How to Export SolidWorks Files for CNC Machining: STEP, DXF, and Parasolid

Getting the File to the Machine Shop

You have finished the 3D model. The design is approved. Now you need to send files to the machine shop. What format? What version? What other information do they need?

Getting this right saves a cycle of back-and-forth emails and prevents parts from being machined incorrectly. Getting it wrong means the machinist misinterprets your geometry, the wrong version gets cut, or the shop’s CAM software cannot open the file at all.

This guide covers the common formats, when to use each, and what supporting documentation a machinist actually needs beyond the CAD file.

STEP: The Standard for 3D Solid Geometry

STEP (Standard for the Exchange of Product model data, ISO 10303) is the safest choice for exchanging 3D solid geometry between CAD systems. Every professional CAD and CAM system reads and writes STEP. The geometry translates as a solid B-rep (boundary representation) — faces, edges, and vertices are preserved with high fidelity.

AP203 vs AP214

SolidWorks offers two STEP application protocols:

• AP203 (Configuration-controlled 3D designs): pure geometry — faces and edges only. No color, no layer information. The standard choice for machined parts.
• AP214 (Automotive design processes): geometry plus color, layers, and other product data. Better for assemblies where visual distinction between components matters.

For single-part machined components going to a shop running Mastercam, Fusion 360, or similar CAM software: use AP203. It is clean, universally supported, and contains no extraneous data that could confuse the CAM import.

For assemblies where the shop needs to understand how components relate: use AP214. The color information helps distinguish parts.

In SolidWorks: File > Save As > STEP AP203 or STEP AP214. Check “Export as STEP” and verify the unit system matches your document (millimeters or inches).

STEP version compatibility

STEP is a stable format — files written today are readable by software from ten years ago and vice versa. Unlike native CAD formats, STEP does not have versioning issues. A STEP file produced in SolidWorks 2025 will open in a 2015-era Mastercam installation without problems.

IGES: Still Alive, Mostly for Legacy

IGES (Initial Graphics Exchange Specification) is an older standard that predates STEP. It is still encountered in legacy workflows, particularly in aerospace and older manufacturing environments.

IGES can carry solid geometry, but it is less reliable than STEP. Surface patches in IGES files frequently have small gaps or mismatches that require healing in the receiving CAM system. The file sizes are larger than STEP for equivalent geometry. The format has effectively been superseded by STEP.

When to use IGES: when a supplier specifically requests it, or when a legacy CAM system cannot read STEP. Otherwise, use STEP.

IGES pitfall: if your SolidWorks IGES export options include “Surfaces” rather than “Solids,” the receiving system gets an open shell rather than a closed solid. Always verify “Export as solid” in the IGES options.

DXF for Laser Cutting and 2.5D Machining

DXF (Drawing Exchange Format) is a 2D vector format. It is the standard for laser cutting, plasma cutting, waterjet cutting, and any flat-material cutting process. It is also used for 2.5D CNC routing where the Z depth is constant and only the XY path matters.

For laser cutting from SolidWorks:

1. For sheet metal: export from Flat Pattern state (File > Save As > DXF, with Flat Pattern selected in the export options).
2. For prismatic parts: create a face sketch on the relevant face, project the necessary edges, and export that sketch as DXF.
3. For machined profiles: export the relevant drawing view as DXF from a SolidWorks drawing file.

Layer practice: outer cut contour on one layer, internal cuts on another, bend lines on a third (for sheet metal). Your laser cutting supplier will specify their layer naming convention — ask before your first order.

DXF version: most shops use DXF 2000 (R15) or DXF 2004 (R16) for maximum compatibility. Avoid AutoCAD 2013+ formats unless the shop confirms they support them.

Parasolid: When You Need Native Kernel Accuracy

SolidWorks is built on the Parasolid geometric kernel. Exporting a Parasolid (.x_t or .x_b) file transfers the geometry at the kernel level — no translation loss, exact B-rep fidelity.

Use Parasolid when:

• The receiving CAD system is also Parasolid-based (SolidEdge, NX, Solid Edge, many CAM systems)
• The geometry is complex and you suspect STEP translation may lose small features or introduce gaps
• The shop requests Parasolid explicitly

Parasolid is not universally supported. CATIA V5, for example, uses its own CGR/CATPart format natively and can read Parasolid but may require the CGM bridge. Confirm with the recipient before sending Parasolid.

File extensions: .x_t (text format, human-readable, larger file) or .x_b (binary format, smaller file). Binary is the standard choice for file transfer.

Version Compatibility Issues

Native SolidWorks files (SLDPRT, SLDASM) are version-specific. A file saved in SolidWorks 2025 cannot be opened in SolidWorks 2022. This affects situations where:

• A supplier uses an older SolidWorks version
• You need to send native files for parametric modification (e.g., to a PDM supplier partner)

Workaround: always also send a STEP file. STEP has no version dependency. If native files are required, ask the supplier’s SolidWorks version and save-down using File > Save As > select “SolidWorks Part” and choose the target version from the Save As Type drop-down.

What the Machinist Needs Beyond the CAD File

The 3D CAD file alone is insufficient for production machining. Experienced machinists will ask for:

• 2D engineering drawing with tolerances: the 3D model shows nominal geometry. Tolerances, surface finish requirements, and critical dimensions are in the drawing. Without a drawing, the machinist must assume everything is ±0.1 mm (or worse, guess).
• Material specification: write it explicitly — not just “stainless steel” but “SUS 304 (AISI 304), annealed condition, minimum 2B finish.” Material affects tooling selection, speeds and feeds, and surface quality.
• Surface finish requirements: Ra value or N-number (N7 = Ra 1.6 μm). Applies to specific faces, not all faces uniformly.
• Thread specifications: thread standard (ISO, UNC, UNF), pitch, tolerance class, and depth. The CAD model shows the nominal hole — the drawing must specify the thread.
• Quantity and delivery requirements: obvious but often forgotten in the rush to send files.

Common Export Mistakes

Key Takeaways

• STEP AP203 is the standard format for 3D machined parts. Universal compatibility, no version issues, clean geometry.
• DXF is for laser cutting and flat geometry. Export from the Flat Pattern state for sheet metal.
• Parasolid is for Parasolid-based systems (NX, SolidEdge, many CAM packages) when maximum geometric fidelity is needed.
• IGES is a legacy format — use it only when specifically requested.
• Always send a 2D drawing PDF alongside the CAD file. Tolerances, surface finish, materials, and threads are not fully communicated by the 3D model alone.