Hollow STL & Mesh Tool
LocalHollow a watertight STL, OBJ, PLY or 3MF mesh to a set wall thickness in your browser — SLA drain holes, before/after volume preview, no upload. Pro feature.
Drag files here, or click to browse
Supports STL, OBJ, PLY, 3MF, GLB, GLTF
Choose fileHollowing works best on watertight meshes (run mesh repair first if needed). Mesh files only — point clouds (.xyz/.pcd, faceless PLY) are rejected with a clear message.
What is it? Mesh Hollow hollows a watertight mesh into a shell with a chosen wall thickness — the inner shell is scaled per axis so all three axes get ≈ the set wall thickness — and optionally drills SLA/DLP drain holes through the bottom wall. The shell previews on the page with before/after volume (estimated material saved) before you download the STL.
TL;DR: Hollow a watertight STL or mesh to a set wall thickness right in your browser — optional SLA drain holes, on-page 3D preview with before/after volume, then download the hollowed STL. Pro feature; nothing is uploaded.
How to use
- Open a watertight model.
- Set the wall thickness (process presets: SLA/DLP ≈1.0mm, FDM ≈2.0mm, SLS ≈2.5mm as common starting points) and the drain-hole count (0 = none; default 2, max 6).
- Click "Hollow (preview on page)" — the shell renders in 3D with volume before → after and an estimated material-saved %; then click "Download hollow STL" to save <name>-hollow.stl.
- Resin-printing? Keep the drain holes on (default 2) so trapped resin can drain, and check on the preview that the hole circle actually lands on the base — tall, thin models can put it outside.
FAQ
Does the model need to be watertight?
Yes — hollowing requires a closed mesh; repair it first if needed.
How is the wall thickness applied?
The inner shell is scaled per axis by 1 − 2t/dimension, so walls are ≈ t on all three axes near the bounding-box faces (curved areas vary). If t exceeds half a dimension, that axis floors the inner shell at 5% — walls end up thinner than set, but never inverted.
How are drain holes placed?
Evenly around a circle of radius ≈ 0.15 × max dimension on the bottom face; the page controls the count only — the hole diameter is fixed at ≈ 2.5% × max dimension — and they pierce the bottom wall. On tall, thin models the circle can fall outside the base — holes are then skipped silently, so check the on-page preview (and a mesh viewer) before printing.
Is it local?
Yes, the operation runs in your browser.
Is it free?
No — Mesh Hollow is a Pro feature; on the Free plan this page shows an upgrade prompt.
Which files can I hollow?
Any watertight mesh you can load — STL, OBJ, PLY, 3MF, GLB and glTF. The hollowed shell is always exported as STL, saved as <name>-hollow.stl, since that is what slicers read.
Why hollow a model for 3D printing?
It cuts material, weight and print time on FDM and SLS, and on resin/SLA it is close to required for larger parts: a solid part acts like a suction cup on the build plate and can fail mid-print or tear the film. Grinding drain holes through the bottom wall is what makes a hollowed part printable. The page offers process starting points — SLA/DLP ≈1.0mm, FDM ≈2.0mm, SLS ≈2.5mm walls — common community/vendor values, not guarantees.
How much material will I save?
The page shows volume before → after and an estimated material-saved % beside the 3D preview, before you download anything. It is an estimate of the same closed volume solid-vs-shell, so non-watertight inputs deviate more.
Hollow or simplify — which saves more?
Different jobs: hollowing removes the interior (weight, resin, material cost) while simplifying removes triangles from the surface (file size, slicer time). For resin print cost hollow first; for file size simplify first — they stack.
Examples
- Upload a watertight mesh → 1mm wall → preview + volume readout → download the hollowed STL
Supported formats
Limitations
- Requires a watertight mesh — repair broken meshes first.
- Mesh files only — point-cloud inputs (.xyz/.pcd and faceless PLY) are rejected with a clear message; convert to a mesh format first.
- Thin walls relative to detail may self-intersect; one enclosed volume is supported reliably.
- Per-axis inner-shell scaling gives ≈ the set wall thickness on all three axes (measured at the bounding-box faces; curved areas vary).
- Wall thickness beyond half of a dimension floors that axis's inner shell at 5% — actual walls are thinner than set, without inversion.
- Drain holes (default 2, max 6, 0 = none; the page controls the count only) sit on a circle of radius ≈ 0.15 × max dimension around the bottom face with a fixed ≈ 2.5% × max dimension diameter, piercing the bottom wall; tall, thin models can put the circle outside the base — holes are silently skipped, verify on the on-page preview before printing.
- Volume / material-saved readouts are estimates (solid vs shell of the same surface); non-watertight inputs deviate more. Thickness and volumes are in model units — STL/OBJ carry no unit field, so rescale non-mm models first.
- Runs locally in your browser; nothing is uploaded.
Privacy
Privacy first: this tool runs entirely in your browser — your input and files never leave your device, and everything is cleared when you close the page.