Re: [ATM] DC Motor for grinding machine question

[Mike Lockwood <melockwo@uiuc.edu>]

Don,

Don Clement wrote:
> There is no contradiction.

Yes, there was.  In one message you said there was no effect, then in 
your next message you said there was.  Maybe it was a typo.  I was 
just trying to follow your reasoning.

> Using a FFT Dynamic Signal Analyzer
> (such as the Agilent 35670A) and the proper sensors one can see the
> effects of rotating equipment using ball bearing races. In fact,
> one can determine detailed information on the ball bearing race
> parameters (such as number of balls, etc) by examining the spectrum
> of rotating machinery. There is no doubt that regular spaced balls
> in ball bearing races add some periodic component to a rotating
> spindle of a polishing machine.

I have no doubt you are correct in that statement - my day job is 
signal processing and I play with FFTs all day.  I also have no doubt 
that the vibrations affect the quality of finish in metal working, and 
I found your post about 3-phase motors and speed controllers very 
interesting and useful.

However, I debate your assertion that the miniscule vibrations will 
cause measurable effects on the surface of a mirror being polished on 
a machine.  I certainly haven't detected any on my DC motor/variac 
setup, or on a machine that uses a PWM controller.

I guess you'll end up with a grinding machine that can double as a 
decent turntable for playing vinyl, should your Marantz experience 
problems.  :)

(Yes, I know vinyl often sounds better.)

	Mike Lockwood

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