View Full Version : Output arcs using R not I,J?

06-19-2007, 03:05 PM
I'm having some problems cutting G2/G3 arcs on my rotary axis. Basically I am using Sheetcam to generate standard X,Y plane G-code, then using a text editor to replace all the Ys with As to use my A axis. Works fine until I,J arc centre words come up, then the REAL Y axis starts to move and not my A. I figured if I used the "G2 R..." notation this problem would go away - is there a setting that I can change to effect this, or does it require a different post? Currently I use the standard Mach2 post with no other problems.


06-20-2007, 03:47 AM
Mach cannot handle X-A arcs. Arcs have to be on the X-Y, X-Z or Y-Z planes.
To get around this you need to break the arcs into lots of short line segments. Go to c:\program files\sheetcam\posts. Make a copy of the post then edit the copy with a text editor. Look for

function arc()

Delete the whole function and replace it with this one:

function arc()

If the line segments are too long, reduce the number. While you are digging into the post, look at function rapid() and function move(). In both functions, change " Y" to " A".

In SheetCam, load the modified post and away you go, no more editing the G-code.


06-20-2007, 01:35 PM
Les, many thanks. Makes my life much easier.