Re: EMC and lead screw compensation

Wally

Yep, Emc development works much faster than the combined fingers of the
Handbook writers. But that will change soon as we are getting some
interest in it from several.

I haven't used lead screw compensation but it is there. It is done by a
lookup of a separate file it one exists for each axis. If you write a
comp file and put it in the correct place, it will be read. The entry
concerning it in the release notes says

-----release notes-----
7. Added bidirectional lead screw compensation. Files of compensation
points look like this (these sample comp values are exaggerated):

0.000000 0.000000 -0.001279
0.100000 0.098742 0.051632
0.200000 0.171529 0.194216
0.300000 0.292485 0.291030
0.400000 0.439511 0.367981
0.500000 0.451323 0.493962
0.600000 0.618011 0.618044
0.700000 0.669925 0.735979
0.800000 0.798637 0.787879
0.900000 0.889286 0.927685
1.000000 1.007024 0.959853
...

where the first column is the commanded axis position, the second
column is the measured position (like with a laser) in the forward
direction, and the last column is the measured position in the reverse
direction.

You specify these files in the .ini file for each axis with the
[AXIS_#] COMP_FILE = <filename>, e.g.,

[AXIS_0]
...
COMP_FILE = x.cmp

This entry is optional. If it's not there, no compensation is done.
-----end of notes-----

It looks to me like it would not only take care of rolled screw error but
might take care of some variable slop (backlash) as well.

Thanks for reminding me that I need to do something with this topic. Hope
this helps

Ray


Message: 15
Date: Wed, 08 Nov 2000 03:26:21 -0000
From: "Wally K" <cnc4me@...>
Subject: EMC and lead screw compensation

I remember a while back there were posts saying EMC now had leadscrew
compensation. I went to the site with the EMC handbook but found no
referance to it.

http://www.linuxcnc.org/handbook/index.html

and also searched the mail list at.

http://www.nist.gov/itl/div896/emaildir/emc/maillist.html

Does anyone know were i can find out if this was implemented and how
you go about using it.

Wally K.