34 n LINEAR MOTION May 2026 www.drivesncontrols.com Custom ballscrews tackle loads on wind turbine gearboxes Ballscrews are used to position the axes in machine tools. They convert rotational motion into linear motion with no backlash and high dynamics. This places high demands on the screws, which must allow fast axis movements while maintaining precision. Recently, a well-known machine-tool builder approached the ballscrew manufacturer, Kammerer Gewindetechnik, located in Germany’s Black Forest region. It needed larger milling heads for gearcutting machines used by a customer that makes gearboxes for wind turbines. As wind turbines get larger, they need bigger gearboxes. The gear-cutting machine used to mill the wind turbine gears needed to be adapted to cope with these changing conditions, but the ballscrews that the customer had been using previously could not withstand the higher loads. It was installing a larger, heavier milling machine that weighed 6 tonnes without weight compensation – a mechanism used to counteract the weight. The ballscrew, which drives the vertical axis of the tool carrier, therefore had to withstand a much higher load in the same installation space. The standard 100 x 30mm ballscrew from another supplier that the manufacturer had used previously could not withstand the higher load over the long term and had to be replaced after two years. Another requirement for the retrofit was a higher load capacity while maintaining a constant idle torque, as a non-constant torque would negatively affect the quality of the surfaces being machined. To meet these requirements – which at first glance seem contradictory – Kammerer drew on its years of experience of designing ballscrews for machine tools. “For the new application, the existing machine design had to serve as the basis for the redesign of the ballscrew,” explains the company’s engineering technician, Marcel Wolber, who oversaw the project. “This meant that the installation space was limited. “Since a larger ballscrew could not be used for this reason, we increased the pitch of the ballscrew by 2mm to 100 x 32mm, which allowed for a two-start thread,” he continues. “By using specially milled deflection pieces, the number of balls could be increased significantly, while keeping the nut length virtually the same. Thanks to the second thread and thus significantly more load-bearing balls, the dynamic load rating was increased from 465kN to 679kN – a rise of nearly 50% – which extended the ballscrew’s service life by a factor of 2.6, to more than 22,000 operating hours.” The new ballscrew, with an internally braced single-flange nut made of 100 CrMo7-3, has an accuracy class of IT3. Its use has resulted in a remarkable improvement in terms of the dynamic load rating and the service life of this important drive element. “The new design is a true space-andstrength marvel – a compact footprint, a high dynamic load capacity, yet smooth running,” says Kammerer product manager, Andreas Rombach, who was also involved in the project. “To date, Kammerer has supplied five of these ballscrews for the gear-cutting machines.” The axes of the manufacturer’s other gear-cutting machines will be retrofitted gradually with the new components. Kammerer, founded in 1938, is a familyowned business that employs around 150 people and is now run by the third generation of the family. Its products include ballscrews, trapezoidal screws, sliding screws and custom assemblies. Its screws are used around the world in machine tools and machining equipment such as lathes, milling machines, grinding machines, sheet-metal-working machines and forming machines. n As wind turbines become more powerful, they are placing increasing demands on their gearboxes – and the machine tools used to produce them. A German ballscrew manufacturer has responded to this with a new design that improves load capacities and service lives of gear-cutting machines. The ballscrews for the vertical axis of the gear-cutting machines have an internally braced single-flange nut. Image: Kammerer Kammerer’s ballscrews offer high dynamic load capacities. Image: Joshua Rzepka / Kammerer
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