Where Did This Neutral CAD File Come From?

Article by TriMech Solutions, LLC updated December 8, 2022


We live and work in a multi-CAD world and we must often use neutral CAD files such as IGES and STEP. These files are provided by clients, collaborators, and vendors and maybe commercial-off-the-shelf (COTS) parts that you incorporate into your design or ancillary or complimentary equipment that you interface with. They may be client parts for manufacturing, or maybe the design space your products fit into. In all these cases we want to be sure that the imported geometry matches the native CAD data accurately and precisely.

Obviously, native SOLIDWORKS files are ideal and should be used whenever possible.  When you download COTS from vendor websites or are provided CAD files from clients or partners, that might not be an option and only neutral CAD files like STEP & IGES are available. Most of the time the SOLIDWORKS default Import settings will result in a high-quality high-fidelity imported model.  However, sometimes the imported geometry has obvious or not-so-obvious errors. Import Diagnostics can usually fix the not-so-obvious errors such as “reverse normal” and “general geometry error,” but a poor-quality import can result in non-manifold surface bodies and/or dramatic distortions in the topology. The resulting model can be problematic or largely unusable.

If the initial import is not satisfactory the next step is to modify SOLIDWORKS’ Import Options and try importing it again (and again). If you use imported geometry with any regularity, you probably have noticed trends where certain Import Options settings are ideal for neutral files from specific vendors or sources. Why is that?

One factor that can inform your ideal Import settings is knowing the originating CAD system from which the neutral file was created.  Every CAD system has programmatic nuances and parameters that are used in generating 3D geometry. Although IGES and STEP are agnostic file formats, native CAD tools use different algorithms to generate the information present in these neutral files. For example, I have found that neutral files created from Autodesk Inventor benefit from activating the B-Rep Mapping option in SOLIDWORKS’ Import Options.

The good news is that you can quickly understand where a STEP or IGES file came from by simply interrogating the file with a text editor like Notepad. STEP and IGES files are commonly plain text files, and the name of the originating CAD system is usually displayed in the header of the file. See two examples below, the first is a STEP file and the other is an IGES file. Now that you know the originating system, you can leverage your experience and adjust your Import settings to bring it into SOLIDWORKS with the highest fidelity.

Also, if you discover that the neutral file was generated out of SOLIDWORKS, there may be an opportunity to ask your supplier to provide the best file type…native SOLIDWORKS files!

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TriMech Solutions, LLC

TriMech provides thousands of engineering teams with 3D design and rapid prototyping solutions that work hand-in-hand, from sketch to manufacturing. Javelin became a subsidiary of TriMech Solutions LLC in 2021.