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News Release
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NSK Develops ROBUST™ Series for Machine Tools and Super-High-Speed Machining Centers |
After NSK exhibited its ROBUST™ Series super-high-speed precision angular ball bearings for main machine tool spindles at the 19th JIMTOF (Japan International Machine Tool Fair) in October 1998, the product has been well-received by more than 20 leading machine tool manufacturers. NSK proudly announces the successful development of super-high-speed cylindrical roller bearings, a dramatic enhancement of the ROBUST Series.
The current trend in the machine tool industry is to have most main spindles motorized, with the understanding that the optimum configuration of spindles places high-speed angular ball bearings at the front, with cylindrical roller bearings at the back to better absorb axial thermal expansion under high-temperature conditions. However, it is difficult to further accelerate rotation using conventional cylindrical roller bearings, requiring companies to install conventional angular ball bearings at the back. To resolve the bottleneck caused by the heat-prone angular ball bearings axis, a streamlining mechanism is required for smoother sliding movement of the bearings, which involves the installation of sleeves on the outer diameter and pushing the bearings with spring force. However, the mechanism is complex and expensive, and the inevitable space between sleeves invites vibration. The all new super-high-speed cylindrical roller bearings realize a low-heat generating-design with an ideal seizure-resistance of dmN = 3 million-by incorporating NSK's unique development technology, including superb SHX steel materials and robust temperature control. While high-speed cylindrical roller bearings are usually made of ceramics, the all new bearings introduce SHX in the rollers as well, demonstrating superb performance equal to that of ceramics rollers. Although ceramic rolling elements feature outstanding seizure-resistant performance, they are expensive. Moreover, bearings with all-ceramic rolling elements build up an insulating effect which can generate sparks between cutting tools and the material being cut after a certain amount of electric charge has accumulated on the spindle. SHX materials are the best solution to these economic and technical challenges, which include high cost and axial insulation.
Retainers made of engineering plastics, which are superior in terms of high rigidity and lightweight, and have excellent wear and heat-resistance, allow stable spindle rotation with a minimum supply of lubricant including oil/air. Prototypes of ideal super high-speed cylindrical roller bearings have been adopted by some businesses, and support the machine tools exhibited at JIMTOF in October 2000. NSK is scheduled to move into mass production of these products in the summer of 2001. NSK is targeting revenues of 500 million yen a year, based on mainstream bearings with inner diameters of f40 to f100.
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