First, the characteristics of metal printing products Metal printing is a metal plate, metal forming products and metal foil and other hard materials for the substrate printing methods, its printing materials are mainly tinplate (tinplate), Wuxi thin steel plate (TFS) , zinc iron plate, black steel plate, aluminum plate, aluminum stamping container, and aluminum, tin plate composite materials.
Metal printing products have the following characteristics:
(1) Bright colors, rich layers, and good visual effects. The surface of the tinplate is a tin-plated layer with a glittering color effect. After the background color printing, the printed graphic is more vivid. For tin-free steel or other metal materials, special flash effects can be reproduced after printing by surface treatment and painting.
(2) Metal printing materials have good mechanical properties and processing and forming properties.
(3) Good performance of metal materials and good abrasion resistance and durability of printing inks not only create conditions for unique design and fine printing, but also improve the durability and maintainability of products, and can be better. It embodies the unity of use value and artistry of goods.
Second, the single sheet metal printing metal printing printing methods vary depending on the form of the substrate. There are four types of printing methods: lithographic offset printing, horizontal offset printing, gravure offset printing and letterpress offset printing. Single sheet metal printing mainly uses lithographic offset printing and letterpress dry offset printing. The tinplate and aluminum materials used for metal packaging containers are hard and inelastic because of their texture. Therefore, the flat-plate cans are mostly printed by lithographic offset printing. The molding cans mostly use the dry offset offset printing process, that is, the elasticity of the ink in the printing plate graphic part passes through a rubber roller. Clearly transfer to the surface of the metal can.
1. Painted and coated single tinplate can be processed into three food cans, beverage cans and spray can containers. According to the characteristics of the substrate and the purpose of use, it should have a suitable corrosion resistance and printing, processing performance, for this purpose, the bottom coating should be carried out before printing. The printing-related painting processes mainly include pre-press coating, surface white coating, and post-print coating.
Pre-press coating: coating with primer coating. The coated surface should be degreased prior to coating to remove oil from the surface. Prepress is coated with two types of inner coating and outer coating. The inner coating is applied on the inner side of the metal skin, that is, the molded product, and a layer of protective light oil is applied to protect the iron skin from corrosion of the contents, and also protect the contents. Since the inner coating is in direct contact with the food, the coating must be non-toxic and odorless. After the inner coating, it should be dried in a desiccator. The outer coating is the coating of the printing surface, and its role is to improve the adhesion of the metal surface and the ink layer. Therefore, it is required that the coating has a strong binding force to the metal surface and also has a good affinity for the ink layer, which requires the coating itself to have good fluidity, water resistance and color rendering properties.
White coating: The use of white paint or colorless transparent coating on the metal surface. It is often used as the background color for printed full-text graphics. The white paint shall have good adhesion and whiteness, and shall not yellow or fade under high-temperature baking conditions, and shall not peel off or peel during the canning process.
Post-printing: A layer of glazing coating is applied on the surface of all graphic printing, the purpose of which is to increase the gloss of the printing surface, protect the printing surface, and improve the light resistance and chemical resistance of the metal surface.
Wrinkle oil coating process: In order to enhance the decorative effect, after printing, it is not necessary to apply varnish, but to apply wrinkle oil, and wrinkle after special technology baking, showing a crystal-like scale-like, with three-dimensional Visual effects.
2. At present, almost all foreign countries use diazo PS plates to make lithographic plates. If the letterpress offset printing method is adopted, photosensitive resin relief printing can be used for printing. If lithographic offset printing method is adopted, the plate-making process should not only satisfy the general PS plate-making process requirements, but also use chain-shaped dots to facilitate the reproducibility of metal printing.
3. Metal printing inks are not able to penetrate the surface of the metal printing materials and are prone to dot gain. Compared with paper printing inks, metal printing lithographic offset printing should use high viscosity inks. The metal surface is a non-absorbent surface. Too much of the wetting water on the plate surface tends to cause emulsification of the ink. Therefore, the water and ink balance on the plate surface should be achieved by controlling the thickness of the water film and the amount of ink on the plate surface.
