From the 2001 Prolaser Newsletter:

A wide range of harmonised standards are available to help manufacturers supply safe laser processing machines, but significant differences nevertheless exist between suppliers, users and various governmental organisations in the interpretation of machine safety requirements. Laser use in industry has an excellent safety record, yet Pro Laser safety audits have highlighted a number of problem areas.

Most modern laser processing machines are adequately guarded to protect the operator during normal operation but a closer inspection often reveals short-comings. Most flatbed CO2 laser cutting machines are open-topped and possess non-essential gaps in the peripheral guarding that prevent them from achieving a Class 1 laser hazard classification. But even where guarding is complete, examples can be found where it is not 'fit for purpose' i.e. it could be easily damaged by 'wear and tear' in normal use. Other common criticisms of the guarding include inadequate provision for safe maintenance and servicing, missing guard interlocks or interlocksof an unacceptable design for a safety-critical application and inadequate protection of gas pipes and other service supplies from laser damage.

High power laser beams have the ability to melt or burn their way through most materials that might be used for guarding, so as well as providing a proper enclosure the integrity of the laser beam path must be maintained from source to workpiece and this in turn raises maintenance and servicing issues related to the condition and alignment of optical components. Indeed, such considerations form an essential part of the risk assessment that the machine manufacturer is required to undertake. Nevertheless, situations are occasionally encountered where the guarding is clearly inadequate to deal with laser exposure under 'worst case reasonably foreseeable conditions' or where space constraints result in an inadequate minimum distance between the focusing head and areas of guarding at which, within its permitted freedom of movement, it could point.

Inspection and alignment of laser beam paths is a key beamline design consideration, yet many examples can be found of poor design, such as: poor access to optics for inspection and adjustment; optical mounts that cannot be removed for inspection without requiring realignment after reinsertion; key optical components (e.g. turning mirrors) that are not interlocked to prevent emission of the laser beam until they are replaced; alignment aides (e.g. a co-linear Class 2 laser, cross-wire jigs) not provided; guarding design that do not facilitate safe alignment.

The factory environment is generally not conducive to maintaining laser beam path stability and high transmission, yet all too often vibration, temperature cycling and mechanical impacts are inadequately accounted for in the preparation of the factory area and the siting of the machine. Manufacturers too have an important part to play, by designing their machines to provide adequate protection of the beamline optics from laser generated fume and airborne dust and moisture, especially during maintenance and service procedures.

High power laser safety is intimately connected with machine reliability and as a result, the cost of engineering-in the safety can generally be justified purely on grounds of increased reliability and performance.

(A more complete version of our report on machine safety can be found in the the proceedings of Lasers in Manufacturing, Munich 2001, or directly from Pro Laser.)

Pro Laser offers machine safety design, assessments and checks for CE conformity