June 2020

42 June 2020 www.drivesncontrols.com n BRAKES, CLUTCHES AND COUPLINGS How should you specify servo brakes? W hether loads are being moved by industrial robots, by the vertical axes of machine tools, or in medical equipment servo axes – they must not drop or crash in an uncontrolled manner after power is turned off or fails, or if there is an emergency stop. Safety brakes designed to hold the axes in position reliably and safely, ensure that this will not happen. Incorrect selection or dimensioning of these brakes can lead to serious injuries and/or damage to property. Therefore, it is essential that you take a critical look at the technical details when specifying brakes for servomotors. Take industrial robots, for example. Their increasing use brings with it higher risks. If, for example, the power fails, the robot arm must be held immediately and accurately. It is important at the design stage to prevent the risks of loads dropping unexpectedly and long stopping distances. This means choosing the correct safety brakes as well as integrating them effectively into the complete system. Failsafe safety brakes are the first choice for servomotors, because they close in a de- energised condition. They provide the required braking torque even in an emergency stop, power failure, or interruption in the power supply caused, for example, by a cable breaking. To ensure that the brakes also provide enough friction in emergency stops and brake movements with a defined braking torque, they need to incorporate a friction lining developed for this purpose, together with a steel counter- friction surface. While this is common for safety brakes, permanent magnet brakes with steel-on-steel friction combinations reach their tribological limits here. There are servomotor safety brakes that Servomotor brakes are critical to the safety of personnel and machinery. Bernd Kees, a product manager at Mayr Power Transmission, offers advice on the key factors that you need to take into consideration when selecting brakes of this type.

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