Bridge acceleration is used for overhang perimeter below the bridge threshold causing bulging

[belotv]

Version

2.3.55.2

Operating system type + version

MacOS 11.0.1

3D printer brand / version + firmware version (if known)

Anycubic Mega i3 - Klipper

Behavior

• Describe the problem
  I use very slow acceleration for bridging (250), to ensure proper binding, and normal acceleration for perimeters (3500). There are some overhang perimeter on 3D Benchy model. These overhangs are below the threshold for bridge flow, so normal settings should be used (only overhang speed shall be used).
• Expected Results
  Default acceleration is used for these overhangs.
• Actual Results
  Bridge acceleration is used for these overhangs (but speed and flow are ok). If this is expected behaviour, then we should have the possibility to give an overhang acceleration control speed because this causes a lot of disgraceful bulging on the perimeter.
  • Screenshots from SuperSlicer preview are preferred
    

Project File (.3MF) where problem occurs

Upload a SuperSlicer Project File (.3MF) (File -> Save / Save Project)
benchy.gcode.zip
benchy.3mf.zip

[supermerill]

I think the problem lies on problems on the slicing side, as it shouldn't have that erratic polygons.

[belotv]

Thanks for the remark, erratic polygons are due to the curve smoothing function. I just disabled it and they disappeared. However it does not really fix the issue.
I would like the hull to be printed slower (with bridge settings), but i do not want the bridge acceleration to be used, only the speed and fan. This does not seems to be feasible today.

[supermerill]

curve smoothing fixed.

So keeping external acceleration until the switch to bridge flow?

• overhangs detected : use bridge fan & overhang speed
• bridge flow threshold: use bridge flow & bridge acceleration

[robthide37]

i think it makes sense to bind the accel with the flow change

[belotv]

Thanks for your replies. I do not really agree there. Contrarily to the other features, overhangs are extension of perimeters, which do not requires the same binding specificity as bridges. Here is an example (top view):