Key Takeaways
- Prefer STEP for exact geometry; use STL at high resolution.
- Always export in millimetres — STL stores no units.
- Ensure the mesh is manifold (watertight, normals outward).
- Boolean-union all overlapping bodies into one solid.
- A clean file means a faster, more accurate quote.
Forty percent of the files we receive at Layer X need at least one repair before printing. Inverted normals, non-manifold edges, gaps between shells, incorrect units — these are all fixable, but each one adds time to your quote and sometimes delays delivery. This checklist takes ten minutes and prevents all of them.
STEP vs STL: Which Format to Use
Send STEP (.stp, .step) whenever possible. STEP preserves the parametric geometry as a continuous mathematical surface — our slicers import it with perfect fidelity regardless of resolution settings. STL tessellates the surface into triangles, and a low-resolution export permanently destroys curved surface quality.
If you must send STL (some older CAD packages export only to STL), export at the highest resolution setting. In SolidWorks: custom deviation 0.001 mm, angle 0.5°. In Fusion 360: high refinement. In Rhino: absolute tolerance 0.001 mm.
Units
Set the export unit to millimetres. STL files do not embed units — our system assumes millimetres. A file designed in inches and exported without conversion arrives at 25.4× the correct size. When in doubt, add a note in the quote description: "Designed in mm."
The Manifold Check
A manifold (watertight) mesh has every edge shared by exactly two faces — no holes, no doubled faces, no faces connected at only a vertex. Slicers model the solid interior from the closed surface; gaps produce phantom voids or incorrect wall thickness. Check in:
- Meshmixer: Analysis → Inspector. Red pins mark non-manifold edges. Auto-repair fixes most cases.
- Netfabb (free tier): Upload STL, run automatic repair, download clean file.
- PrusaSlicer / Cura: Visual check during import — holes appear as obvious discontinuities in the preview.
Inverted Normals
Face normals determine inside vs outside. An inverted face tells the slicer the solid is on the wrong side of the surface, producing hollow interiors or phantom material. In Meshmixer, use Analysis → Inspector → "All". In Blender, toggle Face Orientation overlay (blue = correct outward normals; red = inverted).
Intersecting Geometries
Boolean-union all bodies before exporting. Two overlapping solids that were not unioned remain as separate shells. Some slicers handle this gracefully; others produce random infill inside the intersection. Always export a single unified body.
Minimum Feature Sizes
Verify thin walls against the minimum for your chosen process: 1.2 mm for FDM, 0.5 mm for SLA, 0.7 mm for SLS, 0.4 mm for DMLS. Features below minimums will not print or will print poorly. Use your CAD thickness analysis tool (SolidWorks Draft Analysis or Fusion 360 Draft/Thickness) to identify them before upload.
Oversized Files
STL files above 50 MB slow quote generation. This usually means export resolution is unnecessarily high for the print process. FDM layers are 0.2 mm — triangle edge lengths below 0.1 mm are invisible in the output. Re-export with chord height 0.01 mm for FDM; you will rarely exceed 10 MB.
The Upload Checklist
- ☐ Format: STEP preferred; STL at maximum resolution
- ☐ Units: millimetres
- ☐ Watertight (manifold) mesh — no holes or open edges
- ☐ All normals pointing outward
- ☐ All bodies Boolean-unioned into one shell
- ☐ No features below process minimum wall thickness
- ☐ File size under 50 MB
- ☐ Critical dimensions noted in the quote description
Upload at layerx3d.in/shop or email to team@layerx3d.in. Quotes return within 24 hours.