FEATURE
Issue: 

Powerful protection

With lasers becoming more powerful and with solid-state systems like fibre lasers now more commonly used in manufacturing, Jessica Rowbury examines the safety precautions necessary when using laser equipment

As higher-power laser systems make their appearance in the workplace, more sophisticated safety measures are needed to replace conventional equipment that has been adequate up to now. But relying on equipment is not enough: staff working in facilities where an industrial laser system is deployed, must receive education and training in laser safety.

At the other end of the power spectrum, as laser systems are becoming more affordable, there are concerns that companies may be unknowingly installing materials processing systems that are unsafe. At the end of last year, the UK’s Association of Laser Users (AILU) launched a Special Interest Group (SIG) in machine safety, to address the issue of laser processing machines being imported into Europe that do not comply with EU safety directives.

Industrial lasers that are used for applications such as laser drilling, cutting and welding are labelled as class four, meaning that they have the capability to pose serious injury to workers. ‘If the laser system is not enclosed and there is potential of exposure – either directly to the beam, or from the laser beam reflecting off a specular surface – there is hazard to the eyes and skin,’ said Gus Anibarro, education director at the Laser Institute of America (LIA). In addition, when lasers interact with materials, laser-generated air contaminants can be released into the air, which are hazardous to inhale and can pose a fire risk. ‘A by-product of a laser interacting with a metal is a metal oxide. Exposure to a metal oxide air contaminant may result in metal fever,’ explained Anibarro. ‘In addition to being toxic to breathe, if the material is a plastic, gases are released that may be flammable. So, it’s important that a smoke evacuation system is used,’ Anibarro pointed out.

It is therefore imperative to have comprehensive laser safety protection in place wherever class four lasers are present. According to Anibarro, the easiest way to provide a complete safety solution is to fully enclose the laser: ‘If a company is going to invest money in a laser system, they’re going to make it such that it’s completely enclosed, because you eliminate a lot of the safety requirements.’ By enclosing the laser, it can be reclassified as a class one laser system, meaning that there is no hazard to users under normal operation. A job shop can go about enclosing the laser radiation in two ways, Anibarro added: ‘They may buy the laser system from the laser manufacturer already full enclosed. Or, they may go to a system integrator that buys all the components, builds it, and then installs it into the company as a finished product.’

The walls and ceilings of laser safety enclosures are specially designed to absorb the laser power and block the laser beam if it hits the inside of the enclosed space. At Photonics West in February, laser safety solution provider Lasermet demonstrated its Laser Castle, launched at the end of last year, which provides passive guarding to industrial laser systems. ‘The passive guarding is designed to block the laser beam for substantial amounts of time,’ explained Paul Tozer, managing director of Lasermet.

Because of the high powers of some laser systems, not all materials are capable of blocking the beam long enough for the laser to be shut down, according to Tozer: ‘Other people use steel, but that has problems because, for instance, a 5kW laser with a 50mm beam diameter would go through 2mm of steel in seven seconds,’ said Tozer. ‘Aluminium is a lot more conductive, but it has a much lower melting temperature – once you get to the threshold it will suddenly disappear.’

The inside of the Castle enclosure is lined with composite panels that contain a laser blocking material inside. ‘The composite panels with laser blocking material are capable of containing 5kW lasers and even higher, depending on the beam diameter.’ The enclosure also has two vents built into the rear wall to enable air to enter the enclosure, which is then extracted through a vent in the roof.

To be sure that the material of the enclosure will provide sufficient protection, a calculation of the maximum possible exposure (MPE) and an assessment of the maximum reasonably foreseeable exposure have to be made. Once the maximum exposure is calculated, laser job shops or system integrators will be able to purchase suitable safety.

‘When you buy a viewing window, for example, it’s a bit like buying safety eyewear – you specified for the maximum exposure level you want to provide protection for,’ said Dr Mike Green, certified laser protection advisor at Pro Laser. ‘We will look at the operation of the laser to make some reasonable assumptions about reflectivity, what power the beam will be working at, and whether it’s going to be diverging on its way to the viewing window,’ Green said. ‘And, on that basis, work out what the specifications should be for the viewing window.’

The calculation also helps users of industrial lasers wanting to know if the safety equipment they have is sufficient. ‘In some cases, you estimate what the worst exposure should be and then, when you actually carry out a test, you realise that you should be doing more,’ said Green.

However, the increase in power of industrial fibre lasers has meant that few materials have the capability to contain the higher-power laser beams, according to Tozer: ‘As powers of lasers go up and up, containment of the power becomes extremely difficult. Once you get above 10kW then it can be difficult to find any sort of material that would contain that at all.’ Active guarding is used in higher-powered industrial laser systems to shut down the system automatically if the laser beam diverges from its course. ‘When the power of the beam is so high that, in the worst case, you envisage the material of the enclosure walls will not be able to withstand the laser beam for a sufficient time, then you look for active guarding,’ explained Green.

Active guarding is designed to detect when laser radiation is impinging on the enclosure walls and then will switch off the system within a fraction of a second. ‘There are different designs, but in essence they amount to the same thing – you have a surface which is facing the laser radiation, and some sort of detector which will detect if that surface is being heated or penetrated,’ described Green. ‘You could, for example,  have a fuse wire arrangement, and if the laser radiation melts the thin metal circuit material, a safety control system, which will sense the electrical break in the circuit, will cause the laser to be turned off.’

