Mach3, ESS Smoothstepper, Rhino5, Madcam.

I've tried backlash compensation on and off. Have my CV settings at .1, no other CV boxes checked. Tried IJ mode absolute and incremental. Talked with CAM developer about all settings.  Post is cutting with G2/G3. 

I've played with motor settings. Tried cutting at 1IPM.... I'm stumped.

Pic shows what's going on. Black shape is what I'm trying to cut. Red shape is cut part measured on CMM. I'm always getting this deviation at around the 10 o'clock position no matter what I try. The toolpath is correct, I really believe it's something in mach3

Pic didn't load first time

And pic rotated, so cut issue is at 8 o clock.  Not 10 o clock as mentioned in first post

Can you please attach your Gcode that is causing the problem ?

How is it being measured, 3 or more points on an arc or a digitised path?

I'll have to post the gcode on Monday.
It's measured with 3600 points, .0001" resolution. Very accurate.  The cut part discrepancy is .023", so pretty obvious.

Are you cutting this on a mill or router type machine?

Mill. Cutting mild steel. I can do skim cuts of .001" and it will cut exact wrong shape

If you are cutting cam lobes then teh Black line is bad code. Teh acel / Deacel ramps should be symetrical on each side of teh lobe. The red line appears to be more symetrical than teh black line. The black line has an inverted ramp which is Bad lobe design in most cases.

From what data did you plot the black line. I would like to see teh Gcode that cut it.

Just a thought, (;-) TP

Are you using tool comp?