Pete, I too have seen some unexpected results when using Absolute IJ mode. These gcode snippets all run on my machine, even tho the last two should not. Strange that Mach will error on a very small end point error while other times it will allow over ½ inch.

This cuts an arc in Absolute IJ mode, center at X0 Y0.5, radius 0.5, as expected.

G00 X0 Y0

G01 X0 Y1

G02 X0 Y0 I0 J0.5

G01 X0 Y0

M30

Now change the J to 0.25 and it also runs, but makes a spiral;

G00 X0 Y0

G01 X0 Y1

G02 X0 Y0 I0 J0.25

G01 X0 Y0

M30

For an even more interesting curve change the Y to 0.5;

G00 X0 Y0

G01 X0 Y1

G02 X0 Y0.5 I0 J0.25

G01 X0 Y0

M30

Can anyone else get this code to run? If so maybe a neat way to cut spirals?

I’m running R3.042.027 and should mention this came up while trying to help a poster on another forum.

Al