Troubleshooting of Portable CNC plasma cutting machines

9.5 CNC Controller Troubleshooting

Fault Symptoms Fault Check Fault Analysis Recommended Solutions
Suddenly breakdown in normal operation Always stop at the same position in every operation cycle a. Machining program at fault

b. CNC software at fault

Dispatch the software back to the manufacturer for professional troubleshooting.
The system still runs but the cutting torch stops abnormally along all axes or one axis. a The travel motor is locked.

b The travel motor fails.

Check if the machine is frozen and level enough.
The system still runs but the cutting torch does not move along one axis any more and gives no response to any keystroke, especially to the pause key. The machine operation is interrupted. a. Remove the interference and make sure the grounding wire of plasma power supply is connected to the machine.

b. Check if the motor(previous model) has isolation board or not.

c. If it is flame mode, check if the solenoid valve for cutting oxygen is given arc extinction.

Motor fails to run Check the system wiring. Loose connection or disconnection


Secure the connection.
Check the driver. Check for any alarm message or if the setting is correct or not. Change the setting of driver.
Check system setting. Check if the start speed is zero or too high, the speed regulation time is too short and the electronic gear or pulse equivalency is appropriate to be zero.


Suggest to record the original parameters before making any modification.
Check for axle problem and if the same model of motor is available.


Replace parts one by one to isolate the real cause to the problem. Replace the broken part.
Slow system response Check the power supply. Check if the output voltage of power supply is within the allowable range. Adjust the output voltage or replace the power supply for switch.
Check the system parameters for any error.   Suggest to record the original parameters before making any modification.
Travel limit alarm at power-on Check if any external limit switch is connected. Check if limit switches are functional and if loose connection or disconnection exists.


Secure the connection.
  If no external limit switch is connected, check the system if the current coordinate values are too high and out of the travel limit set by software. Check if the travel limit set by software is too small. Modify it to normal range.
In DIAGNOSE window, trigger the external limit switch. Check for any change with the corresponding input port.  
No response to keystroke or wrong key assignments Check the cable for keyboard.



Check if the keyboard is loosely connected or disconnected. Secure the connection.
The system is locked up in manual/automatic mode. Incorrect parameter setting.


  Record the electronic gear in system parameters and then press G, G and 3 in the system main window successively. Save the parameters in parameter setting mode. Restart the system and fill the recorded value of electronic gear into the corresponding position. Save the parameter and test the system performance.
No input/output Check the cables for input and output. Check if they are well connected. Secure the connection.


Check if 24V power supply is normal or not. Check the voltage of 25-pin port between Pin 24 and Pin 25.


Check the switching power supply.
Check the cables inside the system for any loose connection.   Secure the connection.
Blank screen


Adjust “+” key and “-” key at the upper right corner of keyboard for proper contrast and check for any screen display. If yes, adjust the contrast to normal display. Make readjustment.
If not, check the cables for LCD for any loose connection. Secure the connection.
USB transmission failure USB disk is not compatible with the system.   Try the USB disk of other model or brand.
Incorrect format of USB disk   Reformat the USB disk to FAT format.
Check the lamp indicator of USB port for any light. Check the cables inside the system for any loose connection; check the USB port for any foreign material and all the pins are in normal condition. Secure the connection and remove foreign material from the port.
The system returns to the main window after machining program is started. Replace the machining program and test running the system; initialize the system if any parametric problem.


If the problem is gone, it means that machining program has bug. Check the program.
The system can only machine straight line and fail to machine a circle.


Initialize the system if any parametric problem


  Initialize the system parameters.
Replace the machining program and test run again. If no more problem, check that machining program. Check the program or return it to the manufacturer for diagnosis.
Screen blinks when a solenoid valve is opened or plasma arc ignition is going on.


a. The power supply unit for plasma, CNC system and the enclosure of machine must share a ground wire that is 2mm thick at least in diameter and well connected to the ground.

b. Shielded cables must be used for the system input/output and the exposed part at the cable end must not be longer than 30mm.

c. The unused input end must be connected to 24V ground wire.

d. A 0.01uF capacitor should be used between the 24V ground wire and enclosure(shielded cable).

e. Use an isolation transformer(380V-220V) and as interference suppressor if it is possible.

f. Separate the operational power supply for high-power welding machine/cutting machine from that for CNC system.


Failure to save the program Failure to save the program.   After replacing batteries, press G, G and 3 in the system main window successively to format the program area.
No system output Check if 24V power supply is normal or not. Measure the voltage between Pin 24 and Pin 25. Check and replace the switching power supply unit.


