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Reliable shaft couplings for all drive constellations

18 February 2020

While there no shortage of options when it comes to choosing shaft couplings, the devil is in the detail, so it is worthwhile taking a critical look at the technical product details and the range of services offered by the manufacturer

Even when many shaft couplings appear comparable at first glance – the devil is in the detail. And yet precisely these technical details provide decisive advantages during operation.

In servo technology, preferably steel bellows, elastomer and disk pack couplings are used; these are amongst the most common and most attractive backlash-free shaft couplings. However, each drive has its own special features and places very different demands on the coupling. Therefore users should define the requirements on the servo coupling as precisely as possible based on the technical data of their drive and the drive constellation. Furthermore, they should make sure that the selected coupling fits the ambient conditions which actually prevail in practical applications. Many companies are prepared to provide samples for testing purposes.

Compact design

All-steel disk pack couplings are the preferred choice in the industry, above all for dynamic drive axes, which are used for example in test stand construction. Today, it is important that these couplings offer a high performance density. High performance density means smaller outer diameter, reduced weight and low mass moments of inertia. As a result load alternations can take place more quickly, the drive accelerates and decelerates in a shorter period of time. Due to the reduced amount of mass to be accelerated, the operating expenses are also reduced, and the handling and installation of the coupling becomes easier. Small dimensions are also advantageous in machines of a compact design, where little installation space is available. Over and above this, a compact construction with high performance density also means less raw materials and materials are used during production of the coupling.

Performance density

During the selection of all-steel disk pack couplings, it is important to query the nominal torques defined in the catalogue critically: Can the provider permit the full nominal torque as the alternating torque? Is a reduction of the nominal torque due to misalignment, overall load configuration or balance requirements necessary? Only for technically leading products, the nominal torques stated in the catalogue can be used without restrictions. Such spring steel disk pack couplings with a high performance density can be produced far smaller in size.

it is important to query the nominal torques defined in the catalogue critically

Providers who have to consider misalignments and alternating torques for dimensioning often have to select a larger coupling for the same nominal torque and also the same speed. High-quality shaft couplings such as the ROBA-DS disk pack couplings by mayr power transmission simultaneously unite high performance density with absolute backlash-free function. Design details such as the blasting of the disks and the use of specially-shaped collar bushings provide a backlash-free flow of force with excellent force flow density between the input and output.  

Comprehensive testing

High-quality couplings are backlash-free – and not just in new condition. On mayr power transmission couplings, the backlash-free function is retained over the entire service lifetime. This protects them from wear and premature failure, above all at high speeds. It is also important, in particular in the high-speed range, that the individual parts are manufactured with high levels of precision and narrow axial run-out and shaft run-out tolerances, and that the couplings feature a high balance quality. This is important as the couplings must function accurately and reliably even under extreme conditions. To ensure this, the established family-run company from Mauerstetten has extensive testing possibilities at its disposal and tests the couplings comprehensively under the conditions prevailing in real application cases. Therefore, even for so-called mass products such as shaft couplings, a modern manufacturing process and the required experience and know-how in the field of power transmission are indispensable.

Wide product range

When selecting shaft couplings, users should also make sure that the manufacturer provides a wide and matured product portfolio – as a range of variants means a high degree of flexibility for different applications. mayr power transmission is in a position to offer a comprehensive product portfolio, and thus to cover a wide range of torques – from very small to very large torque values – and speeds. In addition, the company’s wide selection of standard modules with a multitude of available hub designs also ensures adaptability in diverse drive constellations. The couplings can thus also be easily and quickly installed and de-installed even in difficult ambient conditions using the appropriate selected hubs. But also in the area of special designs, which supplement the standard module range, a range of variants is expedient and recommendable. For example, if shafts are to be connected across larger distances in high-speed drive constellations, it is very frequently necessary to place a length-adapted sleeve between the two coupling hubs.

The critical bending speed of the sleeve must not lie within the operating speed range. Intermediate sleeves made from carbon fibre-reinforced plastic (CFRP) permit high speeds even with long couplings.  In comparison to steel, the CFRP versions feature a far higher critical bending speed. In addition, these CFRP sleeves are up to 80% lighter, which plays a particularly significant role in the case of large construction sizes and long sleeves. Another advantage of the plastic composite is its high corrosion resistance. If additional leakage resistance is requested for an application, i.e. electrical insulation is required, then fibreglass-reinforced plastics are used.

Delivery times

mayr power transmission has just supplemented its standard module range with numerous new hub designs and intermediate sleeves. So now the company is in a position to offer solutions for all drive constellations in servo technology easily and quickly. The intelligent modular system also ensures high availability and short delivery times for standard components. Furthermore, the power transmission specialist is equipping itself for the future by reacting to continuously increasing challenges with new, modern production methods and optimised internal handling. For the customers, this means a large selection of couplings, short delivery times and favourable prices – naturally in the accustomed quality, made by mayr power transmission in Mauerstetten.

in many applications combinations of shaft couplings and torque limiters are used.

Another aspect is that in many applications combinations of shaft couplings and torque limiters are used. The latter protect machines against expensive overload damage. Here, mayr power transmission is able to provide expedient complete solutions from a single source. If this fact is taken into consideration during the selection process, users might be able to save on additional suppliers and thus on effort and costs, and profit from attractive complete packages.

Although shaft couplings are frequently classed as simple accessories, they are in fact important components in the overall system. If questions should arise regarding the product, or should consultation be desired or necessary, mayr power transmission supports its customers with technically-competent contact partners. And this not only in Germany, but worldwide. Competent consultation, a quick, controlled and reliable supply of spare parts and a global service network round off the range of offers provided by the company.

Key Points

  • Users should define servo coupling requirements as precisely as possible based on technical data of the drive and drive constellation
  • Providers who have to consider misalignments and alternating torques for dimensioning often have to select a larger coupling
  • On mayr power transmission couplings, the backlash-free function is retained over the entire service lifetime