Technical safety measures for the safe use of hand-held laser processing devices

From an occupational safety point of view, the market launch of hand-held laser processing devices (HLDs) should be closely connected to machine safety qualification. In order to meet demands concerning a safe design of HLDs, research was performed to both develop and evaluate safety concepts for HLDs and to qualify technical measures for HLD laser safety. The work focused on the risk of injury especially for the skin arising from laser beam hazards by continuous-wave high-power laser systems typically used for welding and cutting operations. On the basis of risk assessments, both safety requirements on architectures of safety controls and safety related parts of control systems were defined, and prototype control systems were built. Apart from taking into account criteria claimed in standards, e.g., DIN EN ISO 13849-1, safety related parts were investigated concerning their applicability for use in HLDs and concerning malfunctions, signal propagation delays, and costs. A number of miniaturized sensors with different active principles and safety levels were tested with regard to their appropriateness for the respective type of HLD. For HLDs positioned on a work piece, the investigations covered contact and noncontact sensors such as mechanical switches, inductive, capacitive and ultrasonic sensors. Especially for freely operated HLDs, as they may be used, e.g., for cleaning applications, noncontact optical sensors and movement sensors to isolate the laser beam under fault conditions, e.g., slipping, were tested. Furthermore, sensors to detect faults in HLD beam guidance were qualified. Now, general principles and recommendations for the integration of safety controls into HLDs can be given. The conclusions will be incorporated into guidelines for manufacturers and users of HLDs.