Check if the four relays on the rear panel are reliably connected, if the relay operation is normal and if the contact is functional.  




Replug or replace the relays.



9.6 Common Plasma Malfunction and Trouble Shooting


9.6.1 Common Malfunction and Trouble Shooting

  Malfunction Reasons and Trouble Shooting
1 Penetration power shortage a.Cutting speed is much too fast.

b.Cutting torch inclination is too much large

c.Cutting steel is too much thickness.

d.Spare parts of Cutting torch is damaged.

e.Cutting current is too small.

f.Wrong air pressure.

2 Main Arc off a. Cutting speed is too slow

b. The distance is very large both cutting torch and steel.

c. Cutting current is much too strong.

d. The cable is broken.

e. The parts of cutting torch is damaged

f. Wrong air pressure

3 Too much cutting scrap a. Cutting speed is too slow.

b. The distance is very large between cutting torch and work piece.

c. The parts of cutting torch is damaged

d. Cutting current is not suitable

e. Air pressure is wrong

4 The parts of cutting torch have short lifetime


a. There are oil and humidity in gas resource.

b. Cutting steel is too thick.

c. Time of Starting Arc is too long

d. Air pressure is too low.

e. Assembly of Cutting torch is not suitable.

5 It is difficult for starting Arc. a. The parts of cutting torch is damaged.

b. Air pressure is wrong

6 AC indicator light does not shine 1. The switch of Main power supply keeps OFF. Opening the switch of main power supply.

2. ON/OFF switch of the power supply keeps the situation of OFF. The switch keeps the state of ON.

3. Bad connection between cutting torch and power supply.

First of all, the power supply switch keeps on the state of OFF, then check the cutting torch and power. Secondly, you should screw down or change it by your demand, but please don’t use any tools. Finally, open the switch to keep the state of ON.

4. Do not tighten the Protective Cup and Cutting Torch. Please check the Protective Cup, but you can not over-tighten and not use any tool to screw it.

5. Main cable fuse or the Circuit breakers is damaged. Check the Main cable fuse and branch Cable fuse and change it by instruction.

6. Build-fuse of this device is burned or loose. It is particularly necessary to check the input voltage and replace the fuse in accordance with C of the Chapter 5.04 If it is burned. The device must return the Service Center to repair which is authorized if the fuse is burned again.

7. The build-in parts broken. Return it to the authorized Service Center.

8. The actual input voltage and the device voltage does not match. Check the input voltage is right whether or not.

7 Power on, there is air flow, AC indicator twinkle 1. Torch switch is triggered(close) before turn on power supply. Loose torch switch.

2. Torch switch malfunction. Check it and replace it if necessary.

8 There is the air flow, but cutting torch doesn’t ignite when  triggered . AC indicator is on. 1.The system keeps the state of SET. The RUN, Rapid Auto Restart and SET switch keep the place of RUN.

2. Work cable is not installed well.


9 There is not any air flow, RUN/ Rapid Auto Restart/SET switch under SET position, the fan is running, AC indicator on and air indicator off 1.The air resource is not connected. Check the connect of the air.

2.The power supply can not operate because of the low air pressure.

Adjust the air pressure according to torch manual

3.Build component of the device happen to troubles. Return to repair or let the qualified technician to mend it.

10 The cutting torch do not generate arc, have air flow, AC indicator on, air ,temperature and DC indicator is off. Air pressure is lower than the minimum requirement of power supply.

The pressure will adjust up to 60-75psi/4.1-5.2 Pa.



11 The cutting torch do not generate arc, has air flow, AC and air indicators are on, but the DC and temperature indicators are off 1.The air pressure is lower than the maximum requirement of cutting torch(The maximum pressure of power supply operation is lower than that of cutting torch operation. To adjust the air pressure.


12 The cutting torch do not generate arc , no air flow, AC, air, DC indicators are on  1. There is no trigger box inside the cutting torch. Close the power supply and remove the protective cup, then install the torch ,cutting nozzle and protective cup. The ON/OFF switch of power supply keep the state of ON.

2. Protective cup of the cutting torch is loose. Check the protective cup and tighten it .

13 Cutting torch can not start arc, AC, temperature and air indicator are on,  DC indicator is off.


1.The air is blocked. Check the blocked air flow and rectify the condition.

2.The device is too hot. Cool it down at least 5 minutes.

3.The input voltage is too low. Check and connect the suitable input current.

4.Components inside device have troubles.The device has to return to the authorized Service Center.

