Working with Non-Native CAD Files: Best Practices for Cross-Platform Collaboration 

The fields of design, engineering, construction, and manufacturing often bring together multiple players, including designers, engineers, contractors and subcontractors, suppliers, and clients. Each individual plays a crucial role in achieving project goals and must stay aligned with the team. To be attuned to one another, they must be in constant communication, a key component in their partnership. 

However, they may not always use the same tools and software, owing perhaps to traditional workflows, organizational preferences, lack of knowledge and expertise in some software, or unwillingness to adopt a particular application due to factors like cost. This can lead to communication breakdowns if not addressed. Fortunately, when it comes to the transfer of design data, non-native CAD files are often preferred as a tool for cross-platform collaboration. (In practice, and depending on the industry, these files are often supplemented by other technologies, including product lifecycle management (PLM), the digital thread, and building information modeling (BIM), just to mention a few.)

Non-neutral file formats enable designers and engineers to export design data using software A, say Solid Edge, with other team members importing and opening the files using Solid Edge alternatives like SolidWorks, Rhino, Autodesk Fusion, Onshape, or Inventor. Indeed, the resultant convenience is unmatched, but it is not without its challenges. This article discusses non-native CAD files, including the common types of non-native file formats, their advantages and disadvantages, and how to create them using built-in conversion tools in CAD software or dedicated conversion software. We also delve into the best practices that allow you to maintain data integrity and file compatibility.  

Understanding Non-Native CAD Files

Software corporations, like Autodesk, Dassault Systèmes, PTC Inc., Siemens Digital Industries Software, and more, design their native CAD file formats to efficiently store any and all information (including design data and metadata) their application creates. These proprietary formats – like .dwg, .sldprt, .sldasm, .prt, and .asm (summarized in the table below) – are created to work with the corporations’ own software. 

Most proprietary formats do not publicly share their specifications. These specifications detail how the format stores data, enabling developers to create software that reads or writes these files. 

Besides the design data, the native file formats store certain lines of code associated with the software. This means that the files must be opened by software capable of reading and/or interpreting these lines of code. If you try opening such a file in a different application, you will see an error message or a distorted image on your screen. Such visual elements result from the application’s inability to interpret what is in the native CAD file. With this as the background, non-native CAD files are everything native CAD files aren’t – they are the exact opposite.

What are Non-Native CAD Files?

Non-native file formats are also known as neutral or non-proprietary file formats. Non-native CAD files are standardized file formats that can be read by many software applications, including those associated with their own native CAD file formats. For instance, you can export a drawing to a non-native CAD file format using SolidWorks and open that same file using AutoCAD, provided the latter supports that particular file format.

Common Non-Native CAD Files

There are several common neutral 3D CAD file formats:

1. IGES (Initial Graphics Exchange Specification)
2. Parasolid
3. STEP (Standard for the Exchange of Product model data)
4. STL (StereoLithography)
5. DXF (Drawing Exchange Format)
6. ACIS

1. IGES

IGES (Initial Graphics Exchange Specification) is a non-native CAD format for storing 3D data, including solids, surfaces, and wireframes. It can also store 2D information, text, and dimension data. IGES non-native CAD files are primarily used to export data from one CAD software to another or import CAD data into CAM software. These files feature the .igs or .iges file extension.

According to the technical specifications, this non-native CAD file format represents this data using either of two different forms: the ASCII and Binary form. The Binary form is suited for transferring large files, while the ASCII format is ideal for smaller files. (However, the binary format is not used to create new files.) 

The IGES file format is the result of a project that began in 1979 to create the first national standard for the exchange of CAD data. At this time, CAD was still relatively nascent, with only a few major developments having taken place between the 1950s and late 1970s as detailed in our elaborate article on how CAD has evolved. 

Despite this, players in the industry were increasingly frustrated by the inability to share CAD data between and among available CAD tools. Thus, General Electric (GE) and Boeing, alongside a group of CAD vendors, came together to develop the format: GE and Boeing contributed the CAD translators they had developed, with the CAD vendors providing their database structures.

IGES was officially born in October 1979, while the first draft of the format was released in January 1980. The first version of IGES was later standardized by ANSI and published as Y14.26M-1981. Since then, multiple versions have been published, with version 6.0 the latest.

2. Parasolid

Parasolid is a 3D modeling kernel that is integrated into third-party software – like Shapr3D, SolidWorks, Solid Edge, and NX, just to mention a few – adding powerful product design, simulation, and manufacturing capabilities. To enable compatibility with the hundreds of applications (over 350) that use the kernel, Parasolid has two non-native file formats: .x_t (also known as XT or Parasolid Text) and .x_b (Parasolid Binary). 

