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ForumCSMIO/IP controllers and Software - discussion forum: CSMIO/IP with simCNC softwareWarning: Added arc segment angle …

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Warning: Added arc segment angle > 180°, There is probably a too tight bend to compensate in the trajectory.

#1 · 21 May 2025, 03:28

Hello, I'm using SimCNC for plasma cutting. I've cut many pieces without any issues, but today I ran into this error and haven't been able to fix it. Any idea what the problem might be and how to solve it?

Warning: Added arc segment angle > 180°, There is probably a too tight bend to compensate in the trajectory.

Uploaded files:

#2 · 23 May 2025, 12:25

This is probably related to the tool diameter compensation. Diameter can be too big to fit into some tight areas in the path. To be sure I would need a g-code file and exported configuration profile.

CS-Lab Team

#3 · 6 June 2025, 19:15

Sorry for the delay in my response. I ended up solving it by changing the post-processor I use in my CAM software. Thanks.

#4 · 10 December 2025, 00:16

I ran into the same issue fwiw when writing my own Fusion 360 post processor.

this seems to be triggered by the Fusion cutting tool geometry.

If I use a value < 2, I get the error in SimCNC, even though the arcs are more than 180 degrees in both cases

The error goes away once I change the kerf geometry to be >= 2.

So while Fusion 360 configuration triggers this issue, I think there's a bug on the SimCNC side also, where arc degrees seem to be poorly calculated.

Noteable, I don't use this value at all since I emit G41/ G42 to allow SimCNC to correct for the kerf via tool diamater configuration.

Example that works (Fusion 360 kerf geometry 2.039)

M03

G41 D1

G01 X-35.683 Y23.693

X-36.247 Y23.496

G03 X-27.409 Y6.769 I3.432 J-8.885

X-39.9 Y20.977 I-5.407 J7.842

G01 X-39.144 Y20.298

#4061 = #50

M05

Example that does not work

M03

G41

G01 X-35.89 Y23.625

X-36.247 Y23.496

G03 X-27.485 Y6.717 I3.432 J-8.885

X-39.775 Y21.113 I-5.33 J7.894

G01 X-39.3 Y20.67

#4061 = #50

M05

both cases compensation is set to control, to get the G41/G42 commands.

Snippet 1

First G03 (X-27.409 Y6.769 I3.432 J-8.885):
- Start: (-36.247, 23.496)
- End: (-27.409, 6.769)
- Center: (-32.815, 14.611)
- Arc degree: 193.46°
Second G03 (X-39.9 Y20.977 I-5.407 J7.842):
- Start: (-27.409, 6.769)
- End: (-39.9, 20.977)
- Center: (-32.816, 14.611)
- Arc degree: 193.47°

Snippet 2

First G03 (X-27.485 Y6.717 I3.432 J-8.885):
- Start: (-36.247, 23.496)
- End: (-27.485, 6.717)
- Center: (-32.815, 14.611)
- Arc degree: 192.91°
Second G03 (X-39.775 Y21.113 I-5.33 J7.894):
- Start: (-27.485, 6.717)
- End: (-39.775, 21.113)
- Center: (-32.815, 14.611)
- Arc degree: 192.92°

Simple work around, use a Fusion 360 Kerf width of >= 2mm, and configure the correct kerf width in SimCNC.

With correct G41/G42 the cuts should be accurate still, but Fusion 360 generates better paths that don't break SimCNC

#5 · 15 December 2025, 09:51

Thank you for the feedback. I'll investigate it further, especially the error message seems to not explain clearly cause of the problem. Issue itself can be related with lead-in / lead-out segments.
Look at this visualisation (your sample gcode #1, tool dia: 1.5mm):

start point and leadout almost crossing with compensated path (red).

now same gcode, but tool dia: 2.5mm:

Due to crossing, additional 'strange-loop' segment is created - this is probably what directly triggers error message.

Just for test I've added G40 on lead-out move (tool dia. is still 2.5mm):

It's not ideal, because path is 'cutting in' a bit in the material that rather should be untouched, but now path executes without error.

Hint: you can click 'Show Real Path' on the screen to see how compensated toolpath will look like and verify is it ok or not.