Motorized Spindles / Ceramic Bearings - Vibration Comments Wanted

[StanBognatz]

We are analyzing some 24,000 - 30,000 rpm motorized spindles equipped with ceramic bearings that are classed at ABEC9. I don't have specific bearing numbers, don't know the DN#, or the specific type of lube being used (yet).

The vibration data for the first few units we have looked at has what I would normally call a very noisy signature if they were regular steel bearings - broad-based noise floors out to 30X (running dry??), some asynchronous components in the 4X - 12X range (primary brg faults?), and some high-frequency components in the 50-60x range (lube / natural frequency).

I would like to hear from anyone having experience with high speed motorized spindles, especially if using ceramic bearings, regarding the general signature content on these high speed units. In addition to the bearing signatures, any comments on what frequencies might be introduced by the high speed motor would be appreciated was well.

Thanks,
Stan

 

[Tmoose]

All the bearing literature used to make the claim of "lower vibration" as an HC bearing benefit. The best I could tell is that claim was Probably based on the real nice finish and improved tribology.

The guys that tested our spindles would snort derisively at that claim, as our testing with the then still "standard" IRD 65 lb magnet mounted showed spindles using HC bearings were MUCH noisier. That finding made some sense to me, since the ceramic balls are much stiffer. Also I picture they would wrinkle the relatively softer steel races more than steel balls (hence the greater contact stress at equal loads), and the bearing manufacturers would hint at slightly different geometry and actual preload to enhance speed ratings

 

[StanBognatz]

Anyone else have any experience they can relate?

 

[Tmoose]

Did you find any bearing and lube particulars?
Are you building the spindles?
Is this acceptance, or PdM type measurements?
Are these a proven design, manufactured and assembled by experienced folks at an experienced manufacturer, just uPgRaDed with HC bearings ?

Are they xx13 sized bearings with 65 mm bore?
(A shudder just went up my spine)

There are some legitimate and impressive benefits of HC bearings, but in my experience (now 10 years old) they are indeed "different."

Dan T