Which CAD exports arrive broken, and how often

Roughly one export in three needs sending again, and four failures account for almost all of it: an assembly fused into a single solid (about 25% of first exports), inverted or inconsistent surface normals (around 15%), missing or unresolved sub-assemblies (10%), and wrong unit scale (5%). All four are settings problems, not modelling problems — which means they cost a re-export rather than rework, provided they are caught on day one.

The four failures

1. The assembly arrived as one solid — about 25%

By far the most common and the most damaging. The exporter had a “merge into single body” or “save as part” option checked, so what arrives is geometrically correct and structurally useless: no part boundaries, no hierarchy, nothing that can be moved, opened or exploded.

If you are commissioning a cutaway or a configurator, this failure blocks the entire project. If you only need a static showroom model it is survivable, but it forecloses every future use of the same asset.

The fix: re-export with assembly structure preserved. In SolidWorks that is unchecking “Save all components as a single body”; most systems have an equivalent phrased differently.

2. Inverted or inconsistent normals — about 15%

Every surface has a facing direction. When some are flipped, the real-time renderer sees through parts of the machine — panels vanish from certain angles, interiors show through exteriors. In CAD this is invisible, because a solid modeller does not care which way a face points.

This one is usually repairable at our end rather than needing a re-export, but it costs time proportional to how scattered the problem is.

3. Missing or unresolved sub-assemblies — about 10%

The export references components that were not included — typically purchased parts held in a separate library, or an assembly with unresolved lightweight components. The machine arrives missing its motor, its gearbox, or every fastener.

The fix: resolve all components before exporting, and confirm the export includes referenced libraries. It is worth opening the exported file in a free viewer before sending it; a missing gearbox is obvious in ten seconds.

4. Wrong unit scale — about 5%

The file arrives a thousand times too large or too small, usually a millimetre-versus-metre mismatch. Trivially fixed and worth mentioning only because it is silently dangerous: a machine at 1/1000 scale still looks like a machine, and if nobody notices, the scale reference figure beside it ends up wrong — which undermines the one thing a virtual showroom is uniquely good at.

What good looks like

• STEP AP242 or AP214, or the native assembly file
• Assembly structure preserved, parts still separate
• All components resolved, no lightweight or suppressed parts
• Units stated explicitly, ideally millimetres
• Opened once in a viewer before sending, to confirm nothing is missing
• Named sensibly — part names carry into the model and become the callout labels

That last point is worth more than it sounds. An assembly where parts are named Main casting and Drive housing produces callouts almost for free. One named Part1_v3_FINAL produces a naming exercise for somebody who does not know your machine.

Why this list matters commercially

None of these are difficult problems. All four are settings, and any of them found on day one costs a re-export. Found in week three, the same problem costs a re-export plus whatever was built on the bad geometry.

This is why we triage CAD before quoting rather than after. A file arriving fused changes what is possible, and a manufacturer should know that before signing rather than during.