Re: [CAD_CAM_EDM_DRO] Brushless DC motor repair...

motoproto wrote:

> My cnc mill spindle is driven by a brushless DC motor, with an
> encoder for feedback to control speed. The bearings are a bit noisy,
> and I'd like to replace them, is there anything "tricky" about
> disassembling this type of motor vs. a standard brush type motor?
> I've replaced plenty of bearings in electric motors, but haven't had
> a brushless motor apart.

It will look more like an AC induction motor on the inside. There will
be permanent magnets in the rotor, and fixed windings in a (probably)
slotted stator. There will also be some tiny sensors inside the
motor, unless the commutation is done with extra sensors in the
encoder. If the encoder cannot be removed from the motor, you are in
for serious sweating! It only takes the slightest touch to shatter the
glass encoder disks. If the encoder can be removed, you need to
be able to get the encoder aligned exactly with the rotor position,
otherwise the commutation of the windings will happen at the wrong
phase relative to the magnets in the rotor.

The permanent magnets can make assembly very difficult, and will also
attract swarf. Some motors may lose some of their magnetism if the
rotor is removed from the stator. They usually have a warning label
if this will be a problem.

Jon