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**General Mach Discussion / Milled circle not completely round**

« **on:**November 21, 2009, 06:42:45 PM »

Hi,

I have a cnc'd mini mill which I drive with Mach 3. I use servos rather than steppers and Geco drivers.

I generate the GCode with OneCNC.

I do have some backlash on my X axis which I remove the backlash feature within Mach 3. I believe I have this set to .0025.

When I cut a circle, the circle is not completely round there appears to be a flat area on one side aligned with the X axis which is maybe 20-15 degrees of the circle. This flat area is maybe 10-20 thou shallow.

Below is a fragment o the GCode... If anyone has any suggestions I would really appreciate it.

Code: [Select]

`N00120 Z0.05`

N00130 G01 Z-0.025 F6.0

N00140 X1.8623 Y-0.0564 F12.0

N00150 G03 X1.8095 Y-0.1035 I-0.0029 J-0.0499

N00160 G02 X1.8125 Y0. I-1.8095 J0.1035

N00170 X1.8095 Y-0.1035 I-1.8125 J0.

N00180 G03 X1.8566 Y-0.1562 I0.0499 J-0.0029

N00190 G01 X1.9065 Y-0.1591

N00200 G00 Z0.2

N00210 X1.9122 Y-0.0593

N00220 Z0.025

N00230 G01 Z-0.05 F6.0

N00240 X1.8623 Y-0.0564 F12.0

N00250 G03 X1.8095 Y-0.1035 I-0.0029 J-0.0499

N00260 G02 X1.8125 Y0. I-1.8095 J0.1035

N00270 X1.8095 Y-0.1035 I-1.8125 J0.

N00280 G03 X1.8566 Y-0.1562 I0.0499 J-0.0029

N00290 G01 X1.9065 Y-0.1591

N00300 G00 Z0.2

N00310 X1.9122 Y-0.0593

N00320 Z0.