Gold sweeping technology in surface finishing

The processing of the imitation gold effect is one of the effective means to improve the grade of commodity packaging. At present, there are mainly methods such as gold ink printing, matte printing, bronzing and gold sweeping. Each method has its own characteristics. Let's talk about the gold sweeping technology.

1 What is gold sweeping technology

The so-called gold sweeping is a process of attaching special metal powder to designated parts on commodity packaging or label printed matter through a special process to achieve a metallic gloss effect. This technology can get realistic metal texture and better gloss, while the pattern is fine and the overprint is accurate.

2 Application of gold sweeping technology

Gold sweeping technology is widely used in the packaging of cigarettes, wine, medicines, cosmetics and high-end food, as well as the printing of greeting cards, invitations, calendars and other products, which can greatly increase the added value of commodities. In the 1990s, China's gold sweeping technology has been developed to some extent. Some regions with advanced packaging and printing (such as Guangdong) have also introduced several gold sweeping machines, mainly used in the production of cigarette packets and medicine packets. With the improvement of China's packaging requirements, gold sweeping technology will have greater development.

3 Principle of gold sweeping process

The process of sweeping gold is actually very simple. Put the printed sheets that need to be scanned on a single-color or two-color offset press, apply a layer of sticky adhesive to the parts that need to be scanned with gold, and then print the sheets through the paper feed device It can be finished by sweeping the gold powder and polishing and knocking gold.

At present, the Jazz brand automatic gold sweeping machine produced in Germany is mainly composed of five parts: a paper feeding mechanism, a coating mechanism, a polishing mechanism, a cleaning mechanism, and a paper collecting mechanism. Printable products can be processed from thin paper to paper jam, from four to full sheet, the speed can reach 8000 sheets / hour. When sweeping gold, the gold sweeping machine generally needs a flat sheet single (double) color offset press (removing the paper collection device) to connect with the gold sweeping machine. First, make the special PS version of the gold sweeping machine, install it on the offset printing machine and adjust it. Use the PS version to print a thin and even layer of primer on the gold powder on the printed matter, and then pass this print through the gold sweeping machine. The paper transfer device is sent to the suction rubber conveyor belt of the gold sweeping machine, and the gold powder is evenly distributed by the coating mechanism and applied to the surface of the printed sheet. When the side of the coating roller that attracts the gold powder turns to the top of the printed sheet, this part is changed from suction to blowing, and the gold powder is evenly sprayed on the entire surface of the printed sheet. The four polishers of the polishing mechanism rub and polish the gold powder on the printed sheet, so that the gold powder printed on the printed sheet is firmly adhered. At the same time, the gold sweeping machine also uses 4 special gold tapping belts to make reciprocal movements opposite to each other to improve the metallic luster and adhesion fastness. The latter two have strong suction pipes to remove excess gold powder. The high-vacuum suction multi-channel cleaning circulation system of the cleaning mechanism and the front suction tube can quickly sweep the excess gold powder on the printed sheet. These excess gold powder can be recycled and used without causing environmental pollution or waste. Finally, the paper collection mechanism completes the paper collection and sorting work.

Of course, if the printing plant has a multi-color printing machine and UV drying device, you can perform online gold sweep, that is, print the printed matter in the first few colors of the printing machine, and dry it fully by the UV drying device on the last color group. Print and apply primer, then enter the gold sweeping machine to sweep gold through the connecting device.

4 Features of gold sweeping technology

The gold sweeping technology has advantages in many aspects compared to several other gold-imitation processing technologies, and of course there are also shortcomings.

1) Compared with gold printing, current gold printing can use offset printing, gravure printing, flexo printing and silk printing, especially offset printing and gravure printing, which are relatively fast. The offset ink layer is thin and the metal gloss is not very good; although the gravure ink layer is thicker and the gloss is better than offset printing, the metal texture is not strong enough when printing on a large area, it is easy to deform when printing small prints and small lines, and the quality is not easy to control.

2) Compared with bronzing, bronzing, as a traditional imitation gold processing technology, has strong metal luster and metal texture, and is an indispensable processing technology for some high-end packaging. In this respect, it is more effective than gold sweeping. better. Although the quality effect of bronzing is good, most of it requires heating and consumes more energy. Registration is sometimes not easy, especially on small graphics and large areas of bronzing. The quality is not easy to control, the process is relatively complicated, and the cost is relatively high High, most bronzing equipment is slower and less efficient.

3) Compared with matte printing, matte printing has better metal texture and gloss, but the production efficiency is lower, and the waste packaging is not easy to recycle, which is not conducive to environmental protection. [next]

4) Advantages of gold sweeping technology The gold sweeping technology has a simple operation process, fast speed and low cost. No matter the thickness or area of ​​the picture, the better effect can be obtained.

After gold sweeping, the product has better metal grit feeling and light diffuse reflection effect, and the metal texture is more real, giving a visually obvious three-dimensional feeling, which is different from gold printing and bronzing.

The colors of gold sweeping are rich and colorful. In addition to the most commonly used gold, there are silver, red copper, green, graphite, tan, lemon yellow, peacock blue, and recently imitation diamond gold powder and widely used in Europe and North America. Laser gold powder. These gold powders have different particle sizes and can display a variety of unique effects.

Anti-counterfeiting effect: Because the imitation gold effect obtained by sweeping gold is different from gold printing, bronzing and matte printing, it is unique, not easy to imitate, and has certain anti-counterfeiting functions.

5) Disadvantages of sweeping gold

Although gold sweeping technology has very obvious advantages, it is not perfect.

The most important feature of gold sweeping is the formation of imitation gold effect in specific parts, but the single gold sweeping process is difficult to achieve the best metal gloss and texture at present. It is not as good as bronzing in some aspects.

It is not as convenient as printing gold on printing sheets that require large areas of imitation gold, and there is no advantage in effect. Therefore, gold sweeping is only a mid-range gold imitation effect processing technology, which has certain limitations, which limits its rapid development to a certain extent.

The requirements for the environment of the gold sweeper are very high, the temperature should be controlled at 22 ℃ ~ 25 ℃, and the humidity should be controlled at 50% ~ 55%, otherwise quality problems will easily occur.

Common faults in gold sweeping are sticky and dusting. The main reasons are: â‘  Too much humidity in the gold-scanning workshop or too high water content in the paper will cause the gold wiper to get wet and wipe clean; â‘¡The imprint of the printed matter is not dry, which will cause the gold powder to stick to the parts that do not need the gold sweep; â‘¢The viscosity of the primer on the part of the printed sheet that needs to be scanned for gold is not enough or the glue is not enough to cause powdering.

5 Conclusion

From the above analysis, it can be seen that although the gold sweeping technology still has certain shortcomings, its advantages are still very obvious, especially in anti-counterfeiting, metal texture and advertising effects. At the same time, the cost of sweeping gold is relatively low, and printing manufacturers can obtain higher profits. Although there are not many manufacturers currently using gold sweeping machines in China, with the continuous maturity of gold powder processing technology and gold sweeping technology, as well as the perfect combination with gold sweeping, bronzing and silk screen printing, it will be used in the domestic packaging and printing industry, especially in Cigarette bags, wine bags, and high-end pharmaceuticals, food packaging play a unique role.

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