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This section answers simple questions related to the precautions and safety issues that come up during laser marker installation. All the items of importance prior to using a laser marker are fully covered here.

Installation vol.1

Q25What safety measures should be implemented when operating a laser?

Both manufacturers and end users need to take precautions to ensure that lasers are used in a safe manner.
Below are some typical examples of user safety measures.


Install an interlock mechanism to shut the laser off during emergencies.


Use a diffusing reflector or absorber with suitable reflectance and thermal characteristics to end the laser path. (For example, install a protective cover.)


To protect against exposure to eyes from accidental laser emissions, wear protective goggles as a routine precaution in control areas containing laser products. Always wear goggles during maintenance.


To ensure safety management, appoint a manager with knowledge and experience of how to handle laser products and how to prevent laser injuries.

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Q26What type of protective cover is required for laser markers?

Laser markers need a protective cover made from a material that the laser cannot penetrate—meaning that the material must attenuate the laser beam to a Class 1 beam.
The use of such material is the basic requirement for laser marker protective covers. Protective covers for CO2 lasers (30 Watt class lasers) are generally made of acrylic or polycarbonate, and protective covers for YAG and YVO4 lasers are made of sheet metal. Since completely surrounding a laser in sheet metal prevents the operator from seeing inside the housing, some sheet metal protective covers have a view window covered with a special protective film.

A typical CO2 laser marker protective cover is outlined below.

Penetration of acrylic plates by CO2 lasers

Standards for selecting materials to use in laser device covers

The material used as a cover is deemed intrinsically safe if the laser’s transmitted beam power after being diffused and reflected by the target workpiece is no more than the Class 1 AEL*. The Class 1 AEL for a CO2 laser (10.6 μm wavelength) is 103 W m–2.

*AEL (accessible emission limit): The maximum permitted level of radiation exposure or the exposure emission limit.

Theoretical acrylic plate thickness providing Class 1 AEL (typical example)

Laser medium CO2
Wavelength 10.6μm
Maximum power output 80W
Spot diameter ø60 μm approx. (model ML-G9370)
Spot area 2.82 x 10–9 m2 (calculated using the ø60 μm spot diameter of model ML-G9370)
CO2 laser transmittance of acrylic plate 60% (for plate of 15 μm thickness)

In theory, an acrylic plate thickness of 508 μm attenuates a CO2 laser to the Class 1 level, but a thickness of at least 5 mm is recommended to ensure adequate durability and material workability.

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Q27What is considered a safe distance that an operator must stand away from a laser marker when its protective cover is off?

Answering this question first requires an explanation of the terms ‘MPE’ and ‘NOHD’.


MPE (maximum permissible exposure) is the permissible safety level for a laser beam in contact with eyes or skin. NOHD (nominal ocular hazard distance) is the distance needed for a laser beam to diffuse to an intensity level lower than the MPE (the level deemed safe).

This question is therefore asking what the NOHD of a laser marker is when its safety cover is off. The NOHD values of KEYENCE products are given on the next page.

Note: NOHD should only be used as a safety management indicator. JIS standards specify that “Exposure to laser radiation must be minimized under all circumstances.” NOHD values DO NOT imply that a laser marker can be operated without a safety cover as long as the operator is at least the NOHD distance away.

NOHD (nominal ocular hazard distance) values

CO2 laser markers

YAG (YVO4) laser markers

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Q28Should a beam shielding film be applied to the inner or outer surface of the acrylic plate?

As illustrated in the example above, is it better to place the protective film on side 1 or side 2?

The purpose of the film is to prevent laser emissions from escaping the protective cover. Adhering the film to side 2 (the inner surface) is recommended whenever possible, because placing it on side 1 (the outer surface) may cause laser emissions to scatter as they enter the acrylic plate.

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Q29What is the most accurate way to measure laser power?

A power meter can be used to accurately measure the output power of a laser marker (available from electronics suppliers). To determine the current power output value, direct the laser beam onto the head of the power meter (ensuring that all equipment is not in motion). KEYENCE’s MD-X Series YVO4 laser markers come with a built-in power monitor as a standard feature, allowing users to measure the laser power output easily and precisely without having to buy an external device.

KEYENCE does not sell power meters.

General method of measuring laser power

Measuring the laser power of MD-X (with built-in power monitor)

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Q30What maintenance is required for laser markers?

Laser markers don’t require maintenance, which is one of their major benefits. The lens should be cleaned if its surface gets dirty, since dirty lenses can reduce print quality or cause missing parts in the print image.


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Q31What is the best way to clean the lens?

Wipe the lens lightly with a cloth soaked in acetone or dehydrated ethanol. Wiping in a circular motion, working outward from the center is the most effective method. Never wipe the lens with a dry cloth, this may scratch it or remove the protective coating.

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Installation vol.2

Q32What items are needed for a general installation?

An example of a typical installation is shown below.


Make sure to install a dust collector which filters out dust and smoke generated during marking.
To ensure efficient dust collection and to avoid laser reflection, cover the laser passage with a material which does not allow laser light to pass through it. Moreover, terminate the laser passage so that the laser beam cannot be emitted when there is no target present.

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Q33Is a dust collector necessary?

Yes, a dust collector is required since laser marking generates smoke and dust. Installation of a dust collector will also help to prevent the lens from buildup of contaminants that can cause marking to become faded or partially missing. In addition, gas may be generated when marking plastic targets and the collector should be engineered to filter out potentially harmful air contaminants. To prevent problems, we recommend that every user install a dust collector. Refer to Q32 on the previous page for an example of a typical installation.

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Q34What warning signs and labels are available?

Laser warning labels can be purchased from Rockwell Laser Industries, Inc.
Signs and label types may vary depending on the size.

