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High holding forces

19 August 2016

mayr power transmission is extending the tried-and-tested ROBA-guidestop series with a pneumatically-released version, which provides users with new possibilities thanks to the high holding forces.

For machines, in which a hydraulic system is already available, users can still use the hydraulically-released ROBA-guidestop safety brakes. However, in applications where a hydraulics system would have to be installed first in order to operate a brake with high holding forces or in which several brakes would be necessary to achieve the required forces, the pneumatically-released ROBA-guidestop safety brake is now used. It clamps profiled rails equally accurately and backlash-free while achieving the same high holding forces as the hydraulic design of the brake.

The pneumatic ROBA-guidestop is opened with compressed air at 20 to 30 bar. In order to achieve the necessary operating pressure, a compact pressure booster is used in combination with the brake, which mechanically increases the system pressure from 4 to 6 bar as is usual in pneumatic networks, without the use of external energy. This innovative concept enables a selective pressure increase directly prior to the brake, i.e. directly in the system where the higher pressure is required – as a result, short high-pressure lines suffice. The pneumatic ROBA-guidestop safety brake is available in five construction sizes – each size in both a standard design and in a compact, short design – covering a range of holding forces from 1 to 34 kN. The brake is designed for the different rail construction sizes of conventional linear guidance manufacturers.

Just like the hydraulic brake design, the pneumatic ROBA-guidestop safety brake acts with extremely high rigidity directly applied to the linear guidance. This means that it is mounted directly on the masses which should be held. This provides a decisive advantage, especially concerning gravity-loaded axes, where the hazard risk for people should be reduced: Drive elements between the motor and the moving mass, such as spindles, spindle nuts, shaft couplings or gearboxes, therefore have no influence on the safety – as opposed to the concepts using motor brakes, where all drive elements transmit the braking torque to the carriage. Systems using ROBA-guidestop safety brakes therefore enable a significantly higher rigidity than solutions featuring rotary brakes integrated into servomotors.

The backlash-free clamping of the ROBA-guidestop directly onto the profile rail provides yet further advantages: The additional rigidity of the NC axis increases process accuracy, improves machining performance and can provide further technological advantages for heavy machining, for example. The machining produces less vibrations and therefore the surface quality of the workpiece is positively influenced. In case of a stationary axis, for example during machining, the brake can absorb the load. As a result, it is possible to switch off the drive motor in this phase and remove it from the controls. This eliminates control movements and is therefore gentle on the ball screw spindle. The closed brake absorbs the axial forces. The service life and maintenance intervals of the drive components are extended.