Hot stamping technology operator training knowledge points
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This paper mainly introduces the hot stamping technology from the definition and principle. It also introduces the structural characteristics of the electro-aluminized aluminum material and the hot stamping effect and related hot stamping equipment. It focuses on the production process of hot stamping technology, and finally lists some Problems that are prone to occur in the production process, and analyze the causes and give specific solutions.
First, the definition of hot stamping
The method of hot stamping metal foil or pigment foil onto printed matter or other substrates by means of a certain pressure and temperature is called hot foil processing, commonly known as hot stamping. At present, bronzing is often referred to as 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 action of heat and pressure.
When the printing plate is heated to a certain extent with the attached electric heating plate, the electroless aluminum film and the paper are embossed, and the glue layer, the metal aluminum layer and the color layer attached to the polyester film are rotated by the action of temperature and pressure. Printed on paper.
Third, hot stamping materials
According to the type of material can be divided into: anodized aluminum hot stamping, color foil hot stamping, color film hot stamping, metal foil hot stamping and other hot stamping foil hot stamping. The following focuses on the hot stamping of the electrochemical aluminum material, which is a hot stamping material made by vacuum evaporation of a metal foil on the film base, as shown in Figure 1.
Figure 1 Schematic diagram of the structure of anodized aluminum material
1 The first layer is a base film layer, also called a base layer, which functions as a polyester film or polyester having a thickness of 12, 16, 18, 20, 25 μ, which supports the other layers.
2 The second layer is the isolation layer (release layer), which facilitates the separation of the base film from the electrochemical aluminum foil during hot stamping.
3 The third layer is the dye layer (protective layer): it provides multiple color effects while protecting the aluminum layer.
4 The fourth layer is an aluminized layer: reflecting light, showing metallic luster, using vacuum aluminum plating, see Figure 2. The specific principle is that the film coated with the color material is placed in a vacuum chamber in a vacuum continuous aluminum plating machine, and under a certain degree of vacuum, the aluminum wire is melted by electric resistance heating and continuously evaporated onto the color layer of the film to form a film. Aluminized layer.
Figure 2 Vacuum aluminum plating
5 The fifth layer is an adhesive layer that bonds the aluminized layer to a substrate such as paper. The electro-chemical aluminum foil is mainly made of gold and silver. It has the characteristics of gorgeous beauty, bright color, crystal and eye-catching, easy to use, etc. It is suitable for hot stamping on paper, plastic, leather, coated fabric, plexiglass, plastic and other materials. One of the most commonly used materials for modern hot stamping. The effect picture after hot stamping is shown in Figure 3.
Figure 3 Effect diagram after hot stamping
Fourth, hot stamping equipment
The machine that can transfer the electro-aluminized foil hot stamping material to the printed matter by hot pressing is called a hot stamping machine.
1. Hot stamping machine type and characteristics
1.1 according to the hot stamping method is divided into:
● Flat and flat, the hot stamping method is plane to plane, see Figure 5.
Figure 5 Flat stamping method
● Round flattening, the hot stamping method is the hot stamping wheel to the plane, see Figure 6.
Figure 6 Round flat stamping method Figure 7 Round stamping hot stamping method
● Round and round, the hot stamping method is the hot stamping roller to the bearing roller shown in Figure 7.
1.2 According to the degree of automation: manual, semi-automatic, fully automatic.
1.3 according to the form of the whole machine: vertical, horizontal.
2. Basic mechanism of hot stamping machine
2.1 fuselage frame, including the outer fuselage and the paper feeder, the delivery table and so on.
2.2 hot stamping device, including hot plate, hot stamping plate, plate and bottom plate. The electric heating plate is fixed on the printing plate platform, and the electric heating plate is provided with a winding electric heating wire with a power of 600-250 OW; the hot stamping plate is a corroded copper plate or zinc plate, which is characterized by good heat transfer, non-deformation, pressure resistance and wear resistance. The embossing plate is usually an aluminum plate or an iron plate; the bottom plate is an aluminum plate having a thickness of about 7 mm for attaching a hot stamping plate;
2.3 Anodized aluminum conveying device consists of a discharge reel, a take-up roll and a feed roller, an anodized aluminum winding roll and a feeding mechanism. The anodized aluminum is mounted on the unwinding reel, and the anodized aluminum after the hot stamping passes between the two feeding rollers, and the feeding mechanism of the feeding reel is driven by the feeding mechanism of the cam, the connecting rod, the ratchet and the pawl. The intermittent rotation of the feeding roller drives the feeding of the anodized aluminum, and the feeding distance is set to the length of the hot stamping pattern. The stamped aluminum foil is wound on a take-up roll.
Five, electrochemical aluminum bronzing process
The main process flow is: preparation before hot stamping → plate loading → padding → hot stamping process parameters determination → trial hot → signing → official hot stamping
1. Preparation before hot stamping
Preparations before hot stamping mainly include inspection and selection of anodized aluminum, preparation of hot stamping plates and inspection of hot stamping machines.
1.1 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 electrochemical aluminum raw materials, because the quality of the electrochemical aluminum materials directly affects the grade of the products. The inspection method is: see if the model is correct; open the re-rolled anodized aluminum, observe whether the surface of the film has scratches, blisters, wrinkles and feels flat; observe whether the brightness of the electrochemical aluminum is satisfactory, and the quality of the electrochemical aluminum reflects light. Should be strong, sparkling. Generally determined by visual inspection.
