Re: 4th Axis Concept (long)

> There is still the problem reseting the piece to zero. I think this
> could be handled by turning off the power and rotating the shaft by
> hand to a known position. A fixed position could be established by
> resting an arm, attached at a right angle to the 4th axis shaft, on
> the top of a 1-2-3 block or some such.

If you add in a spindle brake, and an encoder on the servo, you have
a full blown C axis on a lathe. Don't encoders have a master zero
position? Gross/rapid position to a rotary position that is detected
by a photo sensor, and then slowly fine position to the "big" mark on
the encoder. Absolute zero degrees. No mechanical parts to wearout
or misalign. Just the brake. If it's a lathe with CNC threading
capability, you probably already have most of what you need to zero
out the rotary axis.

Best Regards,

Fred Smith
IMService