1. paper feeding device
1. Paper feeding device of sheet-fed printing machine
Sheet-fed printing machines are fed by hand and automatically fed by mechanical devices. Hand paper because of the speed and correctness of the existence of some general problems, is now rarely used. The automatic paper feeding device uses machinery to feed paper, which can save manpower, reduce labor intensity, improve productivity, ensure the correctness of paper feeding and improve printing quality. There are two kinds of paper feeding methods of automatic paper feeder, friction type and pneumatic type.
The friction type relies on the friction wheel to separate the surface paper from the longitudinal stack. This paper feeding method, the structure of the machine is relatively simple, but because the paper is divided by friction, it is easy to make the print paste, the paper is dirty, the thin paper is easy to wear, the paper separation effect is not accurate enough, and the speed is low, the continuous paper feeding method is adopted, the labor intensity is high, and it is rarely used now.
Pneumatic paper conveying is carried out by using an air pump to blow compressed air between several sheets of paper on the paper pile by a blowing nozzle, and then the paper on the surface of the paper pile is sucked up and separated from the paper pile by a paper suction nozzle. According to the conveying mode, it can be divided into intermittent type and continuous type.
Intermittent paper feeding means that there is a certain distance between the paper and the vertical, while continuous paper feeding means that the front edge of the latter vertical is overlapped under the rear edge of the previous paper, and the adjacent two sheets of paper are partially overlapped, so there is sufficient positioning time, more accurate positioning, and it is also conducive to improving the printing speed.
It is a schematic diagram of the action coordination of each part of the continuous paper conveying device. First of all, the paper on the top of the paper pile is blown loose by the loose paper blowing nozzle, the paper separating suction nozzle moves downward to suck the upper paper and lift it up and back to prevent double sheets from being sucked, which is conducive to inserting the paper pressing blowing nozzle into the blowing, pressing the paper pressing nozzle presses the second paper and blows it to separate the upper and lower paper, the suction nozzle moves backward to suck the paper, the paper separating suction nozzle stops, releases and lifts upward, at this time, the paper pressing nozzle stops blowing and leaves the paper pile. The paper feeding nozzle moves forward to output the paper, completing the conveying of a piece of paper. The paper is sent to the rule device for positioning via the input board. The high-speed paper feeder can transport nearly 200 sheets of paper per minute.
2. Paper feeding device of web printing machine
The roll paper printing machine is characterized by high printing speed and large output, and is generally used for double-sided printing. Its paper conveying device is to output the paper tape and feed it to the printing device through the paper transfer roller.
The paper conveying device is generally equipped with 1 to 3 rolls of paper. When the first roll of paper is about to be printed, the second roll of paper immediately enters the paper feeding position from the preparatory position. The paper conveying device is composed of a braking mechanism and a paper receiving mechanism. The braking mechanism is mainly to ensure that the paper tape is tightened during the printing process, so that the paper tape always maintains a certain tension in the working state, so as to achieve the purpose of uniform paper feeding. At the same time, when the grade tape is broken or the printing speed is reduced, the paper tape is prevented from automatically unwinding. The paper splicing mechanism is to realize automatic paper splicing without stopping the machine when replacing the new roll paper, and to ensure that the speed of the new and old paper tapes is equal in the paper splicing process.
2. printing device
1. Printing part
There are various methods in printing. The difference is that the purpose of adding printing pressure is to transfer ink from the printing plate or blanket to the printing material. The pressurized part consists of the printing plate cylinder and the impression cylinder. In the offset printing method, it consists of the printing plate cylinder, the blanket cylinder, the impression cylinder and its auxiliary equipment, all of which are called printing parts. In the printing method, there is also an electrostatic printing method in which the ink is attached to the printing material by electrostatic pressure with physical pressure, and a squeegee method in which a squeegee is used for printing in screen printing.
2. Device version
Letterpress, lithography, intaglio due to their different plates, plate loading methods are also different. In letterpress printing, the lead or resin plate.
Install it on the plate table or plate roller with a needle plug or double-sided adhesive tape. Lithographic printing mainly uses aluminum-based PS plate or zinc plate, the plate is rolled into a cylindrical mounted on the plate cylinder, in the bag plate operation, offset printing rotary machine and offset printing sheet machine plate loading method is different. In gravure printing, the plate has been made directly on the copper plate cylinder and printed with mechanical installation.
3. Inked part
There are a series of related devices from the ink fountain to the uniform attachment of ink to the layout. These devices are similar in lithographic and letterpress printing, but different in intaglio printing.
