I'm trying to mill a spiral. anyone know the code? I found a G2.1 code but Mach3 doesn't like it.
Thanks,
Chuck

Hi,
codes G2 and G3 are circular arc/helical interpolation moves.
See for instance 'CNC Programming Handbook' by Peter Smid, its pretty much the Gcode bible.

They are fixed radius, you cannot to my knowledge use them as a spiral.

The way to do it is use CAD to draw the part including the spiral toolpath then use CAM to generate the Gcode.

Craig

They are fixed radius, you cannot to my knowledge use them as a spiral.

In Mach3, you can cheat with G2/G3 to create a spiral, by specifying the end of the arc to be offset from where it should be.
Load this code into Mach3 and you'll see a spiral.

G40 G90
G91.1
S10000 M3
G0 Z0.1250
G0 X0.0000 Y-0.7400 Z0.1250
G1 X0.0000 Y0.1233 Z-0.1000 F75
G2 X0.0000 Y0.1233 Z-0.1000 I0.0000 J-0.1233 F100
G2 X0.0000 Y0.2467 Z-0.1000 I0.00 J-0.1233
G2 X0.0000 Y0.3700 Z-0.1000 I0.00 J-0.2467
G2 X0.0000 Y0.4933 Z-0.1000 I0.00 J-0.3700
G2 X0.0000 Y0.6167 Z-0.1000 I0.00 J-0.4933
G2 X0.0000 Y0.7400 Z-0.1000 I0.00 J-0.6167
G2 X0.0000 Y0.7400 Z-0.1000 I0.00 J-0.7400
G0 Z0.1250
G0 X0.0000 Y0.7500 Z0.1250
G1 X0.0000 Y0.7500 Z0.0000 F75
G2 X0.0000 Y0.7500 Z-0.1000 I0.0000 J-0.7500 F100
G2 X0.0000 Y0.7500 Z-0.1000 I0.0000 J-0.7500
G0 X0.0000 Y0.7500 Z0.1250
M30

 Thanks  Gerry,
That’s what I’m looking for I will give it a try.
Chuck

Worked great!!!
Did you do this manually or is there a program to create the code?
Chuck

I use this AutoCAD macro that I wrote. It creates these "spirals" when pocketing circles.

http://www.thecncwoodworker.com/ac2gc.html

 Nice, I use solideorks.
 Maybe I can find a macro for it.

 As it turns out Brian wrote a wizard for cutting spirals in Mach3
Chuck

Forgot all about that.

CamBam does spirals too. I cut flange faces to mate to round tanks. I project the spiral onto a surface with the tank radius and spiral inwards from the outside edge. Very efficient tool path.