wrong bridges and top if extrusion width typed in mm

[alexander-kudinov]

Description of the bug

I have 0.4mm nozzle on my printer. I set default extrusion width 0.44 and 0.44 for the first layer.

When I slice my object I see that bridge on Infil do not reach outter border very often. It causes print defects of tops.

But if I set extrusion width less or equal to nozzle (say 0.35) the issue is gone.

Here is screenshot of issue: https://prnt.sc/piI-C43hwJsp

Here is screenshot if I set extrusion width with 0.35: https://prnt.sc/SBOmrsRS3Jjv

Project file & How to reproduce

Open a file with shape of washer with height > 3mm. Set top/bottom to 3 layers, Infil is Cubic. Nozzle 0.4mm, layer height 0.2. Extrusion width bigger than nozzle. Say 0.44.

Go to the preview of layer and check first and second layer after infil.

Set extrusion width to 0.4 or less. Look at the changes. I attached screenshots.

Checklist of files included above

• [ ] Project file
• [X] Screenshot

Version of PrusaSlicer

2.5.0

Operating system

Windows 8.1 x64

Printer model

Kingroon KP3S

[alexander-kudinov]

UNO_Card_Box_top.zip Here is the file to reproduce the problem. If layer height is 0.2, The layers with a problem are 7 and 8.

[DragonFinlay]

I can't reproduce this, even after replicating your settings. Both layers 7 and 8 look good and reach the perimeter lines well.

Please open my 3MF and see if it works for you too. Otherwise, please upload your 3MF (zipped) with the issue.

UNO_Card_Box_top.zip

[alexander-kudinov]

I played a little bit with the settings. If I enable "Ensure vertical shell thickness", the bug is disappears even if I use bigger extrusion width. However, it's not expected behavior.

Please open my 3MF and see if it works for you too. Otherwise, please upload your 3MF (zipped) with the issue. UNO_Card_Box_top.zip

Your file works, So I've attached my version of 3mf with the issue. UNO_Card_Box_top_bug.zip

[DragonFinlay]

Okay, I think I see what's happening. It's about "Extra perimeters if needed". PrusaSlicer thinks it needs 2 additional perimeters for the top layer of the bottom part, and doesn't "support" these layers with infill underneath.

If you disable this option, that layer has the default 4 perimeters and the infill will be fine.

[alexander-kudinov]

your answered helped and I'm able slice my model. Thank you.

PrusaSlicer thinks it needs 2 additional perimeters for the top layer of the bottom part, and doesn't "support" these layers with infill underneath.

I think that this optimization is wrong. I mean it looks good on picture but during printing, the quality is worse on the next layer. The optimization saves 0.0% of time and plastic but reduce quality. PrusaSlicer must add support infil despite of perimeter width.