proper working angle and pressure of the blade. The so-called working angle is the angle between the blade and the tangent of the contact point. For a positive blade, this angle is usually between 55° and 60°. Like the two-roll system, when the printer speed is higher than 100m/min, the hydraulic pressure between the doctor blade and the anilox roller in this system will tend to separate the two, resulting in more ink transfer. To plate and printing materials. For more detailed printing, such results are obviously not allowed.
3. Reverse Scraper System A quantitative ink supply system using a reverse squeegee structure can solve this problem. The only difference in structure with the positive squeegee system is its squeegee position and its working angle. Normally, this angle is between 30° and 35°. Some manufacturers also design it as 40° up and down. With the reverse squeegee system, there is no hydraulic pressure lifting effect, so the printer can work at a higher level. Running speed.
4. Fully sealed double blade cavity ink fountain system The reverse blade structure solves problems that occur when the flexo press operates at high speed. However, whether it is a reverse squeegee, a forward squeegee structure or a two-roll system, both are open-type ink supply structures, and each ink source stores ink. After the ink on the ink roller belt passes through a certain process, some of it is used for printing, and the excess portion is returned to the ink tray. This type of structure allows the ink to be directly exposed to the atmosphere over a large area. For the solvent-based ink, solvents are generated to evaporate into the surrounding air, causing changes in ink characteristics and environmental problems. Bubbles may also occur for water-based inks. Ultimately affect the quality of printing.
Fully sealed double blade cavity ink fountain system consists of anilox roller (usually ceramic anilox roller), two scrapers, sealing strips, ink storage containers, ink pumps, inking hoses and other components. The characteristics of the system can be based on the following: In the quantitative ink supply system, a reverse scraper structure is used, so the printer can work at a high speed; the use of a solvent-based ink reduces the volatilization of the solvent inside the system, and alleviates the problem of environmental pollution; The foam problem that accompanies the use of water-based ink is terminated; the rubber-coated roller used in mining is excluded from the conventional structure; the system can be quickly docked with the cleaning system, and the ink-carrying elements inside the system can be completely cleaned within a short time. Washing reduces ink color change time. The use of pumps and cleaning agents for direct cleaning inside the ink supply seal system eliminates the need to remove rollers and other inked parts, which helps reduce downtime and give full play to the machine's productivity.
Design of the sealed double blade cavity ink fountain system In the closed system, the blade, seal, gasket, and pressure plate are all mounted on a cavity bracket and pushed mechanically (or pneumatically or hydraulically). Ceramic anilox roll, and apply a certain pressure, the pressure can be adjusted within a certain range, and then the ink tube and the return tube to the ink pump and ink storage system. Here is a description of the design issues that must be considered in the process of system composition:
1. Wet Corner, Wet Corner The wet corner of the anilox roll refers to the circumferential angle of the inked surface. For a totally enclosed cavity type structure, the distance between it and the cavity opening, ie the two doctor blades, is closely related to the diameter of the anilox roller. It is recommended that the ratio of the two doctor blade pitches to the anilox roller diameter be 1:3, so that the resulting wet angle is approximately 40[deg.], whereas the typical single doctor blade type structure has a wet corner of approximately 90[deg.]. This parameter of emptying angle is also very important, especially in the case of solvent-based inkless design, pay special attention to the size of the emptying angle in the design. After the anilox roll transfers no ink from the mesh to the printing plate, the ink in the corresponding mesh is emptied until it is re-stained with ink. The circumferential angle between the anilox rolls is called the emptying angle. After the ink is transferred out of the mesh, about 15% of the ink is usually left in the mesh. Due to the volatilization of the solvent, the remaining ink will have a certain degree of drying before being re-inked. Therefore, the emptying angle at design time must be small. A good design should maximize the wet corner and reduce the emptying angle when the system structure is limited.
