On 2013-01-31, wrote:
I am working on a 5th axis for the mill. I think it will need a brake.
I'm not sure if the servo motor will be able to hold position for some
operations. I have looked at magnetic particle brakes and they ain't
cheap. So I'm thinking about making one. Or some type of
electromagnetic brake. The brake, when actuated, must not cause any
motion of the axis, and I'm just not sure what would work best.

DC servos? What amount of motion can you tolerate. I would
expect with steady/slowly-changing loads no more than one or two encoder
steps of motion before it was forced to be right again. (Not sure
where your encoder is relative to the motor, but if you don't have
enough backlash between the axis and the motor for brake to do it, I
would not worry about the ability of the encoder/servo pair to hold
position.

Now -- if there are serious pulse loads, then you might have a
little more error before the servo loop could fix it.

Note that at least some DC servos and AC servos as well have
built-in brakes which the controller has to power to release prior to
motion.

Good Luck,
DoN.

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