Sam Goldwasser wrote:
Tim Wescott writes:

Sam Goldwasser wrote:

Tim Wescott writes:

Sam Goldwasser wrote:


Another thing to note but which probably doesn't apply here is
that if some PM motors are disassembled without a "keeper" for
the PM magnets, it will become partially demagnetized. This
isn't a problem with the cheap PM motors you are probably using
but may be with high quality steppers or servo motors.
--- sam | Sci.Electronics.Repair FAQ Home Page:

I know that's an issue with AlNiCo magnets, and I know it's _not_
an issue with Neodymium-Boron-Iron (temperature will kill those
suckers, but not demagnetization). Is it a problem with Samarium
Cobalt or any other modern high-performance magnet material?
The motors I'm referring to almost certainly used magnets more high
tech than AlNiCo but I don't know what it was. There must be some
info on PM motor maintenance from motor manufacturers on the Web
that would shed some light on this.

I was just curious if you knew.

I'm guessing the motors the original poster was referring to are the
$1.50 variety which probably use ceramic ferrite magnets and really
don't suffer from this problem.

I would go along with that, too. When they first came out, we were
astonished how good the retentivity is and for all practical purposes,
taking apart, putting back together etc, the field strength was retained.


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