Re: Timing Pulleys for CNC Work - OK or Not ???

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Paul Alciatore"
<paulalci@...> wrote:

>
> I have been a lurker here for some time but now is the time to get
> more
> active as I have some CNC projects to work on.
>
> I am presently working on my first CNC adaption on a SB lathe. I
> plan
> to use steppers with a gear train to provide finer control and more
> torque with less expensive steppers. I know that many designs just
> attach a 200 step stepper directly to the lead screws, but I believe
> this approach will be better and perhaps not cost a lot more in
> materials.
>
> Anyway, my question is about the connection of the final shaft of the
> gear train to the lead screw. I would like to avoid an exposed gear
> (the main gear train can be enclosed) so I was wondering about using
> a
> pair of same size timing pulleys to transmit the motion. I know that
> the belts are reinforced and do not appear to stretch much but are
> they
> really suitable for this kind of service? What kind of errors could
> I
> expect from such a linkage? Does anyone here have any experience
> with
> then in CNC work? If suitable, how would I calculate the pulley size
> to use based on the expected torque? Or what should I base the size
> on?
>

The accuracy and power transmisstion of timing belts is extreemly
high. Should not be a concern. Since gears will have some play,
they will have much more error than the belts.

Visit Stock Drive SDI.com and check out the technical data sheets
they have. You can get a belt that will handle your lathe.

I have a 9" and made a bracket that replaced the banjo and mounted a
stepper on that, then used a belt on the leadscrew.

I never did threading with it, but it can spin the leadscrew easily.

Manual pulse generator so I can set the feed rate. The 9" uses the
origional screw and half nuts so the errors are too large now for
considdering going to CNC as yet.

Dave