Precision bellows couplings are simple devices that play an essential role in the performance of motion systems. For high-speed and high-precision applications they have been accepted by much of the global design engineering community to be the most reliable in terms of the mechanical behaviors they exhibit. In this interview, Andy Lechner, VP-Sales and Marketing at R+W America, explains why the manufacturer of precision bellows couplings is scaling up its production operations in the U.S.
Motion Design: There are many different types of precision couplings available. Why are bellows couplings increasingly preferred for high-performance applications?
Andy Lechner: Designers of motion systems are under increasing pressure to make things faster, lighter, more compact, and more energy efficient. Precision manufactured bellows couplings offer advantages in all these areas, while performing the basic work of transmitting rotation and relieving bearing loads between drive components. The formed metal bellows is one of the only types of compensation elements found in couplings that is continuously symmetrical. This lends itself to a natural balance and consistency of output rotation that is ideal for smooth running at high speeds in addition to making angular positioning more reliable within a single rotation. Compared with other types, the bellows are also extremely light weight. The thin-walled stainless steel tubes they are made from carry significant torque loads and maintain a very high torsional stiffness while using minimal material. They are routinely mounted to customized drive interfaces to help avoid unnecessary use of shafts and adapters between components, which aids in reducing overall size and inertia. Along with being free of any wear or moving parts, these features amount to their being an increasingly popular tool in mechanical design for critical applications.
Motion Design: What are some of the potential drawbacks to configuring the ideal bellows coupling for an application?
Lechner: Beyond the smallest sizes and most standard shaft interfaces, bellows couplings tend to be made to order. This is because they are single-piece, permanently mounted assemblies. By the time the ideal bellows size, torque capacity, and stiffness ratings are selected, the odds of any application requiring a widely used combination of hub interface at each end are extremely low. Add to this that best practices include a review of the fit tolerances between the shaft and bore, and the wide variety of shaft and flange dimensions that can be found in motion devices, most precision bellows couplings end up becoming unique when configured for the best possible results.
Motion Design: R+W has expanded its production operations in the U.S. after decades of having centralized assembly activities at its headquarters in Germany. Why now?
Lechner: The assembly process for bellows couplings is critical, and with limited opportunities for high volume production runs. In most cases the two end hub attachments, usually some form of shaft clamping device, are held together by their bores or centering features on a precision mandrel, while high strength bearing retaining compound is used to permanently bond the bellows between them. Assembling in this way helps to guarantee concentricity between the hubs while allowing the bellows to remain in a relaxed state, without any bending or crimping stresses applied to it. This requires a highly flexible production facility and a large variety of tooling. Because of the critical nature of the applications into which bellows couplings are often deployed, the bonding process also needs to be perfectly controlled. Rapid growth in the automation sector, paired with the increasing popularity of precision bellows couplings in North America, have allowed R+W to reach a sort of tipping point wherein investment in the people, tooling, and technology at R+W America is justified to help bring the company closer to the customer and significantly reduce lead times.
Motion Design: Can you describe the scope of the U.S.-based manufacturing operation that R+W America has established?
Lechner: Located near its previous machining and distribution centers in the western suburbs of Chicago, the new 30,000 square foot facility is ramping up to produce for approximately 50 percent of R+W’s overall demand in North America by the end of 2023. The company has already realized a significant reduction to lead times for products which have been brought online. Most orders for elastomer couplings are being completed in less than two weeks, while precision bellows couplings and custom-length line shaft couplings are being brought online in phases. The most frequently used models with clamping hubs up to 500 Nm in torque capacity are being built in the U.S. as of May, while a further expansion to encompass a wider variety of bellows coupling hub designs is scheduled for June of this year. The new machining technology and coupling bonding systems make the facility unique outside of Europe and will position the company to support customer demand more consistently for the foreseeable future.
For more information, visit www.rw-america.com.