Re: [CAD_CAM_EDM_DRO] Re: A little experiment on demagnetization

Howdy guys;

In part, it depends upon which direction the magnet is pointing when vibrated.
You can take an iron/steel rod, point it towards magnetic north, at the right
approximate angle to line it up vertica;;y, and when rapped hard with a hammer
on the southern-most end, it will for a short time, become mildly magnetic.
It's only a surmize, but if you heated the rod up to the point where a magnet
wouldn't stick to it, lined it up, and started rapping/vibrating it till cold,
you'd probably end up with a fairly strong magnet for the material.

Bill

On Mon Feb 10 13:23:50 2003 mayfieldtm <mayfiet@...> wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude
><davemucha@j...>" <davemucha@j...> wrote:
>> Is magnetism lost over time on a
>> shelf ? or in use ? by higher voltage/power ? and disassembly?
>
>More than likely the magnetism is lost over time while
>being used. Magnets DO NOT like heat or vibration.
>Step motors do a lot of vibrating and heating.
>I'm not convinced that slow careful disassembly is
>all that destructive. (some loss not much)
>I'm stating this from a gut feeling fueled with about 10 years
>experience in the magnetic industry, back in the 70's.
>
>The newer fancy magnetic materials are less
>susceptible to heat and vibration.
>
>>"are there any shops/people that re-magnetize?"
>
>Should Be.
>I just took apart a step motor to look at the magnetic circuit.
>
>On the rotor shaft...
>there is a stack of steel laminations,
>then a magnet about 1/8" thick (washer shape),
>another stack of laminations,
>a non magnetic spacer,
>stack of laminations,
>another magnet,
>and a --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude
><davemucha@j...>" <davemucha@j...> wrote:
>> Is magnetism lost over time on a
>> shelf ? or in use ? by higher voltage/power ? and disassembly?
>
>More than likely the magnetism is lost over time while being
>used. Magnets DO NOT like heat or vibration.
>Step motors do a lot of vibrating and heating.
>I'm not convinced that slow carfull disassembly is
>all that destructive.
>I'm stating this from a gut feeling fueled with about 10 years
>experience in the magnetic industry, back in the 70's.
>The newer fancy magnetic materials are less susceptible th this.
>
>>"are there any shops/people that re-magnetize?"
>
>Should Be.
>I just took apart a step motor to look at the magnetic circuit.
>
>On the rotor shaft...
>there is a stack of steel laminations,
>then a magnet about 1/8" thick (washer shape),
>another stack of laminations,
>a non magnetic spacer,
>stack of laminations,
>another magnet,
>and a finale stack of laminations,
>
>So... when the rotor is removed...
>it acts like a bar magnet with the North Pole on the
>shaft end and the South Pole on the Bearing end.
>
>This leads me to believe that the motors can be magnetized
>fully assembled.
>
>Place the motor in the Magnetizer with the shaft against
>the South Pole of the Magnetizer and the bearing end of
>the motor against the North Pole of the Magnetizer.
>Even Better... To get that North Pole even closer to the
>rotor, insert the shaft into the hole of a donut shaped
>pole piece.
>Size of which would be...
>OD ~= OD of Stator
>ID = a little larger than shaft size.
>Thickness > Shaft length.
>
>(in truth, North/South orientation is probably
>of little concern)
>
>Look around for shops that make custom magnetic devices.
>Most any city will have one.
>Take a copy of this e-mail and a box of donuts with you.
>I wouldn't think it would cost much if anything.
>
>If the motors are magnetized using the "Discharge" Type
>Magnetizer. I can visualize a heavy coil that the motor
>can fit into about 1.5 to twice as long as the rotor.
>
>Tom M.

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