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What is a pad printer? What is the difference with silk screen?
What is a pad printer? What is the difference with silk screen?
Pad printing technology is a special printing technology that has just been introduced to China in the 1980s. Because of its obvious advantages in printing on small-area, concave-convex products, it has made up for the shortcomings of screen printing technology. Therefore, it has developed very rapidly in recent years. . In the early 1990s, with the further opening of the Chinese market, a large number of foreign-funded enterprises with traditional industries such as electronics, plastics, gifts, toys and other traditional industries entered the Chinese market one after another. Pad printing technology and screen printing technology became the main decorative methods. According to incomplete statistics, the application of pad printing technology and screen printing technology in the above-mentioned industries has reached 27%, 64%, 51%, and 66% respectively.
Pad printing process and screen printing technology have many similarities, such as wide adaptability to substrates; there are many kinds of inks, pad printing ink and screen printing ink can basically be used in common; it can be done very easily by changing fixtures and printing plates Printing of different products, etc. Therefore, on many occasions, pad printing technology and screen printing technology are inseparable and play an important role in special printing together. Because pad printing technology and screen printing technology are so close, most printing experts classify it as the field of screen printing. According to the investigation, there is no specialized institution to study pad printing technology, and there is also a lack of institutions that specifically investigate the distribution of pad printing technology in the market. Many data involving pad printing companies cannot independently reflect the actual situation of pad printing technology. .
However, there are many differences between pad printing and screen printing, such as: the ink transfer process is obviously different; the structure of the printing press is different; the types of substrates are also very different. In fact, the differences between them are far greater than the similarities. The reason why we are used to tying them together is because they face a common market. In this common market, pad printing cannot be separated from screen printing, and screen printing cannot be separated from pad printing. It is difficult and unnecessary to strip pad printing from the screen printing industry, but if you want to understand the current status of pad printing technology, you cannot look at it from the perspective of the screen printing industry.
We attribute all paper-related printing to mainstream printing. Mainstream printing has always been highly valued by the theoretical community. In recent years, screen printing has received attention. The primary reason is that its advantages in paper printing are discovered rather than people paying attention to it. The advantages in terms of material range, such as: screen printing is used to complete the UV partial glazing of the paper, special UV inks such as coral ink, ice ink, and wrinkle ink are better than printing, and flexographic printing has better results.
Pad printing technology is not so lucky. Today, when all printing processes are exploring and using their respective advantages to merge, pad printing technology still maintains its independent identity. The connection between paper and pad printing technology is still blank, but pad printing Technology does not stop its rapid growth, because the area where pad printing technology is good at cannot be accomplished by any other printing process. The prosperous industry in the Pearl River Delta strongly supports the 18% annual growth rate of the pad printing industry. The employment opportunities created by industries related to pad printing technology have also been paid attention to by government departments every year.
On the whole, the technical content of the pad printing process is not high, and it is very difficult to continue to develop in the case of high production costs in developed countries. Therefore, the pad printing industry is shifting to developing countries with low labor costs such as China. It is an inevitable trend. At present, in addition to a few foreign companies that also manufacture highly automated pad printing production lines, most companies have moved their production bases to China. This is a historical opportunity for China. What is the level of development of pad printing in China? Where is the latest development? The superficial insights of this article hope to give readers a little help.
1. Plate making
Plate making is the prelude to printing. Traditional printing is achieved by first transferring the graphics and texts on the original to the surface of the printing plate. As far as pad printing is concerned, it should be a combination of intaglio plate making technology and corrosion sign technology. . Gravure plate-making technology has now developed to electronic engraving and laser engraving. Sign corrosion has also gradually eliminated acid etching technology, but pad-printing plate-making is still stuck in a very old process, which is related to the conditions of pad printing technology itself. The first is that the cost of pad printing is relatively low, and the cost of electronic engraving and laser engraving is too expensive for ordinary enterprises to afford. Many companies have proposed electro-erosion technology, but no modern warfare company's technology can guarantee that the corroded printing plates can be used for printing. The operation process of acid corrosion is easy to master and low cost. Although there is serious environmental pollution, it is still used by most enterprises.
Two, pad printing steel plate
The use of pad printing steel plates in the pad printing process dominates. 100% oil pan type pad printers and 16% ink cup pad printers use thick steel plates with a thickness of about 15mm; another 77% oil cup type The pad printing machine uses thin steel plates with a thickness of 0.25mm and 0.5mm. Whether it is a thin steel plate or a thick steel plate, the plate making process is the same. The substrate used is also roughly the same. The steel plate must have a fine structure and the surface finish must be sufficiently high. The former ensures the neatness of the edges of the corroded graphics and text, thereby ensuring the integrity of the dot structure, so that the sharpness and color reproduction of the printed graphics can be achieved to the greatest extent; the latter ensures the cleanliness of the ink and the printing durability. The thick steel plate used on the ink cup pad printer requires higher surface tolerance. Excessive surface tolerance on the one hand accelerates the wear of the ink cup, and on the other hand, it is also related to the sealability of the ink. It is used on the oil pan type pad printer. If the steel plate is to be used on the oil cup machine, it is necessary to ensure a higher surface finish and a lower flatness tolerance.
