On Thursday, January 31, 2013 12:20:28 PM UTC-5, 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.

Eric

How much space do you have, and how often will it be locked and unlocked?

What is the rotational range of motion required?

Lots of choices, much fewer depending on the constraints.

A dirt cheap/simple brake would be a few interleaved plates, alternating between turning with one side or the other, and a clamp (solenoid? screw clamp with gear motor?) clamping the stack together. Would impart no motion, and could be in the clamped state with no power applied.