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Full Version: Spindle modulated noise
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Hello everyone,

    For my first post on this forum, I would like to find answers about a modulated sound coming from our spindle. For a project about robotic machining, we are interested in machining aluminum and steel with a Stäubli TX200 robot equipped with a force sensor and a spindle (Teknomotor spindle ATC71 HSK F63) with a nominal speed of 12000 RPM (nominal torque 12000 RPM).

[Image: IMG_0170.jpg]

However, after 12000 RPM, we can clearly hear a modulated sound coming from the spindle. Here is the link for an audio sample:

Audio of the spindle at 18700 RPM.

Video available here:
(Rotating speed 20500 RPM)

Does somebody know where the modulated sound comes from ? (bearings ? imbalance ?)

Does it affect the precision ?

(Also, when the spindle was rotating, forces and torques were recorded with the force sensor of the robot. By analyzing the frequency spectrum of the torque around the axis of rotation, beside the frequency of rotation of the spindle and its harmonics, modulation peaks around those frequencies were clearly visible. Modulations were distant of 10 Hz before 12000 RPM and decreased towards 4 Hz at 24000 RPM. Strangely, the evolution of frequency modulations follows the evolution of the spindle torque which is nominal up to 12000 RPM and decreases beyond).