This article mainly introduces the hot stamping technology from the definition and principle, and also introduces the structural characteristics of the anodized aluminum material and the hot stamping effect and related hot stamping equipment. Problems that are prone to occur in the production process, and analyze the causes and give specific solutions.
1. Definition of hot stamping
With the help of a certain pressure and temperature, the method of hot stamping metal foil or pigment foil onto printed matter or other substrates is called hot foil processing, commonly known as hot stamping. At present, the hot stamping often refers to the hot stamping of anodized aluminum materials.
Second, the principle of hot stamping
The essence of hot stamping is transfer, which is the process of transferring the pattern on the anodized aluminum to the substrate by the effect of heat and pressure.
When the printing plate heats up to a certain level with the attached electric heating base plate, it is imprinted through the anodized aluminum film and paper, and the effect of temperature and pressure is used to transfer the adhesive layer, metal aluminum layer and color layer attached to the polyester film Print onto paper.
3. Hot stamping materials
According to the material type, it can be divided into: aluminum foil hot stamping, color foil hot stamping, color film hot stamping, metal foil hot stamping and other hot stamping foil hot stamping. The following highlights the hot stamping of anodized aluminum material. Anodized aluminum foil is a hot stamping material made by vacuum evaporation of a layer of metal foil on a film substrate.
â‘ The first layer is the base film layer, also known as the film base layer, which plays the role of supporting other layers, and is 12, 16, 18, 20, 25Î¼ polyester film or polyester.
â‘¡ The second layer is the isolation layer (detached layer), which facilitates the separation of the base film and the electrochemical aluminum foil during hot stamping.
â‘¢ The third layer is the dyeing layer (protective layer): provides a variety of color effects while protecting the aluminum layer.
â‘£ The fourth layer is aluminized layer: reflecting light and showing metallic luster, adopt vacuum aluminizing method, see figure two. The specific principle is to put the color-coated film in the vacuum chamber of the vacuum continuous aluminum plating machine. Under a certain vacuum degree, the aluminum wire is melted and continuously evaporated to the color layer of the film by resistance heating, and then formed. Aluminum coating.
â‘¤ The fifth layer is the adhesive layer. The aluminum layer is adhered to the paper and other substrates. Electrochemical aluminum foil is mainly made of gold and silver. It has the characteristics of gorgeous and beautiful, bright color, dazzling and easy to use. It is suitable for hot stamping on paper, plastic, leather, coated fabric, organic glass, plastic and other materials One of the most commonly used materials in modern hot stamping.
Fourth, hot stamping equipment
The machine that can transfer the hot stamping material of the electrified aluminum foil to the printed matter by hot pressing is called hot stamping machine.
1. Type and characteristics of hot stamping machine
â‘ According to the hot stamping method:
â— Flat pressing, the hot stamping method is plane to plane.
â— Circular flattening, its hot stamping method is hot stamping wheel flat surface.
â— Round pressing, its hot stamping method is hot stamping roller to pressure roller.
â‘¡According to the degree of automation: manual, semi-automatic and fully automatic.
â‘¢According to the form of the whole machine: vertical and horizontal.
2. Basic mechanism of hot stamping machine
â‘ Fuselage frame, including the outer shape of the fuselage, the paper conveying table, the paper receiving table, etc.
â‘¡Hot stamping device, including electric hot plate, hot stamping plate, stamping plate and bottom plate. The electric heating plate is fixed on the printing plate platform, and the electric heating plate is equipped with a roundabout electric heating wire with a power of 600 to 250OW; ; The embossed plate is usually an aluminum or iron plate; the bottom plate is an aluminum plate with a thickness of about 7mm, which is used to paste a hot stamped plate;
â‘¢ Anodized aluminum conveying device is composed of unwinding shaft, feeding roller and auxiliary feeding roller, anodized aluminum winding roller and feeding mechanism. The anodized aluminum is mounted on the unwinding shaft, and the hot stamped anodized aluminum passes between the two feeding rollers. , The intermittent rotation of the feeding roller drives the feeding of anodized aluminum, and the feeding distance is set to the length of the stamping pattern. The hot stamped anodized aluminum roll is on the take-up roll. [next]
Fifth, the process of anodized aluminum bronzing
The main process flow is: preparation before hot stamping â†’ plate-setting â†’ padding â†’ determination of hot stamping process parameters â†’ trial ironing â†’ signing â†’ formal hot stamping
1. Preparation before hot stamping
The preparation work before hot stamping mainly includes the inspection and selection of anodized aluminum, the preparation of hot stamping plates and the inspection of hot stamping machines.
â‘ Inspection and selection of anodized aluminum. In addition to choosing the correct anodized aluminum, attention should also be paid to the quality characteristics of the anodized aluminum raw materials, because the quality of the anodized aluminum material directly affects the grade of the product. The inspection method is: to see if the model is correct; open the rewinded anodized aluminum, observe whether the film surface has scratches, trachoma, wrinkles and smooth feel; observe whether the brightness of the anodized aluminum meets the requirements, and the good quality anodized aluminum reflects light It should be strong and shiny. Generally determined by visual inspection.
Reasonable use of anodized aluminum foil is of great significance to make full use of materials, reduce waste and reduce costs. Therefore, it must be considered in the graphic design that it should be used reasonably and that everything is used to the best of its ability, both aesthetically and economically. Before anodized aluminum stamping, the materials are generally calculated accurately, and appropriate gaps are left according to the needs of the product stamping area.
