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mayr0713technical articles

EMO Hall 25 stand B17

Mayr Antriebstechnik presents an alternative to permanent magnet brakes (PMB) for use in servomotors: the new spring-actuated safety brake "ROBA-stop power"Works according to the so-called" fail-safe "principle and thus offers maximum security even in the event of a power failure or emergency stop. For example, it is predestined for use in gravity-loaded axles of machine tools, handling portals or assembly facilities.

Usually servomotors are equipped with PMB. They are relatively inexpensive and power-tight. Meanwhile, however, the cost advantage disappears because the magnetic materials have become very expensive. Therefore, the drive specialist now sees good opportunities for the spring-loaded brake. It is less sensitive than the PMB, because at the often reached high temperatures in the engine of 120 ° C and more, the permanent magnets can lose magnetic force, which leads to the drop of the braking torque.

Due to its design, PMB is also superior to the spring-actuated safety brake: when braking from the movement, the iron-iron and iron friction lining pairing creates a mixed friction. For this friction pair, strong friction fluctuations and low permissible friction work as well as friction losses are typical. For static braking, this is not a problem, because the holding brake with stationary drive einfalls.Bei dynamic emergency braking out of full speed, however, it looks different: friction fluctuations have a direct effect on the amount of braking torque. In addition, PMB are not designed for high friction work and damage up to total failure of the brake is possible.

With the closed spring-actuated safety brake, the rotor is held in place with the friction linings between the armature disk and the brake disk. If the built-in magnetic coil is energized, the magnetic field pulls the armature disk against the force of the springs against the coil carrier and thus releases the brake. Thanks to this fail-safe principle, the servo brake works safely and reliably.

In addition, the ROBA-servostop is suitable for use below Ambient temperatures up to 120 ° C. The high temperature resistance is possible because the braking torque is generated by special organic friction linings. These temperature resistant pads have a high, uniform coefficient of friction.

The ROBA-servostop allows a tenfold increase in the load mass ratios: Normally, in servo drives in favor Good control characteristics and high dynamics Load mass ratios from load to motor in the order of magnitude 3: 1 or less selected. Thanks to its high permissible friction work and friction losses, ROBA-servostop allows load mass ratios of 30: 1 and more. While permanent magnet brakes tend to "eat" under such conditions, potentially causing a sharp increase in braking torque, the ROBA-servostop avoids potential damage to the powertrain.

Low wear and easy installation

In developing the brake torque producing components and all other components involved in the transmission, engineers have paid attention to high performance and low wear. In addition, the simple and robust construction of the ROBA-servostop considerably simplifies installation. The operating air gap does not need to be adjusted and accurate axial positioning on the motor shaft is unnecessary. The brake always works exactly and reliably with the same air gap and is not affected by bearing clearance and temperature expansion. Thus, the installation effort is much lower than permanent magnet brakes. installation errors are almost impossible.

If servo brakes are installed in the A-end shield of the motor, thermal expansions have no serious influencebecause here is the camp. If the brake is located on the B-end shield of the motor, the position of the brake part sitting on the shaft changes with temperature changes to the part of the brake which is attached to the end shield. For example, this can change the working air gap in the brake unacceptably in the case of a PMB. The ROBA-servostop can also be integrated in the B-bearing side of the motor without any restrictions, as thermal expansions and bearing play have no negative influence on the function and reliability of the brake.

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Pepperl + Fuchs