The rational use of electrochemical aluminum foil is of great significance for making full use of materials, reducing waste and reducing costs. Therefore, it must be considered in the graphic design to be reasonable to use, to make the best use of it, both beautiful and economical. Before the anodized aluminum is stamped, it is generally necessary to accurately calculate the materials, and appropriate gaps are required according to the hot stamping area of the product.
1.2 hot stamping preparation. Plates of hot stamped aluminum are generally available in copper, zinc and copper-plated versions. It is better to use the copper plate because the copper plate has strong heat resistance, has certain elasticity, is more durable than other plates, and has good hot stamping effect. The hot stamping plates used for hot stamping are generally processed externally. Before use, check whether the burrs are uneven, the edges and corners are not neat, the graphics are not clear, etc., and the unqualified places should be corroded and then printed on the plate.
2. Loading process
Install the plate, install the prepared copper plate on the bottom plate, and then firmly fix the bottom plate on the hot plate of the machine, and then adjust the rules and pressures to the appropriate process. The copper plate should be fixed at a suitable position on the bottom plate. It is necessary to ensure the heat effect is good, and it is convenient to manually operate the production. The bottom plate is heated by the 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 a sticking or dowel, and the bottom plate is fixed to the hot plate by screws. When installing the copper plate, you can use the graphic version of the Yangtu film to position it to ensure the position of the bronzing.
3. Pad process
According to the bronzing effect, it is not good for the local unevenness and the effect of the bronzing effect, so that the pressure is uniform everywhere.
4. Determination of bronzing process parameters
4.1 bronzing temperature. The hot stamping temperature is determined by the texture of the object to be burned and the hot stamping form (such as plastic, paper, leather, etc.). The general settings are as follows: plate temperature: 100 ~ 150 ° C; machine temperature: 70 ~ 200 ° C. 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, it will appear white or blue when hot stamping, the brightness of the metal will decrease, and there will be defects such as paste, unclear graphics and so on. If the temperature is too low, there will be hot stamping, broken strokes, weak adhesion, easy to wipe off, dull, hair and other defects. When the hot stamping area is large, the temperature is slightly higher; otherwise, it is lower.
4.2 bronzing pressure. The size of the stamping pressure should be determined according to the nature, thickness and hot stamping of the object to be burned, which is greater than the general printing pressure. The pressure is not to be smeared, and the scalding is clear and bright; the pressure is small to be firm and not fall off, and it is not suitable for flowering. If on the same plate, hot stamping two kinds of images with large size and size, we must master the pressure of the unit area, the hot stamping area, the hot stamping pressure should be larger, and vice versa.
4.3 hot stamping time. In actual operation, the hot stamping time is usually regarded as a constant, and it is not easily changed. After fixing the hot stamping time, adjusting the hot stamping temperature and pressure will reduce the variables, simplify the operation, and easily control the quality. In general, changing the hot stamping time is only considered when the conditions are special. In addition, if you do not use any hot stamping materials, the temperature can be appropriately reduced by 10% to 20%, and the time is increased by 1 to 2 s.
The general order of the above three process parameters (temperature, pressure, time) is determined: based on the characteristics of the object to be burned and the suitability of the anodized aluminum, the temperature and pressure are determined by the plate area and the hot stamping time, and then the most Good pressure, make the plate pressure moderate, flat, even everywhere, and finally determine the best temperature. From the point of view of hot stamping, it is ideal to apply hot stamping at a flat pressure, a lower temperature and a slightly slower speed. Because the flat pressure can make each point of the anodized aluminum bond firmly with the object to be burned; properly adopting a lower temperature on the basis of being able to fully bond is beneficial to maintain the metal-like luster inherent in the electrochemical aluminum; lower The speed of the car is to adapt to a slightly lower temperature.
5. Operators try hot
After the current work is ready, you can perform several trials. If the rules are wrong, you can adjust the front or side gauges appropriately. If the quality requirements are not met, you can adjust the bronzing temperature or perform the padding operation to achieve the hot stamping quality. After the specified requirements, you can take the test sample and the standard manuscript to the workshop supervisor for sample production.
6. Supervisor signing
The supervisor of the workshop confirms the qualified hot stamping after repeated comparison, and after the sample is signed, the operator performs formal hot stamping.
7. Official hot stamping production
In the formal production process, the operator must perform self-inspection according to the production requirements, and the workshop supervisor and quality inspector will also conduct spot checks on the machine side.
Sixth, Quality problems and solutions that are prone to occur in production
1. Hot stamping is not possible or hot stamping is not strong
The hot stamping is not possible or the hot stamping is not strong, that is, the electrochemical 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 hot stamping or hot stamping are: low bronzing temperature; short bronzing time; insufficient bronzing pressure; base color ink containing paraffin; print base color ink is thick and smooth; print base color ink is too fast and crystal Chemical, aluminum alloy model is not suitable.
2. Hot stamping reverse phenomenon
The so-called reverse pulling means that after the hot stamping, the layer of the electro-aluminum foil is not firmly adhered to the bottom layer of the printed ink or the surface of the white paper, but some or all of the underlying ink layer is pulled away by the aluminum.
The main reason is that the underlying ink layer is not dry; the underlying ink layer uses too much white ink and is easy to be pulverized. Solution: control the amount of dry oil added; mix the lightening agent with white ink; the hot stamping part does not print ink.
3. Hot stamping text is easy to be distorted
The text of the figure is hairy, lacking pen and drawing, and the gloss is poor. The writing is hairy because of the low temperature; the lack of pen and broken painting is generally caused by the tension of the electric aluminum coil being too tight or the pressure is insufficient; the difference in gloss is due to the temperature being too high. Solution: Adjust the temperature to the appropriate temperature and pressure as appropriate, depending on the specific problem that arises.