Captive Hinge Faces

[gornnr 2]

TL;DR: How far away must overhanging faces be for Cura to detect as a solid face?

Modeled up a captive hinge for a home improvement project. When I tossed it into Cura I wanted to check the faces to make sure they would be separate, not just one solid cylinder. What I've found is Cura has decided to put a solid face several layers away from where the face should be.

Airgap between each of the faces is 0.2mm and print settings are 0.1mm layers. Previously, on other parts I've designed in supports that have worked well with these settings however the faces where much further apart.

STL can be found at this link (TinyUpload.com)

If you drop this in Cura (Using 15.01, see next bit for more info on that) you will find on layer 28 should start the face of the inner hinge but it is only doing infil and walls. Then randomly at layer 38 & 39 there is suddenly a solid face, but this is inside the hinge (and not even at the center). Layer 63 & 64 has another face for the center hinge, then 66 through 74 have infill. Layer 74 should be the top of the center hinge. Layer 77 starts with the upper hinge walls and infill, again no face.

Note from above: If I open the distance between the captured hinges (tried .5mm vs .2mm airgap) then 15.06.03 will provide similar issue of not detecting faces correctly. At .2mm airgap Cura 15.06.03 would fail to provide a sliced model.

PS: New Cura 15.06 (Should have been v16 with such radical UI changes) is missing filament usage and cost estimates. Fonts are way too large and all white/grey color scheme looks poorly done.

[IRobertI 521]

I didn't download the file but I recognise what you're talking about. It's been a bug for a long time. Daid explained it to me at some point but I've forgotten what the reason was for it. The only thing you can do to "fix" it for now is to lower the top/bottom thickness to something really thin.

Would really like to see it fixed as I want to use custom supports with solid top layers.

[gornnr 2]

The only thing you can do to "fix" it for now is to lower the top/bottom thickness to something really thin.

Would really like to see it fixed as I want to use custom supports with solid top layers.

 

Ugh, that's not a fix in any sense.

I've got a feeder similar to yours for 1.75mm filaments and it correctly detected the face on that. So there has to be a minimum gap size before Cura puts in a solid face.

[gornnr 2]

So, did a "Fix for Cura" by making a modification to the inside of the hinge to make the faces at 45degrees.

I then wanted to start testing to see the behavior in how Cura would produce solid faces at given spaces. And the results are interesting. Feel free to Grab this STL with 0.05mm Stepping

Initial bottom face will not become solid until the gap is 1.15mm or larger. The next bottom face will not be a solid until 1.25mm. Interesting part, this is with the Bottom/Top Thickness setting at 1.2mm

Playing around further, and indeed, changing the B/T Thickness moves where the faces are correctly made solid. So, seems there is some bug in the code that is relating the SPACING between solid faces in the Z-Direction and the B/T Thickness setting.

[cloakfiend 996]

I print EVERYTHING with top bottom 1.2, as I found that 0.8 just didn't cut it and i would often have many holes and incomplete surfaces. If I want it thinner then I would model it thinner and print 1.2 shell anyways knowing that my walls aren't even that thick and it would print at the size of the model rather than shell size.

Edited August 3, 2015 by Guest

[Labern 775]

Yes I have also had problems with this and have a few designs with this issue.

Would be a good to have this issue resolved.

[cloakfiend 996]

Yes real top bottom values would be nice, but I'm quite happy with the thickness of 1.2, nice and sturdy and you don't need to bother with infill as a result, so yes this is an issue but one I stopped caring about once thicker top bot solved all my issues. but yes something is clearly wrong there. It think it also depends on the model but thats just a guess.

[Labern 775]

Yes real top bottom values would be nice, but I'm quite happy with the thickness of 1.2, nice and sturdy and you don't need to bother with infill as a result, so yes this is an issue but one I stopped caring about once thicker top bot solved all my issues. but yes something is clearly wrong there. It think it also depends on the model but thats just a guess.

 

I don't think you understand the issue of this topic. If you set 1.2 top and bottom, You don't actually get 1.2 if 2 faces are 2 close together. You might get 1 solid layer then infill on top of the solid layer.

Edited August 4, 2015 by Guest

[cloakfiend 996]

true im not sure what you mean, but i was just saying that when i use the setting at shell top/bot 1.2 everything prints fine regardless of actual shell thickness. ill go now, lol.

[gornnr 2]

You can grab the second file and see for yourself.

From left to right the gap increases from each face by 0.05mm, so the first gap is 0.05mm, the next to the right is a gap of 0.1mm, the next is 0.15mm and so on.

What you will find is if you set the "Bottom/Top thickness (mm):" setting to say 0.2mm then from the 4th extrusions and all to the right of it, being 0.2mm or greater in gap size, will have properly solid faces. All at 0.15mm or lower will have incorrectly generated solid faces.

At 1.0 "Bottom/Top thickness (mm):" the first 19 gaps will not have solid faces, but any at the 20th or further right will as they are at or greater then 1.0mm gap.

The bug is if there are two solid faces overlapping at a gap size SMALLER than that set in the "Bottom/Top thickness (mm):" setting.

All testing that I've done with this bug is ONLY at 1.0mm layer heights and with faces that are parallel. This bug appears even at an angle.