Infill before walls not applied when infill density set to 100%

[tommylux]

Application version 4.8

Platform Windows 10

Printer Geeetech A20T

Reproduction steps

1. Ensure Infill before Walls is selected, note the nozzle path in Preview fills in infill before outer walls.
2. Set the Infill density to 100% note the infill is now applied last.
3. Adjust the infill density to 99% and note the infill is now applied first.

Screenshot(s) (Image showing the problem, perhaps before/after images.)

Actual results Infill is applied last despite the checkbox infill before walls is checked.

Expected results Infill before walls should work despite infill density stting

Additional information I have tired enabling and disabling travel optimization.

[fvrmr]

If you set the top layers and bottom layers on 2 (or something else). You'll see that after the bottom layers the infill is printed first.

[jellespijker]

Hi @tommylux ,

Thank you for bug report.

You're indeed correct that Cura doesn't print infill before walls, when infill is set a 100%. That is because we emulate the infill by replacing it with bottom skin. @Ghostkeeper describes why this approach is taken in the following discussion thread https://github.com/Ultimaker/Cura/discussions/8965#discussioncomment-235730

In Cura, if you set the infill density to 100%, and inspect layer view, you'll find that it didn't actually create infill. That's because it then automatically sets the Bottom Thickness to 9999mm. This eliminates a border between skin and infill where the lines don't match up. You only have walls+skin then. In the end this results in better print quality and fewer air pockets.

As a side effect certain settings, such as infill before walls, don't work as expected anymore. A work around for this can be to set the extra infil wall line count to a higher number like 9999. This would create a 100% infill filled volume, which adheres to the printing order.

I will discuss it with my fellow team members if/when we will adres this. Addressing this behaviour in the new Arachne seems like a logical point to me since Arachne takes care in filling the complete area, without air pockets. Which might occur if you use the proposed work-around.

[fvrmr]

We will create a ticket to investigate this with our process engineers.

If you look at my work around, the infill is not completely 100% if you change it to grid. So you need to add what @jellespijker described above

As a side effect certain settings, such as infill before walls, don't work as expected anymore. A work around for this can be to set the extra infil wall line count to a higher number like 9999. This would create a 100% infill filled volume, which adheres to the printing order.

[tommylux]

Thanks. In fact, I don't particularly mind which is applied first. Only, that I was using the wall to slow down the print speed before it travels to the next place to reduce stringing. I think the better parameter to use is reduce the coasting speed <90% and increase coasted volume. Is there a preference generally within the community to print walls first?

[tommylux]

Fantastic explanation from jellespijker and this makes complete sense and a good insight to how Cura is programmed.

[fvrmr]

Developers see CURA-7984

[GregValiant]

Is this still an issue in current Cura versions (5.8.0 and up)? Can this be closed?