# SAT vs IGES: ACIS Solids or Neutral CAD Surfaces

Choose SAT or IGES by the receiving application. Text SAT is ACIS geometry; IGES is a neutral exchange file. Binary SAB is not enabled.

This guide covers general CAD workflows. CADProps supports STEP, IGES, SolidWorks parts and ZIP assemblies, STL, OBJ, 3MF and static GLB/GLTF. Validated conversions are downloadable. Partial assemblies carry warnings; properties cover loaded geometry only.

SAT and IGES can both carry precise geometry, and neither one is automatically the more accurate file. SAT is the text form of ACIS model data. IGES is a neutral exchange format with a long history in curves and surfaces. Pick the one the receiving software has been qualified to import.

CADProps accepts readable **text SAT** for inspection and STEP output, and accepts IGES for inspection and STEP output. Binary **SAB is not enabled**. Changing a SAB or IGES extension to `.sat` does not convert the model.

## SAT and IGES side by side

| Question | SAT | IGES |
|---|---|---|
| What it is | ASCII ACIS model data | Neutral CAD exchange, often curves and surfaces |
| Binary sibling | SAB exists and is not enabled here | `.iges` and `.igs` are the usual exchange names |
| Where it fits | ACIS-capable applications | Legacy and surface workflows that already test IGES |
| Closed-solid volume | Only for readable solids that meet closure rules | Only when imported geometry forms a valid closed solid |
| Open surfaces | A picture of the shape is not a solid volume | Area can be available when volume is not |
| Native feature tree | Not restored | Not restored |

Spatial describes SAT as the ASCII representation of ACIS data and contrasts it with binary SAB. [Spatial's SAT overview](https://www.spatial.com/glossary/sat-file-type). For the neutral-exchange side of the decision, [STEP vs IGES](https://www.cadprops.com/guides/step-vs-iges/index.md) explains why STEP is often the handoff when the recipient is unknown. [SAT vs STEP](https://www.cadprops.com/guides/sat-vs-step/index.md) is the ACIS-to-STEP comparison.

## Accuracy is not the extension

A SAT file can be an exact ACIS solid and still be the wrong delivery if the recipient cannot read that ACIS version. An IGES file can be the right delivery for a surface process and still fail a solid-volume calculation because the faces do not enclose a solid.

Do not heal a model only to obtain a number. Sewing can join edges that were not meant to meet. Keep the original file, record any repair, and recheck holes, mating faces and one known dimension.

Open CASCADE warns that volume routines rely on closure and consistent orientation and do not verify every precondition. [BRepGProp documentation](https://dev.opencascade.org/doc/refman/html/class_b_rep_g_prop.html). Unavailable volume stays unavailable. It is not written as zero.

## Use SAT when the ACIS path is the agreed one

SAT is a reasonable handoff when the recipient's software is known to import that SAT version and the task needs the ACIS solid or surface model. It is a poor guess when you do not know the recipient.

Open the original file in the [ACIS SAT viewer](https://www.cadprops.com/tools/acis-viewer/index.md). Confirm the expected solids, orientation and one known size before using area, volume or a STEP download. The STEP file is a derivative. It does not recreate ACIS history, and it should stay traceable to the SAT revision you started from. Details are in [open a SAT file online](https://www.cadprops.com/guides/open-sat-file-online/index.md).

## Use IGES when that import path is the qualified one

IGES remains appropriate for a legacy translator, a surface-modeling workflow or a shop that asked for IGES. A newer kernel format is not an upgrade if the receiving process was qualified on IGES.

The [IGES viewer](https://www.cadprops.com/tools/iges-viewer/index.md) can report dimensions and face area for readable geometry. Volume and any density-based mass require a valid closed solid. [IGES surfaces that are not solids](https://www.cadprops.com/guides/iges-surfaces-not-solid/index.md) is the diagnostic when the model looks finished and the volume is missing.

## Checks that apply to both

1. Do not rename the file to change its format.
2. Confirm whether you received SAT, SAB or IGES. Only text SAT and IGES are in the current public workflow.
3. Verify units with one known dimension. Screen fit is not a unit check.
4. Record body or face scope, especially if some geometry failed to load.
5. Convert to STEP only when the next system needs it, then repeat the dimension check on the STEP.
6. Keep the native authoring file when later parametric edits matter.

A density you type produces an estimate, not a material certificate stored in the SAT or IGES file.

## Related reading

- [IGES Surfaces Not Solid? Check Volume and Open Shells](https://www.cadprops.com/guides/iges-surfaces-not-solid/index.md)
- [IGES vs Parasolid: Surfaces, Solids and CAD Exchange](https://www.cadprops.com/guides/iges-vs-parasolid/index.md)
- [How to Open SAT Files Online Without an ACIS CAD System](https://www.cadprops.com/guides/open-sat-file-online/index.md)
- [SAT vs STEP: ACIS Geometry or Neutral CAD Exchange?](https://www.cadprops.com/guides/sat-vs-step/index.md)
- [STEP vs IGES: Which CAD Exchange Format Fits the Job?](https://www.cadprops.com/guides/step-vs-iges/index.md)

Original article: https://www.cadprops.com/guides/sat-vs-iges/

HTML page: https://www.cadprops.com/guides/sat-vs-iges/