Cut 3D model sections at a chosen seam
Open your STL and examine its orientation in the viewer. To cut a 3D model at an angle, rotate it in CAD first and save that orientation; this workspace only makes planes perpendicular to X, Y or Z.
POSITION ONE PLANE IN MODEL COORDINATES
STL cutter for a precise plane.
Choose an axis and position.
Use this STL cutter when a seam needs a specific location: below a mounting flange, behind a visible detail or beside a section you want to test. Set one axis-aligned plane and keep both sides as downloadable solids.
Real, capped geometry 100% local file processing Free to use, no sign-up
LOCAL WORKSPACE Your files stay on your device
01
Your model
.STL02
Split settings
No upload. No account. No installation.
ROOM FOR YOUR NEXT BIG IDEA
Add a model to make it fit.
XYZmm
Drag to rotate · Scroll / pinch to zoom
Waiting for a modelScale 1:1 · mm
All cuts run on your device
Plane positions use the source file’s coordinates, interpreted as millimeters.
A SINGLE CUT WITH AN EXACT POSITION
Place and review a cut with the STL cutter
Choose a coordinate
Select the axis and move the slider, then enter a precise value if needed. The STL cutter measures from the file’s original origin. It does not reset zero to the nearest edge of the model.
Generate both sides
Press Split model, then separate the preview and highlight each result. An STL cut should leave the feature you need intact. Download either piece individually or take both in a ZIP before changing settings.
NEGATIVE COORDINATES, EXPLAINED WITH NUMBERS
STL cutter example: a plane at X = −10 mm
Suppose the model’s X bounds are −60 mm and +40 mm. Its total X span is 100 mm. Entering −10 puts the plane 50 mm from either end: −10 − (−60) = 50 and 40 − (−10) = 50. Entering zero would instead leave spans of 60 mm and 40 mm. To keep a 20 mm section next to the minimum edge, enter −40 mm. These are bounding-box distances, not promises of equal material volume. The selected coordinate must be strictly inside the bounds; −60 or +40 only touches an outer boundary.
Before using the STL cutter, identify which surface can rest on the bed. A new cut face may offer a broad footprint, but rotating onto it can put another overhang above empty space. Look through the sliced layers, check both part dimensions and add supports where your printer and material require them.
For a centered seam, cut the model in half without entering a coordinate.
Need several evenly spaced cuts? Choose a part grid.
For automatic sizing, try the STL splitter for your printer.
Cut STL file sections for a fit check
For a fit-check coupon, cut near the socket or screw boss you need to inspect, then download only that side. Keep enough surrounding wall to reproduce the local stiffness. Cutting directly through the fitting itself may make the test misleading.
Keep the plane inside the solid
If the STL cutter reports that a position is outside the model, compare the value with the selected axis bounds. Switching from X to Z changes the relevant range. A plane through an empty gap may not divide material even when it is inside the bounding box.
Prepare the mating surfaces
The exported pieces retain scale and source coordinates. In the slicer, separate their placement and rotate each as needed. Inspect the capped wall sections around cavities. Dry-fit printed parts before gluing; alignment pins and assembly tolerances are your responsibility.
Know when one plane is insufficient
To slice STL file into parts across several evenly spaced planes, use the part-grid mode below. For a custom seam, the STL cutter handles one plane per operation. Curved cuts, automatic connectors and arbitrary angled planes are outside this version.
FOUR WAYS TO START
A different cut for a different job.
STL splitter
Divide by your printer’s build volume.
STL cutter
Place one precise axis-aligned cut.
Split STL into parts
Choose an equal-width grid of parts.
Cut STL in half
Split at the center on X, Y or Z.
PLANE PLACEMENT AND EXPORT TROUBLESHOOTING
Questions about using the STL cutter online
See the geometry and feature limits or read how selected files are handled.
How to cut STL around a particular feature?+
Choose the axis perpendicular to your intended seam, inspect the amber plane and move it beyond the feature’s outer edge. Cut, highlight the result and verify the feature remains complete. The viewer does not detect critical features for you.
Can I cut STL along axis directions other than Z?+
Yes. Choose X for a plane across the model’s X extent or Y for its Y extent. These directions follow stored model coordinates, so orbiting the camera does not change what the selected axis means.
Does the STL cutter delete the unwanted side?+
No. Both sides remain available after a successful operation. Download only the side you want, or save both for assembly. Changing the axis or position clears the old preview; run the operation again to produce revised files.
Can I cut STL online if the mesh has holes?+
Repair the input first. Open surfaces and non-manifold edges cannot reliably describe a closed solid. If the file is unusually dense, simplify a copy as well; reducing triangles addresses memory use, while repairing topology addresses invalid geometry.
Is the new face always the best printing surface?+
No. Compare stability, visible surface quality and support removal. A thin cut rim may offer little adhesion, while laying a decorative face down may mark it. Choose orientation in the slicer rather than assuming a cap must face the bed.