Re: [CAD_CAM_EDM_DRO] Lathe programming help for a newbie

James Leonard wrote:

>Hi,
>
>I have a Liberty CNC lathe. Their software does NOT implement the
>radius word, so I have to prgram curves using the I, J words. I am
>having a great deal of trouble understanding this. Can someone point
>me to some WEB educational resources or a cheap / free lathe CAM
>package. I just want to design some simple shapes, no threading or
>complex stuff. Maybe a DXF to GCODE converter that does NOT assume
>you are programming a mill? Other suggestions?
>
>

The I and J words generally define the distance in X and Y,
respectively, from the point where
you are before the move to the center of the arc. So, this defines 3
points: Where you are now,
where you are moving to in the X and Y words, and where the center is in
I and J. Most controls
demand that the distance from center to current pos and from center to
ending pos match
within some limit. Some programs require that I and J always be
positive, most require
that the sign be correct for the direction to the center. Many older
CNC systems will only
do 1/2 of a circle (up to 180 degrees inclusive), some will only accept
up to 90 degrees
inclusive.

Really, for most purposes, the CAD package and the CNC control don't
need to know
whether they are controlling a mill or lathe. Other than the X-Y rather
than X-Z axis
names, it all looks like 2-D motion.

Jon