Thank you very much for your replies.
I'm not sure which part you don't understand in that tutorial, tex -- the geometry or the g-code -- but the geometry can be found in the Machinery's Handbook, if you have a copy of that laying around. It's an old practice to fake or approximate an ellipse by connecting 4 circular arcs, 2 long and 2 short. I was just reading that today, actually -- it's in the first section of the book, under the heading "Geometric Constructions." That's essentially all that this tutorial is doing, plus it seems to be dealing with some overhead related to the machine's very small memory footprint.
CAMFUN, that's beautiful. I'm a former software developer who's chosen to change careers into machining (had to satisfy a creative urge that wasn't being met), and I'm currently a student who's just started into g-code. For the moment, I'm actually just trying to work in 2 dimensions, throwing a felt marker into the chuck and writing on a pad in a mill. I can take this and get the math right. We simply hadn't got around to variables, conditional logic, subroutines or any other programming constructs in our class yet. Thanks a lot for the point in the right direction.
Incidentally, I found today in my Machinery's Handbook a reference to G06, which that book describes as "parabolic interpolation." I haven't Googled that yet, but I'll see what I find and report back here in the event that I answer my own question.  |