Trouble Shooting Of Pneumatic Directional Valve In Feeding Part Of Cutting Machine

- Jun 08, 2020-

The failures of the reversing valve of the cutting machine include: the valve cannot be reversing or the reversing action is slow, the gas leaks, and the electromagnetic pilot valve is defective.


(1) The reversing valve cannot be reversed or the reversing action is slow. Generally, it is caused by poor lubrication, springs being stuck or damaged, oil or foreign matter jamming the sliding parts, etc. In this regard, you should first check whether the oil mister works normally; whether the viscosity of the lubricant is appropriate. If necessary, change the lubricant, clean the sliding part of the directional valve, or replace the spring and directional valve.


(2) After a long period of use, the directional valve of the cutting machine is prone to wear of the spool seal ring, damage to the valve stem and valve seat, resulting in gas leakage in the valve, slow movement of the valve, or failure to switch normally. At this time, the sealing ring, valve stem and valve seat should be replaced, or the directional valve should be replaced with a new one.


(3) If the inlet and exhaust holes of the electromagnetic pilot valve are blocked by debris such as oil sludge, the seal is not tight, the movable iron core is stuck, and the circuit is faulty, etc., it can cause the reversing valve to be unable to reverse normally. For the first three cases, the sludge and impurities on the pilot valve and the movable iron core should be cleaned. Circuit faults are generally divided into control circuit faults and electromagnetic coil faults. Before checking the circuit failure, the manual knob of the reversing valve should be turned a few times to see if the reversing valve can be reversed normally under the rated air pressure. If it can be reversed normally, the circuit is faulty. During the inspection, the voltage of the electromagnetic coil can be measured with a meter to see if it reaches the rated voltage. If the voltage is too low, the power supply in the control circuit and the associated travel switch circuit should be further checked. If the directional valve does not commutate normally at the rated voltage, you should check the solenoid coil connector (plug) for looseness or improper contact. The method is to unplug the plug and measure the resistance of the coil. If the resistance is too large or too small, the electromagnetic coil is damaged and should be replaced.