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Failure of the pneumatic system of the CNC system: the prevention of low pressure, leakage and stuck problems of the tool changing mechanism
Troubleshooting and maintenance guide for CNC pneumatic systems

In numerical control (CNC) equipment, pneumatic systems are one of the most crucial yet often underestimated systems. If the gas supply is unstable, it may cause the following risks:

  • The tool change mechanism is stuck
  • Spindle clamping failure
  • Shaft brake release failure
  • Incomplete cleaning of chips and poor spraying effect
  • Pressure or actuator failure alarm

This article will cover the following:

  • Common failures of pneumatic systems
  • How to diagnose leaks and pressure drops
  • Ensure the clean and stable operation of the pneumatic system

 

The role of pneumatic systems in CNC equipment

function
illustrate
Change the knife
Pneumatic cylinder or rotating arm release
Spindle loosening knife
The handle is released by air pressure
Hatch opening and closing assistance
Pneumatic piston control (for automatic opening and closing of the hatch)
Blow or spray
Clean up chips to cool the tool area
Brake release
The brake of the shaft motor is released by air pressure

 

⚠️ Common faults in CNC pneumatic systems

symptom
Possible causes
The tool change mechanism is stuck
Low pressure or jamming solenoid valve
"Low air pressure" alarm
The regulator is set incorrectly, the air leakage, and the air supply is insufficient
The spindle cannot be released
Insufficient air pressure
There is a noticeable hissing sound in the control cabinet
Leaking internal trachea
The solenoid valve does not work
Faulty coil or no air pressure reaching the valve

 

How to diagnose CNC pneumatic system failures

Step 1: Check the input air source

  • Confirm that the air pressure is as low as 5.5-6.5 bar
  • Use dry, filtered compressed air (ISO 8573 is recommended)
  • Install a pressure gauge in front of the air inlet of the CNC equipment

Step 2: Check the air dryer with filter

  • Drain the water separator daily
  • Replace clogged coalescing filters
  • If the equipment is equipped with an air lubricator (which may be installed in older equipment), it needs to be inspected

Step 3: Detect leaks

  • Spray soapy water on the joints to see if bubbles form (if there are bubbles, it indicates a leak)
  • Use an ultrasonic leak detector to detect weak leaks that are difficult to hear
  • Tighten the quick plug connector and inspect the trachea for cracks

 

Automatic tool changer (ATC) lag troubleshooting

issue
Workaround
The robotic arm does not rotate
Check the pneumatic cylinder, solenoid valve and limit sensor
The tool cannot be clamped/released
Check whether the pressure and sensor signal at the broach lever are normal
Random ATC alarms
Solenoid valve coils overheat or malfunction
Air leak sound while ATC is running
Worn cylinder seals or damaged O-rings

Important: Before serving, be sure to turn off the power to the equipment and depress the air pipe.

 

CNC pneumatic system maintenance checklist

task
frequency
Drain the water separator
daily
Clean or replace the filter
monthly
Check the condition of the hoses
monthly
Fastening joints and clamps
quarterly
Replace solenoid valves (if performance is reduced)
Every 2-3 years

 

Fanuc (Fanuc/ Haas system pressure alarm reset technique

  • Make sure the pressure switch wiring is well connected
  • Bypass Test (Diagnostics Only): Jumper the switch input
  • After confirming that the programmable logic controller (PLC) detects normal air pressure, the tool change operation can be resumed
  • After the stable air pressure is restored, the alarm is reset

 

Suggestions to ensure the stable operation of the CNC pneumatic system

  • Use a specialized trachea with 5 micron filtration accuracy
  • Installation of air dryers (refrigerated or adsorption dryers optional)
  • When the equipment is installed, label the solenoid valve and mark the direction of the gas pipe
  • Record all pneumatic-related alarms to track fault patterns
  • Avoid using coiled hoses that are too long, and prefer fixed tubing

 

summary

Pneumatic systems may seem simple, but if not properly maintained, they can lead to downtime of the entire equipment.

To prevent failures in advance, you need to:

  • Make sure the compressed air is dry and clean
  • Regularly maintain regulators and filters
  • Keep an eye out for leaks that indicate a malfunction

Clean air = stable operation. Paying attention to the maintenance of pneumatic systems is crucial.

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