Minimum Polygon Circumference not doing what I would expect

[lancebaa 0]

I have set minimum polygon circumference to 100mm (as shown in screenshot). It does indeed remove several layers, but there remain 2 layers for this particular small feature (isolated at each layer when sliced). See the area with some yellow and travel lines going to/from it.

 

Using 4.12.1. Also attached my .3mf

CFFFP_v2_n_11_25_30_deg.3mf

[lancebaa 0]

Small update with some of my troubleshooting...

 

After looking through CuraEngine source, I figured out that the small polygons must have been part of a larger polygon at slice time, and yep. Small polygons are removed *before* thin walls are culled. If I enable thin walls, the features connect on those two layers (see screenshot), so clearly at slice time it was one big polygon on each of the two layers.

 

However, the whole point of me wanting to exclude small polygons is to avoid travels and retraction. Even with the thin walls (one of them VERY thin) there are still travels and retractions for some reason.

 

Not sure what the solution should be, but IMO small polygons should be removed after thin walls are culled (if thin walls are turned off). I realize that probably creates other problems, though.

[GregValiant 1,141]

A lot of travel moves can be generated with certain combinations of settings.  Where the Z seam is in relation to the layer start X Y location, the combing mode, monotonic lines, etc.

Do you have "Fill Gaps Between Walls" turned to "Everywhere"?

On a "U" shaped section the combing moves will want to stay over the part rather than jump the short gap.  The nozzle may run around the back of the horseshoe a couple of times to do it's job.  It can be really annoying.

For larger models and if Z hops are NOT being used then the post-processor Retract Continue can help the nozzle from oozing on long combing moves.  That helps extrusion starts after combing.

"U" shaped sections do generate a lot of movement.  On the other hand, on that model, pretty much however I set Cura up the print time was 1hr 10min.

You don't have a real need for the infill to provide strength.  You can try setting the "Infill Layer Height" to 2X Layer Height.  The infill will go down every other layer but at 2X flow so you might have to slow the infill down.  There are a lot less retractions though.

You can play with "Gradual Infill Steps" too.  I use that when all my infill has to do is hold up a roof so it can print.

 

 

[lancebaa 0]

Thanks for the tips. I'm trying that Retract Continue right now (hoping it helps with #2 below).

 

I've run into two other issues tonight...

 

1.) If I enable Horizontal Expansion, the Z Seam Alignment setting gets messed up (I have Sharpest Corner selected). My only theory is that with the concave U shape, when it expands, some of the vertices get crossed, creating very sharp corners (this is not apparent when looking at the preview, though). So now the "sharpest corner" becomes part of the U shape somewhere as opposed to by the "feet" of the tunnel.

 

2.) You mention combing, and I've had this issue for over a year (as such I have been using Simplify3D, because this really messes up my prints)-----When it combs the print right before starting a new layer, it increases Z *before* the comb. I do not have z-hop enabled. This makes combing completely useless. All along that U shape I get strings galore.

[lancebaa 0]

I've attached an image of my seam issue when horizontal expansion is enabled. The white spots are the new layer starts.

 

With horizontal expansion disabled, the white spots are all on the inside corner of the "feet" of the tunnel. It's too bad, because if I have horizontal expansion set to 0.45mm, it actually solves the original problem in this post, because the thin walls are no longer thin walls but "real" walls, so I don't get all those travel moves over open space.

 

Here's a link to when I originally asked about the combing Z issue: 

 

Edited December 23, 2021 by lancebaa

[GregValiant 1,141]

"When it combs the print right before starting a new layer, it increases Z *before* the comb"

Yes it does.  That is the Z adjustment to the next layer but Cura always puts it before the last combing move.  In your case that's a long ways from where the next extrusion will be.  For example:

;MESH:NONMESH
G0 F600 X120.836 Y78.54 Z25.3

followed by 23 lines of combing moves before extrusion starts again.

 

This is the best I've been able to do.  I threw out the infill and went with 2 walls.  There is one crossing travel move up high.  Unfortunately, Travel moves can not be assigned per mesh and so the combing mode cannot be changed with a support blocker.  The print time went up by a couple of hours though as the walls require a lot of laps around.

 

 

 

GV_NEW4.3mf

Edited December 23, 2021 by GregValiant

[lancebaa 0]

Would you consider the combing/Z issue a bug? I would, but there may be a reason behind it that I'm not aware of.

 

Edit: Even with the Retract Continue, I get crazy stringing in the concave U shape due to this.

Edited December 23, 2021 by lancebaa

[GregValiant 1,141]

"Would you consider the combing/Z issue a bug?"

I don't think so.  It's doing what it's programmed to do.  I think if you were to change the program so that the Z move was after all the combing moves then someone else would complain about marring a surface because the nozzle is dragging across the skin or because it's banging into the infill or something.

"Horsehoe" shaped sections are tough.  Every time I have to slice one it takes me a while to fiddle with Cura to get the slice where I want it.  I'm rarely 100% happy with it.

 

I was curious how much travel there was in that original 3mf file so I did a study.  There were 606 meters spent extruding and 500 meters spent traveling so it was traveling about 45% of the total distance.

When I checked that last slice (with 2 walls instead of infill) only about 3.3% of the total distance was travel.  The print took longer because the extrusion moves are a lot slower than travel moves but at least the printer would be working instead of just wandering around smoking cigarettes for 9 hours.

Edited December 23, 2021 by GregValiant

[lancebaa 0]

FWIW, moving the block starting on line 1811 above the previous block completely fixed my stringing issue: https://github.com/Ultimaker/CuraEngine/blob/master/src/LayerPlan.cpp#L1811

 

It certainly looks intentional based on the comments. Maybe conditionally doing it before/after based on the type of travel move could be a reasonable change (is it a comb? Is it combing over skin? etc etc). Either that or adding yet another setting.

[GregValiant 1,141]

Well @lancebaa I'm a VB guy so what I'm seeing there is Greek to me.  It sounds like you got it sorted out though.

From what I've read about the engine, altering movement is tough because so many other things can break.

There are a lot of hours being put into the Arachne version of Cura to get it ready for release.  I don't care for the movements I see in Arachne (because of the variable line width) but I'm not well practiced with Arachne.  Maybe it will come along for me, or maybe not.  Time will tell.

 

[lancebaa 0]

Well, that sorts out one of my issues. There are still some more.

 

I tried that Arachne version you mentioned, and it actually fixes the issue where horizontal expansion caused issues with "sharpest corner" seam alignment.

 

If I were to combine my fix along with using Arachne (still haven't even tried building it), it may get be "good enough."

 

I will say this, though... Simplify3D seems to have almost zero travel movements given the same model and similar settings. All this travel causes other issues with my setup that I have to compensate for (.8mm nozzles have issues with oozing, requiring extra priming after retraction, and then it depends on how far it traveled, etc... this is exacerbated by the fact that I print slightly hotter than usual in order to get prints out quickly)