Re: EMC Lathe setup

Chris

I've been off list a bit so this may be late but my comments are mixed in
to your post.

From: Chris Stratton <stratton@...>

>How to set up emc on a lathe that is also a mill?

>I was given an old sherline-based cnc lathe, and have basically

f>inished fixing the things wrong with it, and have made it go with a
t>est program written in basic. I had to use the X slide off a

>sherline mill to replace the missing cross slide, and since that left
>the mill useless I modified the column to attach in place of the lathe
>headstock (which will complicate things in a minute).

>I've gotten EMC (August 2000) up and running on rtlinux-2.0.36-.0.7
>Got the green digits and made it execute code (without motors connected).

One more BSOD defying act and another cause for celebration!!!

>Now I'm trying to figure out how to orient the axis. I understand
>lathe conventions would be with X and Z, although I'm not sure where
>the origin is then, or how to get tkemc to display that nicely.

The first good news is that origin can be anywhere that you choose it to
be. In fact you can shift that origin around as many times as you want
during a single program by using the 10 coordinate systems available and
g92 for temporary changes. There is also a little script
(Set_Coordinates.tcl) in the linuxcnc.org dropbox that you can download and
copy into your emc/tcl/scripts directory that will then appear under the
scripts menu and display and allow you to set coordinate systems for
whatever axes you are using.

You can set home for any value that you want as soon as the home routine
hits a switch. So if the face of the tool holder is 5 Z inches away from
the spindle face and 3 X inches away from center, you can set the control
so that when home routine hits the z switch it sets that location to +5 and
when it finds x home it sets that value to +3. Now g0 x0 z0 should put the
face of the tool holder on the face of the spindle at dead center. (scary
thought for that 13 inch machine)

The second good news is that the newest mods to tkemc allow it to show
whatever axis definitions and names that you have in the .ini file. I just
tested this by defining two, X and Z in a lathe.ini and ran it and got
those axis position displays. Unfortunately this gui will kick up an error
with steppermod when you change from joint to world coordinates. It runs
fine but you need to click okay in the error window to make it go away.
Freqmod and the stg stuff had been modified (5/16/01) to work fine.

The third good news is that you can now specify starting/initial conditions
for the interpreter on a line in the ini. So g20 will establish inch as
default and G18 will establish xz as the default plane for arc moves.

You can get these mods by downloading the latest files from the
cvs repository on sourceforge as an anonymous login. The bad news for BDI
users is that the RPM hasn't been made yet.

HTH

Ray