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Brake monitoring without sensors
20 October 2015
Monitoring electromagnetic safety brakes is increasingly important. The Mayr Roba-Brake-Checker is not only able to energise brakes, but can also monitor them without the use of sensors. Hermann Bestle explains how.
By recognising the switching condition of the actuator and the wear on the brake linings, the Roba-Brake-Checker detects safety-critical conditions prior to their occurrence. Any changes in the braking torque can thus be instantly detected and countermeasures initiated.
The Roba-Brake-Checker can operate safety brakes at reduced power while simultaneously monitoring their switching condition. It is designed for an input voltage of 18-30 VDC or 42-54 VDC, higher than the previous approach of fast-acting rectifiers, and can control brakes with a coil nominal current of 10A or 5A. In addition, a higher cycle frequency is possible.
The device detects when the brake condition changes - whether the armature disk has been applied or released – and emits the respective switching condition of the brake via a signal output. The switching condition of safety brakes can therefore be directly recorded in machines and systems.
The module functions reliably without mechanical contacts and is wear-free, independent of the cycle frequency and count. The additional wiring and possible sealing of switches and sensors are therefore no longer required. In addition, it is possible with sensorless condition monitoring to adapt the over-excitation time automatically if required: here, an integrated automatic system would regulate the voltage to a set lowering voltage after a brake-specific over-excitation time. Using a DIP switch, the automatic system can be switched off, after which it is possible to set certain, specified values manually.
Through comparison of tightening current and holding current, the ROBA-brake-checker is able to detect possible wear, line breakage or, if applicable, to excessive heat-up.
Torque control
For applications which require braking torque control in addition to condition monitoring, the braking torque control module Roba-TorqControl is an upgrade which is additionally able to change the level of braking torque during operation through applying specific values of current and voltage. In this way, devices and machines can be evenly and gently decelerated, ideal for smart, networked machines.
Meanwhile, backlash-free Roba-guidestop safety brakes are now available in new construction sizes, covering nominal holding forces from 5 to 34kN.
Suspended loads present a substantial potential hazard in machines and systems – especially if people are positioned below them. Should an unintended fall or crash occur, the load must be brought to a standstill as quickly as possible in order to protect people and material reliably from damage.
Mayr has developed a reliable safety brake and backlash-free clamping unit for profiled rail guides, which brakes movements safely and quickly, and which clamps the axes rigidly and backlash-free during the running process.
The designs are dimensioned for four rail sizes made by established linear guide manufacturers. Also new are a compact design for the shorter sizes and integrated switching condition monitoring with contactless proximity switch.
The guidestop brakes are directly mounted onto the masses to be braked or held. This creates a decisive advantage, especially for gravity-loaded axes.
Drive elements between the motor and the moving mass - such as spindles, spindle nuts, shaft couplings or gearboxes – have no influence on safety, which differs from concepts featuring a motor brake, in which all drive elements transmit the braking torque up to the carriage. In addition, every element between the brake and the carriage has a negative effect on the rigidity. Therefore, Roba-guidestop safety brakes are significantly more rigid than motor brakes, pole brakes or band brakes.
Key Points
- The Roba-Brake-Checker can operate safety brakes at reduced power while simultaneously monitoring their switching condition
- The module functions reliably without mechanical contacts and is wear-free, independent of the cycle frequency and count
- The Roba-brake-checker is able to detect possible wear, line breakage or, if applicable, to excessive heat-up
- Torque measuring coupling
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