Getting over extrusion leading into front overhang on Benchy and under extrusion when moving away, when enabling "slow down for curling perimeter"

[ImDisaster]

Is there an existing issue for this problem?

• [X] I have searched the existing issues

OrcaSlicer Version

2.2.0

Operating System (OS)

Windows

OS Version

Windows 11 Home, 23H2

Additional system information

No response

Printer

Sovol SV08

How to reproduce

Turn on "slow down for curled perimeters" to create issue. Turn off to fix.

Actual results

About 4mm up from bottom to 12mm from bottom it over extrudes entering front corner of ship and under extrudes leaving the corner. Effect starts about 5mm from corner.

Expected results

Project file & Debug log uploads

[3dbenchy_fixed_hopefully.zip](https://github.com/user-attachments/files/17692061/3dbenchy_fixed_hopefully.zip)

Checklist of files to include

• [ ] Log file
• [X] Project file

Anything else?

Added file project file with slow for curled perimeters off. Turn on to create issue. 3dbenchy_fixed_hopefully.zip

[igiannakas]

Enable extrusion rate smoothing. Your extruder cannot change its filament position fast enough causing it to extruder more when rapid speed changes happen.

Also calibrate your pressure advance - this should mitigate the issue to a large extent

[ImDisaster]

I ran all the calibrations in Orcaslicer slicer including pressure advance and retraction. I have tried with the stock settings in Orcaslicer and with the modified settings. I have had the issue from .02-.04 smoothing. Default setting was .035. .02 smoothing has shown the best results overall. I have tuned retraction as well...but it happens on the stock retraction settings too, which were .5 mm and 30 mm/s.

I also saw the same issue with the Qidi Plus4. Turning off the slow for curling fixed that one too. It is strange it only affects a specific range of the Benchy and an overhang test (50-70). It is almost as if the overhang and curling have an additive effect which creates the issue.

[igiannakas]

I’m confused. You mention smoothing - is that the PA smooth time you are referring to? Lower smooth time puts more demands on the extruder but if it’s up for it it can allow you to run higher accelerations with better looking transitions.

Retraction has nothing to do with this artefact. This is purely the extruder not being able to keep up with the rapid speed change when going from fast to slow print speeds.

Solutions include:

1. Reduce external perimeter and internal perimeter accelerations - higher accelerations cause more stress on the extruder when rapidly changing speeds
2. PA value is not spot on - the tests may be run but real world is showing artefacts so tuning the PA value (not smooth time but PA) is improtant
3. Enable extrusion rate smoothing and set this to 150 with segment length of 1 or 2. This should smooth out the changes in speed on the slicer side if the printer cannot do this well on its own.

you can disable the slowdown for curled perimeters feature but you’re not solving the problem, which is the printer not being able to respond well to rapid speed changes. It’s best to address the cause of this rather a feature that relies on the printer doing what it’s told well, if that makes sense?

[igiannakas]

For context the below with curled perimeters enabled on a calibrated 2.4 Voron, so it can be done :)

[igiannakas]

The extrusion rate smoothing on the wiki explains the above pretty well. Have a read ;)