CNC machine down: what to do in the first hour

When a CNC machine stops in the middle of a job, the pressure is to get it running again immediately. The first hour decides whether the repair takes a morning or a week. Here is what to do, in order.

1. Make it safe

Press the emergency stop if the machine is in an unknown state. If there is smoke, a burning smell, exposed wiring or a hydraulic leak, power the machine down and lock it out. Nothing below matters more than this.

2. Record before you touch

Take photos of:

• The alarm screen, including any secondary messages
• The position display
• The program and line number that was running
• The part and fixture, especially after a crash

Write down what the operator saw and heard in the minute before the stop. Noises, smells and the last operation are often the best clue a technician gets.

3. Do not clear what the technician needs

Alarm history, error logs and parameter screens help diagnosis. Avoid clearing them. Do not change parameters to make an alarm go away. If you are not sure whether a parameter backup exists, ask before anyone experiments.

4. Check the simple things

These cause more downtime than people expect:

Check	Why
Air pressure	Tool changers and clamping depend on it
Coolant and lube levels	Low levels trigger alarms and damage
Door and interlock switches	A loose switch can stop everything
Main power and phase	Supply problems mimic drive faults
Control battery warnings	Low batteries can lose positions and parameters

Only check what is safe for your team to check.

5. Gather the machine details

A technician will ask for make, model, year, control type and software version, plus serial number for parts. Having it ready saves a phone call.

6. Decide how urgent it really is

Be honest about urgency. “Machine down, customer shipment Friday” and “running but losing tolerance” lead to different scheduling. Technicians plan around it.

7. Call the right technician

Technicians specialise by control and builder. A Fanuc specialist may not be the right person for a Heidenhain control. Ask directly whether they work on your exact control generation and whether they can get parts for it.

After the repair

Ask the technician what caused the failure and what would prevent it. Many breakdowns trace back to lubrication, coolant contamination or a crash nobody reported. A simple preventive maintenance plan is cheaper than the next emergency.