In metal printing, in order to improve the adaptability of post-press processing and processing, and to make the printed surface have a certain degree of gloss, the coating should be applied before the printing ink is not completely dried to form a uniform and smooth coating film, to avoid Bleeding. At the same time, the metal printing ink should have a certain hardness and toughness, can not change its properties when repeated heating, the base color coating and glazing paint should have good adhesion.
The UV type lithographic offset printing ink used for metal printing uses UV irradiation for instantaneous drying, which not only accelerates the drying of the ink, but also contributes to environmental protection.
4. Plate printing machine The printing device of the metal plate lithographic printing press consists of a plate cylinder (P), a blanket cylinder (B), an impression cylinder (I), an inking device, and a wetting device. In the lithographic offset printing of metal plates, hard blankets and hard gaskets should be used. Otherwise, defects such as coarse dots and poor reproducibility of dots will occur in the field of printed products. Therefore, the printing components of the metal plate printer should have sufficient rigidity and accuracy, and the size of the lining of the roller must be strictly controlled.
A UV drying device is disposed between the printing cylinders of the offset lithographic printing machine of the metal plate, and a UV type ink is used to realize high-speed and multi-color printing. Since the single base and cleaning agent in the UV ink will have a swell effect on the rubber roller and the blanket, a rubber stick and a rubber blanket dedicated to the UV ink should be used for this purpose. If a diazo-type PS plate is used, it should be prevented from being eroded by the detergent of the ink, and it is preferable to use a photo-polymerized PS plate, an intaglio plate, or a multi-layered metal plate.
5. Drying device:
(1) Sheet drying: After the metal plate is printed or painted, it should be dried by heating. Resin type printing inks are often used for thermal polymerization or oxidative polymerization drying; drying conditions mainly include heating temperature and drying time.
(2) UV irradiation device: The number of UV light source lamps is determined based on the printing speed.
Third, metal cans printing coating and printing are part of the metal can automatic production line. The common metal cans are mainly tin cans or aluminum cans. After molding, they must be cleaned and surface treated before painting and printing. The printing speed of the metal can printing machine is higher, and the use of letterpress dry offset printing method is adopted, that is, the printing method of photosensitive resin relief printing or metal relief printing is adopted through a rubber roller transfer printing. For multi-color printing, the printing speed of the metal cans is high, and sufficient printing pressure should be ensured, and low viscosity inks and linking materials with good drying performance should be selected. After the metal cans are printed and polished, they are sent to a dryer for heating and drying.
The printing part of the six-color two-piece can printing production line produced by Rutherforu of the United States consists of an ink-coating system and a mandrel turntable. The six color groups are arranged in sequence around the blanket turntable, and there are eight fan-shaped blankets on the blanket turntable for transferring various color patterns. The counterclockwise rotation of the blanket turntable transfers the various patterns onto the 24 white cans on the shaft.
In the printing area, a drive belt from the blanket turntable drives the cans on the mandrel and the blanket to rotate together at the same line speed (roll-on). Since there are only 8 blankets and 24 mandrels (or white cans) on the mandrel turntable, to maintain the same linear velocity, the angular velocity of the two turntables should be different, ie the angular velocity of the blanket turntable is the mandrel Three times the turntable speed. After the printing is completed, it is transferred to the side of the tank body varnish, a layer of varnish is applied to the surface of the printed can body to protect the printed pattern and increase its brightness; then the primer is applied to protect The bottom of the can; finally baking in a baking oven at a temperature of 170oC for 2 minutes to complete the full processing of the printed product.
Fourth, the development trend of metal printing technology 1. Automation equipment and centralized control system In order to improve the printing speed, reduce the auxiliary time, shorten the conversion time between different tasks, improve productivity and print quality, foreign advanced single-sheet metal printing press adopts advanced automation equipment and centralized control system. .
(1) Quick change plate and automatic positioning device: For example, the metalstar2 metal printing machine launched by Bauer+Kunzi Company can complete the replacement of six-color printing plates in four minutes, and the speed of printing single iron plates can reach over 12,000 pieces/hour.
(2) Automatic cleaning device: Bauer+Kunzi introduced a new automatic cleaning system for printing plates, backing plates, printing cylinders and ink devices.
(3) Automatic ink-ink balance and printing quality control: Automatically set and control the ink and dampening water, correctly adjust the printing pressure, and improve the stability of multi-color register accuracy and register accuracy.
