MECH-022 · Parametric Mechanical Parts · difficulty 4/5

Stepped shaft with retaining-ring groove

sha256:84a92efb1c0d4e6f…

§1Prompt verbatim

Stepped shaft: Ø 20 × 30 mm, then Ø 16 × 25 mm, then Ø 12 × 20 mm. On the Ø 16 step, machine an external retaining-ring groove per DIN 471 for a 16 mm shaft (groove Ø 15.2 ± 0.05 mm, width 1.1 +0.14/0 mm, edge 7.0 mm from the Ø20→Ø16 shoulder).

§2Ground-truth spec

shells1

watertighttrue

manifoldtrue

acceptance ε±0.05 mm

featuresgroove_DIN471_16, shoulder_20_16, shoulder_16_12

§3Reference render

canonical reference · drag to orbit, scroll to zoom

Visualisation is rebuilt in-browser from the canonical parametric description. Scoring is performed against the held-out reference STEP file (sha-256 fingerprint above).

§4Per-agent renders

reference + 10 agent outputs · scored against the held-out STEP

vol IoU · BREP · manifold

canonical reference

REFERENCE

canonical · ground truth

1.000100✓

Human Baseline (Mech-E)

OpenAI + CadQuery 2.4

Claude Opus 4.7 → CadQuery

Anthropic + CadQuery 2.4

0.51011✗

Gemini 2.5 Pro → OpenSCAD

Google + OpenSCAD 2024.06

no manifold solid produced

Claude Opus 4.7 → OpenSCAD

Anthropic + OpenSCAD 2024.06

—18✗

no manifold solid produced

DeepCAD

Wu et al. 2021 (research)

—74✗

Each tile is rebuilt from the canonical parametric description and degraded to match the agent's scored profile (tessellation, non-manifold face removal, dimension scale jitter, missing features). Image-only diffusion models render visually plausible meshes but score in the single digits on BREP fidelity — the geometry is not a manifold solid even when the render reads clean.

§5Per-agent metrics

ranked by Vol IoU · same data as the leaderboard, restricted to this task

Agent	Watert.	Manif.	Named-Dimension RMSE	GD&T Compliance	FeatRec	P@1	p50	latency	cost
Human Baseline (Mech-E)	✓	0.973	0.081	0.863	0.902	1.000	—	873.8s	$5.178
Adam (CADcrush)	✓	0.939	0.170	0.624	0.734	0.000	—	7.9s	$0.320
GPT-5 → CadQuery	✓	0.939	0.217	0.604	0.693	0.000	—	36.2s	$0.173
Zoo Text-to-CAD	✓	0.934	0.150	0.659	0.705	0.000	—	5.3s	$0.182
Claude Opus 4.7 → CadQuery	✓	0.931	0.216	0.612	0.748	0.000	—	41.5s	$0.335
Gemini 2.5 Pro → OpenSCAD	×	0.912	0.297	0.435	0.504	0.000	—	24.0s	$0.105
Spline AI	×	0.864	0.518	0.027	0.092	0.000	—	6.1s	$0.039
Trellis 3D	×	0.854	0.541	0.056	0.216	0.000	—	12.5s	$0.052
Claude Opus 4.7 → OpenSCAD kernel error: BRepCheck_NotClosed	×	0.000	—	—	—	0.000	—	29.2s	$0.291
DeepCAD kernel error: BRepCheck_NotClosed	×	0.000	—	—	—	0.000	—	4.0s	$0.019