Analysis of bronzing and its quality control from

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Analyze bronzing and its quality control from actual operation

the so-called bronzing suitability refers to the model selection of anodized aluminum and the matching between bronzing speed, temperature, pressure and other factors. When the equipment and other hardware are fixed, correctly mastering the bronzing suitability is the most important means to improve the bronzing quality. The following is an analysis of some quality problems reflected in the actual operation, so as to scientifically grasp the suitability of bronzing

1. poor hot stamping or false hot stamping

this is related to many factors such as the clear front and single side characteristics, the nature of anodized aluminum, hot stamping temperature and pressure given in the print sheet. ① Too much powder is sprayed on the surface of the print or the surface contains additives such as adhesive remover and gloss paste, which will hinder the adsorption of anodized aluminum and paper. Solution: remove the powder on the surface or solve it in the printing process. ② Improper selection of electrochemical aluminum directly affects the fastness of bronzing. According to the size of the bronzing area and the characteristics of the hot stamping material, we should comprehensively consider what type of anodized aluminum to choose. Domestic anodized aluminum is mainly the peacock brand series produced by Shanghai Shenyong bronzing Materials Co., Ltd., while imported anodized aluminum is mainly the PM and LK series of Kurz in Germany, the A, K and H series of Japan, and the SP series of Kolon in South Korea. According to our practice and testing, the selection of anodized aluminum can mainly refer to the following categories: hot stamping (general ink) anodized aluminum on ordinary products has 88-l type and Kurz PM type; There are 88-2 types of gilding anodized aluminum for thick ink printed materials such as cigarette bags and cosmetics (including gold printing and silver printing); There are 88-3, 88-4 types, pm288, etc. of electrochemical aluminum for fine handwriting hot stamping of cigarette labels, cosmetics packaging, etc; Suitable for hot stamping of OPP or pet coated paper, cardboard with UV ink, polishing paper and other products, anodized aluminum has 88-4 type, K series, LK series, and s test with high repeatability; The latter is cheap P series. ⑧ Failure to correctly master the bronzing equipment and the match between the pressing time and the hot stamping temperature will affect the fastness of hot stamping and the clarity of the image and text outline. Due to different equipment and materials to be hot stamped, the pressing time and hot stamping temperature are different. For example, the high-speed rotary press is fast, the stamping line contacts, and the hot stamping temperature is higher than the round flattening or flat flattening. Generally, the temperature of round pressing and hot stamping is 190 ℃ ~ 220 ℃, the round flattening is about 130 ℃ ~ 150 ℃, and the flat flattening is about 100 ℃ ~ 120 ℃. Of course, the hot stamping time, hot stamping temperature and production efficiency are also restricted by the transfer performance of anodized aluminum to a large extent

2. Reverse pull

reverse pull refers to the electrochemical aluminum pulling away the printing ink or varnish on the printed piece after hot stamping. This is mainly because the ink on the surface of the print is not dry or the post-processing treatment of UV on the surface of the print is improper, resulting in the weak combination of the ink and UV oil on the surface of the print and the surface of the paper. Solution: bronzing after printing is dry. In addition, electrochemical aluminum with low separation force and excellent heat transfer can be selected

3. The color change of electrochemical aluminum after pasting and hot stamping

pasting is mainly caused by the poor production of bronzing plate, the loose installation of electrochemical aluminum or the incorrect foil of electrochemical aluminum. The color change of anodized after hot stamping is mainly caused by high hot stamping temperature. In addition, anodized wrinkling is also easy to cause uneven hot stamping and discoloration, which can be solved by appropriately reducing the temperature. For the round flattening machine, a fan can be installed at the foil feeding place to keep the foil floating, so as to avoid the electrochemistry aluminum touching the bronzing plate and scorching before hot stamping

4. The process arrangement is inappropriate, which destroys the surface gloss of anodized aluminum, and the graphic outline is false

for bronzing that requires film covering processing, people often worry that the gold foil is easy to be wiped off and hot stamping before film covering, which is easy to cause: ① the film (especially the matte film) will damage the surface gloss of anodized aluminum, so it is not suitable to use water-soluble glue to cover the film, otherwise it will cause the surface of anodized aluminum to blacken, and it is very easy to cause the gold powder to stick to the edge of the picture and text, resulting in virtual phenomenon. ② After bronzing, it is sunken due to pressure, and the glue is not easy to penetrate the surface of anodized aluminum, which is easy to cause the separation of OPP and paper at the bronzing place and affect the product quality. The correct process is to cover the film before bronzing, and select the anodized aluminum matching opp

principle of electrochemical aluminum stamping process

electrochemical aluminum stamping is a very important post press processing process in packaging printing, mainly hot stamping patterns. written words. Lines to highlight the name and trademark of the product. Ang brand, beautify products, so as to improve the grade of packaging products. Anodized hot stamping is also often used for hardcover book covers and greeting cards. Post press processing of calendars and other products

the structure of anodized aluminum is shown in the figure below, and its hot stamping process is as follows: the anodized aluminum is heated by the hot stamping plate, the stripping layer melts, and then the adhesive layer melts. When the automatic uniform cooling and constant temperature stamping of the sample are achieved, the adhesive layer adheres to the substrate, the coloring layer separates from the polyester substrate, and the aluminized layer and the coloring layer remain on the substrate

stamping anodized aluminum on the package can not only beautify the product and improve the product grade, but also play a certain anti-counterfeiting role

post press hot stamping

one of the purposes of increasing the hot stamping process is to improve the grade of products, but in practical application, only reasonable application can get twice the result with half the effort. On the contrary, it will not only reflect the advantages of products, but also cause waste. The following points should be paid attention to in the rational use of anodized hot stamping process