The intelligent control ink balance device is connected to the sheet feeding device, reducing the number of preheated sheets to five sheets. Because the sheet feeding device and the color registration system are all redesigned for metal decorating, there is no need for any pushing device in the transmission system, and a single iron sheet below 0.14 mm can be printed.
(4) Automatic feeding plate and non-stopping iron plate device (5) Sheet metal printing size preset and register adjustment: When replacing a new job, the time required for the conversion of the entire device to the job is 20 minutes. Within.
(6) All-digital display of control, monitoring and diagnostics: single-color registration of metalstar2 metal printing presses, tonal classification and ring-shaped white spots, etc. can be monitored by the Print Check 300 system. The software in the system can be accessed through 10-12 leaflets. Determine the relevant standards.
(7) Automatic bending device: Using the adjusting switch, the single iron plate can be bent from a square to a reel shape within 30 seconds.
2. UV Eco Ink and Curing System Since the metal surface is a non-absorbent surface, post-printing drying is one of the major technical issues in metal printing. The use of UV drying is the development trend of foreign metal printing, the development of low-temperature drying printing inks and coating materials, in order to achieve the purpose of saving energy and improving productivity. With the development of can making technology, the amount of coating required for can bodies should be reduced as much as possible. This will not only reduce the restrictions on storage and transportation and the difficulty of circulation, but also reduce production costs and improve the production environment.
3. Metal plate without horizontal offset:
Sheet metal-free horizontal offset printing refers to a lithographic offset printing method in which an ink-repelling silicone rubber layer is used as a blank part of a printing plate on a lithographic plate, and no dampening is required. Due to the non-absorbing properties of the metal plate, the elimination of the wetting water is more advantageous for the printing of the metal plate. Therefore, no horizontal offset printing has been promoted and applied in foreign metal plate printing.
The metal plate horizontal offset printing press is an offset printing press which uses a metal plate as a printing material and a horizontal printing plate. It is mainly composed of a plate cylinder, a blanket cylinder, an impression cylinder, and an inking device. The printing plate adopts a positive-type horizontal printing plate or a negative-type horizontal printing plate. The layout of the printing plate is lower than the blank portion, which not only improves the glossiness of the printing plate, but also facilitates the drying of the ink layer.
Metal printing products have the following characteristics:
(1) Bright colors, rich layers, and good visual effects. The surface of the tinplate is a tin-plated layer with a glittering color effect. After the background color printing, the printed graphic is more vivid. For tin-free steel or other metal materials, special flash effects can be reproduced after printing by surface treatment and painting.
(2) Metal printing materials have good mechanical properties and processing and forming properties.
(3) Good performance of metal materials and good abrasion resistance and durability of printing inks not only create conditions for unique design and fine printing, but also improve the durability and maintainability of products, and can be better. It embodies the unity of use value and artistry of goods.
Second, the single sheet metal printing metal printing printing methods vary depending on the form of the substrate. There are four types of printing methods: lithographic offset printing, horizontal offset printing, gravure offset printing and letterpress offset printing. Single sheet metal printing mainly uses lithographic offset printing and letterpress dry offset printing. The tinplate and aluminum materials used for metal packaging containers are hard and inelastic because of their texture. Therefore, the flat-plate cans are mostly printed by lithographic offset printing. The molding cans mostly use the dry offset offset printing process, that is, the elasticity of the ink in the printing plate graphic part passes through a rubber roller. Clearly transfer to the surface of the metal can.
1. Painted and coated single tinplate can be processed into three food cans, beverage cans and spray can containers. According to the characteristics of the substrate and the purpose of use, it should have a suitable corrosion resistance and printing, processing performance, for this purpose, the bottom coating should be carried out before printing. The printing-related painting processes mainly include pre-press coating, surface white coating, and post-print coating.
Pre-press coating: coating with primer coating. The coated surface should be degreased prior to coating to remove oil from the surface. Prepress is coated with two types of inner coating and outer coating. The inner coating is applied on the inner side of the metal skin, that is, the molded product, and a layer of protective light oil is applied to protect the iron skin from corrosion of the contents, and also protect the contents. Since the inner coating is in direct contact with the food, the coating must be non-toxic and odorless. After the inner coating, it should be dried in a desiccator. The outer coating is the coating of the printing surface, and its role is to improve the adhesion of the metal surface and the ink layer. Therefore, it is required that the coating has a strong binding force to the metal surface and also has a good affinity for the ink layer, which requires the coating itself to have good fluidity, water resistance and color rendering properties.
