1. First, check that the air source pressure is 0.55MPa, within the normal range, check the solenoid valve, rotate the manual knob, the air circuit is normally reversed, the cylinder moves and the stroke is sufficient, the material door can be opened, and the weighing can be performed again automatically, and It is possible to loosen even if the material cannot be automatically cut. Stopping the scale, power transmission, and starting the packer again, it's the same failure.
2. Through observation, it is found that the output indicator light turned on by control #4f7 on the PLC flashes quickly, and the output terminal is measured with a multimeter. There is indeed 24VDC output, but the time is very short, so it is judged that the fault is due to the solenoid valve air circuit commutation caused by insensitivity.
3. After replacing the solenoid valve, the packaging machine returned to normal, but the failure reappeared after three days, and then the solenoid valve was replaced. After two or three days, the failure reappeared. Confirm the quality of the solenoid valve is acceptable. Remove the solenoid valve for inspection.
It was found that there was rust powder on the reversing shaft, resulting in insensitive reversing. However, the opening time of the PLC-controlled material door is very short, and the solenoid valve cannot be completely reversed in a short time, which cannot be controlled. The material door is fully open for discharge.
The main reason for this failure of the pellet packaging machine is that although the gas source is relatively pure nitrogen, the nitrogen will still transport the rust through the steel pipe. The original gas filtration device was ineffective, causing rust powder to enter the solenoid valve, and the material door designed in the program opened for a short time, resulting in failure. After replacing the gas filter, the problem was completely solved.