Re: [CAD_CAM_EDM_DRO] Lathe software:

Ejay Hire wrote:

> It seems like you would do it with a high-resolution encoder. I comes
> down
> to a math and accuracy question. If the finest thread you want to cut
> is 1
> TPI, and your machine is accurate to .001, then the _minimum_ pulses
> per
> rotation you would use would be 1 TPI x 1000 Steps per inch = 1000.
> Another
> example;
> 12 TPI x .001 = 12000 pulses per rotation.
> (The Encoders would require an Index pulse for repeatability.)
>
> Is this how it is done?

Not really. Let's say you have a spindle encoder with 1000 cycles/rev,
which produces
4000 counts per revolution, counting all quadrature transitions. And,
let's assume
a 1000 Cycle/Rev encoder on a 5 TPI leadscrew in the Z axis. Now, for 1
TPI, you
would advance the Z one inch for each 4000 spindle counts. What is one
inch, in
counts? 4000 counts/rev x 5 TPI on the leadscrew comes to 20,000
counts.
So, for 4000 spindle counts, you need 20,000 Z counts, or 5 Z counts for
each
spindle count. For 12 TPI, you need a ratio of 5/12, or 4000/1666.667,
which
comes out to .4166667 Z counts to each encoder count. For a 32 TPI
thread,
it is 5/32, or .15625 Z count per spindle count.

Jon