Plain talk, real shop-floor stories, zero fluff. If you build, buy, or maintain machines, this is for you.
Safety Light Curtain Working Principle (emitter/receiver, OSSD, self-checking)
A safety light curtain is two bars facing each other: a transmitter that shoots many invisible IR beams in sequence, and a receiver that listens for that exact pattern. When anything breaks any beam, the curtain drops its OSSD outputs to “off,” and your machine gets a safe-stop signal. The trick isn’t magic; it’s timing, modulation, and constant self-test. The system scans beams in order, rejects stray light, and keeps checking itself every cycle. If something inside fails, it fails safe. That’s the core.
OSSD outputs and control reliability (Type 4 context)
Most modern curtains use dual OSSD outputs. They monitor each other, so a single fault doesn’t sneak by. Pair those with a safety relay or a PL-rated controller and you get the control reliability you actually need. In higher risk jobs—press brakes, large hydraulics, metal forming—you typically pick Type 4 curtains because they do continuous internal diagnostics and catch single-fault issues fast. Dont gamble here.
Light Curtain Safety Distance (EN ISO 13855)
Mounting too close is the classic pitfall. Use the standard formula:
S = K × T + C where K = approach speed (commonly 1600 or 2000 mm/s), T = curtain response + machine stop time, C = reach-in allowance that depends on resolution (beam spacing).
What matters day-to-day?
T is not just the curtain response; it’s t1 + t2 (sensor + machine). If your brake is slow, S grows.
C grows as the curtain resolution gets coarser. A 14 mm curtain “sees” fingers; a 30–40 mm curtain is for hands/body.
Re-measure stop time after maintenance. New pads, new S.
Need tight guarding around end effectors or small-part assembly? Step up the resolution: see our High-Precision and Measurement Light Curtains for dense beam pitches.
Type 2 vs Type 4 (IEC 61496)
Short version: Type 2 is for lower-risk stuff and checks itself mainly at start-up. Type 4 is for higher risk and checks itself continuously during operation. Most production cells with real hazards land in Type 4 land. Match your curtain Type with your required performance level (PLr) from EN ISO 13849-1. If your risk assessment calls for PL e, you already know where this is going.
Muting vs Blanking (material flow without killing safety)
You’ve got to move pallets, totes, sheets, or runners thru the protective field. Do it clean:
Muting: a temporary, automatic bypass when all muting conditions are true—often via extra sensors that detect a load and its direction. Once the load clears, muting ends.
Blanking: ignore a defined beam area long-term (fixed) or allow a limited “floating” blocked zone that can move a bit. Useful for hoses, fixtures, or small conveyors that must sit in the field.
We ship Type 4 options with both functions. If you’re moving heavy stock, look at our Heavy Machine line; for wash-down or sticky environments, go IP—Waterproof Safety Light Curtain.
Point-of-Operation Guarding vs Perimeter Guarding (real-world scenes)
Point-of-operation (presses, injection molding take-out, pick-and-place): high-resolution, short S, fast T. Hand/finger detection prevents reach-in during a hazardous cycle.
Perimeter (robot cells, palletizers, lift gates): taller protective heights, corner mirrors for multi-sided access protection, and muting for staged infeed/outfeed. See: Multi-Sided Access Protection.
Environment: oil mist, coolant, wash-down, glare. Consider Waterproof or front/side window options like Front Ultra-Thin and Side window styles.
Form factor: tight cabinets or door posts? Go Compact or ultra-thin. For standard cells, General Use fits most.
Industry Use Cases (speak the plant’s language)
Press & metal forming: Type 4, 14/20 mm, hard-mount with anti-vibe brackets. Hook OSSD into a Category 4 safety relay; wire EDM to watch your contactors. Re-start requires local reset; no sneak restarts.
Packaging / logistics: pallet infeed with muting sequence; corner mirrors for U-shaped cells; tall curtains (≥1800 mm) for body protection; fork pockets kept clear.
Injection molding / die-casting: auto take-out needs short T; use high-vis alignment LEDs; add blanking for fixed sprue chutes.
3C electronics & battery: High-precision curtains around jigs for finger-safe detection; tie data into MES via IO-Link for downtime analysis.
Woodworking / panel lines: dust, vibration; spec rugged housings and IP seals; longer range optics, regular wipe-downs.
Food & beverage: wash-down and ^chem^ cleaners—go IP and stainless hardware.
DWS / dimensioning (not just safety): deploy Measurement Light Curtains for counting, width/height, and profiling while a separate safety curtain protects the hazard.
Data-Backed Arguments (quick look-up)
Argument
Why it matters on your line
Where to verify
Sequenced, modulated beams + matched receiver = reliable detection; any beam break → OSSD off
Rejects ambient light, reflections, and cross-talk; deterministic stop
Continuous self-checking (Type 4) vs mainly start-up checks (Type 2)
Type 4 suits high risk; detects single-fault conditions during run
IEC 61496 Type 2/Type 4 overviews; Type-comparison notes
Safety distance S = K×T + C (EN ISO 13855)
Get the mounting right; T = sensor + machine stop; C depends on resolution
EN ISO 13855 primers; safety distance calculators; vendor apps
Muting vs Blanking
Keep materials flowing without killing protection
Pilz/SICK function definitions; automation association briefs
PLr drives device choice and architecture
Tie device Type to PL/SIL claims; aim for PL d/e where needed
EN ISO 13849-1 summaries; PL/MTTFd/DCavg explanations
(We’ll happily walk thru your S-calcs if you share resolution and stop-time—no spreadsheet drama.)
Why NEW STAR OEM (One-Stop Machine Safety Sensors Manufacturer)
We build and ship safety curtains for real factories—not just spec sheets. NEW STAR OEM supports Type 4 options, OEM/ODM, private label, and fast sample-to-scale runs. If you need ultra-slim housings, high-res arrays, or odd mounting, we do custom. Explore by duty: General Use, Compact Safety Light Curtain, High-Precision, Heavy Machine, Multi-Sided Access Protection, and Waterproof Safety Light Curtain. We also supply laser scanners, mats, interlock switches, photoelectric sensors, plus flow sensors for water/HVAC/chemical monitoring—so your safety and sensing stack actually matches.
Quick FAQ (shop-floor style)
Can I auto-restart after clear? You can, but most teams use manual reset near the hazard to stop unexpected start-ups.
Do mirrors kill range? Some loss, yep; size your optics accordingly.
What if oil mist coats the window? Plan cleaning; consider IP upgrades and alignment aids.
Can I cascade bars? Sure—reduces blind spots around fixtures and gates.
My robot cell needs entry with parts. Use muting with correct sequence and indicators. Dont disable safety to move pallets.
