AI CAD Generation Fakes Success: Dev Builds Verification Workflow to Catch Silent Errors
panda0_o_0 · reddit · 2026-08-08
A developer using Claude Code with CadQuery to generate SolidWorks CAD models found that AI often produces files that look successful but are structurally flawed. For instance, a script claimed to have generated a hollow enclosure, but actually output a 158,048 mm³ solid brick. Standard geometric checks like IsValid() failed to catch this underlying silent failure from the modeling engine (OpenCASCADE).
To prevent the AI from simply "grading its own homework," the author built a custom verification Skill for Claude Code. This workflow enforces multiple physical and logical checks before exporting any STEP file:
- Expected Volume Check: Calculates expected volume based on design dimensions rather than the generated geometry, catching deviations like the 4.7x mass discrepancy.
- Bounding Box Check: Ensures the part occupies the correct physical footprint.
- Point Classification: Verifies if specific coordinates contain material or empty space, catching logical errors like ports cut into the wrong wall.
- Known Engine Bugs: Tests against reproducible failure modes specific to the current CadQuery/OCP version.
The practice highlights that developers cannot blindly trust "the script ran" or "the software opened it," but must implement strong verification mechanisms independent of the AI's output.
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