complex patterns

[drc]

Hi all, I'm new here so, please be patient.
I run a plasma cutter where I work and have been able to handle cutting squares, rectangles and circles without too much trouble. I was wondering if someone could help me with more complex patterns such as half moons and pie shapes. I was trying to figure out how to write a program for a pie shape with a slight radius but, this seems to go beyond g2, g3, and I and J codes. Am I not using the right codes for something like this? Can someone point me in the right direction?
Thanks in advance for all your help.
drc

[HuFlungDung]

Over there ---------------->



G2 and G3 are all you need for arcs, but you need to know the parameter requirements of your machine controller, just to be sure. Some controllers expect a new command every time the curve crosses a quadrant line (X or Y at 0, 90, 180, 270 degrees), or maybe every 180 degrees.

The other variable which you must determine, is whether the arc center coordinates must be in absolute values, or incremental values. This choice may be dependent on the current mode of your main program, G90 absolute or G91 incremental.

Having said that, the rest is a matter of correct mathematics.

You should be able to get ahold of some very inexpensive software to help you do all this much more quickly and accurately than you can with a calculator. Bobcad comes to mind, or if you are wanting more automated software that will help you with nesting profiles, together, Onecnc Profiler comes to mind.

If you want to talk math, just say so, and we'll launch into that

[drc]

thanks HuFlungDung, I'll check out the software links.
My problems may end up to be mathematical more than anything else.
If I make a pie shape with six inch sides, the only way to make it look half way right is to go with g2 and I3.0 in incremental mode for my radius. If I try to change the radius to something smaller or bigger without changing the sides, it only screws it up. So, if all I need are the codes I am already using, than I must be doing something wrong when I am trying to tell the machine what I want it to do.
So, like I said, I will try to look at the software and see if it will help me.
Thanks again for your help.
drc

[HuFlungDung]

DRC,

FYI, the I and J values in incremental mode are easiest to understand. These are the coordinates of the center of the radius the machine will move through. These coordinates must be equidistant from the position where the machine starts the arc, and the position where it will end the arc movement.

The X and Y values included with the G2 or G3 command are, of course, the exact endpoint of the arc movement, relative to the starting position.

So its not a matter of guesswork, plain old trigonometry, or even the Pythagorean theorem can be used to figure this out. Usually, high accuracy is required in the calculation or else the controller will refuse to move, or it will make a "correction" at the end of the move to get to the commanded endpoint.

[Mortek]

drc,

Here is a sample g-code of a partial moon shape g-code with I,J icremental.

G00 X0. Y3
G03 X0. Y-3. I4. J-3.
G02 X-3. Y0. I0. J3.
X0. Y3. I3. J0.
G00 X0. Y3.

outside arc is 3" radius and insice arc is 5" radius

[Mortek]

Now the pie shape

G01 X0. Y0.
G01 X-1.5 Y2.5981
G02 X1.5 Y2.5981 I1.5 J-2.5981
G01 X0. Y0.

[CDignition]

I would be willing to help ya out on malking the programs you need...if yu send me the drawings, I will use my Cam system and post a file for you and e mail it to you..

[drc]

Thank you Mortek
You've helped me quite a bit with the samples. This is what I was looking for. It's starting to make sense to me now.

Thank you cdignition for your help and offer I will try to get a copy of the drawing for you.

Excellent website by the way, I love your car. I've been a mopar fan for many years. I used to drive a '73 340 Duster but never had the time and money to do what I wanted to do.
Anyway, thanks again to all of you for the help. This is a great site.

drc