SOLIDWORKS File Formats Guide: SLDPRT, SLDASM, SLDDRW & Neutral CAD Exports
Complete reference guide to SOLIDWORKS proprietary file formats (SLDPRT, SLDASM, SLDDRW) and neutral export standards (STEP, IGES, Parasolid, STL, 3MF, DWG) for manufacturing and collaboration.
⚡ Quick Answer / Key Takeaway
SOLIDWORKS uses three core native file types: .SLDPRT (individual 3D parts), .SLDASM (assemblies with mate relationships), and .SLDDRW (2D manufacturing drawings). For vendor collaboration and CNC manufacturing, export to STEP AP214/AP242, Parasolid (.x_t), or STL/3MF for 3D printing.
Step-by-Step Instructions & Commands
1. Native SOLIDWORKS Document Formats
.SLDPRT: Stores 3D solid and surface features, sketch history, material properties, and configurations. .SLDASM: References external part files and contains mate constraints, exploded views, and assembly BOM structures. .SLDDRW: 2D drawing sheets referencing parts/assemblies for shop floor fabrication.
2. High-Fidelity Neutral Formats for CNC & Tooling (STEP & Parasolid)
STEP (.step / .stp): The universal ISO standard. Use AP214 for basic color and layer retention, or AP242 for Model-Based Definition (MBD) including 3D GD&T and PMI. Parasolid (.x_t / .x_b): The native geometric modeling kernel of SOLIDWORKS, NX, and Onshape, delivering 100% loss-free solid geometry transfer without tolerance stitching issues.
3. Additive Manufacturing & 3D Printing Formats (STL vs. 3MF)
STL (.stl): Legacy triangulated surface mesh format. Always adjust Export Options (Set Deviation to <0.02 mm and Angle to <5°) to avoid faceted cylindrical prints. 3MF (.3mf): Modern XML-based standard containing unit data, multi-material assignments, color texture maps, and full assembly structures.
4. Lightweight Collaboration & Viewing Formats (eDrawings & 3D PDF)
eDrawings (.eprt / .easm / .edrw): Compressed lightweight viewer files with built-in measurement, dynamic cross-sectioning, and markup tools. Recipient only needs the free eDrawings Viewer. 3D PDF: Standard PDF containing interactive 3D solid models viewable in Adobe Acrobat Reader.
Common Issues & Troubleshooting Guide
| Common Failure / Problem | Root Cause & Recommended Solution |
|---|---|
| Imported STEP file appears as 'Surface Bodies' with gaps instead of a Solid | The export tolerance in the originating system was too loose. In SOLIDWORKS, run Import Diagnostics (right-click imported body > Import Diagnostics > Heal All), or use 'Knit Surface' with 'Try to form solid' enabled. |
| Cannot open newer SOLIDWORKS files in older software version | SOLIDWORKS files are not backwards compatible across major release years (e.g., SW2024 files cannot be opened in SW2022 directly). To share with older versions, export as Parasolid (.x_t) or STEP (.step). |
| Assembly opens with missing components (Suppressed / Cannot Locate) | SOLIDWORKS .SLDASM files only link to .SLDPRT files by file path; they do not embed them. Always use Pack and Go (File > Pack and Go) to bundle the assembly and all referenced parts into a single folder or zip file. |
Cross-CAD Compatibility & Alternatives
SOLIDWORKS 3D Interconnect allows native opening of Inventor (.ipt), Creo (.prt), CATIA (.CATPart), and Solid Edge files directly without translating to neutral formats, preserving live links to native edits.
Engineering Best Practices Checklist
- Use Pack and Go whenever sharing or archiving multi-part assemblies to avoid broken file references.
- Export to STEP AP242 when sending parts to CNC machine shops to retain exact B-Rep definitions.
- Adopt 3MF format over legacy STL for 3D printing workflows to eliminate unit scaling errors.
- Set Parasolid version export to N-1 or N-2 when transferring to older downstream CAM systems.