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

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

----- Original Message -----
From: wotisname <wotisname@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, December 12, 2008 4:44 PM
Subject: [CAD_CAM_EDM_DRO] Re: Why do stepper motors lose their magnetism
when disassembled?


> Hi,
>
> I have a book here that deals with building a coil and using it to
> magnatize the ignition components of a Ford Model T, not exactly a
> new machine using modern materials. It states that half of the
> magnetic force is lost if a keeper is not connected across the magnet
> before removing it from the magnetizing coil. If the keeper is not
> used the magnet will not generate enough force to make a spark for
> the plugs.
>
> It has been my experience the more powerful the magnet, using modern
> materials, the more marked the loss of power removing it from the
> coil without a keeper.
>
> I have a magnetic chuck which I took to bits and just takin out the
> magnets and putting them back made the chuck useless. I will be
> building a coil soon to remagnetize them and make sure I use a keeper
> to move them from the electro-magnetic coil and while refitting in
> the chuck.
>
> I have no interest in getting into the physics I just know it happens
> and why.
>
> Regards, Terry
>
>
> > I don't understand. Keepers are there to prevent demagnetization
> that
> > takes months or years... and the modern materials like neodymium do
> not
> > self-demagnetize like the old stuff.
> >
> > Danny
> >
> > wotisname wrote:
> > > Hi,
> > >
> > > The reason is very simple. Magnets need a keeper plate to stay
> > > magnetized, some magnets loose their magnetism quicker than
> others
> > > dependent on the material they are made from. When you open a
> stepper
> > > motor you destroy the keeper which in this case is the motor
> armature
> > > and casing and half the magnetium effectively escapes, a bit like
> > > letting the smoke out of electronic components when you blow them
> up:-)
> > >
> > > Regards, Terry
> > >
> >