On lithographic and letterpress printing machines, a small amount of ink is transferred from the ink fountain roller to the ink transfer roller, and then to the ink string roller and the ink leveling roller to make the ink uniform and then ink is applied to the layout by the ink roller. As an accessory device, there is a stirrer.
1-ink fountain roller; 2-ink transfer roller; 3-half ink roller 04,6-ink shimming roller; 5-ink roller
Gravure printing, printing plate cylinder in the ink fountain, high-speed rotation, scraping by the blade to remove excess ink. There are three methods: submerged roller mode, ink roller mode and spray mode, and more spray modes are used in high-speed printing.
4. Water supply
In offset printing, it is very important for the layout to maintain proper moisture. Therefore, there is a water supply part on the printing press, which consists of a water bucket, a water bucket roller, a water transfer roller, a water string roller, and a water roller. The bucket roller and the string roller are made of metal, and most of them are chrome-plated, and the water transfer roller and the water roller are covered with water glue velvet.
Gravure printing inking method: 1-water bucket; 2-water bucket roller; 3-water transfer roller; 4-uniform water roller; 5-water roller;
In offset printing, the micro-adjustment of water supply is a very difficult technology. For this reason, high-speed multi-color printing machines and offset printing rotary machines have adopted new devices. One is a brush roller type water supply device, as shown in Figure 5-5. It replaces the water transfer roller with a brush roller. The water bucket roller rotates continuously in the water bucket to transfer water to the brush roller. The brush roller also rotates continuously. Small water droplets are thrown onto the water string roller, and the water is evenly transferred to the printing plate through the water roller. One is Dalgren water supply device, as shown in fig. 5-6, which cancels the water feeding roller. the water bucket roller rotates in the water bucket. the water conveying roller contacts with the water bucket roller and the ink feeding roller to transfer the moisture on the water bucket roller to the ink feeding roller, and then the ink feeding roller transfers the moisture to the printing plate. the rotation speed of the water conveying roller is about 20 ~ 25% of the ink feeding roller. changing the rotation speed of the water bucket roller can adjust the water feeding amount.
5. Accessory devices
The auxiliary devices in the printing device include regular parts, folding parts on the web rotary machine, paper belt shock absorbers, etc. These can be operated manually or remotely or automatically.
3. drying device
After printing, the ink should be dried on the printed matter as soon as possible to prevent the back from being dirty and affecting the quality of the printed matter,
Therefore, various drying devices have been designed to dry the ink in a very short time.
1. Hot air drying device
The use of thermosetting ink in the rotary machine, which contains a large amount of solvent, the use of gas flame or hot air can make the ink dry in an instant, these dryers and printing machines linked to start printing to start ignition, stop printing when the fire, can prevent the paper from burning. Some immediately after heating through the cooling roller for cooling, can also play a role in accelerating drying. Now the web offset printing rotary machine more use this drying method.
Gravure printing using hot air or hot drum type
2. Infrared, ultraviolet drying device
The use of infrared lamp drying device, printed paper tape through the infrared lamp is equipped with a drying chamber, with a blower to blow air from the lower side of the drying chamber, exhaust gas from the upper side, ink due to the role of infrared radiation will quickly solidify, drying, only a small amount of resin ink is absorbed, therefore, the gloss of the ink is greatly improved.
The printing ink used in the ultraviolet drying method is very expensive, and it has the characteristics of instantaneous drying, no solvent, and odorless, which can meet various needs of printing.
4. delivery device
1. Sheet, roll paper delivery device
The paper delivery part of single-sheet printing is composed of three ways: the paper-turning output device, which is used on simple machines for manual paper feeding, has a slower speed, and the chain-type output device, which is composed of a chain-type paper delivery device and is used more on low-speed printing machines. Paper delivery
The device is now used in many forms. During high-speed printing, the paper delivery pile can automatically descend, and there is an automatic paper management device on the paper delivery table.
2. Hinge device
After the roll paper is printed, when it needs to be rewound, there is a rewinding device, and the roll is wound by friction on the winding roll with the roll core. Generally, the printed grade belt enters the folding device for processing.
It is an accessory device of the web printing press. The printed paper tape is continuously processed to complete the cutting and folding processes and become a bookmark that meets the process requirements. It is longitudinally cut and folded by the angle plate (as shown in Figure 5-8). Then it is sent to the cross-cutting and cross-folding device, and after being folded by several folding rollers, it is sent out by the bookmark conveying device. According to the different requirements of printing, different folding methods can be used.