The hottest metal printing is not difficult

Metal printing is not difficult

first, the characteristics of metal printing products

metal printing is a printing method using hard materials such as metal plates, metal molding products and metal foils as substrates. Its printing materials mainly include tinplate (tinned steel plate), Wuxi thin steel plate (TFs), zinc iron plate, black steel plate, aluminum plate, aluminum stamping containers and aluminum, white iron sheet composite materials

metal printing products have the following characteristics:

(1) bright colors, rich layers and good visual effect. The surface of the tinplate is tinned, which has a flashing color effect. After the background color printing, the printed pictures and texts are more bright. For Wuxi steel plate or other metal materials, special flash effect can also be reproduced after surface treatment, coating and printing

(2) metal substrate materials have good mechanical properties, processing and molding properties

(3) the good performance of metal materials and the good wear resistance and durability of printing ink not only create conditions for the realization of unique shape design and exquisite printing, but also improve the durability and retention of goods, which can better reflect the unity of the use value and artistry of goods

second, single sheet metal printing

the printing method of metal printing varies with the shape of the substrate. There are mainly four printing methods: lithographic offset printing, non horizontal offset printing, gravure offset printing and relief dry offset printing. Sheet metal printing mainly adopts lithographic offset printing and relief dry offset printing. Because the tinplate and aluminum materials used for metal packaging containers are hard and inelastic, flat cans are mostly printed by lithographic offset printing process, and shaped cans are mostly printed by relief dry offset printing process, that is, the ink of the graphic part of the printing plate is clearly transferred to the surface of the metal cans through the elasticity of a rubber drum

1. Coating

single sheet tinplate coated and printed can be processed into three pieces of food cans, beverage cans and spray cans. According to the characteristics and use purposes of the substrate, it should have appropriate corrosion resistance and printing and processing properties. Therefore, the bottom coating should be carried out before printing. The coating processes related to printing mainly include prepress coating, surface white coating and post press coating

prepress coating: coating with primer. Before coating, the coated surface shall be degreased to remove the oil stain on the surface. Prepress coating has two forms: internal coating and external coating. Internal coating is to coat the inside of the iron sheet, that is, the inside of the formed product, and apply a layer of protective gloss to protect the iron sheet from the erosion of the contents, and also protect the contents. As the internal coating is in direct contact with food, it is required that the coating must be non-toxic and tasteless. After internal coating, it should be dried in a dryer. External coating is the coating of the printing surface, and its function is to improve the adhesion between the metal surface and the ink layer. Therefore, the coating is required to have a solid adhesion to the metal surface and a good affinity to the ink layer, which requires that the coating itself should have good fluidity, water resistance and color rendering

white coating: use white paint or colorless transparent paint to paint the metal surface. It is often used as the background color of pictures and texts in the optimization design of automobiles and the utilization of alloy materials and non-metallic materials. The white paint shall have good adhesion and whiteness, and shall not turn yellow or fade under the condition of high temperature baking, and shall not fall off or peel off during the canning process

post press coating: apply a layer of glazing paint on the surface of all graphic printing has been completed. Its purpose is to increase the gloss of the printing surface, protect the printing surface, and improve the light resistance and chemical corrosion resistance of the metal surface

wrinkle oil coating process: in order to enhance the decorative effect, it is not necessary to apply Polish after printing, but to apply wrinkle oil, which is wrinkled and shaped after baking through a special process, showing a crystal transparent scale shape, with a three-dimensional visual effect

2. Plate making

at present, diazo PS plates are basically used abroad to make offset lithographic plates. If the relief dry offset printing method is adopted, the photoresist relief printing can be used to save the cost of the experimental machine. If offset lithography is used, the plate making process should not only meet the requirements of general PS plate making process, but also select chain points to facilitate the step reproduction of metal printing

3. metal printing ink

because the surface of metal substrate cannot penetrate, it is easy to produce dot enlargement. Compared with paper printing ink, metal printing offset lithography should use high viscosity ink. The metal surface is a non absorbent surface, and too much wetting water on the layout is easy to produce ink emulsification. Therefore, the water and ink balance on the layout should be achieved by controlling the water film thickness and ink amount on the layout

in metal printing, in order to improve the adaptability of post press processing and processing, and make the printing surface have a certain gloss, polish and paint before the printing ink is completely dry, so as to form a uniform and smooth film and avoid color bleeding. At the same time, the metal printing ink should have a certain hardness and toughness, and its properties cannot be changed during repeated heating. The base color coating and glazing paint should have good adhesion

UV offset printing ink for metal printing, which is instantaneously dried by UV irradiation, can not only accelerate the drying of the ink, but also be conducive to environmental protection

