> ## Documentation Index
> Fetch the complete documentation index at: https://support.lumafield.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Nominal CAD Import

> Upload a .STEP file as the nominal CAD reference for Profile evaluation

In [Dimensioning Mode](/voyager/voyager-modes#dimensioning-mode), the [Import Tool](/voyager/voyager-import) loads a `.STEP` file as the **nominal CAD body** for your scanned part. [Profile](/voyager/voyager-profile) and [Position](/voyager/voyager-position) measure the scan against that body. [Datums](/voyager/voyager-datums) and Frames can be built on its faces the same way they are built on the scan. [Alignment](/voyager/voyager-alignment) places the scan on the body so those datums can be copied across.

The CAD picker in Profile, Position, and Alignment lists every STEP file in the Project and only lets you select one that has **finished processing**. A file that is still processing, or that failed, is shown with that status and cannot be chosen.

<Note>
  This page covers the Dimensioning Mode workflow for nominal CAD import. For the broader Import Tool — including `.STL` Mesh import in [Analysis Mode](/voyager/voyager-modes#analysis-mode) — see the main [Import Tool](/voyager/voyager-import) article.
</Note>

![Uploading a CAD file and creating Datums](https://lumafield-support-assets.s3.us-east-1.amazonaws.com/nominal-import.gif)

<h2 id="why-separate">
  Why a separate workflow
</h2>

Nominal CAD import is the only point in [3D Auto-Dimensioning](/voyager/voyager-auto-dimensioning) where data enters Voyager from outside the scanner. The CAD body provides:

* The **exact nominal geometry** that Profile compares against your scan.
* A surface on which you can build a CAD-side **Datum Reference Frame** that mirrors the DRF defined on the scanned part.

Because STEP carries native units and exact geometry, no scale entry is required at import time — Voyager preserves the units defined in the file.

<h2 id="workflow">
  Workflow
</h2>

<Steps>
  <Step title="Switch to Dimensioning Mode">
    Select the **Dimensioning** tab from the Mode tabs on the left-hand side of Voyager.
  </Step>

  <Step title="Open the Import Tool">
    Select the Import Tool from the Toolbar. In Dimensioning Mode the Import Tool accepts `.STEP` files.
  </Step>

  <Step title="Upload your .STEP file">
    Choose the STEP file representing the nominal part. The imported body appears in the Data Panel as a new Data Object.
  </Step>

  <Step title="Wait until processing finishes">
    Profile, Position, and Alignment cannot use the CAD until its status is ready. Leave the Project and come back if the import is still marked processing.
  </Step>

  <Step title="Align, then define datums">
    [Align](/voyager/voyager-alignment) the scan to the CAD. Define [datums](/voyager/voyager-datums) on one side and copy them to the other, or build the CAD datums by picking faces directly.
  </Step>

  <Step title="Run Profile or Position">
    Run [Profile](/voyager/voyager-profile) for a surface, or [Position](/voyager/voyager-position) for a hole, against the imported body.
  </Step>
</Steps>

<Tip>
  Export STEP files from your CAD tool with the part isolated as a single body. Multi-body assemblies should be split before upload so Profile evaluates the intended geometry.
</Tip>

<h2 id="file-guidance">
  File guidance
</h2>

A few practical tips for clean STEP imports:

* **Single body per file.** If your CAD model contains assemblies or fixtures, export only the part to be evaluated.
* **Native units preserved.** STEP files declare their own units; Voyager respects them. There is no scale field to set, unlike the `.STL` flow in Analysis Mode.
* **Geometry, not tessellation.** STEP is exact geometry, so polygon count is not a concern — unlike the `.STL` flow used by the [Compare Tool](/voyager/voyager-cad-comparison), where polygon density affects accuracy.

<h2 id="related-pages">
  Related pages
</h2>

* [Import Tool](/voyager/voyager-import) — main article covering both `.STL` and `.STEP` workflows
* [Voyager Modes](/voyager/voyager-modes)
* [3D Auto-Dimensioning](/voyager/voyager-auto-dimensioning)
* [Datum Definition](/voyager/voyager-datums)
* [Alignment](/voyager/voyager-alignment)
* [Profile](/voyager/voyager-profile)
* [Position](/voyager/voyager-position)
* [Voyager 2.0 Release Notes](/platform/voyager-release-notes) and [Monthly Highlights](/platform/monthly-highlights)


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