The model looks complete in the Prepare tab; press Slice, switch to Preview, and a piece of it is gone. In the forum's model, as another user worked out, the missing piece was a support made of two 0.4 mm thick walls that the model included for its middle spring; the thin gap visible at the neck in Prepare also appeared closed in Preview. Send it to the printer and it prints what Preview shows: the missing piece comes out missing.
This is not a printer fault, and most of the time not a file fault either; the slicer is leaving that part out deliberately. What follows is why it does that, and which settings brought it back on the forum.
The symptom: there in Prepare, gone in Preview
What you see in Prepare is the model's geometry, the STL or 3MF file itself. What you see in Preview is the lines that will go to the printer, as much of that geometry as the slicer could produce. The difference between the two is everything the slicer decided it cannot print.
The parts that vanish are always the same kind:
| What disappears | How it looks in Preview |
|---|---|
| A thin wall or thin plate | Missing entirely, or broken in places |
| A narrow neck, arm or handle | A section missing between layers |
| A narrow gap between two surfaces | The gap has closed, the two parts are joined |
| Small text, embossing, notches | The surface comes out flat |
Before hunting for faults in the model file, the first thing to do is drag the layer slider in Preview to the missing region and look at the lines there. If there are none, the slicer could not place anything there; most of the time the file is not broken, the feature is narrow.
If you saw the The 3mf is not from Bambu Lab warning when opening the file, do not connect it to this: that warning only says the geometry was read, and the detail is in the not from Bambu Lab article; the missing part here is down to the slicer itself.
The cause: the line does not fit
The slicer lays plastic down as lines, and every line's width comes from the line width setting, a value close to the nozzle diameter. If a feature is narrower than that width, no line fits there; I wrote about the mechanism, and the Arachne and minimum wall thickness fix, in the thin-wall section of the flow article. The forum's two 0.4 mm walls are exactly this case: on the 0.4 nozzle's default profile the slicer judged them unprintable.
Why the gap at the neck closed is not explained on the forum; the first reply asked about layer height, the user wrote they were on the stock 0.2 mm profile unchanged, and the thread never returned to that gap. If a narrow gap closes in your Preview, see the gap closing item below.
In the thread the first reply suggested switching to Arachne and checking the line width in Preview, that is, diagnosing the problem; lowering the line width and Detect thin wall came after. The accepted answer is line width; I start with that.
The forum's fix: line width down to 0.38 mm
The forum user solved it by lowering three line width settings:
Printed fine when changing the first layer, outer wall and inner wall to 0.38mm with 0.2 layer height and a 0.4 nozzle (on X1CC).
In Bambu Studio the settings are in the Quality → Line width group:
| Setting | Value on the forum |
|---|---|
| Initial layer ("first layer" on the forum) | 0.38 mm |
| Outer wall | 0.38 mm |
| Inner wall | 0.38 mm |
Conditions: 0.4 mm nozzle, 0.2 mm layer height; the user gives the printer as X1CC. In an earlier post the same user wrote that the same three settings also fixed the slicing on the 0.12 mm layer profile. Setting it below the nozzle diameter is worth noting, but it is not out of bounds: the printer can lay a line narrower than the nozzle by reducing flow. The Bambu wiki recommends not changing the default line width; if you do, the range it gives is 0.75-1.5 × nozzle diameter, and 0.38 mm is inside that range for a 0.4 nozzle. With a narrower line, a line fits where none did before.
The cost is strength: the number of walls (wall loops) stays the same while each wall gets thinner. The user who shared the setting also writes that some fine-tuning may be needed to make the part strong enough. Raise Wall loops if necessary, and check on a small test piece before reprinting the whole model.
If only this model needs it, you do not have to apply it to the whole plate. Switch the Global / Objects toggle in the left panel to Objects and you can change the outer and inner wall line width for that object alone; according to another forum thread the Initial layer line width is not in the Objects settings and stays Global; check in the panel.
The forum's second fix: Detect thin wall
The second route in the thread is a one-line reply: turn on Strength → Walls → Detect thin wall. Although the accepted answer is line width, three separate users wrote under that reply in 2024, 2025 and 2026 that this solved their problem; it is the route that kept working in the thread afterwards.
According to the Bambu wiki, with this option on the slicer slightly reduces the shrink width it applies when generating the wall path; in thin walls the spacing between wall centers gets smaller and a path is generated where two lines would normally not fit. The setting's tooltip says the same thing: detect a wall that cannot hold two line widths and print it with a single line.
The side effects are in the wiki too: walls can overlap, the excess filament can stick to the nozzle and spoil the surface; very small regions can come out as a single unclosed line that breaks off during the print. After turning it on, look in Preview at both the missing region and the walls around it.
Other routes
If these two are not enough, or you will be printing the same model repeatedly, go through these in order:
- A smaller nozzle. Line width shrinks with the nozzle; on the forum the same model sliced fine with the 0.2 mm nozzle profile. It is the right tool for fine detail, but the same part takes longer.
- Scaling the model up. Once the feature is wider than the line width it prints on its own. The Scale tool and the lower limit of shrinking are in the scaling article; why walls disappear when you shrink a model is there too.
- Thickening the model in CAD. This is the permanent fix: correcting the thin wall, neck or gap at the source. Even if you did not draw the model yourself, you can open it in a CAD program and thicken that region.
- Arachne and minimum wall thickness. The route the thread's first reply suggested for diagnosis; as a fix, it is in the flow article linked above. It adapts to thin areas without touching the line width.
- Check that the model is closed (manifold). If the model has a hole or opening, the slicer cannot slice some regions. This possibility was discussed on the forum too; in that case the model was sound, but on another model it may be the first suspect.
- Slice gap closing radius. This setting under Quality → Precision fills small cracks and gaps during slicing. If a narrow gap between two surfaces closes in Preview, look at its value.
Whichever route you choose the test is the same: after Slice, go to the missing region in Preview and see whether there is a line. It did not work for everyone on the forum: in May 2025 a user wrote that none of these fixed their model; that is why the list above is a checklist to work through in order, not a single setting.
"Skipping objects" is something else
The second forum thread comes up under a similar search but asks the opposite: deliberately skipping one of the objects on the plate during a print. If an object has lifted or failed you want to abandon it and carry on with the rest.
The user asking writes that they can do this in the Bambu Handy app but cannot find it in Studio. The answer given in November 2024 was correct for its day:
Skipping objects is currently not supported in Bambu Studio software.
That answer is out of date. With Bambu Studio 2.2.0 (July 2025), Studio now supports skipping objects remotely during a print: there is a Part Skip button in the printer status bar on the Device tab, and the window that opens lets you pick the objects to skip. According to the Bambu wiki's Skip Objects page this works from Studio on the X1 series, H2 series and P2S; on the A1 and P1 series it is not there yet and is left to future firmware updates. On those printers you use the Handy app; on the P1 you can also skip from the printer screen, while the A1 series, according to the wiki, does not support skipping from the screen. The wiki also lists Bambu Farm Manager for the P1 and A1.
Deleting an unwanted object from the plate before the print starts is always possible. Skipping from Studio once it has started depends on the printer model; the supported list changes with firmware, so check the current wiki.
In short: if a part vanishes on its own, it is line width or Detect thin wall; if you want to skip an object yourself, it is Part Skip in Studio, or Handy if your printer does not support it.