White coating: The use of white paint or colorless transparent coating on the metal surface. It is often used as the background color for printed full-text graphics. The white paint shall have good adhesion and whiteness, and shall not yellow or fade under high-temperature baking conditions, and shall not peel off or peel during the canning process.
Post-printing: A layer of glazing coating is applied on the surface of all graphic printing, the purpose of which is to increase the gloss of the printing surface, protect the printing surface, and improve the light resistance and chemical resistance of the metal surface.
Wrinkle oil coating process: In order to enhance the decorative effect, after printing, it is not necessary to apply varnish, but to apply wrinkle oil, and wrinkle after special technology baking, showing a crystal-like scale-like, with three-dimensional Visual effects.
2. At present, almost all foreign countries use diazo PS plates to make lithographic plates. If the letterpress offset printing method is adopted, photosensitive resin relief printing can be used for printing. If lithographic offset printing method is adopted, the plate-making process should not only satisfy the general PS plate-making process requirements, but also use chain-shaped dots to facilitate the reproducibility of metal printing.
3. Metal printing inks are not able to penetrate the surface of the metal printing materials and are prone to dot gain. Compared with paper printing inks, metal printing lithographic offset printing should use high viscosity inks. The metal surface is a non-absorbent surface. Too much of the wetting water on the plate surface tends to cause emulsification of the ink. Therefore, the water and ink balance on the plate surface should be achieved by controlling the thickness of the water film and the amount of ink on the plate surface.
In metal printing, in order to improve the adaptability of post-press processing and processing, and to make the printed surface have a certain degree of gloss, the coating should be applied before the printing ink is not completely dried to form a uniform and smooth coating film, to avoid Bleeding. At the same time, the metal printing ink should have a certain hardness and toughness, can not change its properties when repeated heating, the base color coating and glazing paint should have good adhesion.
The UV type lithographic offset printing ink used for metal printing uses UV irradiation for instantaneous drying, which not only accelerates the drying of the ink, but also contributes to environmental protection.
4. Plate printing machine The printing device of the metal plate lithographic printing press consists of a plate cylinder (P), a blanket cylinder (B), an impression cylinder (I), an inking device, and a wetting device. In the lithographic offset printing of metal plates, hard blankets and hard gaskets should be used. Otherwise, defects such as coarse dots and poor reproducibility of dots will occur in the field of printed products. Therefore, the printing components of the metal plate printer should have sufficient rigidity and accuracy, and the size of the lining of the roller must be strictly controlled.
A UV drying device is disposed between the printing cylinders of the offset lithographic printing machine of the metal plate, and a UV type ink is used to realize high-speed and multi-color printing. Since the single base and cleaning agent in the UV ink will have a swell effect on the rubber roller and the blanket, a rubber stick and a rubber blanket dedicated to the UV ink should be used for this purpose. If a diazo-type PS plate is used, it should be prevented from being eroded by the detergent of the ink, and it is preferable to use a photo-polymerized PS plate, an intaglio plate, or a multi-layered metal plate.
5. Drying device:
(1) Sheet drying: After the metal plate is printed or painted, it should be dried by heating. Resin type printing inks are often used for thermal polymerization or oxidative polymerization drying; drying conditions mainly include heating temperature and drying time.
(2) UV irradiation device: The number of UV light source lamps is determined based on the printing speed.
Third, metal cans printing coating and printing are part of the metal can automatic production line. The common metal cans are mainly tin cans or aluminum cans. After molding, they must be cleaned and surface treated before painting and printing. The printing speed of the metal can printing machine is higher, and the use of letterpress dry offset printing method is adopted, that is, the printing method of photosensitive resin relief printing or metal relief printing is adopted through a rubber roller transfer printing. For multi-color printing, the printing speed of the metal cans is high, and sufficient printing pressure should be ensured, and low viscosity inks and linking materials with good drying performance should be selected. After the metal cans are printed and polished, they are sent to a dryer for heating and drying.
