Both speed and precision are desirable attributes for the bearings used in spindles for machine tooling applications. High-speed capability and accuracy are significant factors also for woodworking and other ‘soft material’ industries,
Add the increasing pressures of a globalised market – productivity, efficiency, competition – and the buyers of bearings for electrospindles are eager for ways to improve quality without increasing costs.
SKF is a major supplier of bearings for HSD, one of the world’s leading producers of electrospindles for woodworking applications. As such, SKF decided to work with its long-time customer to develop a new series of bearings that would meet the needs of its client and the industry as a whole. HSD (the name stands for “high speed development”), located in Pesaro, Italy, represents 60 per cent of the world market for electrospindles for light applications, and, as such, is the industry’s point of reference.
HSD and SKF have been collaborating since 1992, when the former was founded. SKF provides a bearing not only for HSD’s spindles but across the customer’s product range, including boring heads, 5-axis heads, and aggregates. From the outset, the Italian company was drawn by SKF’s reputation for quality and its technical support, as well as the breadth and depth of SKF’s assortment of super-precision bearings.
So in 2012, Mario Mattia, SKF Sales Manager Machine tools Italy, and Massimo Sandri, SKF Account Manager Machine tools Italy, sat down with the managers of HSD to define the requisites for a new competitive bearing specifically for woodworking sector spindles. “Our challenge was to develop a standardised product that would satisfy the requirements of different clients. We realised it was a demanding task,” says Mattia. SKF also talked with the technical offices of other clients to define the main requirements of spindles dedicated to this application. The next six months were devoted to internal development and testing.
By 2013, SKF was ready to supply prototypes to HSD. “We got it right the first time because HSD was fully convinced after testing the prototypes,” reports Mattia with satisfaction. By mid 2014, SKF was supplying a series range of bearings and at the end of the year it signed an 18-month contract with HSD.
SKF had developed what is now the S70 .. W series — sealed super-precision hybrid angular contact ball bearings for woodworking applications.
“Listening our customers’ needs, we found that an18° contact angle was the optimized solution,” notes Sandri.
The bearing was also designed to deliver accurate preload, prior to mounting, equal to zero and is available in a range from 25 to 55 mm shaft diameter.
Furthermore, the solution has an optimised PEEK cage with patented design that reduces noise and vibration, especially at low to medium speeds. It combines very high stability at low/medium speeds with the ability to accommodate very high speeds (speed factor A = 1.6 million n dm). “As a result, the client perceives a better-running product,” Mattia points out.
The rolling elements are made of bearing grade silicon nitride Si3N4 and rings of bearing steel. These hybrid bearings offer higher speed capability, more rigidity, less energy consumption, reduced frictional heat, reduced centrifugal and inertial forces within the bearing. They are also less prone to damage in situations of rapid starts and stops.
The bearings have non-contact seals fitted on both sides and are filled with premium grease. These sealed bearings have been filled with the appropriate amount of high-quality grease under exacting conditions at the SKF factory. The seals hold the lubricant inside so the client can use the bearings directly without having to lubricate. Therefore mounting time for the client is faster. This feature also avoids possible contamination or introduction of impurities and has been so well received that, according to Mattia, other clients who had not previously considered sealed bearings are now using them. Special packaging with 15 bearings per box. The result is less handling and materials disposal for the client, and easier logistics for both supplier and customer.
Reactions of the market launch of the SKF S70 .. W series have been very positive, with clients enthusiastic about the performance of the bearings. “At SKF, we are aware of the ever-increasing demands on spindle applications in the workplace. With that in mind, we developed this new cost-effective bearing series that offers high-speed capabilities together with lower sound and vibration levels” notes Sandri.
Meanwhile, both speed and precision continue as change agents in the partnership between SKF and HSD. The two companies have begun discussions on bringing intelligence into HSD spindles through SKF bearings.