19 Jul Safe Selection and Use of Laser Machines in Education
Laser Machine Safety
CO2 laser engraving and cutting machines are now in frequent use in education and can present hazards if not selected and operated correctly. HPC Laser look at some of the fundamental issues that should be considered.
It is a common misconception that the visible red laser is responsible for providing the engraving and cutting function in a laser machine. In fact, this low power device is only used for positioning and it is the much more powerful invisible beam, usually generated in a water cooled glass tube in the rear of the machine that provides the more powerful laser for the engraving and cutting functions.
Similar to the way in which the suns rays can be focussed and intensified using a magnifying glass, CO2 laser engraving and cutting machines work by passing this invisible laser beam of typically 6-7mm diameter through a focussing lens. This reduces the beam diameter down to only microns at the correct focal height (usually around 50mm from workpiece to lens) which increases the intensity of the beam sufficiently to provide the engraving and cutting capabilities of the machine.
Once the unfocussed beam has passed through the lens it begins to diverge at the same rate at which it was focussed. Hence at 50mm below the focal point, the beam returns to its original 6-7mm. As the beam continues to diverge further away from the lens, it continues to grow and weaken and is scattered around the machine cabinet. This scattered beam is then absorbed by the coated metal surfaces of the machine. Because of the relative ease in which the focussed beam weakens and becomes harmless, it is the unfocussed beam that is considered the more hazardous of the two, particularly due to its ability to travel long distances whilst losing only a small proportion of its power.
In compliance with international standards, laser machines are classified from class 1 to 4 depending upon the level of laser radiation emitted from the machine during operation. Class 1 is typical of a DVD player for example where the laser is fully contained within the machine housing. Class 4 would be typical of a machine where direct operator access to the laser beam may be possible. This could include a large industrial flatbed machine with no enclosure, but also of a cabinet type machine being operated with the cabinet doors open in order to process a larger piece of material, a scenario that is entirely possible in an educational environment. In such circumstances the machine operator and any personnel in the immediate vicinity of the machine should be familiar with the safety requirements of a class 4 laser system, including the wearing of appropriate laser safety eyewear.
Firstly, and most importantly NEVER operate the machine unattended. No matter how tedious the cutting or engraving process is, do not leave the machine whilst it is operating. If a small flame does break out whilst the machine is working, simply press the pause button on the machine keypad, wait until the flame is extinguished and then resume operation. The machine will continue once operation is resumed and the quality of your work will not be affected.
The effectiveness of the air assist compressor should be checked periodically. A properly functioning compressor delivering air to the machine nozzle clears away smoke, debris and fumes but also minimises the risk of igniting flames during processing.
HPC Laser operate a strict policy in terms of training in machine safety. There are warning labels on each of our machines, there are warnings and notifications in our operating manuals and machine supervision is a very clear element of our training programme when we supply a new machine. As part of our standard training programme, every customer is fully briefed regarding the risk of leaving the machine unattended.
Cleanliness is another very important factor in fire risk mitigation. Whilst cutting some materials such as wood and plastics, potentially flammable deposits are deposited on the machine bed. If they are allowed to accumulate these can increase the risk of ignition. Addressing this risk is extremely straightforward – just clean these deposits from the machine bed on a regular basis.
Always keep an easily accessible fire extinguisher by the machine, just in case. Because electricity is involved and you may have to tackle a fire whilst the machine is still plugged in, we recommend a Co2 or other electrically-compatible extinguisher. HPC Laser also recommend the training of appropriate personnel in the use of fire extinguishers.
Keys to operate the machine should only be accessible to suitably trained and qualified persons.
Basic machine housekeeping is always recommended and very good practice. Keep your machine cabinet clean and free from dust and material offcuts. Adopt a policy of regularly cleaning and maintenance as part of your operating regime.
Regardless of the brand of your laser machine, NEVER ALLOW YOUR MACHINE TO BE OPERATED UNATTENDED.
Because of the incredible flexibility of modern laser engraving and cutting machines it is easy to forget that not everything can be safely processed. PVC for example produces carbon monoxide, dioxins and chlorinated furans when burned and can seriously damage the machine but more significantly present significant health risks to any personnel in the vicinity of the machine.
If you are in any doubt, it is imperative to discuss your requirements with the material manufacturer and obtain a copy of their appropriate health and safety documentation before starting work.
A very significant aspect of machine safety often overlooked by buyers of laser machines is that of compliance with the appropriate CE safety standards. The relative ease of buying potentially non-compliant and hazardous machines either directly from an overseas manufacturer or through a UK supplier brings with it a potentially serious safety risk.
Any equipment imported into the EU must be in compliance with the appropriate EU directives which specify the legislative requirements of the equipment. Various ISO and EN standards offer product-specific guidance on how to comply with these directives. It is this combination of directives and standards that form the basis of the CE compliance assessment that must be carried out.
Once an assessment of the product has been undertaken and compliance is proven, a technical file of supporting evidence is compiled. The file owner is then able to create their own CE declaration of conformity which states the directives and standards that the machine is compliant with.
The wording of some ISO/EN standards can be open to a degree of interpretation by the reader and good practice is to ensure that assessment is carried out against the most stringent interpretation of the standard. One aspect of compliance that is of particular importance to laser machines is that any cabinet panels that can be opened and are required for servicing and maintenance should be fitted with CE marked failsafe security switches. These panels include the machine lid, any drawer or panel that can be removed for debris recovery and the door containing the laser tube itself. Such switches serve to ensure that under all reasonable circumstances the operator is unable to gain access to the potentially hazardous unfocussed laser beam.
CE compliance also requires the machine supplier to offer a comprehensive operating and maintenance manual with the equipment. Such documentation should include safe location and handling instructions, instructions for safe operation and a map of all machine warning labels with instructions on how to obtain replacements should any be lost.
Laser engraving and cutting machines form an integral part of the UK education curriculum. When selected and operated correctly they can provide safe and reliable operation for many years. If you would like any further guidance regarding safe laser machine operation, certification, selection or please do not hesitate to contact HPC Laser who would be pleased to assist.