The printing part of the six-color two-piece can printing production line produced by Rutherforu of the United States consists of an ink-coating system and a mandrel turntable. The six color groups are arranged in sequence around the blanket turntable, and there are eight fan-shaped blankets on the blanket turntable for transferring various color patterns. The counterclockwise rotation of the blanket turntable transfers the various patterns onto the 24 white cans on the shaft.
In the printing area, a drive belt from the blanket turntable drives the cans on the mandrel and the blanket to rotate together at the same line speed (roll-on). Since there are only 8 blankets and 24 mandrels (or white cans) on the mandrel turntable, to maintain the same linear velocity, the angular velocity of the two turntables should be different, ie the angular velocity of the blanket turntable is the mandrel Three times the turntable speed. After the printing is completed, it is transferred to the side of the tank body varnish, a layer of varnish is applied to the surface of the printed can body to protect the printed pattern and increase its brightness; then the primer is applied to protect The bottom of the can; finally baking in a baking oven at a temperature of 170oC for 2 minutes to complete the full processing of the printed product.
Fourth, the development trend of metal printing technology 1. Automation equipment and centralized control system In order to improve the printing speed, reduce the auxiliary time, shorten the conversion time between different tasks, improve productivity and print quality, foreign advanced single-sheet metal printing press adopts advanced automation equipment and centralized control system. .
(1) Quick change plate and automatic positioning device: For example, the metalstar2 metal printing machine launched by Bauer+Kunzi Company can complete the replacement of six-color printing plates in four minutes, and the speed of printing single iron plates can reach over 12,000 pieces/hour.
(2) Automatic cleaning device: Bauer+Kunzi introduced a new automatic cleaning system for printing plates, backing plates, printing cylinders and ink devices.
(3) Automatic ink-ink balance and printing quality control: Automatically set and control the ink and dampening water, correctly adjust the printing pressure, and improve the stability of multi-color register accuracy and register accuracy.
The intelligent control ink balance device is connected to the sheet feeding device, reducing the number of preheated sheets to five sheets. Because the sheet feeding device and the color registration system are all redesigned for metal decorating, there is no need for any pushing device in the transmission system, and a single iron sheet below 0.14 mm can be printed.
(4) Automatic feeding plate and non-stopping iron plate device (5) Sheet metal printing size preset and register adjustment: When replacing a new job, the time required for the conversion of the entire device to the job is 20 minutes. Within.
(6) All-digital display of control, monitoring and diagnostics: single-color registration of metalstar2 metal printing presses, tonal classification and ring-shaped white spots, etc. can be monitored by the Print Check 300 system. The software in the system can be accessed through 10-12 leaflets. Determine the relevant standards.
(7) Automatic bending device: Using the adjusting switch, the single iron plate can be bent from a square to a reel shape within 30 seconds.
2. UV Eco Ink and Curing System Since the metal surface is a non-absorbent surface, post-printing drying is one of the major technical issues in metal printing. The use of UV drying is the development trend of foreign metal printing, the development of low-temperature drying printing inks and coating materials, in order to achieve the purpose of saving energy and improving productivity. With the development of can making technology, the amount of coating required for can bodies should be reduced as much as possible. This will not only reduce the restrictions on storage and transportation and the difficulty of circulation, but also reduce production costs and improve the production environment.
3. Metal plate without horizontal offset:
Sheet metal-free horizontal offset printing refers to a lithographic offset printing method in which an ink-repelling silicone rubber layer is used as a blank part of a printing plate on a lithographic plate, and no dampening is required. Due to the non-absorbing properties of the metal plate, the elimination of the wetting water is more advantageous for the printing of the metal plate. Therefore, no horizontal offset printing has been promoted and applied in foreign metal plate printing.
The metal plate horizontal offset printing press is an offset printing press which uses a metal plate as a printing material and a horizontal printing plate. It is mainly composed of a plate cylinder, a blanket cylinder, an impression cylinder, and an inking device. The printing plate adopts a positive-type horizontal printing plate or a negative-type horizontal printing plate. The layout of the printing plate is lower than the blank portion, which not only improves the glossiness of the printing plate, but also facilitates the drying of the ink layer.
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