When I go to SurfaceDeleteFace227 and around there, I am still seeing that the walls are hollow. I just removed a tower, but nothing in-side the walls.
@iChris Like itâs so weird⌠When I add a block in one of the empty spaces, and put it into Bambu Labs, it slices the block, but not the windows, or the stuff on top of it. The block is even touching the windows, so there should be no issue with 0mm walls. I donât believe itâs a wall issue as the squares that form a circle, are regular objects with infill, and still wonât slice. I have also tried multiple different slicers, and version, but to no avail.
Post the STL.
From what I can see from the additional pictures you posted, and the comment about non-manifold edges, the issue may simply be that the model isnât âwater tightâ and the slicer canât deal with it.
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Here is the link to the file if this helps: Fusion
Just post the STL? I donât want to give it my email address to download it for myselfâŚ
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Here is a download link to the STL file - https://file.io/hQA2JKqcGsYk
You have holes in your 3D model. Youâre using a mesh body when you really want a CAD model.
While I realize why you donât want to fix manifold edges, you may have no choice. I am assuming that your file link is to the CAD source, your file appears to be a Mesh and not an actual CAD drawing. If that is not the case, then your link is not to the original CAD drawing.
Analysis by file format.
Here is what my findings were just doing an analysis of a STEP file and STL format from your file link.
Put simply, your model is too large and too complex, needlessly so since the printer will never be able to resolve anything that detailed. In other words, youâre asking too much of the slicer.
STL File
- The first hint of a problem is that the file is too complex and too large, 18.3 MB to be exact.
- The second issue is the holes in your mesh. In simple terms, the slicer software needs a 3D model that doesnât have any gaps or holes in it. The algorithm assumes a watertight enclosure. If there are over 4,700 holes in your model, itâs not surprising that some parts of the geometry are being omitted from the model because the slicer canât figure out how to handle them.
Assuming that Fusion360 exported the file correctly, note the build plate behind the model itself for scale.
Albeit a gorgeous model, do you really need a geometry that is almost 1 meter in length? Try Scaling it before you export.
Windows 3D Builder aslo confirmed that the mesh is corrupt.
STEP file analysis.
When imported a STEP file into SolidWorks 3D viewer, it basically tells the whole story. As this image is similar to your observations, this is precisely what one would expect with either non-manifold edges or corrupted geometries in CAD that are disconnected from one another.
Note the floating geometries. This is classic example of disconnected mesh.
DaSSault Systems eDrawings 3D Viewer
Open Source STP viewer which confirms that the STEP file contains no geometry data but rather only mesh data.
OnShape Concurs with these findings
OnShape STEP import no errors but missing geometries
OnShape STL - Complete geometry but confirmation of defective topologies, meaning holes in the mesh.
Summary suggestions
- Simplify the model by scaling it to closer fit the print plate. The Fusion360 gurus here can probably advise you best but if this were brought into OnShape which is what I use, Iâd change the scale from meters to millimeters. Ideally, you want the native model to have itâs largest dimension no larger than 250mm which is the max build on Bambu, not the advertised 255.
- Repair the Manifolds
- Simplify the STL model geometry to fewer triangles. Windows supports this directly but Bambu has a right-click interface that will leverage that OS function.
- Try to export in the lowest version of STEP that you can support and import the STEP file directly. Lower versions do not support complex models so the model will default to the simplest geometry.
In short, Garbage In, Garbage Back 
Itâs not the slicerâs fault.
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Oh wow, thatâs a lot! Thank you so much. I will try your suggestions, and let you know if they work.
Iâm a little bit confused on this part. Do you think you could please expand? Thanks!
There are a lot of issues with this STL. Many places, like this spot, where there are multiple overlapped polygons occupying the same space.
Itâs not a non-manifold edge issue. These polygons are separate entities that overlap each other. Thatâs not going to slice cleanly.
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So do I have have to go through each thing, and make sure itâs not overlapping?
What setting were you on to see the frame of the object?
Itâs my CAD software. I loaded the STL and displayed it as a wire frame, started looking at areas that I had seen disappear in the slicer, saw stuff like this, selected a representative example of polys and did a screengrab.
I donât know enough about Fusion to suggest how to prevent it from doing this. But overlapping unconnected polys can definitely give a slicer a headache. You have a zero-thickness wall. So it disappears when sliced.