The thin steel plate has better flexibility, so the degree of squeegee cleanliness is easy to guarantee, but this is related to the manufacturing accuracy of the substrate supporting the thin steel plate. The surface tolerance of the substrate is not up to the requirements, and the ink will leak during the sliding process of the oil cup and the steel plate. Another factor is the manufacturing accuracy of the sliding guide shaft of the oil cup, such as surface roughness and fit tolerance, which is reflected in the index of the assembly level of the whole machine. How to control the parallelism tolerance between the guide shaft and the steel plate is very important. From this point of view, it is more difficult to manufacture thick steel plate ink cup pad printers.
Three, resin version
The resin plate has not been applied to the pad printing process for a long time, but it has received attention. The resin plate is mainly made of nylon photosensitive glue, cast on the surface of the zinc plate, similar to the resin plate used on the self-adhesive trademark. Nylon has very good abrasion resistance, and can withstand the repeated friction of oil cup or scraper after photosensitive curing. The advantage of using the resin plate is that it is easy to obtain extremely fine dots. When printing fine small items, the resin plate is the first choice. If the manufacture of ink cup pad printers reflects the manufacturing level of an enterprise, it will be more difficult to manufacture pad printers that use resin plates. After all, nylon photosensitive glue is a polymer material. When the substrate supporting it has poor manufacturing accuracy, pad printing It is not easy to complete general printing confidentially. The surface state of the polymer material is very fine, a slight defect will seriously affect the printing quality.
Four, plate making process
At present, the production of pad printing steel plates is mainly corroded by using nitric acid solution and ferric chloride solution added with protective agents. The acid odor used for corrosion is very unpleasant. The formation of nitric oxide and nitrogen dioxide is very harmful to the human body. The development of the steel plate after corrosion is mostly using a chemical solvent with hydrogen peroxide as the main body, which also has certain effects on human skin. damage. Therefore, it has long been banned in European countries. They began to use resin plates or laser engraving to make plates. It should be considered a relatively new idea to use the powder-free corrosion machine that corrodes the zinc plate to corrode the steel plate. Some manufacturers have successfully trial-produced. This method greatly reduces environmental pollution. Resin plate making is much more environmentally friendly and much safer. The resin plate uses nylon photosensitive glue, which can be developed by sprinkling. With the popularity of digitalization, it will not take too long to use digital methods to produce pad printing resin plates.
Pad printing inks are still mainly solvent inks. Pad printing inks have been replaced by screen printing inks, and the effect is also very good. At present, most ink manufacturers treat pad printing inks and screen printing inks as a series of production. . However, there are many problems when screen printing inks are used in the pad printing process. MARABU took the lead in developing pad printing inks. In contrast, special pad printing inks dry faster and more stable, and have better thixotropy. The ink layer of the pad printing process is relatively thin. In order to obtain more eye-catching handwriting, the purity of the pigment in the ink is higher and the fineness is finer. These are the difficulties in manufacturing the pad printing ink. At present, in addition to MARABU's special series of printing inks, the printing inks of DUJO of Germany have also begun to occupy a certain market. In addition, there are few dedicated pad printing inks. The British COATES ink, which is known for producing screen printing inks, has a large market share as an alternative to low-end products.
The printing ink market is large and profitable, attracting many domestic companies to research and develop. The domestic ink production has recently seen a very rapid development. The more prominent ones are Zhongshan Zhongyi Ink Co., Ltd., Hangzhou Kewang Ink Co., Ltd., and Shenzhen Miramar Ink Limited company etc.
UV inks have long been popular in the field of screen printing, and now the last bastion is that UV pad printing inks cannot be replaced by screen printing inks like solvent inks. The production process of UV screen printing ink is much simpler. As long as the ink permeability is good, the printing effect is easy to guarantee, while UV pad printing ink requires the transfer of the acrylic resin monomer in the ink to the pad printing rubber head. Well, generally speaking, the pad printing head is made of silicone rubber. The affinity of the unit monomer of silicone rubber and acrylic resin is very poor, and the transfer efficiency will be affected. On the other hand, the solvent ink must be improved by adding necessary fillers. The trimming and neatness of the print, however, such fillers cannot be added to the UV pad printing ink. In addition to affecting the curing efficiency, the transparency of the ink will be difficult to ensure: when developing UV pad printing inks, ensure the color of the pigment High concentration but good transparency and good transferability are difficult. These problems have now been overcome. MARABU, a professional manufacturer of pad printing inks, has fully introduced their TPC series of UV pad printing inks to the market.