2. Scraper steel and synthetic materials are two commonly used scraper materials. Specific subdivision, the commonly used steel is spring steel and stainless steel, stainless steel soft, short life, can be used under the conditions of use of water-based ink. According to the different processing conditions, the steel scraper can be further divided into a blue steel scraper and a white steel scraper. Steel squeegee is the main candidate for printing machine at present, because the steel is easy to process, the processing precision is high, and the wear resistance is excellent. The edge of the doctor blade can be ground into a beveled and flake shape. The total thickness of the blade is 0.15-0.2 mm, the thickness of the blade is 0.05-0.1 mm, and the blade width is 0.6-2.5 mm.
With the continuous improvement of the requirements for fine prints, the requirements for the performance and life of steel scrapers are also increasing. Therefore, foreign countries are still constantly improving this research and expect to improve the performance of various aspects of this product, such as the composition of steel components, carbon particle size, shape and location distribution. At the same time, measures are taken in the processing of the process to improve certain performance indicators, such as steel knives with special coatings, which have significantly improved wear resistance and uniformity.
Plastic scraper commonly used materials are polyester, high density polyethylene and laminate materials. This kind of blade is about 0.5mm thick. It is used as a seal cutter in a fully-encapsulated cavity fountain system, and plastic squeegees are also commonly used in conventional coating devices and carton printers.
3. Cavity ink fountain and bracket cavity ink fountain commonly used cast aluminum materials, light weight, high strength. When the cavity is equipped with a scraper and combined with an anilox roller, the sealing at both ends is an important question. The sealing surfaces at both ends can be selected on both end faces of the anilox roller, and can also be selected on the outer circle surface near both ends. The former, as long as the anilox roller is accurate in size and the sealing surface is handled properly, has good sealing performance after installation, but such a structure does not allow the ink fountain to vibrate around. The squeegee system with vibrating function helps avoid the damage of the ceramic anilox roller and the knife due to the tiny hard particles mixed in the ink. The latter structure can realize the vibration function. No mesh is made on the anilox roller vibration contact surface, and only the surface polishing treatment is performed.
Sealing conditions The material is usually rubber and foam plastic, its surface energy is less than the ink, not easy to ink, can reduce the possibility of wear of the sealing surface and the seal after the ink is dry.
Anilox Roller In the quantitative ink supply system using a doctor blade, the anilox roller is generally made of a laser-engraved ceramic anilox roller, and the metal anilox roller is not used because the service life of the metal anilox roller is used when used with a doctor blade. Greatly reduced. The use of laser-engraved ceramic anilox rolls has been an important advance in the quantitative ink supply system for many years.
The progress of laser engraving technology is an important basis for obtaining high-quality laser-engraved ceramic anilox rollers. A new generation of laser engraving technology enables the engraved ceramic anilox roller to have up to 2,500 lines per inch. The characteristic parameters of the mesh include openings, wall thickness, hole depth and steepness. The depth of the mesh is deeper, the bottom is flat, and the wall thickness is thin, so a very shallow hole depth can achieve a higher ink storage volume, ink release capability is enhanced, the ink density distribution uniformity is improved, and the mesh hole cleaning is easier. The ceramic anilox roller produced by the new laser engraving technology has relatively less dense carvings due to its production, so the ceramic layer is relatively dense and hard, and the integrity and service life of the edge wall of the anilox roller mesh are improved. advantageous. The emergence of ultra-fine laser-engraved ceramic anilox roller and the overall improvement of the performance of the ceramic anilox roller are the reliable guarantee for the performance improvement of the quantitative ink supply system in high-end flexographic printing presses and the realization of a fine flexographic printing technology.
The application of quantitative ink supply system Domestic flexo printing has made gratifying progress in recent years. From the perspective of the flexographic printing equipment introduced from abroad, the quantitative ink supply systems in medium-to-high-end narrow-width unit flexographic presses and high-precision wide-format satellite flexographic presses use a combination of doctor blades and ceramic anilox rollers. The use of reverse single scraper system, while Others use sealed double scraper cavity ink fountain system. In general, the former are more common in narrow-width units, while the satellite wide-format machines use more of the latter.
