Design aspects of class 1 laser enclosures for a laser-processing machine

Abstract

To achieve Class 1 a laser enclosure must prevent human access to hazardous levels of laser radiation hazard during normal use of the machine.EN 60825-1 defines ‘human access’ in the form of three ‘tests’ or conditions: (a) the capability for any part of the human body to meet hazardous laser radiation as emitted from an aperture, (b) the capability for a straight 12 mm probe up to 80 mm long (i.e. a standard finger) to intercept Class 2, 2M or 3R laser radiation, and (c) (for Class 3B or 4 laser radiation within a housing) the capability for any part of the human body to meet hazardous laser radiation that can be reflected by any single introduced flat surface from the interior of the product through any opening in its protective housing. Informative Annex E, entitled ‘High power laser considerations particularly appropriate to materials processing laser products’ highlights, in particular, the measures available for minimising the likelihood of strong errant laser beams threatening the integrity of the protective housing.This specification for the protective housing is extended in EN60825-4 ‘Laser Guards’, which unlike EN 60825-1, is risk-based. Laser radiation is only one of many hazards encountered in the industrial workplace and by adopting a risk-based approach it can it be treated in the same way as other hazards to be guarded. This allows great flexibility in the design of guards for laser processing machines.EN 12626 is the standard that supports the Machinery Directive for laser processing machines. It requires, among other things, that the machine be a Class 1 laser product. The conflict between this ‘worst single fault’ condition for Class 1 in EN60825-1 and the assessment of machine safety under ‘reasonably foreseeable fault conditions’ is at the heart of much confusion in the industrial laser industry.Here we set out the requirements for Class 1 under the various relevant standards and provide some practical examples of how to satisfy the requirement for preventing access to hazardous levels of laser radiation while at the same time providing the necessary degree of access within the enclosure for the loading and unloading of parts.To achieve Class 1 a laser enclosure must prevent human access to hazardous levels of laser radiation hazard during normal use of the machine.EN 60825-1 defines ‘human access’ in the form of three ‘tests’ or conditions: (a) the capability for any part of the human body to meet hazardous laser radiation as emitted from an aperture, (b) the capability for a straight 12 mm probe up to 80 mm long (i.e. a standard finger) to intercept Class 2, 2M or 3R laser radiation, and (c) (for Class 3B or 4 laser radiation within a housing) the capability for any part of the human body to meet hazardous laser radiation that can be reflected by any single introduced flat surface from the interior of the product through any opening in its protective housing. Informative Annex E, entitled ‘High power laser considerations particularly appropriate to materials processing laser products’ highlights, in particular, the measures available for minimising the likelihood of strong errant laser beams threatening the integrity of the ...