1

**General Mach Discussion / circles are not round - need advice**

« **on:**February 28, 2009, 10:18:05 AM »

I need your help. I'm not sure what questions to ask or where to even begin looking to solve this issue.

I use Bobcad V21 and Mach3 2.0. I am trying to cut a simple round circle. The G-code looks correct in both Bobcad and in Mach3 but the circles are not round. They are off about a 1/16” on a 2” circle. I noticed this when I started to cut out gears and they would not line up correctly, so I thought I would try just a std circle to see if I could identify the problem. The X dimension is correct. The Y dimension is correct. It is the verticals that are off and causing it to be slightly oval.

The frustrating part is that I used to be able to cut circles perfectly on this machine with this software. I have changed nothing (as far as I can recall).

Where should I start looking.

Here is the G code I tested with.

N1 G00 Z0.5

N2 X1.

N3 G01 Z-0.12 F50

N4 G03 I-1. J0.

N5 G01 Z-0.24

N6 G03 I-1. J0.

N7 G01 Z-0.36

N8 G03 I-1. J0.

N9 G01 Z-0.48

N10 G03 I-1. J0.

N11 G00 Z0.5

I use Bobcad V21 and Mach3 2.0. I am trying to cut a simple round circle. The G-code looks correct in both Bobcad and in Mach3 but the circles are not round. They are off about a 1/16” on a 2” circle. I noticed this when I started to cut out gears and they would not line up correctly, so I thought I would try just a std circle to see if I could identify the problem. The X dimension is correct. The Y dimension is correct. It is the verticals that are off and causing it to be slightly oval.

The frustrating part is that I used to be able to cut circles perfectly on this machine with this software. I have changed nothing (as far as I can recall).

Where should I start looking.

Here is the G code I tested with.

N1 G00 Z0.5

N2 X1.

N3 G01 Z-0.12 F50

N4 G03 I-1. J0.

N5 G01 Z-0.24

N6 G03 I-1. J0.

N7 G01 Z-0.36

N8 G03 I-1. J0.

N9 G01 Z-0.48

N10 G03 I-1. J0.

N11 G00 Z0.5