# CAD Versions vs Revisions: Track Models and Exports

Keep upload history, engineering revision labels and converted files separate so a new export does not masquerade as a design change.

A designer saves a file. A project engineer uploads it. A converter creates STEP and GLB outputs. A reviewer adds a comment. These are four events, but they do not necessarily represent four design revisions.

Lightweight file history works best when it separates the source snapshot, the engineering label and the derived artifacts. You do not need a full product-data-management system to make that distinction.

## Use versions for saved snapshots

A version identifies a specific saved state: the source file, its dependencies, selected configuration and the information needed to reopen that state. Once shared, it should not quietly change underneath the same identifier.

Onshape's version model illustrates the distinction between immutable versions and active workspaces. [Versions and history](https://cad.onshape.com/help/Content/versionmanager.htm). A file-based service can use a simpler model while keeping that same clarity about what a reviewer saw.

If an old version is deleted under an explicit retention policy, its links should report that state. They should not silently redirect to a newer version.

## Use revision labels according to the real process

`Rev.A`, `Rev.B` or a drawing issue number carries meaning within the organization's engineering process. The site should allow an explicit label without pretending it knows when a design has been approved.

An internal counter such as V1, V2 and V3 can track uploads. Keep it distinct from the user-entered revision label. An upload note saying “moved the mounting hole” is an author's description, not proof that an algorithm detected that change.

| Record | Example | What caused it |
|---|---|---|
| Source version | V2 | A new source snapshot was uploaded |
| Engineering label | Rev.B | Assigned by the responsible workflow |
| Export artifact | V2 → STEP | A conversion of that snapshot |
| Calculation record | V2, density input changed | A new analysis with recorded parameters |

This is an example convention. Existing organizational naming and approval rules should take precedence.

## Do not create a new design version for every export

A STEP derivative and a preview image can both belong to V2. Rebuilding a preview after a display-engine update should not turn the part into V3. Store the producing engine, settings and date with the artifact instead.

The same applies to a mass estimate. If the geometry is unchanged but a density assumption changes, record a new calculation. Do not describe the event as a detected geometric modification.

A file hash can identify identical bytes, but different bytes do not prove different geometry. A re-export can alter ordering or other representation details without changing the intended shape.

## Freeze assembly dependencies too

A snapshot of only the top-level file may be insufficient if referenced components are later replaced. Store or identify the component versions needed to reopen the same assembly scope.

Two files with the same basename can still be different component definitions. Preserve paths and identifiers where the reading workflow needs them. Keep unresolved references visible rather than creating a clean-looking but incomplete historical view.

## Review supplier changes as fixed version pairs

When a supplier returns a revised file, keep the earlier accepted file and the new file as a fixed pair. Record the exact revisions, the requested change, whether units and scope stayed the same, and which interfaces are expected to differ.

Use the [CAD comparison workflow](https://www.cadprops.com/guides/compare-cad-revisions/index.md) for geometry review. If a drawing travels with the STEP file, the [CNC RFQ checklist](https://www.cadprops.com/guides/prepare-step-file-for-cnc-quote/index.md) helps keep nominal geometry and controlled manufacturing requirements distinct.

Comments and screenshots should remain bound to the version they describe. The goal is not a generic “same/different” label; it is to confirm that observed changes match the requested change and that unexplained changes remain visible.

## Make history readable, not ceremonial

The useful history view answers: what was uploaded, what changed according to the author, which files were produced and which version was sent to whom. It should not claim audit certification or manufacturing approval merely because it has a timeline.

For a small team or occasional task, that simple separation prevents a great deal of confusion. The [fixed-version sharing guide](https://www.cadprops.com/guides/share-fixed-cad-version/index.md) shows how to carry the same idea into external links.

## Record changes to analysis inputs separately

If the geometry is unchanged but density is changed from 2.70 to 7.85 g/cm³, the mass estimate changes without a design revision. Similarly, another tessellation or neutral export is a derivative of the source state unless the controlled engineering process says otherwise.

Keep source identity, calculation inputs and derivative identity in separate fields. A different byte hash establishes a different file, not necessarily a different shape; matching hashes establish identical bytes, not manufacturing approval. CADProps file storage and fixed shares do not constitute an engineering revision-control system. Use the organization’s released identifiers when a drawing, order or inspection package depends on them.

## Sources

- [Onshape Help — Versions and history](https://cad.onshape.com/help/Content/versionmanager.htm)

## Related reading

- [Compare CAD Revisions: Geometry and Property Checks](https://www.cadprops.com/guides/compare-cad-revisions/index.md)
- [Prepare a STEP File for a CNC Quote: A Shop-Ready RFQ Checklist](https://www.cadprops.com/guides/prepare-step-file-for-cnc-quote/index.md)
- [Share CAD Files with Suppliers: STEP Handoff Checklist](https://www.cadprops.com/guides/share-cad-files-with-suppliers/index.md)
- [Share a Fixed CAD Revision: File and Version Checklist](https://www.cadprops.com/guides/share-fixed-cad-version/index.md)

Original article: https://www.cadprops.com/guides/cad-versions-vs-revisions/

HTML page: https://www.cadprops.com/guides/cad-versions-vs-revisions/