Not only do today’s users expect technological products that are safe to use, available quickly and safe. Design engineers and machine and system builders, too, expect comprehensive support from their system partners. Festo’s safety concept covers not only motors and controllers but also axis mechanics.
«While the subject of machine safety is no longer new, it will continue to play a key role in machine and plant construction,» says Fredrik Stal, Head of Product Management Electric Drives at Festo. «This is due to the fact that there is a great deal of uncertainty in the market, and many users cannot handle such a complex issue without support from their system partners.» In applications that are not protected by safety guards, but where people can come into direct contact with plant components, all electromechanical systems must have integrated safety functions to guarantee adequate risk reduction.
Support by system partners
«Users must be offered an overall safety concept, which supports monitoring of the axis mechanics as well as safety-related clamping or braking,» says Stal. In the past, users often had to make do with a retrofitted safety concept. Many would take any safety switching device and wire the STO function. They also replaced the servo motor with a motor with a brake. «Many machine manufacturers think that this is enough,» he adds.
However, this does not take all possible errors into account, as a coupling assembly error or a cracked toothed belt in the reversing unit could render the brake useless. These errors would cause the slide unit and the load to fall, causing serious injury. Furthermore, undetected bearing damage could stretch the toothed belt or damage to the recirculating ball bearing guide could cause the axis to drop by several millimetres after a crash. The slide could therefore cause crushing.
Fully integrated approach
«A fully integrated solution monitors the axis mechanics and allows safety-related clamping or braking,» explains the drive expert. This is exactly what the safety-related electric axis EGC with dual-channel displacement encoder and clamping unit from Festo does. The mechanical system can be monitored by a motor encoder (first channel) and a linear displacement encoder (second channel) (EGC-M). The single-channel or dual-channel clamping units EGC-HPN for holding a position, crash protection and with emergency braking features facilitate safety measures, for example in the case of vertical axes.
These drive-related safety functions can be monitored by the certified safety system CMGA for motor controllers. Conventional safety command devices such as emergency stop switches, protective door switches, light curtains and laser scanners can be connected to the system. As soon as these trigger a safety requirement, a safety-related stop such as an SS1 or SS2 is triggered via the safety system CMGA or safely limited speed is monitored in set-up mode. For ease of use, there are pre-validated application programs for many machines. These reduce the complexity of a programmable safety system to the simplicity of a safety relay.