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 reads text SAT and binary SAB in-house, and accepts IGES; all three can be inspected and exported to STEP. Exact STEP from SAT or SAB needs every face to be reconstructed; otherwise the export is a mesh STEP. Changing an 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, also read by CADProps | .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. For the neutral-exchange side of the decision, STEP vs IGES explains why STEP is often the handoff when the recipient is unknown. SAT vs STEP 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. 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. 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.
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 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 is the diagnostic when the model looks finished and the volume is missing.
Checks that apply to both
- Do not rename the file to change its format.
- Confirm whether you received SAT, SAB or IGES, so the right reader and checks apply.
- Verify units with one known dimension. Screen fit is not a unit check.
- Record body or face scope, especially if some geometry failed to load.
- Convert to STEP only when the next system needs it, then repeat the dimension check on the STEP.
- 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.
A diagnostic matrix for a received pair
| SAT outcome | IGES outcome | Useful question |
|---|---|---|
| Cannot be read | Geometry visible | Was text SAT or binary SAB supplied, and which ACIS version? |
| Solid volume available | Surface area only | Did the IGES export intentionally contain surfaces? |
| Both render | Different extents | Were the source revision, selection and units the same? |
| Both show the expected shape | Downstream operation fails | What geometry/topology does the receiving process require? |
Keep a failed route in the record and avoid healing both inputs before comparing them. Otherwise the repair itself may hide where the disagreement began.
For a useful supplier response, name the missing face, unreadable encoding or known-size mismatch, together with the source application release when available. Ask for a corrected export from the same controlled model. Once the geometry passes, verify any required color, assembly or manufacturing information separately; a successful area or volume calculation does not validate those data categories.
For a comparison with the format most suppliers prefer, open a STEP copy in the online STEP viewer.
Original article: CADProps · https://www.cadprops.com/guides/sat-vs-iges/