# Use a mesh as a CAD reference

A scan or STL captures a surface approximation. Rebuilding it as CAD requires choices about planes, cylinders, symmetry, dimensions, and which details should be preserved.

Ask Adam to inspect the file and propose a reconstruction path supported by your CAD tools. Mesh inspection and repair do not by themselves produce an editable feature tree.

## Define the result you need

Provide the source mesh, units, known measurements, and intended use. Say whether you need a cleaned mesh, a reference model, fitted solid geometry, or an editable parametric reconstruction. For point clouds or proprietary scan formats, first check whether the task's tools can read them; request a supported export when necessary.

## Inspect before rebuilding

```text
Inspect this STL of a mounting adapter. Its measured overall length is [value] mm. Check scale, orientation, disconnected regions, and missing surface areas. Identify which planes and cylindrical features can reasonably be reconstructed in [CAD application]. Propose a feature plan and list details that need additional measurements before modeling.
```

Separate scan artifacts from intentional features. A notch could be damage, missing scan coverage, or a functional detail; the mesh alone may not resolve it.

## Reconstruct and compare

```text
Reconstruct the agreed base, mounting holes, and cylindrical boss as editable features. Use the supplied measurements for the interfaces. Keep the original mesh as a reference and record any smoothing or omitted detail. Compare the resulting CAD surface with the mesh where the tools support it, reporting the method, units, and regions that remain uncertain.
```

## Review the output

Check dimensions at the mounting interfaces, body validity, surface coverage, and the deviation of fitted features. A global average error can hide a large local mismatch at a critical surface.

Keep the original scan, fitted model, measured references, and comparison together. If the result is an approximation, label it accordingly. For dimensioned drawings, use [Drawing to model](/cad/drawing-to-model); for simulation, review simplifications in [Geometry preparation](/cae/geometry-preparation).