Laser machines commonly have the reputation that the laser is the major hazard; some even think that it is only hazard. Of course, this is far from the real life.

In the EU, all machinery put into service is required to conform to the Machinery Directive (Directive 2006/42. being the latest revision of this Directive originally initiated in early 1990’s). This Directive specified the Essential Safety Requirements (ESR’s) for all machinery.

The Machinery Directive is supported by a type-A standard EN ISO 12100 Series that gives the basic concepts and general aspects that can be applied to all machines. The primary purpose of this standard is to provide designers with guidance to enable them to produce machines that are safe for their intended use during the overall lifecycle of the machine.  Part 1 of this standard defines the terms used.  These do include the hazards generated by radiation hazards, say laser radiation, which can have immediate effects (e.g. burns) or long-term effects but also include all hazards relevant to machinery that need to be considered.
It is assumed that when present on machinery, a hazard will sooner or later lead to harm if no protective measures are taken.  Protective measures are recommended to be included at the design stage and should take into account the experience of the user.  Thus the designer should take the following actions in the order indicated:

• Specify the limits and intended use of the machinery;
• Identify the hazards;
• Estimate the risk for each hazard;
• Evaluate the risk and apply risk reductions if required;
• Eliminate the hazard or reduce the risk by using protective measures.

The objective is to apply the greatest risk reduction taking into account:

• The safety of the machine during ALL phases of its lifecycle. This includes:
• Installation and commissioning;
• Operational use;
• Maintenance;
• Service;
• Decommissioning;
• The ability of the machine to perform its function;
• The usability of the machine;
• The manufacturing and operational costs

To meet some of these requirements the protective measures taken may include guards but of equal importance are the safety-related aspects of the machine control and the intended method of operation. Although it is often perceived that the primary hazard associated with laser processing machines is seen as the laser radiation hazard, equal attention is clearly required to be given to any other hazards that may be present.  Thus the selection of the appropriate controls and guards requires close attention.

Part 2 of the standard EN ISO 12100 gives general guidance on this selection.  The exact choice of a safeguard for a particular machine is made on the basis of the risk assessment for that machine.  In selecting an appropriate safeguard, it should be remembered that simple solution is probably the best: for example, a fixed guard is simple and should be used where access of an operator to the danger zone is not required during normal operation.  Where there is a need for frequent access, the fixed guard is not a practicable solution and an alternative protective measure must be adopted such as a movable interlocking guard.  Often a combination of safeguards is required. The standard gives excellent advice covering a wide number of situations. When making these design decisions, all aspects of the machine lifecycle must be considered. The Service Engineer should not be forgotten especially as he may have to remove or displace the normal provided safeguards in order to complete the service activities necessary. Thus, the overall design needs to take into account ALL the potential tasks required to install and keep the machine in operation.

The key preparation to the design of safeguards is risk assessment.  Risk assessment is often not a popular task as it requires careful disciplined thought of just what hazards are around and what might go wrong.  Human exposure to a wide range of hazards in addition to the laser beam can produce a moderate to severe injury. The probability of such an exposure occurring becomes the key variable element in assessing the risk of injury. The reduction of risk to tolerable levels is an iterative process. There is no standard approach to procedure and documentation for this process. Nevertheless, the steps involved are universal and are described in EN 1050 (ISO 14121).

A risk assessment should be performed to identify hazardous situations and to assess the foreseeable exposure level. This assessment should take into account a number of factors, including the following.

• Process: The nature of the process, such as cutting, drilling, welding, marking is important. The machine may be dedicated or offer several processes

• Process control: This factor addresses in particular the time during which laser guards may be exposed under fault conditions.

• Manual operation: Operator intervention considerations include the need and provision for manual control, the means and effectiveness of process observation (including the location of viewing windows or cameras) and the accessibility and effectiveness of service intervention in the event of a fault condition becoming evident.

• Robot operation: The full range of robot movements, impact protection for the robot head and general protection of power source lines including the beam delivery to the robot, and the means of limiting robot head movement and direction (e.g. software limits, hardware limits and physical limits), in particular the closest approach to the periphery of the machine boundaries.

• Work piece: The geometry, composition and surface finish of the work piece.

• Clamping and fixturing: The holding and positioning of the work piece.

• Loading and unloading: The method by which the work piece is introduced and removed, in particular whether it is manual or automatic, single piece or continuous, and the method (e.g. sliding, rolling or lifting door) and control of access to the process zone.

• Features of the laser process zone: Relevant features include the laser power and wavelength, the focal length of optics, the degrees of freedom of the beam delivery (e.g. number of axes of movement).

• Beam delivery: Beam delivery considerations include the optical method (mirror or fibre) and means of inspection, positioning and movement of optical components including the structural integrity of the mounting of beam path components, means of maintaining the condition of optical components, means of maintenance of beam alignment, provision of on-line errant and non-errant beam monitoring, and means of construction of the beam delivery enclosure..

• Location of workers: The defined work area, in particular the minimum distance of permitted approach to the machine. Included in this consideration are overhead locations (e.g. crane operators, office workers on elevated walkways), steps and ladders in the vicinity.

• Maintenance and service provision: This consideration includes the means and control of access to maintenance positions (e.g. removable panels, key control) and the provision of interlock overrides and emergency stops.

In conclusion, consideration of the safety-related controls and guarding for laser installations and particularly industrial laser processing machines needs to be much more than just about the protective requirements for laser radiation.  It is very rare that the laser radiation hazard is the only hazard that the equipment designer is required to take into account.  There are a number of relevant and extremely useful standards (most referenced in EN ISO 12100) that can be used to aid the design.  Some time ago, when the Machinery Directive was first introduced into the UK, back in the early 90’s, there was considerable reticence among many machine designers to review their designs in the light of the, then, “new” requirements.  It soon became apparent that the requirements were extremely sensible. Subsequent to a period of re-education, designers acknowledged the advantages, and all machine design has significantly improved. However even though a decade has passed since the introduction of the Machinery Directive, there are still some designers who need to embark on the path of enlightenment.