The company has introduced a Manroland UNISET 78 high-speed rotary printing production line with two semi- commercial printing towers, four newspaper printing towers, two folding machines and eight paper feeders. Among them, the paper feeder corresponding to the semi-commercial printing tower is the Enmichi MP14 paper feeder. In the process of actually using the paper feeder, the author found that there would be no rotation of the rotating arm and no pre-press tension failure during printing, which seriously affected the printing production and the quality of the printed products. Below, the author analyzes these two faults and proposes solutions for peer reference.
Fault 1: Rotating arm flip alarm
1. Rotating slip ring resistance is too large
(1) Failure analysis
During normal operation, the rotating arm will suddenly stop rotating after turning an angle, and the operation screen of the paper feeder will display an alarm. The two indicators of the T53 inverter that controls the rotation of the rotating arm change from green to red. The initial guess was that the motor that caused the swivel arm to flip was faulty, and after replacing it with the same motor of the same model feeder, it was found that the fault still exists. Later, it was found that the frequency of the failure occurred when the paper feeder did not put the paper roll, but after the paper roll was placed, the frequency of the rotating arm increased during the lifting process. Therefore, it is preliminarily determined that the failure is caused by the excessive resistance of the rotating arm.
(2) Troubleshooting
After investigation, it was found that the gear of the gearbox was flexible and there was no dead point, so the focus was shifted to the rotating slip ring. When the rotating slip ring is eliminated, it is found that when the compressed air entering the rotating slip ring is blocked, the rotating arm rotates normally, and once the compressed air is added, the rotating arm will frequently alarm. After disassembling the rotating slip ring, it was found that due to the moisture contained in the compressed air, the friction between the sealing ring and the inner cavity of the rotating slip ring after the addition of compressed air would increase sharply, resulting in an excessive load and finally driving. The inverter whose swivel arm is turned over alarms due to overload. After the sealing ring is wiped dry and grease is applied, the installation and debugging are carried out. It is found that after adding compressed air, the rotating slip ring can be easily moved with both hands, and the rotating slip ring is mounted on the machine and tested, and the fault is eliminated.
2. The main power switch auxiliary contact is in poor contact
(1) Failure analysis
When working, the rotary arm flip alarm is displayed again on the operation screen of the paper feeder. First, according to the previous steps, the factor of excessive resistance caused by the rotating slip ring was eliminated, and then the inverter that controlled the rotating arm was replaced, and the fault still existed. After comparing the working conditions of the same type of paper feeder, it was found that there was a problem with the DC voltage supplied to the inverter.
(2) Troubleshooting
The DC voltage of the normal paper feeder is 600V, and the DC voltage of the faulty paper feeder is below 380V, so the T26 DC power module is replaced, but the fault still exists. The T26 DC power module was carefully studied, and the enable signal of the DC voltage of 24V on the T26 DC power module was found to be missing. The signal is provided by the auxiliary switch of the main power switch. The auxiliary contact is inspected and found to be in poor contact, resulting in the loss of the enable signal of the DC power module T26 and the DC output voltage being too low. After replacing this auxiliary contact, the fault is eliminated.
Fault 2: No prepress tension during printing
The quality of printed products is closely related to the size of pre-press and post-press tension. Unstable pre-press and post-press tensions can cause prints and wrinkles, and can cause paper breaks in severe cases. The following two types of faults often lead to unstable prepress tension, which in turn affects print quality.
1.B251 encoder failure
(1) Failure analysis
In the startup phase of the printing press, it was found that the prepress tension value displayed on the control panel of the printing press was zero. Checking the components related to the prepress tension, and found that the B251 encoder mounted on the prepress tension measuring roller had no output signal, so the preliminary judgment was made. The B251 encoder has failed.
(2) Troubleshooting
First, replace the B251 encoder and restart the press. It is found that the prepress tension value displayed on the control panel of the press is still zero. Check the output signal of the B251 encoder and find that everything is normal. Then, carefully study the operating instructions of the printing press and find that the printing machine needs to reset its position after replacing the B251 encoder. That is, when the printing machine is stationary, find the setting option of the “Maintenance†menu on the display, press “Settingsâ€. The tension adjustment minimum position setting box is more than 3 seconds, the current position value of the B251 encoder can be stored in the PLC, and the press control screen will immediately display the current position value of the B251 encoder. After setting the current position of the B251 encoder and then starting the printing press, it is found that the prepress tension value displayed on the control panel of the printing press is normal.
2.B166 safety relay failure
(1) Failure analysis
After solving the fault of the B251 encoder, it was soon found that the prepress tension was again unstable. After troubleshooting the B251 encoder according to the previous steps, the fault still could not be solved. The initial guess may be that the B166 safety relay has failed. When the electrical cabinet is turned on, we find that the error indicator (ERR) of the B166 safety relay is blinking, indicating that the relay has failed.
(2) Troubleshooting
First, a B166 safety relay of the same type was replaced. After restarting the switch, it was found that the error indicator of the newly replaced B166 safety relay was still flashing. After careful study of the manual of the B166 safety relay, it was found that a reset should be done after replacing the B166 safety relay. When the power supply of the paper feeder is turned on, press and hold the ENTER button on the B166 safety relay for 3 seconds. After the B166 safety relay is reset, its error indicator is turned off, the power is turned on again, and the prepress tension is restored.
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