Light Curtains and Safety Guarding
Muting, safety distance, device types and why guarding must be specified for your smallest part, not your largest.
Guarding a press brake is harder than guarding most machine tools, because the hazard is the point of operation itself and because the operator has to hold the part there. This page explains how guarding systems work and what you have to decide — it does not replace a risk assessment or your local regulations, which govern.
Responsibility note. Requirements differ by jurisdiction, and final compliance is the responsibility of the buyer, installer or employer — the party that puts the machine into service. In the EU, press brake safety is addressed by EN 12622 and the Machinery Directive 2006/42/EC. Elsewhere, your national rules apply. We supply guarding options; we do not certify your installation.
How a press brake guarding system works
An opto-electronic protective device — a light curtain or a laser/camera-based AOPD — creates a sensing field in front of the tooling. If the field is interrupted while the ram is in a hazardous part of its stroke, the machine stops. The crucial part is what happens next: the system has to stop the ram before it closes to a dangerous gap, which is why response time and stopping performance determine the mounting distance, not convenience.
Muting: why it exists and why it is delicate
Normal bending puts the sheet itself in the sensing field. If the system simply stopped on any interruption, you could never bend anything. So the field is muted — suppressed — once the ram has passed a defined point and the closing gap is small enough that a hand cannot be in it. That mute point, and the speed at which the ram is allowed to travel once muted, are the safety-critical parameters.
Speed-dependent muting is the standard approach: above the mute point the ram may travel fast; below it, the field is muted but the ram is limited to a slow closing speed. Getting this wrong is how accidents happen with a guard fitted and working.
Safety distance
The device must be mounted far enough from the point of operation that the machine can stop before a hand reaching through the field arrives at the tooling. The distance depends on the response time of the whole system — sensor, control, valve and brake — and on the ram's stopping distance, not just on the sensor's datasheet. Machine builders and installers calculate this; if you are retrofitting, it must be recalculated for your machine's actual stopping performance.
Technology choices
| Type | How it works | Trade-offs |
|---|---|---|
| Multi-beam light curtain | Separate emitter and receiver, discrete beams | Proven and simple; resolution limited by beam spacing; alignment matters |
| Laser AOPD | Scanning laser field around the tooling | Flexible field shapes, good for box bending; sensitive to setup |
| Camera / vision system | Images the point of operation | Can cover complex geometry; needs correct configuration and verification |
| Mechanical guard | Physical barrier | Simple and unambiguous; restricts access and part handling |
The small-part problem
Guarding is specified for the smallest part you will run, not the largest. On a small bracket the operator's hands are close to the tooling, the part is light enough to be ejected if the tooling releases it unexpectedly, and a field sized for a 2 m panel does not protect anything. Some shops solve this with dedicated fixtures, handling tools or a different process for the small parts. If you run small parts, say so when specifying the machine — seebrackets and frames.
Verification is ongoing
A guard is not fit-and-forget. Test it at the start of each shift and after any tooling change or maintenance, using the test piece supplied with the device. Log the test. Most guarding failures found in the field are configuration drift — somebody changed a parameter to make a job easier — rather than component failure.
What to tell us when specifying
- Your market and the standards that apply to it.
- The smallest and largest parts you will run.
- Whether you bend boxes (which needs muting capable of handling formed legs in the field).
- Whether you need to run in automatic or single-stroke mode.
Questions we get asked
Is a light curtain legally required on a press brake?
It depends on your jurisdiction and on the machine as supplied. In the EU, press brake safety is addressed by EN 12622 under the Machinery Directive. Your national rules govern, and final compliance belongs to whoever puts the machine into service.
What is muting and is it safe?
Muting suppresses part of the sensing field once the closing gap is too small for a hand to enter, so the sheet itself does not stop the machine. It is safe when correctly configured, with the mute point and the permitted closing speed set properly. Misconfiguration is the common failure mode.
How far from the tooling should a light curtain be mounted?
At a calculated safety distance based on the total stopping performance of your machine — sensor, control, valve and brake — not just the sensor datasheet. It must be recalculated after any retrofit or change to ram speed.
Can I bend boxes with a light curtain fitted?
Yes, but the system has to handle formed legs entering the field, which is a configuration question. Tell your supplier you bend boxes so the muting and field geometry are set up for it.
How often should guarding be tested?
Test at the start of each shift and after any tooling change or maintenance, using the device test piece, and log the result. Most real-world failures come from changed parameters rather than failed components.
Specify guarding for your parts
Tell us your market, part size range and whether you bend boxes. We will specify a guarding option that suits the work — and tell you where a mechanical guard is the better answer.