POC - Do not slow down external perimeters to meet minimum layer time

[igiannakas]

This experimental, proof of concept PR aims to allow the user to skip adjusting the speed of external perimeters to meet the minimum layer time threshold.

Varying print speeds especially on external perimeters can result in variations in shine as well as extrusion consistency, which can be partly mitigated by not changing the external perimeter speeds.

This PR is draft, there's plenty to be done before it's prod ready.

To do:

1. Calculate slow down target speeds correctly - currently it includes external perimeter slowdown but doesnt use it (which means the overall layer time will be ever so slightly shorter than desired)
2. Make this an option in the filament settings
3. Make it compatible with slowdown for overhangs - currently it doesn’t play well with that option enabled
4. Maybe adjust slowdown to prefer slowing down internal features first instead of touching the external perimeter down to a minimum speed, then adjust external perimeter speeds.

However seeking testers to see whether this is an option worth pursuing.

Testing ask:
Print a model with this build and the standard 2.0 build

1. Test with a shiny filament - PLA or petg. Demonstrate whether there is a difference in gloss consistency
2. Test with a shrinking filament (ABS). Demonstrate whether there is a difference in layer shrinking due to speed changes
3. Ideally test with slowdown for overhangs turned off as looking to maintain uniform external wall print speeds. Also with a small object that results in layer speed variations
4. Ideally test with inner outer inner mode to ensure internal wall speeds do not affect the external wall surface finish.

Before:

After:

Fixes #5147

[celtare21]

Really hope to see this integrated!

[Ataraxia-Mechanica]

Currently does not seem to be working. Can't wait for this to be a thing.

[igiannakas]

Currently does not seem to be working. Can't wait for this to be a thing.

New version is up, waiting for the build. Screenshots are up showing the difference.

[ramosglauco]

Big idea! I hope it is implemented soon.

[Ataraxia-Mechanica]

No idea why nobody came up with this idea till now, and why I didn't come up with this till I modded my 3d printer to print so fast that almost all things I print have to slow down due to cooling XD.

[Ataraxia-Mechanica]

Found one case where this would be extremely useful. When printing with "infill combination" on, the layers with infill would take significantly more time than non-infill layers, causing uneven outer surface. Printing the test model right now.

[Ataraxia-Mechanica]

In this case, the outer wall in 2.0.0 would slow down just enough to hit the VFA speed of my printer causing resonance, while with no outer wall slowdown POC, the outer surface is much smoother.
Tested with PETG, with belts overtightened to show the artifacts as much as possible.
Used inner/outer/inner wall order.

girdfinity-1x1x6-voron.zip

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[igiannakas]

Thank you!

[SoftFever]

Wow!
This is a fantastic idea!
It will be especially helpful when we print those cooling-sensitive materials.

[igiannakas]

I’ll spend a bit of time working this feature as it’s by far incomplete right now, to get it to a better testing state ;)

[StuSerious]

@igiannakas let me know if you need some testing like I did for #4333 ;)

[igiannakas]

@igiannakas let me know if you need some testing like I did for #4333 ;)

Yes please - testing requirements are in the top post together with limitations. Please disable slowdown for overhangs as it doesn’t play well with it yet. Also try a small model - benchy is a good one as it has layer time variations accross the board (hull, top part where the windows are). This PR is not ready for daily use and only in a controlled environment as there are many things that don’t work yet - trying to demonstrate value and then I can devote time to productionise it.

please be aware that there is no option to enable yet - it’s always on in this Pr. So the before and after need to be done between the current nightly and this.