RE: [CAD_CAM_EDM_DRO] Adding a Tail shaft to servo's with no tail shaft

I’ve pulled loads and loads never had a problem.

On many of the EDM machines I pull the armateurs, resurface them in a lathe,
rebuild and re-brush them and away they go.

On some we have had to fit new armateurs when we can get them, this takes
days to weeks to get the parts. These particular motors go down every two
years, I normally manage 8 to 10 rebuilds, and about 20 re-brushings before
the motor is scrap. Keeps the customer happy when they are £600 each. They
even have a screwed and glued tail shaft with the tacho windings and small
armature on them.

At the Parvalux factory, there are hundreds of motor casings sitting on the
shelves without armateurs and without keepers for many days before being
used.

If you leave some magnet materials for years without a keeper they will
losses their magnetism, but a few day’s isn’t going to make any noticeable
difference, if it did and they were that easy to demagnetise they wouldn’t
be much good as a motor, first time you’d power them up the magnet would be
dead. These would be the ones with a soft iron magnet and field coil, we
don’t call them permament magnet.



We do sometimes find old machinery from the 1960’s and before where motors
lack strength and the cores need to be remagnetised. Happens quite a lot to
magneto’s used to develop te spark on older car ad tractor engines.



There are circumstances where you can demag them, a very hi current pulse
can sometimes do it but it is rare.

Some special motors need to be demagnetised before you can strip them, they
normally charge a special capacitor bank and discharge that into these. I
think there’s only one guy in the UK that rebuilds these motors, but they
are only found on vintage kit. There are several guys that will redo
magneto’s, and I have a friend that refurbs vintage kit that is presently
developing his own rig for this.



Simple don’t worry about it.



One thing we have all forgotten though, magnets attract things and in a
machine shop it is very difficult to keep them clean, no matter how much you
sweep the bench, the magnet will find something. I strip the motor casings
on a big sheet and keep the casing on that sheet at all times. I use the
same sheet for stripping ball screws.



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of vrsculptor
Sent: 28 April 2007 03:58
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Adding a Tail shaft to servo's with no tail
shaft



Jarrett,
Its not good to pull the armature on permanent magnet DC motors. You
may partially demagnatize them.

Roger

> Thanks Mark, how tough is it to pull the armature out of the motor

to machine the shaft? I've got a machinist who I think would gladly
tackle it but I don't want to wreck the motor by pulling it appart or
something. Also, what is the reasoning behind the flex coupling to the
encoder? I could see it if the tail wasn't running true but.. if it is..??





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