June 2020

Contact our dedicated Couplings & Drives division COUPLING SOLUTIONS FROM SKF ® Tyre Couplings www.acorn-ind.co.uk T: 0800 8766 441 E: couplings&drives@acorn-ind.co.uk Your authorised SKF distributor Grid Couplings Jaw Couplings n BRAKES, CLUTCHES AND COUPLINGS are especially adapted to the needs of robotics. Users can choose between classic servobrakes in the motor (with hubs and toothed rotors), or pad systems with large inner diameters. The latter are designed to be integrated into robot joints. But even classic brakes can be adapted and integrated directly into a joint. In the motor, it is preferable to install servobrakes in the A-bearing shield, because the fixed bearing is located here and thermal expansion cannot affect the brake severely. However, brakes can also be integrated into the B-bearing side of the motor without restriction, as thermal expansion and bearing backlash here do not influence the function and reliability of the brakes negatively. Alternatively, you can also use brakes attached to the motor in a modular fashion. When it comes to magnetic actuation, high-quality servo brakes are small, light and extremely fast. They are also wear-resistant. For servodrive applications, load/motor mass ratios of 3:1 or smaller are normally chosen to achieve of good control characteristics and high dynamics. With some brakes, high permitted friction work and friction powers mean that load-mass ratios of 30:1 or higher are possible. Stopping distances Short stopping distances are important for the safety of people and machinery. Brake switching times are decisive to achieving these distances, because during free-fall before the brake closes and retardation takes effect, the mass continues to accelerate – possibly to such high values that the capabilities of the brake are exceeded. When choosing safety brakes, you should therefore ensure that verified switching times are as short as possible – and that these switching times can be maintained throughout the brake’s life. Monitoring is important here. Previously it was not possible to monitor servobrakes due to their small air gaps. Now, however, there are “intelligent” systems that can monitor brakes without needing sensors. Modules that not only supply the brakes, but also monitor them without sensors, can provide data on switching times, currents, voltages, resistance, power and relative attraction current. This last parameter can be used to draw conclusions about critical brake operating conditions. Using an evaluation programme, you can see whether everything is running smoothly, or whether maintenance is needed. For example, by detecting an air gap that has become too large in good time, safety becomes “visible” and you can plan maintenance, with the operator or manufacturer undertaking this in a targeted manner. Error or warning signals also allow the installation to be integrated into remote maintenance systems. To ensure that brakes always deliver the highest level of safety, it is important that the static and dynamic braking torques suit the application. You need to check these conditions in trials. I recommend that you also find out whether the brake manufacturer has subjected them to realistic tests. Every safety brake leaving the manufacturer’s plant should undergo a 100% inspection after assembly and adjustment. The measured values should be kept in an electronic database with the brake’s serial number, thus ensuring 100% traceability. n Servomotor safety brakes are available that have been specially adapted for robotic applications. Users can choose between traditional designs incorporating rotors and teeth (above) or pad brakes with large inner diameters (left), designed to fit inside a robot joint. Images: mayr power transmission

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