The Parasolid file formats enable customers to use any of the over 350 Parasolid-based applications to open .x_t and .x_b non-native CAD files without translation. In fact, software vendors who use different 3D modelers but license Parasolid prefer these file formats. This is because the Parasolid file formats ensure their users enjoy the resulting interoperability. In addition, vendors also develop conversion kits that facilitate data exchange between Parasolid-based software and native file formats.

3. STEP

STEP, which stands for STandard for the Exchange of Product data, is a neutral file format that stores 3D modeling data, part and assembly data, and their associated metadata in plain-text ASCII format. These files use the .stp or .step file extension. 

The STEP format is a file exchange format for 2D design and 3D part and modeling data. For this reason, many popular CAD and CAM software applications support it. From Autodesk Fusion, CATIA, and SolidWorks to Solid Edge, FreeCAD, NX, and more. This way, STEP enhances interoperability. It also eases design workflow within internal and external teams that may not be using the same software application. However, this file format is somewhat constrained because it only stores geometry data. It does not store both geometric and feature or parametric data.

Like IGES, STEP is a standardized non-native CAD file format. It is crystallized in Part 21 of the ISO 10303 standard (ISO 10303-21). Part 21 of the standard specifies a data exchange format that facilitates the transfer of data that conforms to the framework and structure of the EXPRESS data modeling language, defined in Part 11 of the standard. (It is worth pointing out that EXPRESS is not a programming language.)

According to a National Institute of Standards and Technology (NIST) report, STEP was the culmination of concerted national and international efforts to create a common output format for CAD tools. As part of these efforts, two Product Data Exchange Specification (PDES) reports were issued in 1984. They laid the groundwork for an exercise to build a data exchange standard. Thus, the development of STEP began in 1984, with the initial release of STEP becoming an international standard in 1994.

4. STL

Stereolithography, or STL for short, is a non-native file format primarily used in 3D printing – a form of additive manufacturing – and rapid prototyping. The STL format has both binary and ASCII representations, with binary files being more common because of their smaller file sizes. Both representations describe the surfaces of objects as triangular meshes – a series of interconnected triangles. Complex models feature more triangles, while simple models have relatively fewer triangles. And with the number of triangles determining the resolution of the model, complex models generally have a comparatively higher resolution as a result.

STL was first created in 1987 by 3D Systems, Inc. The first specification of this non-native CAD file format was subsequently released in October 1989, according to the Library of Congress.

5. DXF

DXF is an acronym that stands for Drawing eXchange Format. The DXF file format was created in 1982 by Autodesk to store, in a non-proprietary way, the same data stored by AutoCAD’s native file format .dwg. The aim was to enable non-Autodesk software applications to open these designs, enabling the exchange of design data from one application to another. Decades later, the CAD industry uses DXF non-native CAD files to store 2D and 3D data.

The technical dissection of the DXF file format shows that these non-native CAD files represent AutoCAD drawings in two main forms: the ASCII text form and the Binary form. ASCII DXF files used plain text, making them easy to read and write using other programs. Binary DXF files, on the other hand, store drawings using a non-textual binary encoding schema comprising a series of 0s and 1s. Binary DXF files take up 25% less space than ASCII DXF files and can be read and written 5x faster by AutoCAD. Additionally, Binary DXF files are more accurate than ASCII files. 

6. ACIS

ACIS is a 3D geometric modeling kernel developed by Spatial Technology, a subsidiary of Dassault Systèmes. It functions similarly to Parasolid in that it is integrated into third-party software to add powerful modeling capabilities. Software vendors that add the ACIS kernel can develop native file formats or use ACIS’s non-native file format. The latter category nonetheless offers numerous advantages because its close relationship with the kernel eliminates the need for translators, which can be a source of inaccuracies.

There are two types of ACIS file formats: binary (.sab) and text-based (.sat). These files represent/store solid geometries, wireframes, sheet bodies, curves, and surfaces. They also store data like colors, names, dimensions, and annotations. Additionally, the ACIS files store information required to calculate these geometries to enable exact definitions, but they can sometimes represent approximate NURBS geometry.

Nonetheless, the ACIS file formats suffer from the common challenge affecting other non-native CAD files: they do not store certain information. For its part, .sat does not store the hierarchical structures of parts and assemblies.

Benefits of Non-Native CAD Files

Non-native CAD files offer a few benefits, including:

1. Multiple CAD systems can read neutral or non-native CAD files, making them highly interoperable
2. These files are typically smaller in size than native CAD files since they are either highly compressed or do not store as much information as native files
3. They allow team members and clients to view, review, print, or modify CAD designs and models without needing a subscription for certain expensive software applications or knowing how they work.

