Leuze / MLC light curtains and MLD light beam devices

The transmitter is always an MLC 500. The receiver number is the feature class: 510 Basic, 520 Standard, 530 Extended. So the two halves of one curtain never share a number, and the receiver number tells you what the curtain can do.

MLC is the Leuze safety light curtain family and MLD the multiple light beam range for access guarding. Both are widespread on New Zealand packaging and materials handling.

The receiver number is the class

The decode that makes the whole range readable.

Leuze describes the series as characterised by four different receiver classes: Basic, Standard, Extended and SPG.

So an MLC500T pairs with an MLC510R, an MLC520R or an MLC530R, and the receiver you have decides the function set.

Two consequences when ordering

A transmitter is a transmitter. If the transmitter end has been hit, the replacement is an MLC500T of the right resolution and height, regardless of which receiver class sits opposite.

A receiver is not just a receiver. Fitting a 510 where a 530 was removes blanking and the extended functions, and the machine will not behave as it did.

Send both numbers. The receiver number is the one that matters most.

What the Extended class adds

Blanking, and it is the usual reason a machine has a 530.

Leuze describes blanking as being used when objects must be located in the protective field for operational reasons, so they can pass through or sit permanently in the field without triggering a switching signal.

Blanking is configuration, not hardware

Which matters on a replacement.

A replacement MLC530R arrives without the blanking configuration. The blanked areas were set for that specific machine, around a specific fixture or product path.

So a like-for-like receiver still needs configuring, and the blanked areas are a safety-relevant setting. Blanking a region means the curtain no longer detects there.

If a machine has a 530 and nobody knows what is blanked, that is worth resolving before it fails.

Synchronisation is optical, not wired

A real installation advantage worth knowing about.

Leuze synchronises receiver and transmitter optically, without cables, via two specially coded synchronisation beams.

So a curtain that is not synchronising is an alignment problem, not a missing cable. Two of the beams are doing the synchronising, and if they are obstructed or misaligned the whole field will not form.

Channel switching and reducible range

The Leuze answer to curtains interfering with each other.

Even the basic MLC 510 carries channel switching and a reducible operating range, so that adjacent machines operate reliably.

So if two curtains on adjacent machines are tripping each other, that is a setting rather than a fault. Worth checking before ordering replacements.

The MLC 510 also carries a wide temperature range of -30 to +55 degrees C, which covers cold store and outdoor applications that stop many devices.

Alignment and the display

Leuze specifies that the transmitter and receiver be parallel to each other, the same distance apart at the beginning and end of the device.

Alignment is done with a clear protective field, watching the LEDs and the 7-segment display.

The 7-segment display is the diagnostic tool most people do not use. On a curtain that will not go clear, it reports why.

A curtain that was working and now will not align is usually mechanical: a knocked bracket, a sagging mount, or something new in the field.

Holding the reset for 30 seconds faults the receiver

A specific behaviour that looks like a failure.

Leuze states that starting at 30 seconds, a +24 V short circuit is assumed on the reset input and the receiver switches to the interlock state.

So a curtain that goes into interlock and stays there is worth checking at the reset button before the receiver. A jammed pushbutton on a panel does exactly this.

The behaviour exists so a permanently made reset cannot defeat the restart interlock.

Leuze also notes that an individual acknowledgement unit must be provided for each MLC 530 receiver. Two curtains cannot share one reset button.

The two halves take different cables

Easy to get wrong when ordering.

The receiver needs more conductors because it carries the OSSD outputs, the reset and the diagnostics. The transmitter mostly needs power.

So ordering two of the same cable leaves you a connector short at one end. Tell us which halves you are cabling.

Smart Process Gating

What the SPG receiver adds, and why it exists.

SPG replaces conventional muting on a cyclic process. Rather than muting sensors watching for a pallet, the machine control itself tells the curtain when a process interruption is legitimate.

Leuze documents several operating modes selected by external wiring, working with:

An optional teach key switch is part of several arrangements.

The operating mode is set by wiring, not software. So a replacement SPG receiver behaves according to how it is connected, and rewiring it differently changes the safety function.

If a machine uses SPG, record the operating mode before changing anything.

MLD, the multiple light beam range

For access guarding rather than point of operation, and the ratings differ sharply between the two series.