In the past two or three years, domestic printing manufacturers have adopted international advanced technologies and have successively developed narrow-width unit flexo presses, wide-satellite flexographic presses, and higher-precision carton printing slotting machines of various specifications with mid-range and above, among which Most ink supply systems use a squeegee blade and a ceramic anilox roller structure. There are also a small number of dual roller systems using rubber rollers and ceramic anilox rollers.
Due to the continuous improvement of product quality and environmental protection requirements, old-style flexo printers, coaters, and polishers are all faced with the task of upgrading or technological transformation. For the transformation of the ink supply system or the coating glazing system, most manufacturers prefer to use a combination of a doctor blade and a ceramic anilox roller, and many of them wish to directly use a sealed double blade ink fountain system.
At present, China has the conditions to provide comprehensive services for users of quantitative ink supply systems. In addition to supporting the production of ceramic anilox rollers and high-quality multi-spec squeegee blades for domestic and imported flexographic printing presses, Shanghai Laser Group Corporation also carried out preliminary development work on sealed double-squeegee cavity-type ink supply systems. The foundation for the transformation of old ink or coating or glazing systems was laid. (Author: Lu Shanghai Laser Group TIH)
Ink Supply System Development Overview 1. Two-Roll System Usually, the quantitative ink supply of a flexographic printing press is completed by two rollers, referred to as a two-roll system. After the anilox roll is inked from the ink plate, another rubber squeegee roller scrapes the ink, and then the anilox roller transfers the ink remaining in the mesh to the plate to complete the entire process of ink transfer. From this two-roll system, a quantitative procedural ink supply can be achieved. This structure is still widely used in middle and low flexo printing presses, coaters and carton printers. Such a structure is still very suitable for occasions where the printing and coating quality requirements are not high.
2. Forward squeegee system When the control of the amount of ink is more precise, this two-roll system will have problems. Particularly when the printer speed reaches or exceeds 100 m/min, the hydraulic pressure generated by the high-speed flow of the ink between the anilox roller and the doctor roller tends to increase the gap between the two rollers, eventually causing excessive ink transfer to the plate. And printing materials. Taking into account the above problems and the requirement of accurate ink supply, people first proposed a positive-squeegee-type quantitative ink supply system similar to a gravure printing system. In this system, the rubber inking roller transfers the ink ribbon in the ink tray to the anilox roller, and then the scraper removes the ink not deposited in the mesh from the surface of the anilox roller, and transfers the ink in the mesh hole to the printing plate. Above, the function of quantitative ink supply was realized.
The anilox roller can use metal anilox roller, but its life is short. The ink supply system combined with a doctor blade is preferably made of a ceramic anilox roll for use as a metering roll. Scrapers are often made of steel, with the backing against the metal pad lining the pressure plate, and after being fitted to the metal frame, the bracket provides the proper working angle and pressure of the blade. The so-called working angle is the angle between the blade and the tangent of the contact point. For a positive blade, this angle is usually between 55° and 60°. Like the two-roll system, when the printer speed is higher than 100m/min, the hydraulic pressure between the doctor blade and the anilox roller in this system will tend to separate the two, resulting in more ink transfer. To plate and printing materials. For more detailed printing, such results are obviously not allowed.
3. Reverse Scraper System A quantitative ink supply system using a reverse squeegee structure can solve this problem. The only difference in structure with the positive squeegee system is its squeegee position and its working angle. Normally, this angle is between 30° and 35°. Some manufacturers also design it as 40° up and down. With the reverse squeegee system, there is no hydraulic pressure lifting effect, so the printer can work at a higher level. Running speed.
4. Fully sealed double blade cavity ink fountain system The reverse blade structure solves problems that occur when the flexo press operates at high speed. However, whether it is a reverse squeegee, a forward squeegee structure or a two-roll system, both are open-type ink supply structures, and each ink source stores ink. After the ink on the ink roller belt passes through a certain process, some of it is used for printing, and the excess portion is returned to the ink tray. This type of structure allows the ink to be directly exposed to the atmosphere over a large area. For the solvent-based ink, solvents are generated to evaporate into the surrounding air, causing changes in ink characteristics and environmental problems. Bubbles may also occur for water-based inks. Ultimately affect the quality of printing.