4. metal plate printing machine

the printing device of metal plate lithographic printing machine is composed of plate cylinder (P), rubber cylinder (b), embossing cylinder (I), inking device and wetting device. In metal plate offset lithography, hard blanket and hard liner should be used, otherwise, there will be some faults such as dot coarsening and poor dot reproducibility in the field of printing. Therefore, the printing parts of the metal plate printing machine should have sufficient stiffness and accuracy, and the lining size of the drum should be strictly controlled

a UV drying device is set between the printing cylinders of the metal plate offset press, and UV ink is used to realize high-speed and multi-color printing. As the single base and cleaning agent in UV ink will expand the rubber roller and blanket, therefore, the rubber stick and blanket dedicated to UV ink should be selected. If diazo PS version is used, it should be prevented from being eroded by the detergent of the ink. It is best to use photopolymerization PS version, Gravure version or multi-layer metal version

5. drying device:

(1) sheet drying: after printing or coating, the metal plate should be heated and dried. Resin printing inks are often dried by thermal polymerization or oxidative polymerization; Drying conditions mainly include heating temperature and drying time

(2) UV irradiation device: determine the number of UV irradiation light source lamps according to the printing speed

III. metal can printing

painting and printing are the automatic production of metal cans. 7. According to the stress ratio, it can be divided into: the component of symmetrical fatigue test line. Common metal cans are mainly tinplate cans or aluminum cans. After forming, they must be cleaned and surface treated before painting and printing. The printing speed of the metal can printing machine is high, and the relief dry offset printing method is selected, that is, the photosensitive resin relief or metal relief is used, and the printing method is transferred through the rubber drum. When multi-color printing is carried out, the printing speed of metal cans is high, enough printing pressure should be guaranteed, and low viscosity ink and binder with good drying performance should be selected. After printing and polishing, the metal cans are sent to the dryer for heating and drying

the printing part of the 6-color two-piece can printing production line produced by rutherforu company in the United States consists of an inking system and a spindle turntable. Six color decks are arranged around the blanket turntable in order. There are eight fan-shaped blanket on the blanket turntable, which are used to transfer various color patterns. The blanket turntable rotates counterclockwise to transfer various patterns to 24 white cans with the shaft core and sleeve in mind

in the printing area, a drive belt led out by the blanket turntable drives the can on the mandrel and the blanket to rotate together at the same line speed (counter roll). Since there are only 8 pieces of blanket, and there are 24 mandrels (or white cans) on the spindle turntable, to maintain the same linear speed, the angular speed of the two turntables should be different, that is, the angular speed of the blanket turntable is 3 times that of the spindle turntable. After printing, turn to the varnish part on the side of the can body, and apply a layer of varnish on the surface of the can body with the pattern to protect the printed pattern and increase its brightness; Then primer to protect the bottom of the can; Finally, bake in the oven at a temperature of 170oc for 2 minutes to complete all the processing of prints

IV. development trend of metal printing technology

1. Automation device and centralized control system

in order to improve printing speed, reduce auxiliary time, shorten the conversion time between different work tasks, improve productivity and print quality, foreign advanced single sheet metal printing machines adopt advanced automation device and centralized control system

(1) fast version change and automatic positioning device: for example, metalstar 2 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 a single iron plate can reach more than 12000 pieces/hour

(2) automatic cleaning device: Bauer + kunzi company launched a new automatic cleaning system for printing plates, backing plates, printing cylinders and ink devices

(3) automatic control of ink balance and printing quality: automatically set and control the ink and wetting water, correctly adjust the printing pressure, and improve the multi-color registration accuracy and the stability of registration accuracy

the intelligently controlled ink balance device is connected with the film feeding device to reduce the number of preheated sheets to 5. Since both the film feeding device and the chromatic system are redesigned for metal decoration, there is no need for any pushing device in the transmission system, and a single iron plate less than 0.14mm can be printed

(4) automatic iron plate supply and non-stop iron plate receiving device

(5) single iron plate printing size presetting and registration adjustment: when replacing new live parts, the time required for the conversion of the whole set of equipment to live parts is within 20 minutes

(6) full digital display of control, monitoring and diagnosis: problems such as single sheet chromaticity, tone classification and circular white spots of metalstar 2 metal printing machine can be monitored by print check 300 system, and the software in the system determines relevant standards through 10-12 single sheets

(7) automatic bending device: using the adjustment switch, a single iron plate can be bent from a square into a reel shape within 30 seconds

2. UV environment-friendly ink and curing system

as the metal surface is non absorbent, the problem of post press drying is one of the main technical problems of metal printing. To realize the localization of PEEK, PPS and other materials as soon as possible is one of the main technical problems of metal printing. UV drying is the development trend of foreign metal printing. Developing low-temperature drying printing ink and coating materials can save energy and improve productivity. With the development of can making technology, we should try our best to reduce the coating amount of the tank body, which can 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 offset printing without horizontal version:

metal plate offset printing without horizontal version refers to a lithographic offset printing method that uses an ink repellent silicone rubber layer as the blank part of the printing plate on the lithography, and does not need to moisten the plate, but uses special ink for printing. Due to the non absorbability of metal plate, it is more beneficial to eliminate wetting water for metal plate printing. Therefore, there is no horizontal offset printing in foreign metal plate printing