I’ve been helping Andrew Staton (@Quadhurst) to model (among other things) mid 20th C lighting fixtures.
It was remarkably tricky to figure out the geometry, but eventually we managed to draw this one.
Andrew wants to make a few 3D prints of some of his models at 1:10th scale, but this one is proving very difficult.
It’s called a Stanton 7B bracket - a reinforced concrete bracket that sits on top of a reinforced concrete column, and carries a lantern suspended from the top on the spigot shown (at least, in the 3D model - in the original, the lantern was bolted on).
The overall height is approximately 3ft, and the sideways ‘reach’ between the centre of the round part of the base and the lantern attachment is 1’ 9".
When exported to STL at full size, in inch units, the STL on re-import into SU is no longer solid. Solid Inspector 2 reports 1 stray edge, 5 Surface border issues, and 384 internal face edges.
I’ve changed the model units to metres, and scaled the model up 100x, to export in metres, but import into the slicer in mm to create the desired 1:10 scale version.
The scaled up model also reports as solid (in Solid Inspector 2) but not in SU.
I exported it to STL with metres as the unit, and reimported it to SU using mm as the import units, as well as having the model units set to mm.
It comes in at the correct size, but the STL is not solid.
I attach both the original model, made of a mixture of solid components and non-solid surfaces (as groups) created by Fredo’s Curviloft/Skin Contours, and the exploded and cleaned up model, created with a mixture of Outer Shell for the solid components, and manual editing of the exploded result combined with the exploded group surfaces.
The edges for the Curviloft/Skin Contours were copied and pasted in place from the underlying components, but it looks from the STL import that the problem surface border issues are at edges where the Curviloft surfaces are located.
Why does SU think the result of the original exploded model is not solid, when SI thinks it is?
Why is the exported STL from what SI thinks is “solid” not still a solid?
Is there any way of fixing this?
It behaves the same in both SU2021 and 2022, both the latest versions at the time of writing.
I’ve saved the models back to SU2017 to make it easier for more people to review the model and possibly help.
Stanton 7B 13 Mar - problem.skp (2.7 MB)
Interestingly, when opened in SU 2017 Solid Inspector reports over 2700 ‘Short Edges’ - mainly in and around the base, but with a few at the upper end of the arm.
I’ve tried the STL in a Cura slicer, but the slicer isn’t creating layers, though it doesn’t show errors either.