Hi, my tool diameter is D6mm.

If in program i make radius on corner R3, mach3 don't understand how to do it. Here is attached screen.
Green dots are the way my tool is going by.
If i make my corners with radius R3.1 everything works fine. Cam program is sheetcam.

you can not have a G02 or G03 with a radius of zero, if you tell Mach3 your tool is 2,999mm it will work.