Durability testing of innovative materials for laser safety barriers


A mobile test rig is designed at the institute for machine tools and industrial management (IWB) of the Technische Universität München in order to undertake standardized safety barrier tests according to iec 60825-4 with his own system technology. An innovative material – “Ipmaterial” is tested in addition to conventional materials for laser protection walls using this test rig.

The system technology and the beam sources in the field of laser material processing were subject to a rapid development during the past few years. In addition to the considerable increase of the commercially available output power and the beam quality, the handling solutions became significantly more flexible. The kinematics for generating the relative movement between the optics and the workpiece evolved during time; while portal systems and modified CNC machine tools were used in early systems, six-axis industrial  robots have been considered as standard since the beginning of this century1 . The light applicators have reached a new stage of evolution as well: Besides the conventional fixed optics, deflection optics are available today, which allow to sweep a wide area with the laser beam during a small time by a small deflection of a mirror  system.
On the one hand this leads to the development of new processing methods, such as the Remote Ablation Cutting (RAC)2  or the Remote Fusion Cutting (RFC)3 , but on the other hand it also increases the risk for the machine operator and the environment. To respond to this threat, it is important to develop and implement new and sustainable safety concepts. For this purpose, a profound knowledge of the influences on the protection time of passive laser barriers is needed.

Measurement method for the time to failure of passive laser safety barriers
For  this  reason, a mobile  test  rig  has been designed at  the  Institute of Machine Tools and Industrial Management (Iwb) of the Technische Universität München, which will enable all users to perform standardized barrier tests according to IEC  60825-44  with their own system technology. Thus, a suitable measuring device (see figure 1) was designed and built  to determine the time to failure of passive barriers: Via a potential-free contact of the laser control and an A/D converter card, the time measurement of the software is triggered by the emission signal of the beam source. Simultaneously to the failure of the protective wall sample, the radiation penetrates the housing of the measurement setup, is subsequently scattered over a copper cone and dectected by an infrared sensitive photodiode. At this moment, the time recording stops.

Figure 1
To use the measurement setup described above in a mobile way and to collect a multitude  of data within  the framework of the AiF-funded research project „ PaLaSi “, it is equipped with a telescopic double-walled laser cabin including active laser safety sensors of the type „LaserSpy“6 . Furthermore, a particle measuring device is installed, which allows to measure the pollution  by smoke. In addition,  an exhaust ventilation system is provided which removes the generated fumes from the cell. A section of the overall structure of the test rig is shown in figure 2.