Fully sealed double blade cavity ink fountain system consists of anilox roller (usually ceramic anilox roller), two scrapers, sealing strips, ink storage containers, ink pumps, inking hoses and other components. The characteristics of the system can be based on the following: In the quantitative ink supply system, a reverse scraper structure is used, so the printer can work at a high speed; the use of a solvent-based ink reduces the volatilization of the solvent inside the system, and alleviates the problem of environmental pollution; The foam problem that accompanies the use of water-based ink is terminated; the rubber-coated roller used in mining is excluded from the conventional structure; the system can be quickly docked with the cleaning system, and the ink-carrying elements inside the system can be completely cleaned within a short time. Washing reduces ink color change time. The use of pumps and cleaning agents for direct cleaning inside the ink supply seal system eliminates the need to remove rollers and other inked parts, which helps reduce downtime and give full play to the machine's productivity.
Design of the sealed double blade cavity ink fountain system In the closed system, the blade, seal, gasket, and pressure plate are all mounted on a cavity bracket and pushed mechanically (or pneumatically or hydraulically). Ceramic anilox roll, and apply a certain pressure, the pressure can be adjusted within a certain range, and then the ink tube and the return tube to the ink pump and ink storage system. Here is a description of the design issues that must be considered in the process of system composition:
1. Wet Corner, Wet Corner The wet corner of the anilox roll refers to the circumferential angle of the inked surface. For a totally enclosed cavity type structure, the distance between it and the cavity opening, ie the two doctor blades, is closely related to the diameter of the anilox roller. It is recommended that the ratio of the two doctor blade pitches to the anilox roller diameter be 1:3, so that the resulting wet angle is approximately 40[deg.], whereas the typical single doctor blade type structure has a wet corner of approximately 90[deg.]. This parameter of emptying angle is also very important, especially in the case of solvent-based inkless design, pay special attention to the size of the emptying angle in the design. After the anilox roll transfers no ink from the mesh to the printing plate, the ink in the corresponding mesh is emptied until it is re-stained with ink. The circumferential angle between the anilox rolls is called the emptying angle. After the ink is transferred out of the mesh, about 15% of the ink is usually left in the mesh. Due to the volatilization of the solvent, the remaining ink will have a certain degree of drying before being re-inked. Therefore, the emptying angle at design time must be small. A good design should maximize the wet corner and reduce the emptying angle when the system structure is limited.
2. Scraper steel and synthetic materials are two commonly used scraper materials. Specific subdivision, the commonly used steel is spring steel and stainless steel, stainless steel soft, short life, can be used under the conditions of use of water-based ink. According to the different processing conditions, the steel scraper can be further divided into a blue steel scraper and a white steel scraper. Steel squeegee is the main candidate for printing machine at present, because the steel is easy to process, the processing precision is high, and the wear resistance is excellent. The edge of the doctor blade can be ground into a beveled and flake shape. The total thickness of the blade is 0.15-0.2 mm, the thickness of the blade is 0.05-0.1 mm, and the blade width is 0.6-2.5 mm.
With the continuous improvement of the requirements for fine prints, the requirements for the performance and life of steel scrapers are also increasing. Therefore, foreign countries are still constantly improving this research and expect to improve the performance of various aspects of this product, such as the composition of steel components, carbon particle size, shape and location distribution. At the same time, measures are taken in the processing of the process to improve certain performance indicators, such as steel knives with special coatings, which have significantly improved wear resistance and uniformity.
Plastic scraper commonly used materials are polyester, high density polyethylene and laminate materials. This kind of blade is about 0.5mm thick. It is used as a seal cutter in a fully-encapsulated cavity fountain system, and plastic squeegees are also commonly used in conventional coating devices and carton printers.
