RE: [CAD_CAM_EDM_DRO] vex or lego cnc

Hi Ebiz (?),

For other then simple "one axis at a time" moves, you will need to
coordinate the axis moves. Start the motors at the same time; end them at
the same time. For example, if they move the same distance, then you get a
45 deg. angle. To get an arc, use the radius and the "length" of the arc to
calculate a series of X,Y points along that arc. Move to each point in
sequence around the arc.

The G0, G1, G2 and G3 Gcode commands will need to be decoded to get the X,
Y, Z, I, J, and K parameters, and you'll have to decide which mode (absolute
or relative) you're in. Arcs are often done with the X,Y,Z in absolute, and
the I,J,K in relative. It's a place to start.

A simple Gcode simulator program will help you "see" what the moves do.
Study them, and then implement your code to interpret and do the same thing.

Alan KM6VV

> -----Original Message-----
> On Behalf Of ebiz_59
>
> My curiosity has overcome my fear of probable embarrassment so here we go.
> I have several VEX robotics kits (erector set with a PIC brain) and now a
> couple Lego NxT kits. We've done robotics competitions with both kinds of
> kits, as well as the big FIRST robotics 120 lb unit. And have done
> programming to get the robots to do autonomous stuff, so we have a little
> "C" and "NxTG" programming capability. But now I want to use these
> platforms as teaching platforms for CNC. I've googled lego cnc and vex
> cnc and there are those doing some work, but I'm having trouble figuring
> out the software steps to get the VEX or NxT micro controllers to do
> actual CNC. The little NxT motors have encoders built into them, so we
> could actually know how far we were moving, I'm just stuck with what to do
> beyond writing code for each move. As an example, I'd like to hook these
> little motors to an etchasketch. I can see how one might draw a square,
> but I'd like to draw a circle. Do we just have to learn more "C", or is
> there a way we can get closer to "real cnc" - gcode and an interpreter for
> the NxT or VEX? Thanks.