Question to Mariss about demagnetion was Re: Torque when usin

Thanks for your very helpful comments Mariss.
I dont see major mechanical problem dismantling a stepper without removing the rotor. The small ballraces used won't need heaps of pressure to slip them off a shaft.

Its really just a matter of making a simple puller and a simple clamp system that will allow an end housing to be slipped off a shaft without displacing the rotor.

I agree making up loose pole pieces to slip the rotor into to maintain a magnetic circuit would be an engineering exercize not worth considering.

In the US its certainly worthwhile just getting new motors rather than mess around but here in Australia steppers are not cheap or easy to find and international mail at about $25 or far worse Fedex at about $95 for goodies about 6lb weight can mean ebay might be impractical sometimes. (especially if the vendor dislikes mail)

Again, thank you Mariss, forwarned is forearmed.

Bob

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "krnldmp <krnldmp@y...>" <krnldmp@y...> wrote:
> Fiddly it would be if you wanna save the rotor. I heard someone
> somewhere try to tell me that the rotors could be magnetized by
> applying a pulse to the stator windings. I think that's bull on
> account of the PM field being at right angles to the stator field but
> I don't know. I don't actually know how they are magnetized, but I'm
> guessing by a fixture with a moveable set of pole pieces that would
> cost you just enough to slap together that no matter how thriftily you
> went about it you'd end up cheaper buying a new motor.
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "echnidna <echnidna@y...>"
> <echnidna@y...> wrote:
> > So can the rotors be remagnetised easily at home?
> > If so what procedure would you suggest?
> >
> > or would I need to remove each end housings one at a time fit new
> bearings and replace without removing the rotor itself from the
> stator. Bit fiddly mechanically but seems possible.
> >
> > Regards
> > Bob Thomas
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "krnldmp <krnldmp@y...>"
> <krnldmp@y...> wrote:
> > > The permanent drop in flux density happens before you even get the
> > > rotor all the way out of the stator. The rotors are magnetized
> while
> > > they are in the stator and must stay there or be re-magnetized.
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "echnidna <echnidna@y...>"
> > > <echnidna@y...> wrote:
> > > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
> > > <mariss92705@y...>" <mariss92705@y...> wrote:
> > > >
> > > > > .... Regarding your motor. Check carefully to see if it has
> not
> > > been
> > > > > disassembled. Look for marks on its screws. A step motor that
> has
> > > had
> > > > > its rotor removed from the stator can lose a lot of its rated
> > > torque
> > > > > due to demagnetization.
> > > > >
> > > > > Mariss
> > > >
> > > > Mariss, I assume dismantling a stepper motor and leaving it that
> way
> > > for some time could demagnetise it.
> > > >
> > > > but would dismantling a stepper for a short time to fit new
> bearings
> > > be likely to cause any significant loss of magnetism
> > > >
> > > > Regards
> > > > Bob Thomas