3. Cavity ink fountain and bracket cavity ink fountain commonly used cast aluminum materials, light weight, high strength. When the cavity is equipped with a scraper and combined with an anilox roller, the sealing at both ends is an important question. The sealing surfaces at both ends can be selected on both end faces of the anilox roller, and can also be selected on the outer circle surface near both ends. The former, as long as the anilox roller is accurate in size and the sealing surface is handled properly, has good sealing performance after installation, but such a structure does not allow the ink fountain to vibrate around. The squeegee system with vibrating function helps avoid the damage of the ceramic anilox roller and the knife due to the tiny hard particles mixed in the ink. The latter structure can realize the vibration function. No mesh is made on the anilox roller vibration contact surface, and only the surface polishing treatment is performed.
Sealing conditions The material is usually rubber and foam plastic, its surface energy is less than the ink, not easy to ink, can reduce the possibility of wear of the sealing surface and the seal after the ink is dry.
Anilox Roller In the quantitative ink supply system using a doctor blade, the anilox roller is generally made of a laser-engraved ceramic anilox roller, and the metal anilox roller is not used because the service life of the metal anilox roller is used when used with a doctor blade. Greatly reduced. The use of laser-engraved ceramic anilox rolls has been an important advance in the quantitative ink supply system for many years.
The progress of laser engraving technology is an important basis for obtaining high-quality laser-engraved ceramic anilox rollers. A new generation of laser engraving technology enables the engraved ceramic anilox roller to have up to 2,500 lines per inch. The characteristic parameters of the mesh include openings, wall thickness, hole depth and steepness. The depth of the mesh is deeper, the bottom is flat, and the wall thickness is thin, so a very shallow hole depth can achieve a higher ink storage volume, ink release capability is enhanced, the ink density distribution uniformity is improved, and the mesh hole cleaning is easier. The ceramic anilox roller produced by the new laser engraving technology has relatively less dense carvings due to its production, so the ceramic layer is relatively dense and hard, and the integrity and service life of the edge wall of the anilox roller mesh are improved. advantageous. The emergence of ultra-fine laser-engraved ceramic anilox roller and the overall improvement of the performance of the ceramic anilox roller are the reliable guarantee for the performance improvement of the quantitative ink supply system in high-end flexographic printing presses and the realization of a fine flexographic printing technology.
The application of quantitative ink supply system Domestic flexo printing has made gratifying progress in recent years. From the perspective of the flexographic printing equipment introduced from abroad, the quantitative ink supply systems in medium-to-high-end narrow-width unit flexographic presses and high-precision wide-format satellite flexographic presses use a combination of doctor blades and ceramic anilox rollers. The use of reverse single scraper system, while Others use sealed double scraper cavity ink fountain system. In general, the former are more common in narrow-width units, while the satellite wide-format machines use more of the latter.
In the past two or three years, domestic printing manufacturers have adopted international advanced technologies and have successively developed narrow-width unit flexo presses, wide-satellite flexographic presses, and higher-precision carton printing slotting machines of various specifications with mid-range and above, among which Most ink supply systems use a squeegee blade and a ceramic anilox roller structure. There are also a small number of dual roller systems using rubber rollers and ceramic anilox rollers.
Due to the continuous improvement of product quality and environmental protection requirements, old-style flexo printers, coaters, and polishers are all faced with the task of upgrading or technological transformation. For the transformation of the ink supply system or the coating glazing system, most manufacturers prefer to use a combination of a doctor blade and a ceramic anilox roller, and many of them wish to directly use a sealed double blade ink fountain system.
At present, China has the conditions to provide comprehensive services for users of quantitative ink supply systems. In addition to supporting the production of ceramic anilox rollers and high-quality multi-spec squeegee blades for domestic and imported flexographic printing presses, Shanghai Laser Group Corporation also carried out preliminary development work on sealed double-squeegee cavity-type ink supply systems. The foundation for the transformation of old ink or coating or glazing systems was laid. (Author: Lu Shanghai Laser Group TIH)
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