That is a large gap and it is the whole basis of the choice. An MLD 300 is not a cheaper MLD 500; it is a lower performance level, and swapping one for the other changes what the machine achieves.

Across the range Leuze cites PL d and PL e to EN ISO 13849-1, Categories 2, 3 and 4, SIL 2 and SIL 3 to IEC 61508 and EN IEC 62061, and Types 2 and 4 to EN IEC 61496-1. All versions are laser class 1.

Transmitter-receiver or transceiver

The architectural choice, and the transceiver version halves the wiring.

A transceiver has the transmitter and receiver in one housing, with a passive mirror on the far side. Leuze describes it as an economical solution with low installation effort.

Why that matters practically

Only one side needs power and wiring. On a wide doorway or across a conveyor aisle, that removes a cable run entirely.

And the mirror is a passive part. If it is damaged, that is a cheap replacement rather than a safety device.

So on an MLD installation, establish whether the far side is a receiver or a mirror before quoting. They are very different orders.

Muting on the MLD

Where a pallet must pass but a person must not.

Leuze describes muting as temporarily and properly suppressing the protective function, with the OSSDs remaining in the ON state while an object is transported through.

Four rules Leuze states

The timeout is the safety net

If a pallet jams in the muted zone, muting does not stay on indefinitely. The timeout forces it to end.

So a line that stops after a jam and needs a manual restart is behaving correctly. Leuze specifically cites power failure and violation of the concurrency condition during timed two-sensor muting as cases needing a manual reset and override.

Muting is a system

Muting sensors are separate devices, and the muting signals can come from Leuze optoelectronic sensors.

Leuze also specifies a minimum distance between the protective field of the device and the detection points of the muting sensor beams.

So the muting sensor geometry is part of the safety design, not an installation convenience. Moving a muting sensor changes it.

If a muted installation is nuisance-tripping, the muting sensors are worth checking before the light beam device. Their alignment drifts and they sit where they get knocked.

The wider Leuze safety family

Devices that connect to the same monitoring arrangements.

SOLID, RS4, RD800 and COMPACTplus turn up on older New Zealand machinery. They are long discontinued and the secondary market is where they live. We source them.

Important: safety replacements

Light curtains and light beam devices form part of a machine's certified safety function.

A like-for-like replacement of the same type preserves the assessment. A substitution may not. Resolution and protective field height are not interchangeable, because the mounting distance was calculated from them. Receiver class is not interchangeable, because the function set differs. And an MLD 300 is a lower performance level than an MLD 500.

We will supply exactly what you specify. If you ask for an alternative we will say what we believe is equivalent and what differs, but the decision belongs with whoever is responsible for the machine's safety. We are a parts supplier, not your safety engineer.

What to send us

Both type codes and both 8-digit order numbers, transmitter and receiver.

Which half you need.

The receiver class. 510, 520, 530 or SPG.

Whether blanking is configured, on a 530.

Whether the far side is a receiver or a mirror, on an MLD.

Whether the installation is muted, and what the muting sensors are.

Before ordering a replacement

What we can supply

Current production. MLC 300 and MLC 500 transmitters and receivers across resolutions, heights and receiver classes, MLD 300 and MLD 500 in transmitter-receiver and transceiver versions, deflecting mirrors, MSI controllers, RSL scanners, plus CB series cables, mounting brackets and muting accessories. Quoted with a delivered lead time.

Discontinued. SOLID, COMPACTplus, RS4 and RD800. Surplus and tested used, which keeps an existing installation exactly as assessed.

Halves, mirrors and cables separately. Usually the cheaper order.

We buy Leuze safety

Leuze safety devices hold real value, because a like-for-like replacement lets a plant avoid a reassessment.

Keep pairs together. Transmitters with receivers, and transceivers with their mirrors. Matched sets are worth considerably more than orphaned halves. See Sell To Us.

Related

Leuze overview.

For light curtains from other brands see SICK deTec4 and C4000, Pilz PSENopt, Allen-Bradley GuardShield and Omron.

Send us your part numbers

Send the receiver number. It is the one that tells us what the curtain can do. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Leuze electronic. Leuze, Leuze electronic, COMPACTplus and SOLID are trademarks of Leuze electronic GmbH + Co. KG. All trademarks, brand names and part numbers are the property of their respective owners and are used here for identification purposes only. Information on this page is for identification and does not constitute a safety assessment.