Convert PAR to STP in your application
3D InterOp is a CAD interoperability SDK that lets your software read PAR files and write STP, with exact B-Rep geometry carried across and nothing tessellated.
Spatial does not offer an online converter or a desktop conversion app. 3D InterOp is a component that software vendors embed in their own products.
- Reads Solid Edge part · Writes STEP
- Exact geometry → exact geometry
- C++ / C# APIs
PAR to STP at a glance
Both formats store exact geometry, so the model stays exact. The differences are in the product data each one can carry.
| Solid Edge part (source) | STEP (target) | |
|---|---|---|
| Full name | Solid Edge Part | Standard for the Exchange of Product model data |
| Standard / owner | Siemens | ISO 10303 — AP203, AP214, AP242 |
| File extensions | .par | .stp, .step |
| Geometry | Exact B-Rep | Exact B-Rep |
| Assemblies / structure | Part file | Yes |
| PMI | Not imported by 3D InterOp | Graphical and semantic (AP242) |
| 3D InterOp support | Read only | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from Solid Edge part to STEP.
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Preserved
Exact geometrySolids and surfaces stay exact B-Rep. The model is never reduced to a triangle mesh.
Why software vendors add PAR to STP conversion
Supplier and OEM exchange
STEP is the ISO standard most supply chains specify for exchanging 3D models. Writing it lets your users send data to partners on any CAD system.
Model-based definition
STEP AP242 can carry semantic PMI next to exact geometry, so your users can share models together with their manufacturing data.
Long-term archiving
As an ISO standard independent of any CAD vendor, STEP is widely used to archive product data.
Things to check before you ship
- Written STP versions: AP203, AP214 or AP242 (.stp, .step or .stpx).
- Supported PAR input: Solid Edge V18 to SE 2026.
- Validate a sample of translated files in the target system your users actually work with.
Working with Spatial was a real milestone for us: Thanks to the powerful 3DInterOp library, we were able to successfully bring our complex CAD-based solutions to the cloud while remaining flexible to meet individual customer requirements. For us, Spatial is not just a technology partner, but a true enabler of our product strategy.
Dr. Arno Michelis, Founder, Simus Systems
Read the Case StudyAbout the formats
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Source format
What is a PAR (.par) file?
A PAR file is a Siemens Solid Edge part. Solid Edge is built on the Parasolid kernel and stores sheet metal parts in PSM files and assemblies in ASM files.
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Target format
What is a STEP (.stp) file?
STEP is the ISO 10303 standard for exchanging 3D product data between CAD systems. Its application protocols range from exact geometry (AP203, AP214) to full model-based definition with PMI (AP242).
Frequently asked questions
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
The STEP writer supports AP203, AP214 and AP242, with AP214 as the default. Your application sets the version at export; semantic PMI is written to AP242 only.
Yes. If your application uses Parasolid, a Parasolid-based Solid Edge reader is available.
3D InterOp reads Solid Edge V18 to SE 2026.
No. 3D InterOp reads PAR but doesn’t write it. To send data back to Solid Edge users, write a neutral format they can import, such as STEP.
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Building software that needs to convert PAR to STP?
3D InterOp is an SDK that lets your application read Solid Edge part and write STEP alongside 30+ CAD and BIM formats.