Visualization · Advanced
Repair solids for 3D printing and CNC
Why is my group not a solid, and how do I make it watertight?
A group is only solid when every edge is shared by exactly two faces. Entity Info tells you whether it qualifies but not why it fails. Common causes are internal faces, stray edges, tiny holes, and coincident geometry. Check Entity Info for a volume reading, run Fix Problems, then hunt the remaining faults manually or with an inspector extension.
Before you start
The native SketchUp method
Uses only what ships with SketchUp: Entity Info, Fix Problems, Solid Tools, Hidden Geometry. No extension required.
- Test with Entity Info Select the group. If Entity Info shows a volume, it is solid. If not, it is not — regardless of how it looks.
- Run Fix Problems Model Info > Statistics > Fix Problems catches a subset of automatic repairs.
- Show hidden geometry View > Hidden Geometry reveals stray edges and internal faces that were smoothed out of sight.
- Delete internal faces Any face inside the volume breaks the two-faces-per-edge rule. Remove them.
- Close the holes Trace missing faces with the Line tool. A single missing face is enough to disqualify the whole group.
- Retest and export Confirm the volume reading, then export. Solid Tools will also now work on it.
Where this usually goes wrong
- • Assuming a closed-looking shape is solid without checking the volume field.
- • Leaving one internal divider face inside an otherwise clean shell.
- • Scaling a tiny object down before modelling, which produces missing micro-faces from SketchUp’s tolerance.
Native method vs extension
| Native method | Entity Info volume test, Fix Problems, then manual repair with Hidden Geometry visible. |
|---|---|
| What it costs you | Workable but blind — you know it fails, not where. |
| Extension option | Solid Inspector² names each fault, points at it, and auto-repairs what it can. |
| Worth it when | You export for fabrication regularly. This is one of the clearest cases where an extension saves real time. |
Extensions to consider
Options, not requirements. Facts last checked 28 August 2026.
- Solid Inspector² Free · Thomas Thomassen (ThomThom)
Finds the specific reasons a group or component is not a solid — internal faces, holes, stray edges, reversed geometry — and offers to repair the ones it can repair automatically.
Full profile and sources - CleanUp³ Free · Thomas Thomassen (ThomThom)
Housekeeping pass for a model that has grown messy: it merges coplanar faces, erases duplicate and stray edges, and repairs the small geometry faults that accumulate over a long modelling session.
Full profile and sources
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Reviewed 28 August 2026. Spotted something out of date? Let us know and we will recheck the source.
