Pad printing is a very simple printing process in which a graphic image on a steel intaglio or photosensitive intaglio plate is transferred to a substrate by a silicone rubber-made transfer head. Pad printing can be used for printing flat or various shaped objects, such as glass products, plastic products, metal products, watches, and electronic and optical products. Its main feature is that it can print irregular irregularities on the uneven surface. This is difficult or even impossible to achieve with other printing methods. The use of pad printing can be easily accomplished, and multicolor printing can be realized. This is an ideal printing method for the surface printing of instruments, equipment and some small products. In addition, the printing is stable and continuous. Even if it is printed for a long time, the printing accuracy will not be changed, and the drying procedure will be omitted and multi-color printing can be performed continuously.
There are mainly monochrome, two-color, four-color, six-color, and eight-color printing machines; they are divided into manual, semi-automatic, and fully-automatic types from the degree of automation. Currently, there are CTP systems. The printing machine makes the degree of automation further improved. Here mainly from the overall structure of the printing machine and some local key components on the current market, the main printing machine for analysis.
The main printing machine type
1. Manual type pad printer
The structure of this type of pad printer is the simplest. Some people think that such a machine should disappear in the market. In fact, until now, many high-end clocks and other equipment panels have been printed using such pad printers. Of course, this kind of machine will not appear in large-scale printing companies in general, but there are more applications in many small workshops. The shortcomings are very obvious, such as low production efficiency, once the print volume is very large, it is difficult to ensure the consistency of all the print quality, but it is easy to operate, small investment, so it is still very active in the market.
2. Open ink tank printing machine
The print head can be moved up and down, left and right, and there is a printing plate underneath it. The ink in the ink tank is scraped into the steel plate by the above squeegee device, and the printing head is in contact with the steel plate and inked. This kind of design scheme is simple and widely used in large printing presses.
3. Closed oil system
This system was considered in the past as a universal pad printing design. A Swiss watch company has used the system for 35 years. The ink is contained in a closed oil pan which can be moved parallel to the steel plate for ink supply. When the oil pan is directly above the steel plate, the ink can flow to the graphic part on the steel plate, and when the oil pan leaves, the ink scraper on the oil pan scrapes off the ink in the non-graphic part.
4. Wheel transfer printing machine
This structure is derived from the gravure design and is more suitable for printing roll-type or continuous sheet-fed substrates. The machine is mainly composed of a printing plate, an ink tank and a pad printing silicone roller. The roller type steel plate is immersed in the ink tank. When the printing plate rotates clockwise, the upper ink is scraped and scraped off; the printing roller is reversed. The hour hand rotates and presses against the steel plate roller so that the ink on the steel plate is transferred to the pad roller; finally, the pad roller contacts the substrate and the ink is transferred.
5. Hybrid printing machine
This machine was originally designed for ceramic printing, using a combination of pad printing and screen printing. Instead of using pad printing plates, the ink is screen printed onto the underlying silicone coating. Afterwards, the pad is in contact with the silicone layer to remove the upper ink and finally print onto the substrate. This structure synthesizes many advantages of screen printing and pad printing, such as printing a lot of screen printing surfaces that cannot be completed (such as a hyperboloid), and has stronger ink selectivity than screen printing.
6. Satellite
This pad printing machine is a multi-color printing press designed on the rotating plane, controlled by the central cam, up to 750 rpm, and up to 250 if printing four colors per hour. This machine is suitable for small and medium sized machines. Quantity.
The machine is mainly composed of two rotating platforms and central control components. One platform places the substrate and the other platform prints. This kind of machine is more suitable for companies that mainly receive foreign orders. Because the workload of these jobs is relatively small and multi-color, it is more cost-effective to use this model.
7. Pad printing machine with CTP system
In the field of printing, CTP is not new. At present, it has been widely used in offset printing and flexo printing. Even in the field of screen printing, CTP can be seen to be popularized. But for the pad printing industry, the application of the CTP system has only just begun. The CTP system is applied to gravure printing to ensure that users get digital image files and use lasers to produce high-quality gravure printing plates without the use of film, exposure equipment, and chemicals. Increased automation, improved productivity, cost savings, and high-fidelity imaging quality make gravure pad printing a clear lead over other existing platemaking technologies. Of course, this investment is a problem that many users first consider.
Other Accessories
From the structural point of view above, the major printing machine structures on the domestic and foreign markets are briefly analyzed. When considering the printing contents, the characteristics of substrates, and the amount of printing, etc., the first choice is the most reasonable model. In addition, you should also consider whether the printer supplier provides the following accessories. Of course, many accessories are selected by the customer.
1. Is there a print head cleaning device?
The automatic cleaning device of the printing head can quickly and conveniently clean the printing head, so that the ink delivery is more accurate and saves the manufacturer a lot of time. Of course, the device is not a necessity, and it is generally an accessory in a high-end machine.
2. Is there an ink pump
This device is mainly suitable for occasions where the ink type and color rarely change. In this case, a large amount of ink is stored in the ink pool, and the ink pump can be used to transfer the ink from the ink pool to the ink fountain of the printing machine, or to return the unused ink to the ink pool.
3. Is there a hair dryer
Since the printing ink mainly uses the principle of ink viscosity change to complete the ink transfer, the ink viscosity change is generated by the solvent evaporation in the ink. Therefore, if there is a compressed air device or a blower device, the volatilization of the ink solvent can be faster.
4 whether to provide online detection device
The on-line inspection device can check the minor changes in prints in real time and feed it back to the press control personnel in a timely manner, which greatly reduces the burden on operators and improves the quality of printing. The prices of these devices are declining, and most CD printing companies use online testing devices.
When purchasing a pad printer, many issues need to be considered. This paper focuses on analyzing the principle and features of various models from the perspective of the machine structure. Customers can compare and analyze the characteristics of the printed products. Of course, the selection of the printing press must take into account other aspects such as brand, price, and so on. This article does not deal with it. This requires negotiating with the printing press supplier, and conducting analysis and comparison, and finally making the right choice.