As intelligent manufacturing becomes increasingly widespread, safety light curtains, acting as the “goalkeepers” of industrial automation, are now widely applied in hazardous operation areas such as punch presses, injection molding machines, and packaging equipment to ensure personnel safety. However, no matter how “smart” a device is, malfunctions are sometimes inevitable. If these issues are not discovered and dealt with in time, they can lead to minor consequences such as production downtime, or major incidents such as safety accidents.
In this article, we will discuss several common fault phenomena of safety light curtains and the corresponding troubleshooting and maintenance methods, to ensure the smooth operation of your equipment.
1. Light curtain not working, power indicator off
Fault phenomenon: No response from the light curtain, power indicator off, controller not operating.
Possible causes:
- Power supply not connected or voltage unstable;
- Loose or disconnected wiring;
- Controller malfunction.
Maintenance methods:
- Use a multimeter to check whether the power supply voltage is normal (generally 24V DC);
- Check the wiring terminals to ensure there is no looseness;
- If the power supply is normal but there is still no response, it is recommended to replace the controller or send the mainboard for repair.
2. Red light always on after power-up, equipment cannot start
Fault phenomenon: Red light on the light curtain stays on, indicating blockage or interference.
Possible causes:
- Foreign objects blocking the emitter or receiver;
- Light axis misalignment or skewed installation;
- Ambient light interference (e.g., strong sunlight, flashing lamps, etc.).
Maintenance methods:
- Remove obstacles in front of the light curtain;
- Use alignment tools to calibrate the light axis and ensure alignment between emitter and receiver;
- Install a light shield or adjust the position to avoid interference sources.
3. Equipment gives false alarms or stops by mistake
Fault phenomenon: The light curtain misjudges blockage, frequently alarms, and restricts equipment operation.
Possible causes:
- Slight misalignment of the light axis causes reduced sensitivity;
- Electromagnetic interference or poor grounding;
- The light curtain has been used for many years, leading to sensor aging.
Maintenance methods:
- Re-fix the light curtain to ensure stable installation;
- Check if the grounding wire is properly connected to avoid electromagnetic interference;
- If used for more than five years, it is recommended to replace with a new sensor.
4. Delayed response or intermittent failure of light curtain
Fault phenomenon: The light curtain occasionally responds slowly, and the safety function is unstable.
Possible causes:
- Controller response abnormal;
- Poor contact of data cable;
- Control signal interference.
Maintenance methods:
- Replace or upgrade the controller’s software/hardware;
- Check whether the connecting cables are damaged, cold-soldered, or aged;
- Avoid running cables parallel to inverters or motor control lines to reduce interference.
Warm reminder:
Safety light curtains are not passive protective devices that only need to be installed once, but proactive safety systems that require regular maintenance and periodic inspection. It is recommended to check the working status of the light curtain weekly, perform light axis calibration monthly, and record maintenance logs.
In case of complex or difficult problems, be sure to contact the original manufacturer’s after-sales service or a qualified repair service provider. Do not disassemble it yourself, to avoid expanding the fault range or even losing the safety guarantee.
There is no such thing as a small matter when it comes to safety — prevention is better than repair. Making good use of safety light curtains is to build the strongest “invisible defense line” for the enterprise.
