What negative space is and why you need it in Bambu Studio

Negative space in Bambu Studio is the empty area around or inside your 3D model that the printer will not fill with material. Creating it deliberately makes your prints lighter, faster to produce, and uses less filament — which saves money on every job. In Bambu Studio, you build negative space by using the hollowing tool, adding internal voids, or designing cutouts before you import your model.

The most common reason to add negative space is weight. A solid print of a large object can be heavy and brittle. A hollowed version of the same object prints in half the time and weighs a fraction as much. Bambu Studio gives you three main ways to do this: you can hollow the entire model, you can add internal structures like ribs or walls, or you can design the negative space into your model before you bring it into the software.

Key Takeaways

  • Bambu Studio's Hollow tool automatically removes the interior of a model and leaves a thin shell, which you control by setting wall thickness in millimeters.
  • You can add internal support structures by creating ribs or walls inside your model using the Paint tool or by editing the model file before import.
  • Negative space reduces print time, filament use, and weight without changing the outside appearance of your finished object.
  • Always preview your model before printing to make sure the hollowed areas will not collapse during printing or cause support material to fail.
  • Test wall thickness on a small print first — too thin and the shell cracks, too thick and you lose the benefit of hollowing.

Using the Hollow tool to remove the interior

The Hollow tool is the fastest way to create negative space in Bambu Studio. Open your model in the software, right-click on it in the left panel, and select Hollow. A dialog box will appear with a slider for wall thickness, measured in millimeters. The default is usually 2 mm, which works for most small to medium prints. Drag the slider left to make thinner walls (faster print, less material) or right to make thicker walls (stronger, more material).

After you set the thickness, click OK. Bambu Studio will calculate the hollow version and show you a preview. The software automatically creates a small hole in the model so the interior can drain during printing — you will see this hole marked on the preview. This drainage hole is essential; without it, uncured resin or support material can get trapped inside and ruin your print. The hole is usually small enough that you can sand it smooth or fill it with a tiny amount of epoxy after printing.

Before you confirm, rotate the model and look at the preview from all angles. Make sure the wall thickness looks even and that no thin sections have disappeared. If the walls look too thin in any spot, increase the thickness and preview again. Once you are satisfied, the model is ready to slice and print.

Adding internal ribs and walls for strength

Hollowing removes all the interior, but sometimes you need internal structure to keep the walls from flexing or collapsing during printing. You can add ribs — thin internal walls that run from one side of the model to the other — by editing your model file before you import it, or by using Bambu Studio's Paint tool to mark areas for support.

If you are comfortable with 3D modeling software like Fusion 360 or Blender, the easiest approach is to design the ribs into your model before you bring it into Bambu Studio. Create thin vertical or horizontal walls inside the model that connect opposite sides of the shell. Make them 1 to 2 mm thick so they do not add much weight. When you import the model and hollow it, these ribs will remain in place and give the walls something to anchor to.

If you do not have access to modeling software, you can use Bambu Studio's Paint tool to mark internal areas. Select the Paint tool from the left toolbar, choose a brush size, and paint on the model surface where you want internal support. The software will create a solid region in that area. This method is less precise than designing ribs beforehand, but it works for adding local reinforcement where you know the model will experience stress.

Designing negative space before you import

The most control comes from building negative space into your model before you ever open Bambu Studio. If you use Fusion 360, Blender, or another 3D design tool, you can create the exact internal structure you want — hollow chambers, internal walls, cutouts, or lattice patterns — and export the model as an STL or OBJ file. Bambu Studio will import it as-is, and you skip the hollowing step entirely.

This approach is best for complex models or production runs where you want consistent results. You can test different wall thicknesses and rib patterns in your design software, print a test version, and refine before you commit to a full batch. You also have the freedom to create shapes that the Hollow tool cannot produce — for example, a model with multiple separate chambers, or internal details that serve a function beyond just saving weight.

When you design negative space this way, remember that Bambu Studio still needs to be able to slice the model and generate support material. Make sure any internal voids are not so small or complex that the slicer cannot handle them. A good rule is to keep internal features at least 2 mm thick and 5 mm apart from each other.

Checking your negative space before you print

After you hollow your model or add internal structures, always preview the sliced version before you send it to the printer. In Bambu Studio, click the Preview button at the bottom of the screen. The software will show you a layer-by-layer view of what the printer will actually produce. Scroll through the preview and look for any of these problems: thin walls that disappear in certain layers, support material that fills internal voids you wanted to keep empty, or drainage holes that are blocked by support.

If you see support material inside a hollow chamber, you have two options. You can increase the wall thickness so the chamber becomes too small for support to reach, or you can adjust the support settings in the Supports panel — for example, by raising the support density threshold or changing the support angle. Test these changes in the preview before you print.

Pay special attention to the drainage hole. Make sure it is not blocked by support material and that it is large enough to actually drain. If the hole is too small or in an awkward location, you can manually move it by editing the model or by using the Paint tool to mark a better spot. A drainage hole that is 3 to 5 mm in diameter usually works well for most models.

Common mistakes and how to avoid them

The most common mistake is making the walls too thin. A 1 mm wall sounds light, but it often cracks during printing or peels away from support material. Start with 2 mm and only go thinner after you have successfully printed a test. The second mistake is forgetting about the drainage hole. If you hollow a model and the hole gets blocked or sealed, the interior will fill with uncured resin and the print will fail. Always check the preview to confirm the hole is clear.

A third mistake is hollowing a model that has internal details you wanted to keep. If your model has a hollow chamber with a small opening, the Hollow tool will fill that chamber with a thin shell, destroying the detail. In this case, design the negative space manually before you import, so you have full control over what stays and what goes.

Finally, do not assume that thicker walls are always better. A 5 mm wall on a small model will print slowly and use a lot of filament — you lose the whole benefit of hollowing. Test different thicknesses on small prints and find the minimum that still gives you the strength you need.

Frequently Asked Questions

Can I hollow a model that has a closed interior with no opening?

Yes. Bambu Studio's Hollow tool will automatically create a small drainage hole so the interior can drain during printing. You will see the hole location in the preview. If you do not like where the software places it, you can manually move it using the Paint tool or by editing the model file before import.

What wall thickness should I use for a small figurine?

Start with 2 mm for a figurine under 10 cm tall. If it prints successfully and feels strong enough, try 1.5 mm on the next one. If it cracks or feels fragile, go back to 2 mm or increase to 2.5 mm. The right thickness depends on the material, the shape, and how much stress the object will experience.

Will hollowing make my model weaker?

A properly hollowed model with adequate wall thickness is nearly as strong as a solid one, but weighs much less. The key is choosing the right wall thickness for your material and design. A 2 mm wall in most resins is strong enough for decorative objects and light-duty functional parts. For high-stress parts, increase the wall thickness or add internal ribs.

Can I add negative space to a model that is already imported?

Yes. Right-click the model in the left panel and select Hollow. You can also use the Paint tool to mark areas for internal support or voids. If you need more control, export the model, edit it in a 3D design tool, and re-import it.

What happens if the drainage hole is too small?

If the hole is too small, liquid resin or support material can get trapped inside and prevent the interior from draining properly. This usually causes the print to fail or the interior to cure incorrectly. A hole 3 to 5 mm in diameter is usually sufficient. If your model has a very large interior chamber, you may need a larger hole or multiple holes.