Challenges with Non-Native CAD Files

You are likely to face the following challenges when working with neutral file formats:

1. Non-native CAD files do not store all the information generated by the software used to export them. For instance, given that STEP and IGES files only store geometry data, information related to features is lost when you export CAD designs to these formats. Similarly, STL does not store metadata such as the creator’s name, location, and copyright.
2. Incompatibility: some software applications may not open older versions of non-native CAD file formats (more on this below)

Converting Non-Native CAD Files

There are two ways to create non-native CAD files:

1. Exporting drawings to non-native CAD formats using software’s built-in conversion tools or translators
2. Using dedicated conversion software

1. Built-in Conversion Tools

Multiple CAD software applications let you export or save non-native CAD files. They do this through built-in conversion tools or translators that convert or translate the design data and package or encode it according to the structure of the non-native file format. For the best results, it is advisable to use the recent releases of these applications, as their recency increases the likelihood of supporting the latest versions of the file formats. This, as we detail later, helps enhance compatibility.

The table below summarizes various CAD systems and their supported neutral file formats.  

2. Third-Party Conversion Software

Alternatively, you can use third-party conversion software to convert native file formats to non-native file formats. These tools are handy in cases where you have proprietary files and do not have access to the aforementioned software or do not know how to use them yet still need to use the neutral file formats. In such instances, software like Scan2CAD can be – and often are – a lifesaver. Scan2CAD lets you convert DWG files to DXF. The software also converts raster images and PDFs to DXF and images to DWG. 

A Floor Plan Drawing Converted to Non-Native DXF CAD Format in Scan2CAD

Maintaining Data Integrity and Compatibility

Data integrity issues and incompatibility are not uncommon when using non-native file formats. Fortunately, there are workarounds that enable you to maintain data integrity and compatibility.

1. Use Tools to Repair Data Loss or Retrieve Data

Non-native file formats trail their native counterparts when it comes to the amount of data they can store. By their very nature, they do not store certain information about the drawings and 3D models. For instance, IGES, STL, and STEP do not store the parametric design history of 3D models. This happens even when non-native CAD files are created using software that ordinarily captures the design history. Thus, new software does not automatically recognize this missing information when you import the file. 

At the same time, the data export and exchange processes are not always flawless. Crucial geometric data can get lost, creating non-native CAD files with missing information or degraded quality. 

Fortunately, some software applications provide solutions to some of these problems. Fusion lets you partially retrieve parametric design features using the ‘Find Features’ tool. However, you can only use this function in direct modeling mode. On the other hand, Inventor allows you to repair the translated data using the Quality Check and Refit Facecommands. These commands specifically address IGES or STEP data. SolidWorks also offers an option to repair corrupted files and imported geometry. 

2. Use Latest Software Versions to Solve File Incompatibility

Another issue is incompatibility: some releases of software may only export and import a specific version of the non-native file format. What ends up happening is that these applications will fail to open older versions of these file formats, creating a compatibility issue.

SolidWorks 2024, for instance, can import or export IGES version 5.3, Parasolid files between 9.0 and 35.0.x, the STEP files created using the AP203, AP214, and AP242 Application Protocols, and STL version 1. It also supports all versions of the DXF file format. Against this backdrop, SolidWorks cannot open unsupported versions of the aforementioned non-native CAD files, which can rightly be described as incompatible.

Unlike data loss, file incompatibility is often impossible to resolve with software that didn’t create the file. Thus, to deal with the incompatibility issue, you must first re-export the non-native file format using a more recent release of the application, which is likely to support the latest version of the file format.

Conclusion

Non-native CAD files like IGES, STEP, STL, ACIS, Parasolid, and DXF help teams to collaborate even when team members use different CAD software applications. The key to this cross-platform collaboration lies in the fact that various software applications can export and import these file formats. For instance, you can create a STEP file using SolidWorks and import it into Solid Edge. While such a file will lack parametric elements, it will still represent all the geometric data contained in the original design on SolidWorks. 

Some applications, like Fusion, can partially retrieve parametric design features, while SolidWorks and Inventor can repair files, enhancing the quality of exported drawings. Nonetheless, it is crucial to use the latest releases of software applications, as they are more likely to support the latest versions of file formats and, ergo, help you deal with any incompatibility issues. Neutral CAD files enable cross-platform collaboration, removing the need for team members to learn multiple software systems. They can use their preferred software applications, provided they can read or write non-native CAD files.