Five classic causes. Not water-tight (open surfaces). Walls below 0.8 mm. Closed cavities without outflow. Wrong units (mm vs inch). Internal overlaps in assemblies. Also: low-resolution STL files give facet artefacts. Our DfAM check flags these on upload; usually we solve them together in one iteration.
Five causes explained
Not water-tight. Your geometry has open surfaces or holes. Usually from mesh tools or incomplete boolean operations. Fix: close surfaces in CAD, or let us close small gaps.
Walls below 0.8 mm. SLS can print it, but the part is not reliable. Fix: thicken to 1 mm+ (1.5-2 mm loaded).
Closed cavities without outflow. Powder stays inside. Fix: add at least one opening of 5 mm.
Wrong units. STEP import sometimes reads mm as inch. Always check dimensions after upload.
Internal overlaps. Assemblies where parts overlap. Fix in CAD before export.
When STL causes trouble
STL is a triangle mesh approximation. At too low resolution you see facets on curved surfaces, the file looks angular. In production: a print that shows facets too.
Fix: export at high tolerance (chord deviation 0.01 mm or lower). In SolidWorks/Fusion: choose “High” resolution on STL export, or set deviation manually.
For critical curved surfaces: STEP is always better. STL cannot carry colour, multiple materials or textures; use 3MF for those.
What we do automatically on upload
Our quote tool checks file integrity, water-tightness (basic check), volume calculation and global wall thickness analysis.
Your quote is rejected if the file is corrupt. We flag warnings on thin walls or closed cavities. For large or complex orders an engineer runs a manual DfAM check. We email concrete pointers before you place the order.
For files that just do not work: mail us the original CAD (native format is fine). We help with the export to production-ready format.