Analysis and elimination of vacuum pumping failure

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Analysis and elimination of vacuum pumping failure of sb1150 type plate printer

the plate printer used in our factory is sb1150 type vacuum plate printer produced by Shanghai printing equipment factory. The main features of this machine are:

1 It is made of square tubular steel. The upper printing frame is equipped with 8mm thick double-sided polished transparent glass, which is supported by long tension springs and hinges on both sides to form a replica structure

2. According to the requirements of the printing process, the lower frame must be equipped with a lattice rubber pad, which is made into a shape slightly higher than the drum in the middle. There are 8 compression springs under the lower frame platen for support, so that the rubber pad can naturally cling to the glass of the printing plate. The frame is equipped with a lightweight compression device, which is specially used to compress the upper and lower frames

3. The printing machine adopts the automatic control of secondary air extraction, slow air extraction in advance, and then rapid air extraction to ensure the quality of printing

4. A set of automatic printing workflow is adopted. When the half power of the gallium iodide lamp is maintained, as long as the frame is put down, there is a cycle to automatically complete the printing process. If you have entered the cycle and need to stop working, you can stop the electrical automatic cycle through the switch on the panel. It is very convenient to use. It can be controlled automatically or manually to start and close the vacuum pump and gallium iodide lamp exposure

working principle of plate printer. Sb1150 type plate printer when the zinc plate, PS plate, resin plate and other printing photosensitive plates are loaded into the sb1150 type plate printer frame, with the help of the sealing effect of the surrounding edges of the lower frame elastic rubber cloth pad and the upper plate glass frame, the vacuum pump of the plate printer pulls out the air between the glass frame and the rubber cloth pad, presses the layout of the printing plate by relying on the atmospheric pressure outside the frame, and then uses the iodine gallium lamp ultraviolet light to irradiate and expose, From the time of zero adjustment, the printing plate printing work is realized

plate printer is one of the necessary equipment for offset printing. The quality of plate printing depends on the following two factors:

1 Whether the vacuum pumping system of the plate printer works normally. Whether the film surface and sulfuric acid paper carbon powder surface are closely matched with the photosensitive film surface of other printing plates of PS plate

2. When gallium iodide lamp, xenon lamp, purple fluorescent tube and other light sources are exposed, whether the illumination on the whole panel is uniform, and whether the illumination in the middle and around is consistent and uniform is the standard to measure the performance and quality of the printer

the most common fault of the offset vacuum printer is that the film surface of the film, the carbon powder surface of the sulfuric acid paper and the photosensitive film surface of the PS version are not closely matched enough, and the air pumping is not solid, which will seriously affect the printing quality. Because the vacuum pumping can not reach a certain vacuum degree, the air leakage phenomenon is serious, especially for the electric four-color film with the drying line. If the pumping is not solid, the drug film surface of the film cannot be closely absorbed and matched with the PS version photosensitive film, and the small dots, thin lines and fine layers of the PS version will be lost. The main reason is that there is a gap between the film surface of the film and the photosensitive film of the PS version, which is not compact and solid. During exposure, the void of the image and text points of the PS version is tilted and cannot be closely closed on the photosensitive film of the PS version. If the iodine gallium lamp is exposed from above, the points of the void and the false places will be exposed and the photosensitive film will be decomposed by light. After the automatic and manual development process of the PS version, the weak points of the void contact and the image and text will be lost

the most common fault of the offset printing machine is that the vacuum pump is not strong enough. The whole machine of the pressure testing machine made by Jinan new era Gold Testing Instrument Co., Ltd. is mainly composed of 4 parts: the main machine, oil source, control cabinet and digital display meter. When printing, the PS plate is not in close contact with the film of film, sulfuric acid paper and carbon powder. There are many reasons for the formation. When encountering faults in this area, we should comprehensively analyze the causes of the faults and treat them differently, so as to eliminate the problem of insufficient vacuum pumping

1. There are two types of vacuum devices. First, the vacuum device of the plate printer includes a high-speed direct connected vacuum pump and a motor, that is, the motor and the vacuum pump share a rotor, and the speed of the motor is synchronized with the speed of the vacuum pump. Second, there is a device that separates the motor from the vacuum pump, and the energy of the motor is transferred to the vacuum pump by the V-belt. The offset press has been used for a long time, and the V-belt is damaged, relatively easy to slip, and the V-belt is elongated and deformed, which will affect the transmission of power. The reduction of the rotating speed of the vacuum pump per minute will affect the vacuum degree. The amount of air pumped is small, the suction is not solid, and the printing quality is poor

