In machining centers and machine tools, rotating instruments present a possible hazard to the operator. Manufacturers of machines are required to follow strict regulations to guarantee workplace safety. With the SD2 drive controller, SIEB & MEYER provides an intelligent solution: the built-in sensorless safety features SFM (Safe Frequency Monitor) and SLOF (Safe Limited Output Frequency) enable standstill monitoring and secure restriction of the rotating field of production spindles – all without extra speed sensors. The result is increased safety with reduced costs and maintenance effort.
“Mechanical engineers face the challenge of ensuring personal safety as well as productivity in the best possible way and in compliance with the standards,” explained Markus Finselberger, head of sales drive technology at SIEB & MEYER. “Classic safety solutions require speed sensors at motors or spindles to detect or prevent dangerous operational states. These sensors need space, harbor risks of failure and cause costs for installation, maintenance and replacement.”
With the TÜV-certified safety functions of SD2 by SIEB & MEYER, an additional speed sensor at the spindle is not necessary. The two functions SFM and SLOF are directly integrated in the drive controller:
SFM (Safe Frequency Monitor) detects after the switch-off command whether a sensorless spindle has reached a safe standstill or dropped below the previously defined non-critical speed value. If not, the access to the machine interior or a protective door remains locked, for example.
SLOF (Safe Limited Output Frequency) prevents a spindle from exceeding a critical speed – for example, to prevent tool breakage due to overspeed or to keep the spindle speed below a critical value during setup. If the defined limit value is exceeded, the system disables the output stage using the function STO (Safe Torque Off) and therefore stops generating torque. The spindle comes to a controlled standstill.
Another advantage: all drive controllers of the series SD2x and SD4x provide a load indicator function that evaluates the torque-forming current of the motor and therefore can be used to replace acoustic emission sensors. The load indicator determines load changes of the motor very precisely – a valuable function for tool monitoring, e.g. for early detection of tool wear or breakage.