29 Mar 2016


The uncovering of ball screw noise

Drives that use a ball screw have been deemed as noisy by classification, however, companies which purchase and make use of them are progressively demanding that their machine tools should be able to operate rather quietly to raise the level of work environment through the elimination of noise pollution. Thus, several engineers have looked into the matter of ball screw noise to see if the issue can somehow be resolved for betterment. To make sure that the experts were handling the problems in an appropriate manner, the help of Prof. Dr.-Ing. Paul Helmut Nebeling at Reutlingen University was sought who is a professional in the field of the dynamic, static, acoustic and thermal behavior of machines tools as well as components.

What causes the noise?

The fact that ballscrew noise is somewhat due to the thread geometry was already identified. All of this can be attributed to the undulating motion of the balls in their very paths, the typically huge powers these drives must specifically diffuse, along with the predominantly critical point- the smoothness of the thread surfaces on which the balls run. It was determined by a team of engineers that the high-frequency resonance of moving ball screw drives was the chief source causing the troubling noise in the machine tools. The ball screws go through a cycle of high acceleration followed by deceleration and this specific tend is the reason behind the disturbing “whistling noise” which can be heard. After the team measured torque and sound emissions followed by the carrying out of suitable FFT investigation. It was identified that minute corrugations on the shaft thread suggestively affect the general sound produced by moving ball screw drives.

Later when the team of engineer investigated the surface of the shaft’s leveled thread under enlargement; they observed minute features measuring about one-half of one thousandth of a millimeter about the same wavelength of that of blue light. The facets apparently come into being because of the vibrations of the grinding wheel when it moves to ground the shaft. The team concluded they were the main cause of the irritating clamor; it was noticed by them that the noise’s incidence peak at 265 Hz matches precisely to that forecasted from the magnitude of the surfaces and the rotation rate of the drive’s shaft. When the bearing balls reel and move over the slight bumps or tiny facets, there is a certain amount of slipping, which causes the distressing whistle sounds which are quite noticeable.

How should ball screw noise be reduced?

As one of the measures to eradicate the noise, it was decided to reduce to grinding speed however that would lead to the problem of the shafts manufacturing becoming less economical. There is another treatment for noise reduction which is still in its testing stage. This is a new oil treatment in the grinding shop where cutting oil is maintained at a constant temperature. Using this procedure, the temperature in the grinding wheel’s contact zone does not increase during machining and the end result is the production of smooth shafts with this method.