NSK has developed a new generation of ball screws which aim to achieve higher surface finish quality, designed for high-accuracy machine tools used in die, mould machining and other applications.
NSK Ltd has undergone extensive research and development to improve machining surface quality, thereby eliminating or reducing the time needed for burnishing or polishing work, while also reducing the amount of drive torque. The new ball screws, NSK claims, embodies this ideal.
In recent years, machine tools, such as 5-axis milling machines, have been demanding higher accuracy to produce higher quality die or mould surfaces and the ball screws used in these machines must further improve their motion accuracy.
When a ball screw reverses direction, sudden fluctuations in friction cause ‘quadrant glitch’ motion errors with two peaks, leaving streak marks on the machined surface and reducing surface quality. Numerous studies have been conducted on quadrant glitches, and the first peak can be corrected through numerical control of machine tools. However, it is more difficult to fully compensate for the second peak due to the combined effects of more factors compared to the first peak and the machining industry is seeking a solution to this problem.
Using NSK Real Digital Twin simulation and friction analysis, the company has developed a new ball screw with an optimised internal design formulated by understanding the underlying mechanism of the friction fluctuations in ball screws which causes quadrant glitches. A stable drive torque is necessary during reversals. The new product has reduced friction fluctuations when the ball screw reverses direction, thereby improving motion accuracy and reducing quadrant glitch motion errors to nearly eliminate the second peak. Through this, friction fluctuations have been reduced by up to 20%, this contributes to reducing the height of the first peak.
NSK plans to start taking orders of the product in select regions from April 2023, followed shortly by a global rollout. The company also says, through this ball screw technology, it aims to achieve ¥100 million in sales by 2024.
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