Inkjet plate making equipment technology
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With the increasingly serious environmental conditions, the green and environmental protection trends of the printing industry have become the consensus of the whole society. From recycled paper to soy ink, more and more new technologies and processes are being applied to the printing industry. As a key part of the electronic material “materialization” in the printing process, the HW16 toxic waste liquid generated by this process can only be disposed of by passive methods such as concentration and third-party containment, and the cost is high and the detoxification effect is poor. The emergence of inkjet plate-making technology has fundamentally solved this problem. The pollution-free and non-emission advantages of the plate-making process will surely become the mainstream of future development.
Inkjet plate making adopts inkjet method to print and solidify functional ink on the surface of printing plate. How to ensure the shape and positional accuracy of ink dot becomes the focus of plate making equipment, and the ink path system and nozzle control directly related to it are guaranteed printing plates. The key to quality. From a functional point of view, the inkjet plate making equipment consists of four parts: the main frame, the ink path system, the nozzle control, and the auxiliary system that ensures the stable operation of the equipment.
Main frame
The main frame is the bearing foundation of the plate making equipment, which determines important performances such as the operation mode, imaging speed and accuracy of the equipment. From the current point of view, the main frame of the plate making equipment mainly has three ways: platform type, outer drum type, and traditional paper feeding type. Each of these methods has its own advantages and disadvantages.
Platform type
The platform type is the most mature frame structure for inkjet plate making equipment, and the inkjet plate making equipment with better performance adopts this structure. The so-called platform type, that is, the main body of the device is a flat plate bearing platform, and the nozzle module is suspended above the platform for reciprocating motion, and the relative translation of the platform is used to realize the two-dimensional scanning of the entire surface of the nozzle.
The platform structure is very compatible with the format of the plate material. Basically, as long as the plate is not larger than the size of the plate, the plate can be prepared, and the plate loading efficiency is high, and the manual plate can be completed in a few seconds. At the same time, the loading accuracy of the plate is much higher than other methods. The compatibility of the flatbed inkjet plate making equipment with the nozzle is also the best of several ways and can be applied to almost all nozzle combinations.
However, since the platform is horizontally placed in practical applications, the size of such devices is too large, and the processing of large-format platforms is difficult and the equipment cost is high.
2. Drum type
Drum type is widely used in traditional laser plate making equipment, and is divided into outer drum type and inner drum type, but the inner drum type is less applied in inkjet plate making equipment. In the outer drum plate making process, the printing plate is wrapped on the outer surface of the drum, rotates with the drum, and the nozzle moves along the direction of the roller busbar to realize scanning of the entire printing plate.
Because the printing plate can be curled, the shape of such an inkjet plate making device is relatively compact, and the reciprocating motion of the nozzle is avoided, and the ink path system is more stable.
However, since the surface of the drum is covered with the plate material, the eccentricity of the mass is likely to cause an imbalance in the rotation of the drum. Moreover, the current nozzle orifices are arranged in a planar array, and the surface of the nozzle and the roller cannot form a gap, which is easy to cause the shape and position deviation of the ink dots. If a part of the linearly arranged orifices is selected, the efficiency is low, so Drum equipment is less adaptable to inkjet platemaking techniques.
3. Traditional paper feeding
Most inkjet printers on the market use this structure, but in inkjet plate-making equipment, because of the lack of reliable positioning during the feeding process of the plate, the imaging accuracy is not stable enough, and the current high-performance inkjet plate-making equipment This structure is no longer used.
Ink system
The ink path system generally consists of a nozzle, an ink supply system, and a nozzle maintenance system. The printhead is a key component in the transfer of ink to the print base. The performance of the printhead determines the plate making speed and plate quality. The main parameters of the nozzle include the number of nozzles, ignition frequency, print resolution, and ink drop volume. Among them, the number of nozzles and the ignition frequency determine the plate making speed. The more nozzles, the higher the ignition frequency, the faster the plate making speed. The print resolution and drop volume determine the size of the base dot on the plate, directly affecting the fineness of the image. Excellent performance nozzles also have good ink latitude, stable working condition and long service life. With the growing development of inkjet technology and market-oriented customer needs, small ink droplet inkjet printing technology is also rapidly increasing. In inkjet plate making technology, in order to achieve higher plate making accuracy, the ink drop volume usually needs to be below 10 pL.
The ink supply system is an "artery" that connects the ink to the spray head and continuously supplies ink to the spray head while the device is in operation. The system is generally divided into a gas path portion and an ink path portion. The gas path portion is usually composed of two modules: a negative pressure ink supply and a positive pressure ink supply, wherein the negative pressure ink supply module is responsible for providing a stable negative pressure to the nozzle to balance the ink with its own gravity to ensure the formation of ink in the nozzle. The perfect meniscus improves the stability of the inkjet. To maintain a good print state, the nozzle must have a continuous ink supply and a stable ink supply pressure, especially in high-speed and large-format inkjet operation, which requires higher performance of the ink supply system. The components of the ink supply system not only need to have high cleanliness and reliability, but also good air tightness.
The maintenance of the nozzle is critical to the stability of the equipment. The influence of ambient temperature and humidity, abnormal operation, air bubbles and ink during the use of the equipment may cause slight blockage or oblique spray of the nozzle. Therefore, the cleaning system of the nozzle is a guarantee for its normal operation. The system integrates the functions of bubble elimination, positive pressure squeeze cleaning, mechanical scraping and protective liquid cleaning nozzle.
Nozzle control
In the inkjet plate making system, the dots on the printing plate are composed of a plurality of ink dots, and the shape and position of each ink dot affect the molding of the final dot. How to effectively control the position and shape of the ink dot is a priority. weight.
Position accuracy control
Inkjet plate making uses a two-dimensional motion mode to position the nozzle at a specified coordinate and perform ink drop ejection. Since any mechanical motion method has inherent accuracy errors, in order to solve this problem, accuracy compensation measures are generally adopted: first, use high Accurate position calibration equipment, such as laser interferometer, performs differential calibration on two-dimensional motion coordinates, compares actual running distance parameters with theoretical values, and forms a set of differential compensation data; then, the set of data is input into motion control software. When controlling the two-dimensional movement of the plate making equipment, the integral calculation is performed to calculate the actual running distance, and the nozzle is accurately sent to the specified two-dimensional motion coordinates for ink ejection. This precision compensation measure can reduce the single-step two-dimensional motion accuracy error of the plate making equipment from 5 micrometers to less than 0.5 micrometers, and the cumulative error is reduced from 50 micrometers to less than 3 micrometers.
2. Shape accuracy control
The shape of the ink dots ejected by the nozzle is affected by factors such as ink fluency and viscosity, and the properties of the ink mainly change with fluctuations in ambient temperature and humidity. The shape accuracy control system needs to collect the operating environment parameters of the equipment in real time, adjust the inkjet force of the nozzles according to the change of the temperature and humidity of the environment, so that the image size and shape of the ink droplets on the printing plate are consistent.
auxiliary system
The auxiliary system is a non-negligible part of the overall equipment. The plate positioning module, the plate monitoring module, the upper plate and the receiving module, and the user interface are all indispensable components of the inkjet plate making equipment, and the stability of the plate making quality. The ease of use of the device is directly related to it.
In recent years, with the maturity of inkjet technology and precision control technology, inkjet plate-making equipment has made breakthroughs, and its speed and precision have gradually reached or exceeded traditional plate-making equipment. Under the general trend of increasing environmental protection, inkjet plate-making technology will surely lead the printing industry into a green and digital era.