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There is a very long thread here recently on STL vs STEP. If you want the long version and have a few hours, read this.
To spare you the wall of words, let me simplify.
- STL files are a mesh of triangles
- STEP files are geometric descriptions of geometric shapes such as lines, circles, arcs and angles. They are far more accurate and Slicers support them as well as STL.
- After a STEP file is imported into a slicer, the model is converted into a mesh and all geometry data is lost.
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So when I say import with the lowest version, thatâs only if your CAD supports versions. There are three versions. STEP AP203, AP214 and AP242. AP203 is the earliest and oldest and will not contain the same complex data that later versions might hold. Thus allowing for less information to be processed by the slicer.
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STEP files and STL files in a text editor can look remarkably similar but there are very stark differences. STEP is covered under ISO 10303-21 and was designed specifically for CAD portability. Itâs predecessor was IGES. STL was designed by 3D Labs specifically for 3D printing.
In the world youâre trying to live in, CAD 
FDM, mastering the concepts between the two formats will help you develop a more intuitive understanding of what will and will not work in a 3D printing or CAD use-case. You donât need to be an expert to get the feel of which file format performs in a specific manner. In fact, you can know nothing about the file syntax so long as you wrap your mind around the differences between a parametric geometry and a mesh. Itâs been demonstrated in this forum that many who believe they understand the concepts actually do not.
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May I ask what CAD software you are using? Fusion 360âs wireframe is pretty trash.
You can ask. 
I started doing CAD a long time ago as part of generating computer animations, using a piece of software called âLightwaveâ. I think Iâm on the 6th or 7th version, now.
Itâs not parametric like Fusion, itâs focus is editing meshes. Can be a limitation when designing something big (itâs hard to make changes after youâve designed a section of something). But since 3D printing is all about triangle meshes, itâs great for looking for problems.
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I am very confused beacuse @RocketSled is saying that is isnât a malifold issue, but it is just overlapping lines, but @Olias is saying that it is a mailifold issue, and that is the only way to fix it beacuse of all the holes in the model.
There are manifold errors, too. But those arenât the reasons these walls are disappearing. The exterior walls disappear because they are coincident with an interior wall. The resulting wall has no thickness. The âinsideâ and âoutsideâ are in the same place.
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You may be reading these two posts to literally. Both posts can be true at the same time. Rocketsledâs explanation focuses more on the cause, my post focuses more on the affect. One can have a CAD issue that creates a âdimensionlessâ object which would then be interpreted within the slicer as an open manifold. Both conditions can exist at the same time.
The bottom line here is that if you have multiple problems reported by multiple software such as the file analysis I did above, that is your red flag that your model is corrupt.
I took a second pass at the model file and if I were to hazard a guess, it looks like this model has been passed through multiple translator or import/export processes. You can almost see the pattern where objects were not correctly accounted for in the geometry. One smoking gun is that the STL file reported over 1,300 parts but most of them under examination are tiny random stuctures.
You can quickly see the damaged model if one hides all the surfaces and shows just the objects. The disconnected geometries become more obvious.
If I may ask, what was the source of this model file? It is quite curious.
This challenge admittedly has me very curious. So I took this an extra step just to see what might be possible.
Here are the steps. I tried to use as few external program as possible but the final step did require a CAD import in OnShape before bringing it back into the slicer. I use Orca Slicer which is a fork of Bambu Studio. It uses the same libraries so the import/export functions should be identical.
- Model was brought into Orca at itâs native scale.
- Using Orca, I right clicked and did the following
- Scaled the model down to 200mm which was approximately 10% of the original
- Repaired the manifold
- Right-clicked and simplified the model down to 30% of the original polygons.
- Exported from the slicer as an STL and then imported it into OnShape and then exported it as a STEP file.
Bringing in the STEP file into eDrawings showed that the most of the orphaned shapes were reconnected.
And this what the sliced model geometry looked like on the plate at 10% scale and without supports.
Itâs a 7 hour print and Iâm going to bed. Iâm using some crappy $10 filament that I need to burn up anyway. It was one of my failed filament adventures. Tomorrow will show if I get a pile of spaghetti or an actual model. 
Iâll use supports to print it.
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