1. Matters to be considered in product design

① hot stamping parts should be fully considered, that is, the matching of the color of hot stamping words or patterns with the printing color and the influence of post hot stamping processing on hot stamping

② consider the overall effect and cost of hot stamping. For example, some products often only hot stamping the outline and text of the pattern, not directly hot stamping the pattern, so as to achieve the effect of dot lining; For the printing design of some aluminized cigarette packs, we can replace hot stamping by printing transparent yellow first and then pressing concave convex, so as to reduce the cost

③ for hot stamping on a large area of the field, the paper connection of the hot stamping position and the printed pattern should also be considered, which should be determined according to the overprint accuracy of the product, which is generally set to 0..5mm. Of course, we should also consider the hot stamping suitability of anodized itself

2. Influence of pre press printing and post press processing

generally, hot stamping products must be printed before hot stamping, including monochrome printing and multicolor printing; After hot stamping, press concave convex, UV glazing, film coating, then printing, die cutting, paste box and other processing

several points that should be paid attention to before hot stamping: dark thin printing, using ink with strong coloring power, adding less anti adhesion agent and anti adhesion agent in the ink as far as possible, and avoiding powder spraying. The printing suitability of printing ink, glazing oil and anodized aluminum hot stamping should be matched, and the influence of ink crystallization on hot stamping should also be prevented

press concave convex and die cutting after ironing. The effect of paste box on hot stamping is not great, just pay attention to prevent scratches on hot stamping foil. If you want to apply UV varnish after hot stamping, you should consider the acceptability of anodized aluminum, that is, the surface tension of anodized aluminum is greater than that of UV varnish. If allowed:, the hot stamping part of some products can be hollowed out. If you want to print UV varnish first and then hot stamping according to the process requirements, you should first check the hot stamping suitability of the UV varnish surface. Generally, use a dyne pen to test the UV varnish film, and its surface tension is 3 Above n/m, anodized hot stamping can be carried out

3. Selection of hot stamping materials and equipment

hot stamping materials and equipment are the two most critical factors affecting the hot stamping effect

① hot stamping material

hot stamping material is anodized. At present, there are many kinds of electrochemical aluminum on the market, including ceramic electrochemical aluminum and paper electrochemical aluminum. Glass, anodized aluminum, etc; The grades are complex, including Shanghai's programmable composite materials that can bring changes in shape with environmental changes such as temperature, air pressure or other factors, domestic anodized aluminum from Zhejiang, Fujian and other places, and American products. The imported electrochemical aluminum made in Japan and Germany have their own advantages and disadvantages. Here we mainly discuss paper electrochemical aluminum

the hot stamping suitability of electrochemical aluminum includes the surface smoothness, brightness and clarity, the hot stamping suitability for graphics and small texts, surface gold flying and burr problems, etc., which should be weighed and selected according to different printing materials, the level of packaging products, the price of electrochemical aluminum and the hot stamping suitability

② hot stamping equipment

hot stamping equipment is widely used in China. The main hot stamping requirements are not very high packaging products. It has the advantages of low cost, small floor area, simple operation and strong hot stamping adaptability. However, products with high requirements for hot stamping accuracy have large errors and high scrap rate. If the packaging box of high-quality products is used for hot stamping, most domestic printing plants choose boster bronzing machine, which has very high hot stamping accuracy and better control of hot stamping temperature, pressure and speed than other bronzing machines. At present, some domestic bronzing machines also have high precision, and the price is much cheaper than imported high-end equipment

post press printing

post press printing is a top technology, which is widely used in cigarette bag printing, and its three-dimensional effect is beyond the reach of other processes. Post scalding printing is generally hot stamping a large area of laser anodized aluminum on spot color ink, and then printing UV ink on anodized aluminum. Its impact on the printing materials. Printing ink, printing equipment and printing personnel have high requirements. In this process, the following points should be paid attention to:

① select electrochemical aluminum with surface tension of (4..6) xn/m to ensure good adhesion of the ink

② in the process of hot stamping, it should be noted that no paste is allowed in hot stamping. Reverse pulling, poor hot stamping, etc. Otherwise, during the second printing, the anodized hot stamping will fall off and accumulate on the blanket, seriously affecting the product quality and production efficiency

③ comprehensively consider the printing between printing, hot stamping and post hot stamping, and properly control the ambient temperature and humidity of the workshop, so as to avoid human factors as far as possible

④ during the design, we should pay attention to whether we can hollowed out or separate hot stamping in large-area field hot stamping, so as to reduce the difficulty of hot stamping

hot stamping anti-counterfeiting

with the development of society, people pay more and more attention to the anti-counterfeiting of high-end products. Anti counterfeiting is almost applied to the whole packaging industry, such as ink anti-counterfeiting, printing pattern anti-counterfeiting, paper anti-counterfeiting, hot stamping anti-counterfeiting, UV oil anti-counterfeiting, etc. Hot stamping anti-counterfeiting is relatively demanding. This is an anti-counterfeiting technology with complex control. Here we mainly introduce two anti-counterfeiting methods

① electrochemical aluminum itself has laser patterns. By transferring the hot stamping patterns to the substrate, the hot stamping surface of the substrate has various rainbow patterns, which plays an anti-counterfeiting role. This kind of electrochemical aluminum technology is more advanced, more difficult to manufacture, and more expensive, which makes imitators flinch

② use the holographic anti-counterfeiting pattern on electrochemical aluminum to position the complete pattern on the pattern fixed on the substrate through mechanical control. This process uses the trinity of hot stamping plate, holographic anti-counterfeiting anodized pattern and substrate pattern for positioning and registration, which is difficult

as hot stamping anti-counterfeiting is a relatively new technology: the requirements for operators are high, so it must be reasonably controlled to minimize unnecessary waste

source: Zhejiang Hengfeng Packaging Co., Ltd

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