On 1 Feb 2013 05:27:47 GMT, "DoN. Nichols"
wrote:

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.
Grewetings DoN,
There will be pulsed loads. Such as when an end mill is spotfacing
and/or counterboring a curved surface. I don't know yet if I will be
contour milling with the 5th axis. Probably not at first. I just need
to be able index the parts. To do this I will be using an M code to
send a signal to an Arduino. The Arduino will then command the 5th
axis to move. I'm still learning how to use the Arduino and the LCD
touchscreen display I bought for the Arduino. I still need to figure
out how to get the signals from the encoder to the servo amp. I don't
know yet if slip rings will do or if I need to get some type of
wireless setup. But I need to approach this project with what I do
best first, and that's mechanical stuff. I think I have the drive
figured out, now I need the brake.
Eric