14 Cutting torch can not triggered, AC indicator twinkle, air indicator is on, temperature and DC indicators are off. 1.The system keeps on the state of protection.(Component of cutting torch is missing or loose.) Open cutting torch trigger and keep the ON/OFF switch on the state of ON, then cut the main off switch and check the components of cutting torch, Replace it if necessary. To install the protective cup again and tighten it by hands. Please do not use any tools. Closing the main off switch, then keep the ON/OFF switch on the state of ON.
15 Even though the cutting torch switch do not trigger, the airflow also keeps the state of on-off cycle, AC indicator twinkle, air indicator is on, DC indicator is off Nozzle or electrode broken. Cut off power supply, uninstall protective cup, replace nozzle or electrode, make ON/OFF switch under ON position.
16 Can not cut, the cutting torch can ignite arc, has air flow and fan is running. AC, air and DC indicators are on, but the temperature indicator is off 1. Working cable and work piece has not connected well. Make sure the working cable connected well and connected to dry and clear place of work piece.

 2. Cutting torch trouble. The device has to return to the authorized Service Center.

3. Built in Components have troubles. The device has to return to the authorized Service Center.

17 Cutting torch can cut, but not deep enough. 1. Wrong input current control setting. Check and adjust it.

2. Cutting torch consumable is worn, check and replace it.

3. Connection between working cable and work piece is bad. Make sure the working cable connected well and connected to dry and clear place of work piece.

4. The cutting speed is too rapidly. Slow it.

5. Cutting torch on the work piece is dragged(The gas saver of cutting nozzle return road triggered).The power supply will automatically reduce the 40A if the cutting nozzle touched work piece when the setting parameter of output current is more than 40A. The cutting torch must  be moved out the work piece.

6. There are too much the oil and humidity inside cutting torch. The switch RUN/ Rapid Auto Restart/SET keeps on the state of SET,and holding the cutting torch at the 1/8 inch(3mm)of the tidy side. Watching the oil and humidity when operator cleans them, but pay attention not to trigger the cutting torch. The air need to filter again if there is the pollution.

7. The input powers supply have the problem of the fluctuation. Let the electrician check the voltage of input cable.

8. Components inside device has trouble.Return to the authorized Service Center.

18 The arc off during running, no arc after trigger torch switch again. 1.The power supply is too hot.(Temperature indicator is on). Cool the device down at least 5 minutes.

2.The fan blade is blocked.(Temperature indicator is on) Check and clean it.

3. The airflow is blocked.(Temperature indicator is on). Check the blocked airflow around the machine and change the blocked condition.

4. Air pressure is too low.(Air indicator is not on when the cutting torch triggered). Check and adjust the air resource according to requirements. Make sure the air resource at least 60psi/4.1Pa.(The lowest working air pressure of power supply is lower than that of cutting torch).

5.Cutting torch consumables worn. Replace the consumables.

6.Components inside device have troubles. Return to the authorized Service Center.



There is the dangerous voltage inside the device. Please do not look for the faults or repair it if the operator who didn’t be trained by the technicians about the inspection of the electronic component and the skill of trouble shooting.

The content of Operator Manual says common faults and trouble shooting. It is very helpful for solving many common faults of this system. The system has to return the Service Center which has been authorized to repair if the main complex components have some faults. You should operate in accordance with instruction.



Under normal condition, there will be a little air flow between protective cup and torch handle when operate torch. Don’t tighten protective cup too much, it will cause built in components damage.


9.6.2 Plasma Power Source Daily Care and Check

The actual maintenance frequency can be adjusted by the operation environment.

Check the machine after it work for 6 hours or Daily operation.

  1. To replace the cutting torch consumables if they are damaged or worn.
  2. To replace the cutting torch or the cable if they were damaged.
  3. Check the plasma power, twice opening power supply and voltage and flow rate.
  4. Cleaning the cable of plasma power and get rid of the humidity.
  5. To replace the input power cable and wire if they were damaged.

Check the machine after it work for 36 hours or every week:

  1. Check if the fan is formal and air current is enough.
  2. Operator must below out all dusty and filth form machine.



Please do not blow the air into power supply when to clean the machine. The metal particle will disturb the sensitive electronic component and cause of the damage of device.

Check the machine after it work for six months or 720 hours:

  1. Check the air filter, then clean and replace it by requirement.
  2. Replace the wire and hose if it is the leakage and flaw.
  3. Replace the switch if it is hit by arc or wornbadly.


Posted in CNC cutting machine technology.