Light Curtain, Area Scanner, or Fixed Guard?
Machine guarding comes in three basic tools. A fixed guard physically prevents access, a safety light curtain senses reaching through an opening and stops the machine, and an area scanner watches a zone on the floor and slows or stops the machine when someone enters. The risk assessment decides which one each hazard needs.
GUIDE
Machine guarding comes in three basic tools. A fixed guard physically prevents access. A safety light curtain senses reaching through an opening and stops the machine. An area scanner watches a zone on the floor and slows or stops the machine when someone enters. Which one your cell needs is decided by the risk assessment, hazard by hazard, and most real cells use a combination. This guide gives you the plain-language version of how the choice works so you can walk into that assessment knowing what each option costs and buys.
Start from the risk assessment, always
Guarding is a compliance deliverable. A risk assessment identifies each hazard, how someone could reach it, and how fast the machine can stop, and the guarding follows from those answers. A guard that passes the eye test can still fail the inspection: a curtain with the wrong resolution for the reach distance, a guard door with no interlock, a scanner zone shorter than the stopping distance. Specify the guard and the safety devices together or you rebuild the cell after the audit.
The three tools and what each protects
- Fixed guard (no access): panels on extrusion framing with interlocked doors where access is needed. Cheapest per meter, zero cycle-time cost, and the right answer wherever nobody needs to reach during operation. The interlock is what makes the door part of the safety system instead of a hole in it.
- Light curtain (protected opening): for openings people reach through on purpose, loading a press, tending a station. Two specs matter in plain terms: resolution (finger, hand, or body detection, matched to how close the opening is to the hazard) and safety distance (the curtain must sit far enough from the hazard that the machine stops before a hand arrives). Higher resolution buys shorter safety distance at higher cost.
- Area scanner (protected zone): for floor zones around robots and large machines where fencing is impractical. Scanners can run warning and stop zones, slowing the machine as someone approaches and stopping it when they're inside. They trade cost and setup complexity for floor-space flexibility.
The part that makes it a system
Curtains, interlocks, and e-stops don't stop anything by themselves. Safety relays and controllers tie them into a monitored stop circuit, and "monitored" is the word auditors care about: the circuit proves the stop function works instead of assuming it. ISO 13849-1, the machine-safety performance standard, is the yardstick the assessment will use. Budget for the safety logic, wiring, and validation, which routinely cost as much as the sensing devices.
Cost and cycle-time trade-offs
Fixed guarding is cheap but slows any task that needs access. Curtains keep operators fast at load stations and cost more per opening. Scanners free the floor plan and cost the most to specify well. There is also a real cycle-time question: muting and blanking functions let product pass while people can't, and specifying them correctly is the difference between a guarded line and a guarded line everyone bypasses. An overridden guard is a liability with a paper trail.
The retrofit path for an existing machine
Older machines rarely need to be replaced to be compliant. The usual path: risk assessment on the machine as used today, then extrusion guarding with interlocked access, then curtains or a scanner only where the assessment demands presence sensing, tied through a safety relay to a verified stop. Sometimes the right answer is the cheap one, a panel and an interlock, and we'll tell you when it is. The framing and guarding page covers the extrusion side; the sensing page covers the safety devices.
You leave able to say which of the three guarding tools each hazard in your cell wants, and what the safety logic behind them has to prove.
WHAT WE REPRESENT
The lines M6 represents for this application
- mk North America: aluminum extrusion framing, guarding panels, and interlocked access doors.
- Omron: safety light curtains, area scanners, interlocks, and safety relays and controllers.
KEEP READING
Related guides and pages
COMMON QUESTIONS
Common questions
Light curtain, area scanner, or fixed guard for my cell?
Fixed guard wherever access isn't needed during operation, curtain at openings people reach through, scanner for floor zones where fencing is impractical. The risk assessment makes the call per hazard.
What safety devices does my guard need to pass a risk assessment?
Interlocks on every access door, presence sensing at deliberate openings sized to the reach and stopping distance, and a safety relay or controller that monitors the stop circuit.
Can I retrofit guarding on an old machine instead of replacing it?
Usually yes: assessment first, extrusion guarding with interlocks, presence sensing only where required, all tied to a monitored stop.
Can a cobot run without guarding?
Sometimes, after a risk assessment of the whole application, including the part and the tooling. The robot being collaborative doesn't make the sharp part in its gripper collaborative.
Who supplies machine guarding and safety devices in the Northwest?
M6 Revolutions carries the framing and guarding line and the safety sensing behind it, across Washington, Oregon, Idaho, British Columbia, and California. Call 509-310-3584.