Common faults and troubleshooting methods for vacuum pumping system of offset printing machine
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The vacuum pumping device of the offset printing machine is composed of a high-speed direct-connected vacuum pump and a three-phase motor. In addition, there are accessories such as rubber pipes, solenoid valves, gas valves and pressure gauges.
The vacuum pump of the offset printing machine is composed of a stator, a rotor and a rotary disc. The rotor is eccentrically placed in the cylinder, and two rotor blades are inserted into the rotor groove, and the cylinder wall is pressed by the elastic force of the spring. Therefore, the inlet and exhaust ports of the stator are separated into two parts by the rotor and the rotor. When the rotor rotates in the cylinder, the volume of the intake port is gradually enlarged to inhale the gas, and at the same time, the volume of the exhaust port is gradually reduced, and the sucked gas is compressed and discharged from the exhaust valve, thereby achieving pumping. purpose.
There are two common faults in the vacuum pumping device of the offset printing machine: one is that the vacuum degree of the vacuum pump of the printing machine is reduced; the other is the problem of oil leakage of the vacuum pump.
1. The vacuum pump of the printing machine is insufficiently pumped, and the vacuum is reduced. It is often easy to cause the film surface of the film or the positive image of the laser printer output. The suction between the sulfuric acid paper and the PS plate is not tight, and the suction is not good. The PS version cannot guarantee the quality, and the text, lines, images, and dots are transferred to the printing plate to meet the requirements.
The quality of the offset printing vacuum printing machine depends mainly on two factors: First, whether the film surface of the photosensitive film is closely matched with the PS film, there is no slight gap, which requires the vacuum pump to work normally. The pumping rate is about 2~4 liters/secret. Secondly, when the PS version is exposed, the blue-violet illuminance of the whole glass surface on the periphery and the edge and the middle area is uniform, which is a measure of the performance of the offset printing machine. standard.
The reason why the vacuum pump of the plate-printing machine is insufficiently pumped and the degree of vacuum is lowered is:
(1) The rubber pipeline of the gas transmission leaks due to rat biting, aging, and rupture;
(2) The tempering and sealing of the elastic rubber sealing cloth pad of the printing machine frame;
(3) The rubber pipeline of the gas transmission is too long, and the gas consumption affects the vacuum degree;
(4) The amount of oil in the vacuum pump is insufficient;
(5) There is too much oil in the vacuum pump;
(6) The vacuum pump seal is worn and leaks and leaks oil;
(7) The oil supply hole in the pump is blocked or the oil supply is insufficient;
(8) Wear and damage of the exhaust valve;
(9) The rotary spring is broken or the like.
Accordingly, the ways to eliminate these failures are:
(1) Replace the damaged rubber pipe;
(2) Use tape or tape to stick the place where the elastic rubber seal cloth of the drying frame leaks. Pay attention to the maintenance every week. Wipe the rubber frame with glycerin once to prevent aging, keep the elasticity of the blanket frame and reduce the leakage of the frame. Gas problem
(3) The length of the rubber pipe for gas transmission should not exceed 2 meters, avoiding the consumption of gas on the pipeline.
(4) Add new vacuum oil to the center line of the oil mark;
(5) Replace the fresh vacuum oil;
(6) Replace with a new seal or re-adjust the assembly;
(7) Clean the oil inlet hole;
(8) Replace the new exhaust valve piece;
(9) Replace the new rotary vane spring.
In addition, the gas path should be kept clean, and there should be no dust or any foreign matter on the inner wall of the pipe. It is often cleaned with a thin wire to keep the hose pipe unobstructed.
At the same time, it is necessary to pay attention to the positive and negative rotation of the three-phase motor of the vacuum pump. The installation of the phase circuit of the motor will be reversed. The air pump of the vacuum pump may be blown. At this time, the phase of the motor wiring must be changed to make the vacuum pump inhale.
2. Offset printing machine vacuum pump oil leakage is a common problem. The main reason is that the pump shaft of the vacuum pump and the oil seal device parts have been used for many years, resulting in the wear of the seal ring. When the oil spill is serious, the vacuum oil that has just been injected will leak a large amount of oil after a while, which pollutes the environment and affects the normal operation of the vacuum pump. Reduce the coils or replace with a new oil seal when servicing. When disassembling the assembly and repair, the sealing gasket is coated with a sealant to prevent oil leakage and air leakage. In addition, the gasket of the vacuum pump tank connection is damaged, which may also cause oil leakage. The solution is to replace the gasket. Do not add excessive amount when filling the vacuum pump oil. Just aim at the oil level line. If the vacuum oil is added too much, the vacuum pump will splash and remove oil when it is working.
Keep the pumping system function intact in your daily work. The vacuum pump should be inspected once a week. The oil level should always be aligned with the oil level line. New vacuum oil must be replaced during one year of operation.
The vacuum pump and the motor are generally installed in the back position of the printing machine. The environment around the vacuum pump and the motor should be kept clean frequently to reduce dust and debris from sticking to the pump body and the motor. At the same time, it is necessary to be able to ventilate and heat the vacuum pump. It must be opened and repaired once a year.
From the suction hole of the plate printing machine to the rubber hose of the vacuum pump nozzle, the working time is easy to be sucked and damaged, and should be replaced in time to prevent air leakage.
The surface and back of the glass table must be kept clean. Clean it with a soft brush before wiping it, then wipe it off with absorbent cotton or gauze and alcohol.