Electromagnetic printing
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Electromagnetic printing was the main application technology of the Nipson press, which was invented by Bull in 1980 and commercialized in 1984. The printing technology consists of a set of small electromagnetic recording heads that produce magnetic latent images on the surface of the hard metal drum. After that, the toner is developed by magnetic toner, and the toner is adsorbed on the magnetic latent image portion. After being transferred to the paper surface, it is heated and fixed to form a fixed image. This printing is a new application technology for the printing industry.
First, the print engine
The printing engine is composed of several simple and reliable subsystems. The basic body of the engine is a roller. It is made of hard metal and is similar to the application of photocopying technology. The other subsystem is similar in function to other non-contact technologies, but in fact its structure is quite different. The surface structure of the printing cylinder is an electromagnetic hard layer which is electromagnetically placed on a magnetically soft material with a magnetic strength of approximately 500 oerst.
In fact, the surface of the drum is mechanically strong, and without the use of soft coating, the life of the drum is more than 15 million feet.
And electromagnetic printing can match different image lengths to meet the needs of printing applications, without having to change the diameter of the drum, just increase the speed of the printing engine.
The magnetic image on the drum can be demagnetized by the elimination rod each time it is rotated so that the drum can continue to accept new magnetic images.
Second, the recording head
The image recording station consists of an array of electromagnetic recording heads that are axially parallel to the drum. The processing is similar to that of a disk drive in a computer, and is specifically designed for electromagnetic printing applications. The first-generation recording head used in the early stage was used for vertical recording, and the coil did not change continuously during operation. Thus, a lower driving current of about 100 - 150 μA can be used, which can produce high magnetic efficiency. The lateral density can be made higher. It is impossible to use a traditional recording structure. This recording head has a density of 240 poles per inch to form 336 poles per square. The development of electronics has made the recording head of the second-generation electromagnetic printing machine better, that is, in order to exceed the 240dpi currently used, it is necessary to consider the use of collective recording components, combined with standard silicon micro-electric treatment and silicon electrochemical precipitation, so that the collection magnetic With the electromagnetic microstructure is made possible. The electromagnetic silicon recording head includes a silicon chip of one inch square. The recording head records electromagnetic for a high-density array and is positioned by a diode matrix on the chip. This new recording head can achieve higher print quality, better stability and higher speed recording head.
The function of the electromagnetic recording head is similar to that of a reflected beam in a laser copier, an LED in an electrophotography, or an ion card clamped in an electron beam.
Third, latent image and imaging
After the recording head is opened, a magnetic point is written on the surface of the drum, each magnetic point forms a permanent magnetic field to form a latent image, and the external magnetic field around the surface image of the drum is very low (maximum about 100 to 200 oersted), however The magnetic field shows a particularly high sharpness, which is due to the use of toner imaging.
The main advantage of electromagnetic printing is the permanent image. When the image is produced, many copies can be printed without re-writing. In fact, once recorded on the roller, it can be kept for a long time without magnetic interference. This feature is related to other non-contact printing technologies. different places. When the drum rotates past the developing station, a single set of toner fine particles is adsorbed on the magnetic image, which can reduce many problems of the conventional two-group toner, such as monitoring the concentration of the toner to the stretcher at any time. In fact, in the past, the problem of eliminating a single set of toner was to remove the toner after the image was developed by using a vacuum knife or a trimming pinhole, so that the excess toner was removed and a sharper image was formed.
Fourth, image transfer
Image transfer is based on 60% mechanical stress and 40% electrostatic power, resulting in a transfer efficiency of approximately 80-85%. The use of electrostatic power has a considerable relationship with air humidity in some respects. If you want to get the ideal transfer, the surface of the printed material should not have too high humidity. If the resistance of the toner is about 103 W / cm, the charge of the conductor is charged. The voltage is 500 - 1000 V, and the selected concentration is 1.1. The resistance can be maintained at 1012 W/cm. If you charge the toner first, the selected density value is 1.3 and 1.1, which can reduce the resistance of the paper to 1010 W/cm.
Fifth, the image is fixed
The method of image fixation is the same as that of any dry powder printing technique, except that it is dried at a high speed. When fixing, it is necessary to convert the toner into a semi-liquid state with radiant heat or xenon flash. In low-speed devices, heated rollers can be used, and in magnetic printers, radiant heat is used to fix the image. In recent years, the flash fixing method has been cited, which has the advantages of greatly reducing the temperature of the paper surface, and simultaneously reducing many problems caused by heat, such as reducing heat consumption, maintenance costs, and the like, which are very attractive. The next processing unit on the drum is the cleaning station, which removes the remaining toner that has not been transferred to the paper on the drum. In fact, a steel roller is used together with a scraper and a vacuum suction device to draw the toner into the bottle.
The final step is to remove the magnetic image on the drum, that is, to replace the bulb in the electronic copier and the high voltage pre-charged ring discharge line with a low voltage removal rod.
Sixth, commercial application of electromagnetic printing
Electromagnetic printing presses can be widely used in the printing industry. From text printing to traditional printing environments, reliability, simplicity, and low operating costs will be the advantages of the printing industry. The application range is very wide, such as: very high printing speed, wide variety of printable materials, simple mechanical structure and high durability. Unlike early printing techniques, electromagnetic printing guarantees a lot of room for growth in the future. Today's presses can print 800 pages per minute and can print 1,400 pages in the future. Nowadays, I am working on new technologies for multi-color printing and higher resolution. I believe that in the 21st century, this printing method will become the leading position in the printing industry, and complete high-speed printing operations for changing prints on different materials.