Top 7 Neutral 3D CAD File Formats

11 Nov 2019 by Jimmy Nguyen


CAD (computer-aided design) files are digital files that house 3D & 2D designs as well as information regarding materials, processes, tolerances, and other data.

From design to production, everything begins with the CAD file.

However, many companies, internal departments, suppliers, sub-contractors and customers use different CAD software, making interchange difficult for all stakeholders– especially when geometric information and other crucial data such as 3D annotations and GD&T must maintain integrity.


Native CAD file formats from PTC Creo, Siemens NX, CATIA, SolidWorks, Autodesk Inventor, and others are proprietary and need to be translated & validated for downstream processing.

Neutral CAD file formats, however, are interoperable between different CAD software. Today we look at the best 7 neutral CAD file formats, especially pertaining to mechanical CAD conversion. 

Have Questions About Translating To & From Neutral CAD Files?

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Capvidia is a leader in CAD translation & validation, especially pertaining to digital transformation and the MBD journey. Have questions? Talk to our team today.

Table of Contents:

  1. STEP
  2. QIF
  3. 3D PDF
  4. IGES
  5. STL
  6. ACIS

STEP (File Extension: .STEP, .STP)

  • Year Introduced: 1994, Last Update: Continuously Updated.
  • Standard: ISO 10303
  • Representation: B-rep (precise) & Vis-rep (approximation)
  • Organization: International Organization for Standardization and PDES Inc.

STEP files are the most widely used & accepted neutral CAD format today, therefore, making it a standard across multiple industries.

Most CAD software supports importing & exporting STEP files, allowing it to be interoperable between different systems including CAM (computer-aided manufacturing), CAI (computer-aided inspection), and CAE (computer-aided engineering). 

In regards to mechanical CAD there are three major STEP file formats:

  1. STEP AP203: Defines geometry, topology, and configuration management data of solid models for mechanical parts & assemblies. 
  2. STEP AP214: Includes STEP AP203 features along with colors, layers, GD&T, and design intent.
  3. STEP AP242: Merges both STEP 203 & STEP 214 to introduce model-based definition (MBD) engineering.


  1. Developed by ISO, a reputable organization.
  2. Mature file format.
  3. MBD-ready if using AP242


  1. Big organization means slow to release new updates quickly.

QIF (File Extension: .QIF)


  • Year Introduced: 2013, Last Updated: Continuously Updated.
  • Standard: ANSI, ISO DIS (2020)
  • Representation: B-rep (precise) & Vis-rep (approximation)
  • Organization: DMSC (Digital Metrology Standards Consortium), an ISO A-Liaison

QIF (Quality Information Framework) files are made for digital transformation, optimizing for semantic PMI which allows for human & machine-readable CAD leading to two main things: interoperability & traceability.

Built for 21st smart factory in mind with all data connected to a single source of truth: the 3D CAD model. Slowly getting more attention as more stakeholders need a robust file format to exchange downstream from design to manufacturing to quality.


  1. Most robust neutral MBD CAD file.
  2. XML-based framework: easy integration & interoperability with other systems, web/internet applications, and other formal standards. 
  3. Highly valued in Metrology and Quality departments.


  1. Still early, not widespread adoption, some major metrology vendors coming online in 2020. Learn more about QIF.

3D PDF (File Extension: .PDF) 


  • Year Introduced: 2004, Last Updated: 2017
  • Standard: ISO 32000; ISO 14739
  • Representation: Vis-rep (approximation)
  • Organization: 3D PDF Consortium 

3D PDF files are popular for a reason. It’s a ubiquitous format, easily viewed on computers, smartphones, and tablets. Especially convenient for those who don’t have CAD systems or viewers.


  1. Only requires Adobe Reader to view files.
  2. PDF files can be used as containers for other files like STEP, QIF, or other documentation.


  1. Huge file size and slow performance.
  2. 3D ergonomics in Adobe aren’t great.
  3. What this file type is capable of doing is sharply limited by the Adobe environment.

Stereolithography Files (File Extension: .STL)

  • Year Introduced: 1987, Last Updated: None.
  • Standard: None.
  • Representation: Vis-rep (approximation)
  • Organization: 3D Systems

STL files are universal 3D formats that focuses on surface geometry and shapes but not for colors, textures, or other model attributes, which is good for rapid prototyping, 3D printing, and some CAM software.

However, it uses triangulated mesh surface which is acceptable for visual representation, but not workable in CAD systems since most work in solids.

When complicated CAD is not required, STL files are acceptable in most basic situations.


  1. Widely supported file format.
  2. Popular for 3D printing.


  1. Describes surface geometry only — it is not precise B-rep.
  2. Very simple data model — no support for color, surface grouping, or even user-defined attributes.

IGES (File Extension: .IGS, .IGES)

  • Year Introduced: 1980, Last Updated: 1996
  • Standard: ANSI
  • Representation: B-rep (precise)
  • Organization: American National Standards Institute

IGES files were the first neutral CAD file invented and deployed in the late 1970s/early 1980s. 

Although an older standard technologically superseded by STEP & QIF, it’s still used today since it’s been around for a long time and it is very widely supported.

Mostly used for surface geometry (although it can support solid models) and design work. Can often get translated with gaps between surfaces, missing faces, and even surfaces with wrong orientation. So it’s recommended to go with STEP or QIF or have a tool for repairing bad geometry and stitching surfaces.


  1. It’s your grandfather’s CAD file.
  2. Ubiquitously supported.


  1. IGES doesn’t support solid models, just surface geometry. 

ACIS (File Extension: .SAT)

  • Year Introduced: 1989, Last Updated: 2016
  • Standard: None.
  • Representation: B-rep (precise) & Vis-rep (approximation)
  • Organization: Dassault Systemes

ACIS files are 3D solid and surface CAD files from Spatial, a Dassault Systemes division. It is a geometric modeling kernel compiled in C++ and used in CAD, CAM, CAE, and CMM. 


  1. The internal modeling language used by lots of downstream software.


  1. Not a standard data format.
  2. Usually requires a custom translators to export to ACIS.
  3. Doesn’t support semantic PMI in any standard way.

PARASOLID (File Extension: .X_T)

  • Year Introduced: 1989, Last Updated: 2016
  • Standard: None.
  • Representation:  B-rep (precise)
  • Organization: Siemens 

Parasolid files are used by the geometric modeling kernel currently owned by Siemens and used in CAD, CAD exchange, CAM, CAE, and product visualization.

Licensed and used in products such as NX, SolidWorks, SolidEdge, MasterCAM, Onshape, and others.

Can represent wireframe, surface, solid, and general non-manifold models. Most Parasolid files migrate 3D solids and/or surface data. 


  1. The internal modeling language used by lots of CAD and downstream software.
  2. Great CAD export option if you use NX or SolidWorks.


  1. Not a standard data format.
  2. Uses some proprietary blend recipes, making some data inaccessible to non-Parasolid modelers.

Need to Learn More About Translating To & From Neutral CAD Files?

Contact Us

Capvidia is a leader in CAD translation & validation, especially pertaining to digital transformation and the MBD journey. Have questions? Talk to our team today.

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