2. All gas circuits shall be kept clean, and the inner wall of the pipeline shall be free of dust, fibers, sundries and foreign matters, so as to prevent blocking the gas circuit and affecting the extraction, so as to keep the pipeline unblocked. In the process of vacuum pump pumping, the inner wall of the gas path is easy to be blocked by debris. During maintenance, it is necessary to take out the dirt with thin iron wire in time, so as to cultivate civilized production, cleanliness and hygiene as a good habit

3. The rubber cloth pad of offset printing machine and the rubber around the edge frame of elastic sealing rubber are aging, damaged and air leakage, resulting in inaccurate air extraction. The rubber cloth pad and elastic sealed rubber frame of the printing machine will have the disadvantages of aging, cracking and desulfurization when the rubber products encounter light, heat, acid and alkali, and chemicals. Any article also has a service life. In daily work, when the rubber cloth pad and elastic seal rubber frame are damaged and cracked, we can use rubber adhesive (to repair the rubber adhesive in the tires of cars and bicycles) to meet the growing market demand. First, polish the damaged rubber with a wooden file, remove the oil stain, and then apply a layer of rubber adhesive on the damaged part, After compacting with heavy objects for a period of time and bonding firmly, it can be used for printing

4. The pipeline of the plate printer, especially the rubber pipe closest to the air outlet of the vacuum pump, is most likely to be sucked by the vacuum pump, causing the damage of the air pipeline. The effective way to prevent the rubber pipe from being sucked is to install several springs with the same diameter as the air pipeline in the rubber pipe. In this way, whether the rubber pipe is pumped by vacuum pump or the rubber pipe bends at the corner, it will not be sucked, deformed, damaged or leaked

5. Vacuum Figure 2 stress-strain curve of PLA polyurethane: the left figure shows thermoplastic PLA polyurethane; The right figure shows the thermosetting polylactic acid polyurethane pump. The direction of motor rotation should be the same as the direction of arrow on the air pump. The wrong rotation direction of the motor is caused by the reverse phase of the three-phase power connection. As long as the line position is changed, the rotation direction can be changed. The rotation in the same direction as the arrow direction of the vacuum pump is air extraction, and the reverse direction is air blowing. Avoid the phenomenon of vacuum pump blowing when printing. The blowing is easy to make the suction between the film and the photosensitive film of PS version not solid and tight, and there is a gap, resulting in quality problems

6. Selection of vacuum degree of air extraction. When the vacuum pump pumps air to the selected value, the vacuum pump automatically stops pumping. When the vacuum degree in the air chamber decreases, the vacuum pump automatically starts pumping air to a certain value of vacuum degree. When the negative pressure gauge (vacuum pressure gauge) reaches the range of 300 ~ 650mm/hg, the gallium iodide lamp can be opened for exposure. If the negative pressure gauge is broken, it should be repaired and replaced to ensure that the indicator needle is sensitive, accurate and properly programmed

in addition, the plate printer, like other printing equipment, must be properly maintained frequently in order to be in good working condition for a long time. Therefore, the following points need to be done:

① maintain the integrity of the function of the air extraction system. The vacuum pump should be checked once a week. The vacuum oil level should always be aligned with the oil level line. All oil must be replaced after one year of operation. ② The frame of the blanket shall be wiped and moistened with glycerin once a week. When the machine is not in use, the blanket shall be padded on the glass table, which shall be covered with a cloth curtain to prevent dust and debris from entering. ③ The surface of the glass table must be kept clean. When wiping, first clean it with a soft brush, and then wipe it with degreasing gauze and anhydrous alcohol. ④ The lamp curtain, which is used to block the scattered UV light and avoid exposure to human skin and eyes, is composed of two layers of cloth, which is a white polyester cloth, which plays the role of reflecting light. There is a layer of red velour cloth on the outside to block out ultraviolet rays. The inner layer will affect the effect of reflecting ultraviolet rays due to yellowing over time, dust, oil, dirt and other reasons, resulting in an increase in exposure time. At this time, it is best to replace a layer of white polyester cloth. (text/WangXinCheng)

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