Lasermet’s Laser Castle has the option to be upgraded to include its ‘Laser Jailer’ active laser guarding system. Within the system, modular active tiles cover the internal walls, ceiling and doors and will detect high-power laser beam strikes, terminating the laser radiation. It is expected that this type of guarding will be used more and more as laser systems continue to become more powerful, according to Tozer: ‘Effectively, the active guarding system will protect from any power,’ adding that Lasermet will concentrate on this aspect of laser safety for the future.

Not only are fibre lasers being used more in job shops, but they are starting to replace CO₂ lasers in certain applications. ‘Fibre lasers are very reliable laser sources – they are taking some of the applications that traditionally only CO2 lasers have been used for in job shops,’ said Green. This poses additional safety concerns if the differences between the laser systems are not properly understood. ‘With CO₂ lasers operating in the far infrared, they are much less hazardous to the eye, and polymer panels are able to block the beam. So, laser job shops have got used to the idea of having clear plastic guarding,’ Green pointed out.

Pro Laser has been consulting with an increasing number of job shops that have fibre laser installations, where changes in safety equipment can create potential problems, according to Green: ‘We have to point out the fact that these lasers are working in the NIR. The beams are still invisible to the eye, and it is important to be aware that in some job shops one set of eyewear for certain servicing activities for a fibre laser can look the same as another set which is to be used with a CO₂ laser. [Laser job shops] need to be aware of differences such as these.’

In cases where industrial laser systems aren’t fully enclosed, other safety controls need to be implemented. ‘There are some systems that are wide open, for example on a sheet metal flat bed cutter that has no guarding around it,’ said Anibarro. Light curtains can be used for these laser systems, which consist of LEDs that are placed along the perimeter of the laser system. If a person steps close enough to the cutting table during operation and they break the light curtain, the laser will then cut off. In addition: ‘Safety mats can be used around the edge of the machine, which acts as a sensor – if you step on it, it deactivates the laser,’ added Anibarro.  

In situations where an industrial laser is not enclosed, companies providing laser safety services will work with a laser job shop to increase the safety of the facility. ‘We provide advice on how to implement as much in the way of enclosure of the beam as is reasonably practicable, along with additional procedures to be followed to make up for the imperfections of the enclosure,’ Green explained. ‘There are sometimes gaps in enclosures which are not easy to seal, and in situations like that you need to make the user aware of these shortcomings, and then implement administrative controls of their behaviour around the laser.’

However, according to Anibarro, an increasing number of companies are deciding to purchase all-in-one systems rather than address safety separately: ‘I’ve seen a change over the years. I’m finding more and more that companies are moving towards enclosing and purchasing systems that are already enclosed –even if they are just doing marking of products.’

Lasermet’s Paul Tozer also pointed out that the company’s dealings with system integrators that provide all-in-one systems has increased over the years: ‘We do a lot of work with OEMs that provide the whole system complete to their customers: the laser, the robot, the controller, along with the enclosure and interlocks that they get from us. The user then doesn’t have to think about the laser aspect because they have bought a complete finished system.’

When asked what needs to happen to increase laser safety further, both Anibarro and Green agreed that it isn’t the laser safety products that need to improve, but the training and education of industrial laser users. ‘The turnover in manufacturing facilities and job shops is so much that people need to be trained,’ Anibarro explained. ‘Also, there are job shops owned by small business owners, who may not be aware that there is a hazard there until an accident occurs or if they get visited by a regulatory agency.’

And it’s not just training of laser safety officers and people that work directly with the laser that is important, but the education of all members of staff, according to Green: ‘For a lot of people, if they notice a laser machine, they have no real knowledge of what that really means, and may be quite anxious about working with, or even in the same vicinity as, the laser.’ Anibarro agreed that a lot of uncertainty can arise when employees are not informed about the basics of how a laser system works: ‘Sometimes companies will put a sign up on a class one laser system that says “Danger – Laser Radiation” when there is no need for a danger sign since no hazard exists from a class one laser system during normal operation.

‘Another result of uneducated employees is, when the employees see the word radiation, they aren’t thinking non-ionising radiation, they are thinking of ionising radiation such as nuclear or x-ray. This will create an unrealistic fear of a perfectly safe system.’

Both Pro Laser and LIA provide laser safety training in the workplace not only to raise awareness of potential hazards, but to clear up any confusion regarding the dangers of laser systems. ‘Simple education will alleviate a lot of worries and keep staff from doing things that will put them in unsafe positions,’ commented Anibarro. ‘And it doesn’t have to be anything elaborate – even the sources on our website will enable people to get familiar with what lasers are, how they work, and how you can get injured.’

A growing problem, of which few companies buying industrial lasers are aware, is laser processing machines being imported from outside the EU that do not comply with safety regulations. Any laser processing machine that operates inside the EU has to be CE compliant. Machines that are bought in from outside the EU must be declared as CE compliant and have a declaration of conformity certificate. However, exporters can falsify paperwork, or present a real test certificate that does not apply to the specified machine.

According to AILU, anyone can import low-cost equipment through the internet, and a trend is growing for people jumping on the bandwagon insofar as lasers are concerned. A significant amount of the non-compliant laser processing machines arrive at the end user without being brought into compliance. ‘The machines are not being properly built, and may not comply with the laser safety standard,’ stated Green. ‘There are people who have purchased laser equipment, and are not familiar with laser standards. The machines are also supplied by companies who cannot provide the correct servicing of the equipment when it goes wrong.’

AILU is currently trying to raise awareness of this issue through its machine safety Special Interest Group (SIG), by collaborating with laser safety organisations to disseminate information to those selling and buying non-compliant laser materials processing machines.

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