As a smelting, a die-casting or extrusion professional, are you considering the use of laser direct part marking to improve traceability? Laserax’s open-air laser marking system may be the solution you are looking for.
How to Safely Use High-power Lasers With an Open-air Enclosure
A properly designed laser enclosure is as safe as any other industrial machinery. If you outsource the maintenance and servicing of your laser systems to a reputable organization, there is no requirements for specific laser safety training on your part.
That being said, there is a lot to learn regarding the design of a Class 1 open-air laser safety enclosures. The difference between an open-air enclosure and other types of laser safety enclosures is the fact that the part to be marked is a removable portion of the open-air enclosure.
Let’s review the components of an open-air enclosure, specific considerations for this type of equipment, the use of articulated robotic arms or linear actuators, and other special circumstances, such as service, maintenance and laser beam alignment.
You will find a few more definitions at the end of the text that might help you get a better understanding of laser safety theory.
Embedding a Class 4 Laser Down to a Class 1 Laser System
Open-air enclosures are devices designed to significantly reduce the access to laser radiation (red arrow in the image below). Open-air enclosures, like other laser safety enclosures, require a hazard analysis to establish the zone where laser radiation levels are above the Maximum Permissible Exposure (MPE). Laser safety standards recommend using the fictive mirror concept to do so. In these zones, specific control measures might have to be enforced to prevent exposure to hazardous laser radiation.
Open-air Enclosure with direct beam
Proper engineering control measures, which are implemented by the manufacturer of the laser system, are usually sufficient to achieve Class 1 laser safety conditions. A Class 1 laser system requires very limited user control measures. No laser safety glass is required and no special training. Moreover, signage, a laser control area, and an area warning signal are not required.
The Construction of an Open-air Enclosure
An open-air enclosure is composed of two layers of enclosures. There is the inner enclosure and the outer enclosure.
Access to the immediate vicinity of the open-air enclosure may have to be controlled. This can be achieved with a human access barrier. But since this kind of laser system is often used in conjunction with robot, the access problem is often solved by the robot safety cage.
(2) Inner Laser Safety Enclosure
Open-air enclosure with specular reflections
The goal of the inner laser safety enclosure is to limit the range of angles that may be generated due to an unanticipated reflection. We have to make the inner enclosure almost touch the part to be marked to improve its effectiveness. In the image above, direct laser radiation is illustrated in dark red. The clear red triangles represent the first specular reflection.
(1) Outer Laser Safety Enclosure
Open-air enclosure with specular and diffuse reflections
That’s where the outer enclosure comes into play. It blocks the reflections that might be created by a tool left there by accident, defective parts, etc... The main task of the outer enclosure is to catch the specular reflections from the surface to be marked, absorb it, and reflect it back in a diffused pattern.
Black anodised aluminum, painting the inside of the enclosure mat black, or using other funky materials such as the one described in this article by Photonics Media are examples of ways to diffuse the laser beam. The diffuse reflections are illustrated in the image above as the two orange semicircles.
(7) Human Access Barrier
Diffuse reflections are much less intense and their intensities decrease much faster than specular reflections. A diffuse reflection of our 100 W fiber laser will be dangerous for no more than 80 cm. In order to prevent all exposure to hazardous laser radiation (i.e. intensities above 5 W/cm2 for wavelengths of 1064 nm and pulses of 100 ns), national laser safety standards recommend the use of a human access barrier.
Windows and viewports
If there are windows or viewports on the open-air enclosure, they have to prevent the exposure to radiation that might hurt operator and passersby.
Interlocks and sensors
The protective housings of Class 1 laser systems have to be interlocked so that power to the lasers is cut when the housings are opened as part of the normal operation of the lasers. In the case of the open-air enclosures, the part itself is part of the protective housing. Its presence has to be confirmed with safety rated proximity sensors to activate the laser.
Robotic and other Automated Installations
Laser systems are often used in conjunction with articulated robotic arms. In some cases, the robot brings the part to an open-air laser enclosure. In others, the robot brings an open-air enclosure to the part to be marked. Lastly, the robot can place the part on a feeding mechanism that will manage the marking of the part with a standalone laser system.