The successful development of UV pad printing ink has solved some problems that have been plagued by people. For a long time, the gloss and abrasion resistance requirements of computer keyboard text have not met customer requirements. The use of UV ink has become the goal pursued by many manufacturers. However, printing UV ink with screen printing has a lot of trouble, and now it is adopted The transfer of UV ink is completed by pad printing, which can easily meet customer requirements. The characteristic of the pad printing process is to generate pressure from directly above the substrate to complete the printing. Then, the printing process can easily prevent the shaking of the product.
Six, ink cup type pad printer
China has developed rapidly in recent years. The advantages of Western countries in traditional industries have been gradually replaced by China. In order to protect the development of their industries, some European and American countries have formulated very strict market access systems to restrict Chinese products from entering the EU market, such as requirements Manufacturers of products exported to the EU comply with ISO14001 environmental protection standards. Objectively speaking, the technical barriers of European and American countries are very detrimental to Chinese companies. However, in the long run, the pressure on Chinese companies from these systems may force us to continuously adopt new technologies to improve our country. The technology and safety level of the product. In the field of pad printing technology, the use of more environmentally friendly technologies must attract the attention of Chinese enterprises.
The solvent in the solvent ink volatilized into the air will be captured by the human respiratory system, and most of them are harmful to the human body. This is generally resisted by Western society whose main demand is to protect the safety of life. European and American countries have successively formulated strict Regulations to control the use of solvent-based inks. Germany first produced a pad printer that cut off the way of solvent volatilization to control the volatilization of the solvent. This is the ink cup pad printer. The main difference between it and the traditional open pad printer is the difference in ink supply.
The ink supply part of the ink cup type pad printer uses the ink cup containing ink and solvent that is reversed on the pad printing plate to continuously supply ink to the printing plate. Since the volatilization of the solvent is controlled, the viscosity of the ink during use And the change of the drying speed tends to be stable, which is more conducive to obtaining uniform printing quality. The stability of the gondola is the most commendable advantage of the ink cup pad printer. The effective reduction of solvent volatilization also improves the working environment of operators. It is worth pointing out that the manufacturing level of the ink cup pad printer reflects the manufacturing level of an enterprise. At present, there are only a handful of domestic companies that manufacture ink cup pad printers with very good quality.
Seven, the application of UV pad printing technology
The advantages of ink-cup pad printers are favored by companies that are applying for or have obtained ISO14000 environmental management certification. However, we have to admit that ink-cup pad printers have not absolutely prevented environmental damage. A part of the enclosed solvent in the oil cup achieves a dynamic balance inside the oil cup, and the other part must be transferred to the surface of the product along with the pigment and resin. The solvent will eventually volatilize into the air. The main function of the oil cup is to remove the solvent in the ink. The volatilization becomes an effective volatilization. Whether it's the ink installation process or the cleaning process, we still can't rule out the volatilization of solvents. Therefore, the ink cup type pad printer will sooner or later face the challenge of UV pad printing technology. UV technology is an environmentally friendly technology that has become popular since the 1980s. It uses a photosensitive ink with acrylic resin as the main component to replace the long-standing solvent ink. In the field of offset printing, gravure printing, flexographic printing and screen printing, UV technology is gaining popularity. In contrast, UV pad printing technology is long overdue.
The reason why UV technology progresses slowly is that the development of UV inks is facing some difficulties, as mentioned above. Any new technology will face various difficulties, but no difficulty can stop the development of UV pad printing technology. As more companies pay attention to UV pad printing technology, it will be sooner or later that UV technology will become popular in the field of pad printing.
Because of the successful development of UV inks, the main obstacles of UV technology have been removed. Other related technologies can be put into production with only slight modifications. For example, the products involved in pad printing are relatively small, and it is easy to set up a compact curing device. The pre-processing, printing system and curing device integrated pad printer should be on the agenda. It is believed that the recent years will be a critical period for the further improvement and maturity of UV pad printing technology.
8. New highlights of pad printer technology
The development of pad printers towards automation should be the consensus of the industry. This is the fundamental way to improve production efficiency and reduce costs. It is also an inevitable requirement for the transformation of pad printing technology from labor-intensive industries to technology-intensive industries.
At present, the most commonly used pad printers with a high degree of automation are the pad printers with turntable conveying. The printing process is completely automatic, but the process of placing and removing the workpiece is still manual. The degree of automation loves to affect. The vast majority of production companies still have imperfect countermeasures in considering the quality problems that occur in the printing process. Even such a pad printer must face many challenges in order to complete the real automated printing.
General purpose automatic pad printers are relatively rare, but there are still many surprises in automatic pad printers targeting specific products. For example, an automatic pad printer for printing CDs, and an automatic pad printer for printing wine bottle caps. The automation of the pad printing machine essentially means the automation of the product conveying, while the pad printing and printing part has little change. A variety of new technical information has broadened our horizons, the infiltration of other printing technologies has given us new inspiration, and customer interviews have made us passionate about the realistic requirements of pad printer automation. The text below may not represent the development direction of the pad printer, but can you reject its freshness?
Common mistakes and countermeasures in the process of screen printing