The principle and function of safety light curtain application on punch press

Have you ever worked on a punch press in a factory? That thing is, to put it bluntly, a “tiger’s jaws,” biting down and down to press steel into shape. But if your hand is still inside when it bites down… you know the consequences: pinching or severed fingers, potentially requiring hospitalization at best, or lifelong disability at worst.

So, while punch presses are money-making machines, they’re also prone to accidents. And that’s when “safety light curtains” are lifesavers!

1. What is a light curtain? It’s an “infrared watchdog”!

It’s essentially a pair of infrared transmitters and receivers, like a couple looking at each other. One end emits light, the other receives it, and dozens or even hundreds of infrared beams are arrayed in between. The human eye can’t see them, but they’re constantly “watching.”

When something, like a hand, a tool, or the corner of clothing, blocks any of these beams, the system immediately responds—”Someone’s inside! Don’t move!” The punch press stops immediately! Stop punching!

This is called “non-contact protection.” Before you even touch the machine, the light curtain “stops” you.

2. How to Use It on a Punch Press?

Let’s discuss a practical operational scenario:

Manually-fed Punch Press

A worker feeds the material while operating a foot pedal or button. If they rush, become distracted, or move slowly, the punch press will fall before they can retract their hand, potentially injuring them. A safety light curtain is installed in front of the punch press workbench. If the light curtain is “interrupted” while the worker is still inside, the press system will not start. The worker must wait until the worker is retracted and the light is restored before the press can start. This prevents injuries caused by misoperation and rushing for time.

Automatic-fed Punch Press

On this type of press press, the machine feeds the material, eliminating the need for workers to approach the die. However, workers may still need to inspect the die during maintenance or when a problem occurs. Without a light curtain, the press would continue to operate even if a worker approaches, creating a significant risk. With a light curtain installed, the press automatically pauses when a person enters the area, and resumes operation only after the person leaves.

3. Light curtains protect not only people but also the business!

Think about it: if a worker gets into an accident, not only does the worker suffer, but the company suffers too, with losses, work stoppages, and investigations. Installing a light curtain offers a one-time investment with long-term benefits: fewer accidents, greater safety, and peace of mind for everyone.

Furthermore, many manufacturers now require factory inspections and ISO safety certifications. If you don’t even install the most basic safety light curtains, they’ll simply shake their heads and say you’re “non-compliant.”

Fourth, let’s briefly explain the working principle:

The transmitter emits infrared light;

The receiver receives this light, forming an “invisible wall”;

If the “wall” is breached (for example, if you reach in), the light is interrupted;

The controller receives the signal and immediately disconnects the press circuit or control loop;

The press stops and doesn’t resume operation until the person leaves.

The entire process takes less than 0.05 seconds—faster than your reaction time.