Bob Engelhardt wrote:
Bob Engelhardt wrote:
...

... the turning feed uses a shaft with a key slot in it - not really a
"lead screw". I guess that avoids the stick-slip problem (?).

...

Oh, no - wait. There's a sliding gear on the shaft that's driven by a
key in that slot & that gear & key slide along the shaft as the carriage
moves. I guess there could be a lot of stick-slip!! Ahhh ... damn - I
really wanted to be able to slow feed. Well, I'll see what happens.

I bought a servo amp on eBay last night - $17.50. "Too good to be true"
comes to mind, but I found some data for it & I think it'll work. eBay
180282383302 & data:
http://www.a-m-c.com/download/datasheet/25a20i.pdf
I think this is the same as a Copley 412, their setup and
install data may be more understandable and complete.

You will need a DC tach. The motor can have some velocity
ripple, the tach MUST NOT! So, you do need to use an ironless
rotor tach. The best deal is to find a Maxon motor (These are
tiny, about 1.25" diameter) with silver brushes. They sell the
same design as a tach. A number of surplus dealers have them,
or look on eBay. You will be able to hook a 10-turn pot to
either the -10 or +10 V supply with a switch (for direction) and
signal ground, and the wiper of the pot to +ref in. ground -ref
in. Set it up for tach mode as shown in the chart. I think you
want to ground both +inhibit and -inhibit, and put a run-stop
switch on inhibit that grounds it to run. (You could also set
up the direction switch to be center off for the stop setting.)

Jon