Which AP should I use?

While many Application Protocols (APs) exist in STEP, three are primarily used in modern manufacturing and design environments.

1. Quick Diagnosis Flow

Do you need to include PMI (dimensions and geometric tolerances) in the data?
- Yes → AP242 is your only choice.
- No → Next
Is this for Aerospace, Defense, or modern MBD (Model Based Definition) processes?
- Yes → AP242 is recommended.
- No → Next
Is this for the automotive industry, or is preserving "Colors and Layers" important?
- Yes → AP214 is the de-facto standard.
- No (simple geometry only) → AP203 (e1/e2) might suffice, but AP214 or later is now more common.

AP	Common Name	Characteristics	Key Data Preserved (beyond geometry)
AP203	Configuration Controlled Design	Legacy standard. Stable but limited in features.	Basic geometry, Management data
AP214	Core Data for Automotive Design	Originating from the automotive industry. Strong support for colors, layers, and assemblies.	Colors, Layers, Styling
AP242	Managed Model-based 3D Engineering	Latest standard. Integrates and evolves AP203 and AP214.	PMI, Tessellated geometry, LOTAR, etc.

If you need “face names” for automation (e.g., mapping boundary conditions via Ansys Named Selections), prioritize a workflow that preserves attributes (layers/colors/user-defined attributes) end-to-end and configure the importer’s mapping accordingly.
- In many practical pipelines, this matters more than the presence of a particular entity name.
AP242 is usually the safest default for modern CAE exchange (PMI + best available semantic structures), but AP214 can still be a pragmatic choice when you mainly need robust geometry + colors/layers and maximum compatibility.
Regardless of AP, always validate: units, healing/stitch tolerances, and that key selections (inlet/outlet/walls) scope correctly after import.