HI, I am facing a problem with stl export.
The original model in MOI looks like this



It is an extrusion of a profile and union with other objects.
Originally the longest edges were “straight” (no rounding)



I wanted to extend it a bit and make rounded, so I added solid cylinder and made a union.



Despite the union is OK, the .stl export produces false faces (faces inside the solid object)



The strangest part is, I cannot repeat the procedure how I made to union, I just remember I selected 3 objects at once and run union.
Attached is the strange solid and it’s stl export.
Until now I fully thrusted to the stl export, I had never such issue (exported hundreds of complex models).
The consequences are “fatal”… The 3D printer slicer does not recognize the false faces, but the slicer routine is confused, and creates wrong layers (partly missing layer) and it causes faild prints



What have I made wrong?
Is it a problem with .stl export?
How to prevent making mistakes in design leading to such strange behavior?

Thanks you in advance for answers :-)
Jozef

if the file is in mm then parts are thinner than 1mm. Can your printer handle that? Most printers can't.

Val

Hi Jozef, it looks like the piece that you unioned on did not share the same plane as the existing piece, making some extra area with a very small width:





It looks like that is what is causing the problem. I'll see if I can produce a fixed version for you.

- Michael

@val
Yes, I have an SLA printer, (Phrozen SM4K), i can print walls starting at 0,25mm
But reliable print starts at 0,4mm




the "V" shaped L profile is 0,3x0,3mm

J.

Hi Michael,
thank you
I noticed the "extra" edge, but I did not zoom it soo close to see the that detail. But still I do not understand where the faces inside the "healthy" solid came from...

But in this case I have a new and issue:
Time to time happens the snapping is somehow not precise. In this case I draw a circle exactly on the middle of the edge, and extruded to the opposite edge. The difference is 0,001mm but still enough to casue fatal problems...
Sometimes operations like mirroring, copy etc produces such small differences... Drawing a lot of symmetrical objects related to a fixed center point ends up in having a small "cloud" of center points in area of 0,01mm.
Is there a setting how precisely should objects snap?

Jozef

Hi Jozef, I've attached a fixed version here with that little tiny extra slivers removed. Please give this one a try.

- Michael

With one simple cut operation (cutting the protruding cylinders) the stl export is OK.
J.

Hi Michael
thank you...

I did not refresh the page, I achieved the same result.
Jozef

HI I use Microsoft 3d BUILDER to repiair STL or OBJs before printing its free its built on NETFABB engine which AUTODESK bought its super tough in doing repairs I use frequently when going from MOI to ZBRUSH or back. Even in complex ZBRUSH models with inner non manifold surfaces it always corrects the STL to be watertight for printing. I also do resin based jewellery prints and pass it through 3d builder to correct any problems before printing. Hope that helps.

https://www.microsoft.com/en-us/p/3d-builder/9wzdncrfj3t6

You have also the MeshMixer who has a function Analyse / Repear... for STL files

https://www.meshmixer.com