How to troubleshoot CNC power supply issues

Start at the source

It’s funny, but when most technicians start diagnosing a machine problem, the first place they look is to see if it’s plugged in. That may seem elementary, but it’s the sign of a professional. It’s troubleshooting 101. It follows that if the power isn’t right, nothing downstream will be either and if a power supply isn’t right, the entire CNC machine will suffer.

How does a CNC power supply function

The main job done by a power supply is to convert electrical voltage from one source to a modified level of power used by a device. In other words, the power supply “conditions” electricity so that it can flow in the right amount, at the right time, and do it consistently. Power supplies are used preventing power surges from reaching sensitive electronic equipment. They are also used as a part of safety protocols in emergency shut-off routines. Some power supplies act as backup batteries in case of unexpected power outages.

Power supply issues can cost you, so take evasive action!

Even CNC machines utilizing Artificial Intelligence (AI) are still machines and, as such, they require power to think and function. Uneven power distribution or diminished electrical flow through a power supply relay results in time-consuming and cost-elevating breakdowns. Inspection and maintenance are the best offense against a downtime defense.

Where to start looking for power supply problems

Power Supplies in CNC machines come in many different configurations and capabilities. Some machines use a variety of power supply modules that are divided among the different mechanical and electrical systems. Many machines utilize multiple power supplies connected to a variety of machine functions like lights, automated door locks, and other non-essential machining activities. Here are a few areas to investigate if you suspect power supply issues:


  • Input line damage or disconnect. As stated earlier, sometimes the power supply gets unplugged and plugged back in incorrectly.
  • DC Motor malfunction. Over time, the brushes and other components contained inside the motor windings can deteriorate and become damaged. This can place a higher than normal load on electric circuits, damaging power supplies.
  • Emergency Stop button or system failure. The big red button gets jammed down too hard and the power supply it serves gets damaged. This can short-circuit the system’s actuation hardware and send out an intermittent electrical signal.
  • Relay board deterioration. Most CNC machines operate in harsh environments which can cause sensitive electronic equipment to wear out or disintegrate. Cleaning and inspecting printed circuit board power supply connections is a good way to avoid downtime.

“Testing…testing 1, 2, 3…”

When you go to the theater for a live performance, the first person you see on stage usually goes out to test the microphone. That’s a good example to follow when it comes to CNC machines and their power supplies. Small supply or large, complex, or simple, it doesn’t really matter. Due to the importance each power supply carries toward keeping a CNC machine producing, no effort should be spared keeping all power supplies operating at peak efficiency. Scheduling preventative CNC maintenance together with routine testing will keep a CNC machine in the game for a long time.

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