Where Should We Use Laser Systems With Open-air Laser Safety Enclosure?
Open-air enclosures are the ideal solution for bulky parts that cannot fit in a regular safety enclosure. Think billets, T-ingots and sows. The integration can be done with an industrial robot but most likely with linear actuators. The enclosure, handled by the actuator, is brought in close proximity to the parts to be marked. Each part is marked and the linear actuator withdraws the laser safety enclosure. The next part is now ready to be marked.
Laser marking system using open-air enclosures can be beneficial to die-casters. The ability to uniquely identify all parts within an automated process can add value to end users
The parts can be presented by a robot to the open-air enclosure. The laser system marks the parts and then the robot takes them to the next step in the production process.
In another scenario, a robot can put the part in a standalone enclosure. While the part is being marked by the laser, the robot can complete other tasks and come back to pick the part when it’s ready. For more information on laser safety for this type of enclosure, read our blog, entitled The Basics of Laser Safety... for Sealed Enclosures.
Did you recognise yourself in any of these scenarios? You are interested to learn more about the integration of lasers in your facility to improve traceability and process control, get in touch with our laser technology experts.
Service and Maintenance
Service and maintenance of a class 4 laser enclosed in an open-air enclosure have to be done by authorized trained personnel. Get a quote on our maintenance program for Laserax laser systems.
Alignment of the Laser Beam
This is usually done once when the laser system is installed, but major change to the system might require the realignment of the laser beam. Some special precautions have to be taken, as the risk to eye are dramatically increased during that operation. It should be left to the most cognizant laser experts.
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Designing an open-air enclosures is a much more complex task then designing a sealed enclosures. But once it is designed, assembled, installed, commissioned and working under normal conditions it is just as safe as any other class 1 laser systems. It requires no personal protective equipment.
If you would like to get more information on the laser safety of other types of laser safety enclosures read our post: The Basics of Laser Safety.
There are seven laser safety classes: Class 1, Class 1M, Class 2, Class 2M, Class 3R, Class 3B and Class 4. Only Laser Safety Classes 1 and 4 are pertinent to applications that are covered by Laserax’s industrial lasers.Laser Safety Class 1: Lasers or laser systems that do not, under normal operating conditions, pose a hazard. (p. 9)
Laser Safety Class 4: Lasers or laser systems that produce a hazard from not only direct or specular, but may also produce hazardous diffuse reflections. Such lasers may produce significant skin hazards as well as fire hazards. (p. 10)
In order to be able to mark metallic surfaces efficiently, Laserax is using lasers with an optical power well in excess of 0.5 W for period of time greater than 0.25 s. According to ANSI Z136.9-2013 it makes it a Class 4 laser.
The Standard requires that management o
f a facilities where a class 4 laser is used creates a program for the control of laser hazards. But fear not, if you are using a laser embedded inside a properly designed laser safety enclosure and if you decide to have the laser serviced and maintained by an outside vendor then that requirement falls. [back to text]
The maximum permissible exposure, as defined by the Standard, is the maximum level of laser radiation to which an unprotected person may be exposed without adverse biological changes in the eye or skin. [back to text]
This concept, not part of the standards, is used to help the designers to visualize how the reflections of the laser behave. The fictive mirror is placed everywhere between the laser aperture and the part to be marked at every angles. The reflections are studied and those that make their way out of the enclosure are used to determine the nominal hazard zone.
Nominal Hazard Zone (NHZ)
The standard defines the nominal hazard zone as the space within which the level of the direct, reflected or scattered radiation may exceed the applicable MPE.[back to text]
Laser Institute of America. (2013). American National Standard for Safe Use of Lasers in Manufacturing Environments. Orlando, FL. Laser Institute of America, 196 p.
Rockwell, Benjamin. (Ed.). (2015). Laser Safety Guide (12th ed.). Orlando, FL: Laser Institute of America, 50 p.
Laserax User’s Manual - LXQ Series v 2.1
Posted by Normand Lemieux
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