Re: [CAD_CAM_EDM_DRO] re:Re: re: IJK interp

When using R with G02 and G03, a plus or minus sign tells the machine where
the center of the circle is.
For a given move having a known end point and a given radius there are only
four possible curves. Two of them are cut using G02 and the others are cut
using G03. If the desired arc is less than 180 degrees, just plug in the
numbers. If the desired arc is greater than 180 degrees but less than 360
degrees, insert a minus sign immediately after the R. It DOES NOT WORK for
360 degrees. It also uses the existing location of the spindle for the start
position.

Therefore, the location of the center of the circular arc (using Ballendo's
example) will depend on where the cutter is. If it is already at position
X0 Y0, the command won't work, because you are trying to cut a full circle.

If you want to cut a full circle begining from where you are, all you need
to do is enter G02 I# J#. you can omit either I or J if either one is zero.
The I and J dimensions will locate the center. If you MUST use the R method,
you will have to cut the circle in several steps.

I really prefer the R method because I sketch the part to scale using
QuickCAD, select the part and read the radius and end points right off the
drawing. For a full circle move I do the same thing. Sketch the part, so
its to scale relative to the existing location (which I place on the drawing
origin) click on the circle read the X Y (IJ) center point and plug it
(copy and paste) into the program.

This way, the only time I need to use IJK is when making full circle moves.
And it eliminates all the calculations required for IJK moves.

Hope this helps?

Smoke

>Art,
>
>Let's assume we're currently at X0 Y0.
>
>I give your program the arc command:
>
>G02 X0 Y0 R.5
>
>Please tell me where the arc CENTER is???
>
>Ballendo
>
>P.S. The R word breaks down terribly (in G02 and G03) after 180
>degrees of arc, and is indeterminate (with respect to center point)
>at 360 degrees. That's why IJK still exist! R is good for fillets,
>tho...
>
>P.P.S. IJK itself is VERY easy. It is the number of different WAYS it
>has been implemented over the years (and the explanations of same)
>which has made it SEEM so hard!
>