June 2021

36 n BRAKES, CLUTCHES AND COUPLINGS June 2021 www.drivesncontrols.com Choosing high-speed clutches and couplings I n many industries, there is a growing demand for dynamic, fast-rotating drive axes. Safety and reliability are important considerations because at high speeds, collisions can cause serious injuries or damage materials. For applications such as measuring and testing, high-speed axes need to be extremely precise. In such applications, mechanical torque-limiting clutches can safeguard test pieces and measuring systems. They can open a drive line and decouple the running masses within fractions of a second – faster than using electronic monitoring functions. Clutches need to be chosen carefully because an imprecise or slow clutch that affects a measurement system or triggers at the wrong time not only makes evaluation in the test field difficult, but also simply defeats its purpose. Torque limiters that protect against damage caused by overloads, must be suitable for high-speed operation. It is also important that the clutches transmit the torque backlash-free and with high torsional rigidity. They should also be compact and have a low mass moment of inertia, but a high performance density. Compact, high-performance clutches have a small outer diameter with a relatively large bore diameter. The integrated elements, via which the torque is transmitted, are arranged symmetrically. The bore diameter, outer diameter and element size must be harmonious to achieve a low- vibration system that works precisely. In addition to torque limiters, shaft misalignment compensation couplings can minimise interference from affecting measurement flanges. So-called parasitic forces can occur due to alignment errors in the driveline. Misalignments between the input and the output will occur in almost all applications, and shaft misalignment compensation couplings are therefore used together with measurement flanges. It is important that the geometrical basis is right and that the clutches are designed for high-speed operation. Precise manufacturing and high balance quality An important criterion is that couplings need to have a high performance density. Designs made of steel should be characterised by a low mass and mass inertia, and at the same time be capable of achieving speeds of up to 30,000 rpm. In the high-speed range, you should make sure that a relatively large coupling is not simply made of aluminium or titanium to save weight. A compact version made of steel, which is more rigid and can handle more alternating loads, might be more suitable. It is important that you consider the application when selecting the coupling and its materials. Here, however, it is necessary to weigh up between the material properties – such as weight, rigidity or fatigue strength – and the final application parameters such as actual speeds, load cycles and variations, bearing distances, and bore diameters. Last, but not least, the price/performance ratio is also important. Torsional rigidity is often an critical criterion, especially when measuring torsion angles or elasticities, for example. Not even titanium can match the rigidity of steel in such applications. However, if the focus is on many acceleration cycles and the mass moment of inertia, then components made from lightweight materials such as aluminium or titanium may be a better choice. Titanium is particularly suitable for endurance applications and when variations in load occur frequently. n High-speed axes need reliable clutches and couplings, both for overload protection and to compensate for shaft misalignments. This article from Mayr offers advice on choosing torque limiters and shaft couplings for high-speed applications. Checklist for high-speed clutches and couplings n Define the requirements for the clutch/coupling as precisely as possible. Make sure that it suits the ambient conditions. n Ensure that the clutch/coupling is suitable for high-speed applications. This can cut costs such as balancing. n Ensure that the backlash-free capability is retained over the entire service life of the clutch/coupling. This guards against wear and premature failure. n Make sure that the catalogue data can be achieved reliably under real operating conditions. High-speed clutches, such as mayr’s EAS-HSE models, can offer reliable protection for equipment without influencing signals.