Post the following warning sign at the entrance of the room where a laser product is installed in order to warn people before they enter the room.

A warning label is attached to the head of the laser marker before shipment.
The following is an example of the warning labels for the ML-G Series CO2 laser marker.

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Q35Can marking details be controlled by an external device?

Yes, the laser marker can be controlled by sending serial communication commands from a PC or PLC.
Every operation available on the editing software including a "Change character string" or a "Switch program" command can be used.
This allows:

  • - 2D code marking by using the measurement data from an inspection machine.
  • - Part identification marking on products arranged on a pallet by specifying coordinates.
  • - Product type changeover by reading barcodes.

Example: barcode verification

Users can change the data to be marked on products by reading a barcode with the correct registered data. This ensures smooth change-overs of product lines and prevents marking errors.

Combination with a handheld laser barcode reader

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Q36What kind of communication interface can be used?

Users can establish communication via RS-232C or RS-422A in order to send or receive information between the marker and an external device. A shielded cable is recommended for use when communicating with the marker.
This will prevent noise from affecting the transmission of data.

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Q37Why is the communication control failing?

This is one of the most frequently asked questions.
First, you need to determine whether the problem is due to the instrument settings or the communication program.
KEYENCE's laser markers have an extremely useful function designed for this purpose, which is called a "Communication history monitor".
This function allows users to record the exchanged communication commands in a text file format. The file can then be emailed to KEYENCE in order to quickly determine the cause.

Communication history monitor (sample screen)

This function displays the history of communication exchanged with an external device (PC or PLC) via an RS-232C interface.

  • - Use when troubleshooting abnormal communication.
  • - Compare the actual data sent and received on the monitor and verify the transmission of data.

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Q38Is it possible to control the operation of the laser with only the I/O terminal block?

Yes, the rear panel of the controller is equipped with a terminal block and an MIL connector which allows users to wire a sensor, a PLC, or a control device to the laser marker. By registering the marking settings beforehand, the user can switch the marking type with the I/O terminals. A wide range of control is possible with just the I/O terminals. The terminal block can be detached by releasing the locks at the upper and lower ends.

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Q39What type of input signals can be used via the I/O terminals?

Typical signals are as follows.
* Many more signals are available. Contact KEYENCE for more information.


Starts marking.
The Marking Start Input can be turned on by a sensor or another device.
(Minimum pulse width: 1 ms or more)


Stops the laser emission in the case of an emergency.
When this terminal is opened, all marking operations stop (Laser power OFF) and the internal shutter closes.


Checks whether the marking is performed properly.
An external sensor detects the laser emission and sends an input to the marker. If the marker does not receive the input from the sensor during marking, it outputs an error.


When the marking operation is completed successfully, a pulse output turns on (100 ms max.). If the next trigger is input during the output, the output turns off immediately.


Increments the value of a selected counter by one step.


Changes the settings or programs in order to compensate for adjustments in marking due to product changes or updates made to the data being marked. Changes can be made to adjust for a variance of up to 2000 parts.

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Installation vol.3

Q40How do I connect external devices?

An example of a typical installation is shown below.

System Configuration

Connecting external devices

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Q41How do I connect timing sensors?

Examples of sensor connections are shown below.
Input and output supports both NPN and PNP, and allows them to be used simultaneously.

* Contact KEYENCE for advice on selecting the best sensors to suit your needs.

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Q42Will laser marking be affected if the equipment vibrates?

Laser markers use precise optical control. For this reason, if vibration occurs during marking:

  • - Marking coordinates may become misaligned
  • - Text may become distorted

Additional problems may also occur. If ambient vibration affects the laser marker, use a vibration-resistant stand or other preventative measures in order to eliminate vibration.

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Q43Will marking with the laser in an upside down orientation cause any problems?

Since KEYENCE laser marker heads can be mounted at any angle, there are no problems.
* Take cautionary measures to prevent the build up of dust and debris on the lens.

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Q44Can laser markers be used with a 200V power supply?

Yes. KEYENCE laser markers support AC power supplies from 100-120V or 200-240V.
* Use a cable that meets power supply specifications.

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Q45How do I prevent the laser from oscillating when the protective cover is opened?

Use a remote interlock.
Shutter control terminals are used to close the shutter and stop laser scanning when the cover is opened.
See below for more details.

Remote interlock (Controller units have shutter control input terminals)

Remote interlock is a function that prevents laser radiation from being emitted. The laser is disabled when the connector pins are released. Shutter control input is controlled by two circuits: terminal A and terminal B. If either one is released, the shutter closes and laser scanning stops. If both ends short at the same time, the shutter opens and the sensor switches to standby mode.
* When shipped, the terminals are shorted together by means of a connecting bar.

* The ML-G and MD-H9800 Series control is via a single circuit: the laser control input terminal (terminal no. 10).

WARNING: The laser control interlock should not be used when the door to the enclosure needs to be opened frequently. Contact Keyence for alternative measures.

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Q46I want to move the laser to another factory.
What should I be aware of when packing it?

Laser markers are high-precision devices.
Packaging supplied by KEYENCE or a similar substitute must be used when transporting laser markers.


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Q47Should I replace the air filter when it gets dirty?

Yes. The air filter should be cleaned or replaced when it gets dirty. If the condition of the filter is ignored, cooling performance will diminish which may reduce laser output or cause damage.

Use a mild detergent to clean the air filter and let it dry naturally (do not apply heat).

* Replacement filters are available. Consult your nearest KEYENCE office for details.

Service Parts

Maintenance work on laser markers must be performed by technicians who possess specialist electrical knowledge.

*1 Use fuses that satisfy the following ratings and are also EN standards compliant for the CE mark model (ML-Z9500C).

Rating : 250V, 10A, Compliant with European Standard EN60127-2

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