Re: Why do stepper motors lose their magnetism when disassembled?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jim Register <jtregister@...>
wrote:

>
> Yahoo wrote:
> > I figured it was something like that. I suppose if you had an

iron plug the

> > same size as the rotor you could slide it in as you remove the

rotor and

> > maybe not ruin the motor.
> > --
> > Phil Mattison
>
> The rotor is the permanent magnet; you'd need an iron/steel tube to
> slide it into, I think.
>
> Jim Register
>

Yes that will work !!

We (at my old company ) have been doing that for years with tacho
generators. It just needs a soft iron(mild steel) cylinder about the
same diameter length and thickness as the actual stator with the
diameter that the rotor slides into being the most critical. Push
the rotor in to it and when you need to re-insert the rotor later
put the cylinder against the side of the stator and push the rotor
across.

Magnetics and permanent magnets are not rocket science, but to get
the most out of a given stepper motor frame size you need the
strongest flux you can get. This comes from using some of the very
fancy rare earth magnets. No magnet likes to have only the air as a
return path for its flux since it has to work about 10,000 times
harder to make the circuit. Doing this tends to distroy the top end of
magnetic curve. So if you give the stepper motor magnets an
alternative path with a keeper it will be alot happier. The rare
earth magnets are much more sensitive to this and can lose a large
part of their remanence (I think they call it) if there is too much
air in their magnetic circuit.

Regards Bob