Reverse Engineering

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Overview

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What Nexus can help with

• Feature recognition — Identify planar faces, cylindrical bosses and bores, fillets, and other primitives directly from mesh data.
• Parametric reconstruction — Build a native feature tree (extrudes, revolves, fillets) fitted to the recognised features, editable like any modelled part.
• Alignment and datums — Establish a coordinate system on the scan from reference features, so the reconstructed model lands in a usable orientation.
• Scan-to-model deviation — Compare a scan against an existing CAD model (or the reconstruction itself) and report where they diverge, for inspection or as-built verification.
• Mixed-fidelity modelling — Model functional, mating features (bores, mounting faces, threads) exactly, while approximating organic or cosmetic surfaces where exact reconstruction isn’t the goal.

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Example prompts

Import C:/Scans/housing_scan.stl (structured-light scan, units millimetres). Identify the primary planar and cylindrical features and build a parametric solid matching the scan within 0.1mm. This part has no functional surfaces requiring higher precision — a good general fit is fine.

On the imported mesh, identify the bottom mounting face, the two dowel-pin bores, and use them to establish an aligned coordinate system: bottom face as the XY plane, one bore as the origin, the second bore defining the X axis. Reorient the scan to that coordinate system before reconstruction.

Compare the scan at C:/Scans/pump_housing_asbuilt.stl against the nominal CAD model at C:/Projects/Pump/pump_housing.SLDPRT. Generate a colour deviation map and report the maximum positive and negative deviation, and any region exceeding ±0.5mm.

This bracket has no existing CAD model — it's out-of-production tooling we scanned to replicate. Reconstruct it as a fully parametric part from C:/Scans/bracket_legacy.stl. The two bolt holes and the mating flange face are functional and must match the scan within 0.05mm; the rest of the body can be a clean approximation of the scanned surface.

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Tips for reverse engineering prompts

• Say how the scan was captured — structured-light, laser, CT, or photogrammetry scans differ in noise characteristics and typical accuracy. This helps Nexus judge what’s real geometry versus scan noise.
• State a target tolerance — “within 0.1mm” gives Nexus a concrete fit criterion. Without one, it has to guess how tightly to chase the mesh.
• Separate functional from cosmetic features — call out which features must match exactly (mating faces, bores, thread engagement) versus which can be a clean approximation (organic surfaces, cosmetic curvature). This is the single biggest lever on how usable the result is.
• Give a reference for alignment — if the part needs to sit in a specific orientation or coordinate system (to mate with another part, or match a drawing), name the reference features to align to.
• Ask for a deviation report when accuracy matters — for inspection or as-built verification, always request the scan-to-model comparison rather than assuming the fit is good.