Re: G02 / G02 I and J arguments

Larry,

First, let's clear some confusion. G02 is CW arc/circle. G03 is CCW
arc/circle. The older controls required programming arcs in one
quadrant only (at a time). A circle WAS broken into 4 lines(blocks)
of gcode.

I and J are the distance TO the center FROM the current position.
Whether these values are Absolute/relative and signed or unsigned
will depend on the "flavor" of the gcode/ controller used...

The AA HPGL command will convert fairly easily to gcode. Since it is
Absolute Arc, you will need to resolve any relative coords currently
in use on the machine (when the command is processed) "back" to an
absolute zero point. The X,Y will then be the same as the I,J for
gcode. The final step is to convert the endpoint, (which is an
angular displacement from the current position in HPGL's AA command)
to the x,y "endpoint" coords the gcode format expects. SIN,COS should
do this for you. The tolerance parameter of the HPGL command is not
used in Gcode. (for those who don't know: The tolerance allows the
arc to be made of chords of a defined angular length. 5 degrees is
the default.)

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., "Larry Edington" <ledington@c...> wrote:
> Could someone explain to me how the I and J values are used on the
circular interpolation commands?
>
> I understand the G02 and G03 commands when using the R "Radius"
argument but haven't found a good example of the I and J calculations
necessary for arcs. I understand if you need to do a 360 degree
circle, in G code you have to split it up into a G02 and then a G03
command.
>
> I'm trying to convert an HPGL AA ( arc absolute ) command to it's G
code equivilent. AA gives you X and Y center along with the arc's
angle in degrees.
>
> thanks,
> Larry E.