"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:



I understand that. I'm not using loose ballscrews, I'm just resorting to
C7 precision screws rather than what I'd like to use -- can't afford the
good ones.

OK, that is good. By the way, EMC2 also has leadscrew error correction.
So, you can create error compensation tables, and it will correct for
pitch variation in the screw.

The scales come from India, from Electronica Mechatronic Systems Pvt.
Ltd. I'm buying them on a "piggyback" order from DRO Pros in California.
(they get a cut, of course)

You really want to make sure these scales are DESIGNED for CNC motion
CONTROL applications, and not just DRO or static position reading use.
I just went through a mess with a CUI capacitive encoder that looked
great, but I couldn't tune the servo loop well. I finally discovered there
was a really nasty LAG in the encoder's response to acceleration. I found
it by putting a plain old optical encoder on the same motor shaft and
reading both into EMC at the same time. I worry that a 1 uInch scale
must be using interpolation also, and may suffer the same problem.

I mis-typed the precision of the scales. Mine are 1 micron (not micro-
inch) in X and 5 microns in Z. That makes a difference.
Ah, yes, that makes more sense, nobody makes much Imperial-measure stuff
anymore. 1 um is pretty good, about 39 uInch. 5 um is really just basic
DRO resolution, approximately .0002", and a bit rough for a high-accuracy
CNC machine.

Jon