TraceHaus/drs-endplate

TraceHaus DRS Endplate

A real, shipped part, published three ways:

1. source/endplate.step: the designer's original SolidWorks solid. This is the master geometry.
2. simready/tracehaus_drs_endplate/: an OpenUSD asset that passes NVIDIA SimReady Robotics-Prop 4.0.0 (validator report in ground_truth/validation/).
3. ground_truth/: what SimReady has no field for: where every number came from, a measured mass, and how an AI rebuild of this part scored against the original.

Designed by TraceHaus LLC (Pasadena, CA). Printed in Polymaker Fiberon PET-CF17 on a Creality K2 Plus, flange down, and shipped.

The part

The endplate of a rear wing with a drag reduction system (DRS). The flange carries the flap pivot (Ø8.2 mm) and an arc slot for the flap pin that sets 11.99° of DRS travel. The endplate curls up roughly 200 mm off the flange and carries a ramp with three submerged ducts.

Numbers and their sources

Quantity	Value	Source
Mass	1.005 kg	MEASURED: the printed part, weighed
Volume	1302.5 cm³	CAD (watertight tessellation; Fusion very-high accuracy agrees within 0.02%)
Material	PET-CF17, FDM	CONFIRMED
Center of mass	not measured	ASSUMED uniform; the real part has infill, so this is wrong in detail
USD mesh	0.2 mm / 2° chordal tessellation, 0.94M triangles	Build setting; use the STEP when you need the exact surface
Origin	DRS pivot axis on the flange mating datum	CAD

Mass is not solid volume × density: an FDM part with infill weighs far less, which is why it's measured.

Known limitations

• Collider. 93 convex hulls (CoACD). The part has 2–4 mm curled walls, and convex hulls thicken them: outward standoff P95 2.9 mm, max 5.2 mm, about 51% extra volume. Good for coarse contact; not for close-tolerance contact. A PhysX SDF collider variant is planned.
• No physics material. Friction and restitution are not authored, because they haven't been measured.
• Not listed in SimReady Central. The asset passes the public validator; catalog listing requires NVIDIA's partner onboarding.

AI rebuild ground truth

The original design was rebuilt by an AI agent (Claude, driving Autodesk Fusion) as a native 105-feature parametric tree, then graded against source/endplate.step, B-rep to B-rep, 30,000 samples each way:

	RMS	P50	P95	P99	Max
Original → rebuild	0.134 mm	0.003 mm	0.114 mm	0.64 mm	2.41 mm
Rebuild → original	0.148 mm	0.003 mm	0.122 mm	0.74 mm	3.08 mm

Most of the surface matches to a few microns. The error sits at feature edges: duct and slot lips, the blade tip (0.34 mm low), and fillets the rebuild didn't model.

One interface is wrong, and the deviation stats hide it. The rebuild's M6 hole is mirrored in X: (+9.6, 134.9) instead of (−9.6, 134.9), 19.2 mm off. A nearest-surface metric can't see that; it reports the hole as a 2–3 mm error because the flange is only 5 mm thick. A feature-level check (hole centres) caught it. Our inference is that the rebuild faithfully copied a Fusion import of the design that carries the hole at +9.6, which is why an earlier grade against that import looked better (P95 0.055 mm). That inference has not been verified against the Fusion file.Verified on the printed part (Nov 5, 2026): pivot-to-M6 centre distance measured at 131 mm, matching the original STEP (131.0 mm) and not the rebuild (119.4 mm).

Lesson for anyone grading AI-CAD: grade against the designer's native export, and check interface features directly, not only surface deviation.

Per-region numbers, the hole check, editability results and both rubric scores are in ground_truth/ai_rebuild_deviation.json; the deviation map and a flange section overlay are beside it. Everything that went wrong while building this package is in ground_truth/failures.md.

Reproduce

ground_truth/build_simready.py builds the SimReady package from the STEP; every driving value is at the top with its source tag. regrade.py and dev_summary.py reproduce the deviation numbers; collider_metric.py reproduces the collider numbers; thumb.py renders the thumbnail.

License

CC BY-NC 4.0. Non-commercial use with attribution to TraceHaus LLC. For commercial use, contact TraceHaus.