â‘¡ Preparation of hot stamping plate. There are generally three types of plate materials for hot stamping anodized aluminum: copper plate, zinc plate and copper plated zinc plate. It is better to use copper plate, because copper plate has high heat resistance, has a certain elasticity, is more durable than other plates, and has good hot stamping effect. Hot stamping plates used for hot stamping are generally processed externally. Before use, check the plate for burrs, uneven corners, and unclear graphics and other deficiencies. Corrosion and repair unqualified places before hot stamping.
2. The process of loading
Install the plate, install the prepared copper plate on the bottom plate, and then firmly fix the bottom plate on the electric heating plate of the machine, and then adjust the rules and pressure to the appropriate process. The copper plate should be fixed on the proper position of the bottom plate, not only to ensure good heating effect, but also to facilitate manual operation and production, the bottom plate is heated by an electric heating plate, and the heat is transferred to the printing plate for hot stamping. The method of fixing the copper plate is generally a method of fixing by pasting or screwing, and the bottom plate is fixed on the electric heating plate with screws. When installing the copper plate, you can use the graphic version of the Yangtu film to locate it to ensure the location of the bronzing.
3. Pad version process
According to the bronzing effect, the local unevenness and the unfavorable bronzing effect will be processed by padding, so that the pressure everywhere is even.
4. Determination of bronzing process parameters
â‘ Bronzing temperature. The stamping temperature is determined according to the texture of the object to be stamped and the stamping form (such as plastic, paper, leather, etc.). The general settings are as follows: printing plate temperature: 100 ï½ž 150 â„ƒ; machine temperature: 70 ï½ž 200 â„ƒ. The machine temperature for paper bronzing can be set according to different paper materials, different types of anodized aluminum, different bronzing pressures, and different bronzing times. If the temperature is too high, white or blue will appear during hot stamping, the brightness of the metal will decrease, and there will be ills such as pasting and unclear graphics. If the temperature is too low, there will be defects such as hot stamping, broken strokes, weak adhesion, easy to wipe off, dullness, and flowering. When the hot stamping area is larger, the temperature is slightly higher; otherwise it is lower.
â‘¡Bronzing pressure. The size of the stamping pressure should be determined according to the nature, thickness and form of the object to be ironed, which is greater than the general printing pressure. The great pressure is not confusing, and the burnt marks are clear and bright. The small pressure is preferably firm and does not fall off or flower. If you are hot stamping two kinds of graphics with disparity in size on the same plate, you should master the equal pressure per unit area. The larger the hot stamping area, the greater the hot stamping pressure, and vice versa.
â‘¢Bronzing time. In actual operation, the stamping time is usually regarded as a constant, and it is not easy to change it. After fixing the stamping time, adjusting the stamping temperature and pressure will reduce the variables, simplify the operation, and make it easy to control the quality. Generally speaking, only change the stamping time when the conditions are special. In addition, if no hot stamping material is used, the temperature can be appropriately reduced by 10% to 20% only when stamping the uneven marks, and the time should be increased by 1 to 2s.
The general sequence for the determination of the above three process parameters (temperature, pressure, time) is: based on the characteristics of the object to be hot and the suitability of anodized aluminum, the temperature and pressure are determined based on the plate area and hot stamping time, and then the most Good pressure, make the layout pressure moderate, smooth, uniform everywhere, and finally determine the best temperature. From the perspective of hot stamping effect, hot stamping with flat pressure, lower temperature and slightly slower speed is ideal. Because the flatter pressure can make the anodized aluminum bond firmly with the object to be ironed at every point; appropriately adopting a lower temperature on the basis of being able to fully bond is conducive to maintaining the inherent metallic luster of the anodized aluminum; lower The speed of the car is to adapt to a slightly lower temperature.
5. The operator tried to iron
After the current period of work is ready, you can conduct a trial ironing. If the rules are not correct, you can adjust the front or side regulations appropriately; if it is because you do not meet the quality requirements, you can adjust the bronzing temperature again or perform the pad operation to achieve the quality of the stamp After the stipulated requirements, you can bring the trial ironing proofs and standard manuscripts to the workshop supervisor for signature production.
6. Supervisor signing
The workshop supervisor confirmed the qualified hot stamping after repeated comparisons, and after signing the samples, the operators performed formal hot stamping.
7. Formal hot stamping production
In the formal production process, the operator should conduct self-inspection according to the production requirements, and at the same time, the workshop supervisor and quality inspection personnel will also conduct random inspections at the machine table.
6. Quality problems and solutions in production
1. Hot stamping does not work or hot stamping is not strong
The hot stamping cannot be achieved or the hot stamping is not strong, that is, the anodized aluminum cannot be ideally transferred to the surface of the substrate or the anodized aluminum cannot adhere well to the substrate. The main reasons for the lack of hot stamping or the poor hot stamping are: low bronzing temperature; short bronzing time; insufficient bronzing pressure; background ink contains paraffin; the background ink of the printed product is thick and smooth; the background ink of the printed product dries too fast and crystals Chemical, anodized aluminum models are not suitable.
2. Hot stamping and anti-pull phenomenon
The so-called reverse pull refers to that after the hot stamping, the anodized aluminum foil layer is not firmly attached to the background ink layer or white paper surface of the printed product, but part or all of the background ink layer is pulled away by the anodized aluminum.
The main reason: the background ink layer is not dry; too much white ink is used in the background ink layer, which is easy to powder. Solution: Control the amount of dry oil added; mix the desalting agent with white ink; no ink on the hot stamping area.
3. Hot stamping graphics are easy to be distorted
Phenomenon of pictures, hair, lack of strokes, poor gloss, etc. The handwriting is sloppy due to the temperature being too low; the lack of strokes is usually caused by the tension of the anodized aluminum coil being too tight, or the pressure is not enough; the difference in gloss is due to the temperature being too high. Solution: According to the specific problems, adjust the temperature to the appropriate temperature and pressure.
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