For a straightforward planar split, use the PrusaSlicer cut tool and keep both parts. Use Blender when the cut needs to follow a shape, then close the cut surfaces and test how the parts will join.
Use the PrusaSlicer cut tool for a planar split
To split a 3D model into parts for printing, use a planar cut when a straight cut is enough. PrusaSlicer can retain the resulting objects and add several connector types. Use a mesh editor for a shaped boundary or a more involved redesign. Use the simplest suitable cut.
These steps follow the official PrusaSlicer cut-tool guide. They are documentation-led; this page does not claim a physical assembly test or a universal connector tolerance.
Practice on a box with known dimensions
For the first cut, download our original 20 × 30 × 40 box STL. Interpret its coordinates as millimeters. A horizontal cut halfway up an unrotated box should produce two pieces whose geometric extents are 20 × 30 × 20 mm before connectors are added. These are calculated bounds, not recorded slicer output.
Before cutting, save the original, measure usable bed space and plan how to hide and join the seam.
1. Place the cutting plane at Z 20 mm
Start by importing the STL into PrusaSlicer and selecting the object. Press C or choose the Cut tool in the left toolbar. Select Planar mode. The cutting widget lets you position and rotate the plane; the official guide documents an exact millimeter value for its Z position.
For the practice box resting unrotated on the bed, put the horizontal plane at Z 20 mm. Keep the first exercise free of connectors so the cut dimensions are easy to check. For an actual object, inspect the plane from several angles before confirming it.
A seam below a roof may be less visible than one through a detailed wall. The new flat face can improve bed contact; the central cut is not always the best choice.
2. Keep both halves as separate objects
For this exercise, choose to keep both sides of the cut. Distinguish separate objects from parts inside one object: the latter can remain associated and receive different settings, while separate objects are easier to arrange independently for this exercise.
Before confirming the cut, review orientation: keep it, place the cut face on the bed, or flip the result. Retain the original axes for this dimension exercise.
After the cut, select each result in the object list. If one is missing, reopen the original and check which side you retained.
3. Choose a plug, dowel or snap joint
For a jointed assembly, reopen the original project and plan the connector before making the final cut. The official tool offers Plug, Dowel and Snap connectors. A dowel removes matching spaces and creates an additional pin object; a plug or snap changes how the two primary pieces mate.
Choose connectors to suit the material and load. A decorative display piece may only need alignment for glue. A load-bearing part needs a design review: a cut and glued seam can change its strength. Clearance is printer- and process-dependent, so print a small joint test before two large halves.
The joint must leave enough material around sockets. If the model is a hollow shell or contains intersecting geometry, a connector placed on the visible surface may still break through a wall.
4. Export each part and check its dimensions
Save the slicer project to preserve the model splitting settings. Use the selected object’s Export as STL action for each part, with names such as body-left and body-right. Menu wording can vary by version; check that you are exporting the selected object rather than the entire plate.
Open each STL in the Model Size Checker and choose millimeters. For the practice cut with no rotation or connector, compare against 20 × 30 × 20 mm. After model splitting on your own object, compare all three bounds with the usable bed area and chosen orientation.
Then rotate each cut face in the STL Viewer. The viewer displays the surface but does not certify a closed mesh. Return to PrusaSlicer, slice each part and inspect the layers around the cut and joint before printing.
When model splitting needs a shaped boundary
For shaped model splitting, move to Blender or another mesh editor when the seam must follow an irregular boundary. Keep a duplicate, separate the intended geometry and close newly exposed boundaries before export. An open surface that looks divided is not necessarily two closed solids.
If the part is defined by dimensions and needs a designed joint, a parametric CAD workflow may make later changes easier than repeatedly cutting an imported mesh.
Troubleshoot missing parts and poor fit
- One half disappeared: check the keep/discard options on the original model.
- Both halves move together: check whether you created parts within one object rather than separate objects.
- Unexpected dimensions: check units, rotations and connector protrusions before changing scale.
- The connection is too tight: adjust and retest the joint clearance; scaling the entire model also changes other fitted dimensions.
- The cut face looks open: inspect the input and resulting geometry in an editor before relying on it as a solid.
Can I shrink the model instead of cutting it?
Yes, if the smaller size still meets the purpose. Scaling also changes wall thickness, holes and connection features. Check those before choosing scaling over a split.
Can I cut the model in your online tools?
No. Our tools preview STL geometry and calculate dimensions. Cut the mesh in a slicer or editor, then use them to inspect the exported parts.
Research method & official sources
Initial source review . This page uses official documentation; later source checks and any executed file examples are dated and scoped in the text. We have not benchmarked AI generation quality or performed physical print tests.
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