JL5205 offset press failure
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First, JLS205 offset printing machine
Fault phenomenon: not increasing the maximum speed.
Analysis and overhaul: According to the experience of previous maintenance, most of the low-speed running relay (JAJ) is caused by the poor opening of the normally open contact for transmitting the acceleration and deceleration signals. However, this time, the secondary contact was tightened with a screwdriver (so that the moving and static contacts were closed well), but the effect of increasing the speed (indicating that the relay was working properly) could not be seen. Use the multimeter DC voltage to measure the output of the last stage of the control circuit - the phase shift limiter, while increasing the given voltage, it can be seen that its output value can follow the increase. This shows that there is no problem with the control circuit. Look at the output values of the two regulated power supply boards (in the table) (for the operating voltage of the control circuit): -15 volts and +15 volts, respectively, also normal; this seems to indicate: three-phase AC power supply voltage (380 volts) ) is also normal, otherwise it will reduce, rectify and stabilize the output voltage value should be reduced? However, after further comparison and analysis of the two, it is more likely that the problem will be hidden in the three-phase AC power supply voltage (because the operation of the control circuit has been detected is normal). Use a multimeter AC voltage to detect the three-phase voltage on the main AC contactor (ixc) contacts in the power distribution cabinet: found to be very unequal (some phase is 380 volts between phase and phase is only 120 between phase and phase) Volt), indicating that the three-phase AC power supply voltage has a phase loss or undervoltage output. Close the gate. Unplug the three porcelain plug-in AC power fuses on the power distribution board and find that the fuse of one of the phases has been blown, which causes the current phenomenon: no work on the small current circuit (regulated power supply circuit) The effect is still to make the output stable and normal positive and negative 15 VDC power supply voltage, and make the control circuit work normally; and the operation of the high current circuit (thyristor DC main circuit) has a great influence on its output Seriously insufficient, and the speed of the machine is not increased at the highest speed. After the phase fuse is replaced, try again: troubleshooting.
Second, JLS206 offset printing machine
Fault phenomenon 1: During normal power-on, the machine suddenly depresses itself, and its water-transfer and other circuits also stop working.
Analysis and overhaul: From the point of view of the phenomenon of the fault, it should be caused by a short circuit in the control circuit to which the 2ZK air switch belongs. After testing, its total insurance - 4A spiral fuse burned! All control lines were tested with a multimeter resistance file, and no short circuit was found. After switching to a new insurance test machine: press the bell, jog, low speed operation, increase and deceleration, etc. (main drive) running functions; press the "auxiliary power" button, 4 sets of water transfer ink circuit All resumed operation; but when the "I pump" button was pressed, the fault reappeared - the insurance was broken! This shows that the fault is in the circuit of the "I pump" (the strange thing is: the circuit was detected with a multimeter resistance file, and no short circuit was found)! Power off. No trace of the burnt odor of the contact and coil of the AC contactor of the circuit was detected, and the short circuit was not found by detecting the parts with the multimeter resistance file. What is going on here? After further analysis, it is considered that the fault point may still be hidden in its coil, because the fault is caused by pressing the button of the "I water pump" - the AC contactor coil. [The possible reason is: the coil is internally Short circuit, but not in the cold state; but only in the hot state - can not withstand the impact of current after the impact. This is really a rare phenomenon! According to this analysis, after switching to a new AC contactor, try again: all the running functions of the machine are restored to normal!
Symptom 2: Start the machine, but the oil pressure will not rise.
Analysis and overhaul: In the test machine, the indication in the oil pressure gauge can only rise to "3". This is obviously farther than if it could rise to "5" in normal times. According to the experience of previous maintenance, such failures are caused by one or the following reasons: 1.
The travel switch in the pressure relay is damaged, so that it cannot transmit the signal voltage (by the contact of the AC contactor in the power distribution cabinet after its operation) to the lubrication solenoid valve and make it work - draining the oil, thus making the oil pump only The idling will cause the oil pressure to rise; 2.
The oil pressure device in the pressure relay is damaged (the inner rubber gasket is cracked or the piston is not moving due to excessive sludge in the cylinder), so that the bending rod top travel switch cannot be pushed;
The oil pump is not working well (the speed is not high) or the oil circuit has oil leakage, which causes the oil supply to drop sharply. Power off. Open the machine wall panel, check that there is no oil leakage at the joints of each oil pipe and each pipe joint; remove the pressure relay, use the multimeter resistance gear to detect the normalization and disconnection of the stroke switch, then remove the oil pressure part and find the piston There is some sludge on it, clean it, assemble it and put it back in the machine. Test machine: the oil pressure is still not up; and the valve core of the lubrication solenoid valve is repeatedly pressed with a screwdriver (manually operated), and no reaction is observed. (If the oil supply to the oil pump is normal, repeatedly pressing the valve core can cause it to cause Intermittent oil discharge causes the oil pressure to rise gradually)! This shows that the problem is in its fuel supply system! In order to confirm this, after the power is cut off, the rubber output pipe of the oil pump is disconnected from the oil inlet pipe of the machine, and then the output pipe is aligned with the fuel tank, and then the test machine: the oil pump has a small amount of oil, and the hand is pinched The output tube also feels that the bulging degree and the vibration amount of the inner flow oil are not large; then the surface of the oil pump is touched by hand, and the temperature is not high [the same as the previous oil pressure does not rise (the oil pump idling), the surface temperature is higher. ], touch the surface of the motor by hand, the temperature is not high (if the motor has a problem, its surface temperature should also be higher). It seems to be normal. But I think there should still be problems. Then put your hand to the side of the fan blade of the motor and feel the amount of air blown by the inner blade - not big! So the epiphany: It must be that the three-phase winding of the motor has a problem or the three-phase voltage added is insufficient, and the speed of the oil pump that is linked with it is reduced, thus the phenomenon that the oil supply amount is sharply reduced! Power off, open the junction box of the motor, use the multimeter resistance file to detect the resistance of the three-phase winding is normal, indicating that the motor has no problem. Test machine: The voltage on the three-phase winding of the motor is 380 volts with a multimeter AC voltage file, which is also normal. However, according to the fact that the wind blown by the fan blades was small by hand, it is considered that the motor or the voltage applied thereto is still problematic. After the power is turned off again, use the small wrench to further tighten the respective wiring screws on the three-phase winding one by one, and find that two of the nuts are not tightened, resulting in poor wiring contact failure. Re-tighten it and cover the box, then connect the oil pump output tube to the machine's oil inlet pipe, and then test the machine: the sound of the oil pump works immediately becomes larger, and the output tube is pinched by hand and the inner flow is obviously felt. The bulging degree and vibration of the oil are both increased; the indication in the oil pressure gauge has gradually increased from "0" to "5", at the same time, the pressure relay operates (and through the AC contactor in the power distribution cabinet) Pull-in - the voltage transmitted from its contacts makes the lubrication solenoid valve work - draining oil, after the oil pressure drops (under the operation of the oil pump), it quickly rises to the specified pressure and then drains the lubrication solenoid valve. Reciprocating. The failure that the oil pressure could not rise was eventually ruled out.