Cura tries to print non-closed paths if line width is too thick

[dma_k 1]

Dear community,

 

I am observing the following issue: in vase (spiral) mode with 1.6 mm width Cura 5.1.1 tries to print the isolated paths (first issue) while extruding during the travelling (second issue). The hope was that Cura will take advantage of variable width feature and "narrow" the path to the island (0.8 mm in my case) so when it is passed twice it finally gets the needed width (1.6 mm). If that is not possible, then Cura should better avoid printing such places (show error / warning), as it contradicts the vase mode.

 

 

Similar issue:

Project is attached.

CE3_Vase_Dominik_Cisar.zip

Edited January 21, 2023 by dma_k

[RogueWave 15]

Cura Vase Mode: The Basics Simply Explained | All3DP

 

[dma_k 1]

Thanks for mentioning the link – I have read it before and also mentioned in my post. The options mentioned in the article are enabled. Have you managed to slice the attached project without above issues? Please attach the project then. Thanks!

Edited January 8, 2023 by dma_k

[GregValiant 1,409]

Spiralize was changed at some point.  the 4.x versions of Cura are definitely different.  The new implementation has been called a regression but I don't think so.

In the previous versions Cura would make decisions on what would print and what would not.  If there were islands they were mostly ignored.

This is a slice of that vase with 4.13.1 at your 0.8 line width.  You can see that 4.13.1 ignored the folds in this area because they could not be part of a spiral path.

 

This is that same area in 5.2.1.  Cura is trying to incorporate the islands into the spiral path and failing.

 

This is the same area in 5.2.1 at a line width of 0.4.  The folds in the model are dictating the maximum line width that can print it properly.  The narrower line width allows Cura to keep the islands from forming.

 

So part of the problem is the model.  If those folds came together but allowed a .8 path to move around then there wouldn't be a problem.  You are getting the model sliced with your settings.  That's why I don't view the changed behavior as a regression.  The problem is that either the model isn't appropriate for the settings, or the settings aren't appropriate for the model.

 

If you insist on using the .8 nozzle then you would need to do something like set the Outer Wall Inset to -0.2 or round-a-bouts.  The entire model gets bigger in the XY though.

 

 

Edited January 8, 2023 by GregValiant

[dma_k 1]

3 hours ago, GregValiant said:

So part of the problem is the model.

Well, yes/no. Model is a zero-width shell after all and it's thickness is defied in slicer settings. If the desired shell size is 1.6, then it should be theoretically possible to follow the path twice with variable width gradually shrinking from 1.6 to 0.8 in the tangent point. There should be some physical limit of course, like you cannot extrude a 0.1mm width line with 1mm nozzle.

[GregValiant 1,409]

At this point the cross-section of the model is only 0.55 thick.  You can squeeze a .4 nozzle through there twice but a .8 won't make it.  So there can't be a "continuous" loop around the outside at this height (about 15mm).  This happens at 6 places around the periphery.  One you get up higher then the walls separate and it's all good again.  But those necked down areas present a problem.  The problem was solved in the 4.x versions by cutting off the loop and simply not printing those areas (the "hole in the bottom" problem is the best example of this).  5.x tries to work it into the toolpath but it can't be done and you get those long extrusions that criss-cross the print and make a mess.

Changing the Outer Wall Inset to -.2 adds another .4mm to the .55 and so Cura can then calculate getting the nozzle through there twice without lifting.

 

And then there is the "hole in the bottom" problem when using spiralize.

[dma_k 1]

Thanks for advice. In my case I had to set "Outer Wall Inset" to -0.6mm so that all problematic extrusions are eliminated.

However I didn't get what is the issue with a "hole in the bottom". Have you made it using the additional body?

If I may ask additionally: I see that the bottom pattern is "Lines" or "ZigZag". However whatever option I choose for "Top/Bottom pattern", the setting is ignored and "Concentric" is always generated.

[dma_k 1]

@GregValiant Just curios how have you managed to generate "Lines" / "ZigZag" pattern on the bottom? In my case I always end up with "Circular" path irrespective the settings. Is it because you drilled a hole in the bottom? Thanks in advance!

[GregValiant 1,409]

If you are using Cura 5.1.1 then the only option for the base is "Concentric".  There was a lot of complaining about that and it was changed so that other patterns could be used.  I can't remember if it was 5.2 or 5.2.1 but I use 5.2.1 and as you can see - "Lines" is once again available.

 

Did you figure out how I got the hole in there?  It's a test ya' know.

Edited January 29, 2023 by GregValiant

[dma_k 1]

Thanks for the hint! Indeed v5.2.2 worked smoothly in that respect.

Were you able to create a model without loops, i.e. which can be printed in "real" vase mode (no retractions)? I have played with inset parameter, but I was not able to create a smooth model. There are always loops which require nozzle to move to that part and print it. Please attach a project, if you succeed. Thanks in advance!

If hole in the model was created artificially by you then it is fine. I don't need it, unless it fixes some issue or side effect 😃

[GregValiant 1,409]

I've attached a project file.  I think this looks pretty good.  "Outer Wall Inset" = -0.8 and "Horizontal Expansion" = -0.14.

 

The hole is created by a support blocker in the bottom that is exactly as thick as "Bottom Layer Thickness".  It's configured as a Cutting Mesh with no top or bottom layers, no walls, and no infill.

GV_Vase_Dominik_Cisar.3mf