The 8 Most Commonly Used 3D CAD Neutral Formats

CAD (Computer Aided Design) files are digital files that contain 3D and 2D models of physical objects.

CAD files can contain information such as geometric data, manufacturing data, material properties, and other product/process data.

From design to production, everything starts with a CAD file.

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0. Overview of CAD file format

CAD files can be classified as native CAD or neutral CAD formats (also known as interoperable CAD data).

0.1 Native CAD file format

Native CAD file formats are designed to be used only with certain proprietary CAD software.

For example, .CATPart (a CATIA format) is only available for CATIA-approved software. It is not easy to read or edit on other CAD software like AutoDesk, Creo, NX, etc.

native format	expand
AutoCAD	.dwg
CATIA	.CATPart, .CATProduct or 3DExperience cloud data
Believe	.prt、.asm
Inventor	.ipt，.aim
NX	.prt
SolidWorks	.sldprt、.sldasm

0.2 Neutral CAD file format

The neutral CAD file format is interoperable between different CAD software, allowing different applications to import and export data.

For example, .STP (STEP format) is a popular neutral format that can be exchanged between different software systems.

neutral format	expand
IGES	.igs、.iges
STEP	.stp、.step
STL	.stl
QIF	.qif
3D	PDF .pdf

0.3 Which is better: native or neutral?

If the only software you use is native CAT, a native CAD file is the preferred format because it retains all the data and functionality of the original design. But a modern manufacturing software stack is much more complex than a single software tool.

With over 100 types of CAD software on the market and hundreds of others that require CAD data to test and manufacture products, it's nearly impossible for everyone to use the same native CAD system.

Different stakeholders need to work on this file:

• different company
• Different businesses within the same company
• internal department
• employee
• supplier
• Subcontractor
• customer

All of these use different CAD-based software, making interoperability difficult, especially when geometric information and 3D annotations such as PMI (Product Manufacturing Information) must remain intact.

In many cases, native CAD file formats from PTC Creo, Siemens NX, CATIA, SolidWorks, Autodesk Inventor, etc. are often translated and validated for downstream processing.

However, the neutral CAD file format is interoperable between different CAD software and is useful in collaboration.

0.4 How do neutral CAD file formats rank?

Today we take a look at eight of the best neutral CAD file formats.

Our standards:

• This list is for mechanical engineering and manufacturing.
• CAD formats must comply with standards (such as ISO, ANSI, CEN, etc.) to ensure quality and consistency.
• CAD files are preferably Model Based Definition (MBD), Capvidia defined by human and machine readable PMI.
• MBD-ready CAD files include geometry, product manufacturing and quality requirements - usually done on 2D drawings.

Combining 2D drawing information into 3D CAD models becomes the authoritative source for the product lifecycle. This enables design-to-manufacturing automation, data insights, and connectivity from a single human- and machine-readable source of truth.

1、STEP

• File extension: .STEP, .STP
• Year launched: 1994, last updated: 2022.
• Standard: ISO 10303-242:2022
• Representation: B-rep (exact) and Vis-rep (approximate)
• Organizations: ISO and PDES Inc.

STEP files are the most widely used and accepted neutral CAD format today, making them the standard across several industries.

Most CAD software supports the import and export of STEP files, making them interoperable between different systems, including CAM (Computer Aided Manufacturing), CAI (Computer Aided Inspection), and CAE (Computer Aided Engineering).

As far as mechanical CAD is concerned, there are three main STEP file formats:

• STEP AP203: Define geometry, topology, and configuration management data for solid models of mechanical parts and assemblies. AP203 is not an MBD ready format.
• STEP AP214: Includes STEP AP203 functionality plus Color, Layers, GD&T, and Design Intent. AP214 is not an MBD ready format.
• STEP AP242: Merges STEP 203 and STEP 214 to introduce the Model Based Definition (MBD) workflow and is in MBD ready format.
• STEP AP203 and STEP AP214 have been deprecated in favor of STEP AP242, but they are still the most commonly used STEP file types.

Advantages of the STEP format:

• Mature and ubiquitous file format.
• MBD ready if using AP242.

Disadvantages of the STEP format:

• There is some confusion between AP203/214 and AP242.
• Downstream CAD-based tools for AP242 Semantic PMI are not widely supported.

Related tools: STEP to STL | STEP to GLB | STEP to OBJ | STEP to PLY

2、QIF

• File extension: .QIF
• Year launched: 2013 Last updated: 2020
• Standard: ISO 23952:2020
• Representation: B-rep (exact) and Vis-rep (approximate)
• Organization: DMSC (Digital Metrology Standards Consortium)

QIF (Quality Information Framework) files are designed for 21st century digital manufacturing. It is optimized for Semantic PMI, allowing human- and machine-readable CAD to achieve two main goals: downstream interoperability and traceability.

Although the newest format on this list, it's gaining more traction as more and more OEMs require a robust file format to exchange downstream data from design to manufacturing to quality.

Advantages of the QIF format:

• The most powerful neutral MBD CAD file.
• XML-based framework: Easily integrate and interoperate with other systems, Web/Internet applications, and other formal standards.
• Highly valued by metrology and quality departments.

Disadvantages of QIF format:

• Despite the credibility MBD has gained, it is still in the early stages of adoption. Learn more about QIFs.

3、JT

• File extension: .JT
• Year launched: 2007 Last updated: 2017
• Standard: ISO 14306:2017
• Representation: B-rep (exact) and Vis-rep (approximate)
• Organization: Siemens PLM Software

JT (Jupiter Tessellation) files are the most confusing of the neutral group of CAD formats. Although known as a vis-rep, it can also have a full B-rep and PMI, thus making it suitable for MBD.

Its internal B-rep representation is very flexible and includes support for ISO 10303 (STEP) and Parasolid. If the JT exported from NX contains B-rep data, it will be in Parasolid format.

Although JT is technically an open format, many vendors use Siemens' JT Open Toolkit. This toolkit is especially important when working with Parasolid data mixed using proprietary recipes. Therefore, it is not widely accepted as STEP or QIF.

Advantages of JT format:

• A common interoperable format for Siemens users.
• JT is mainly used in the automotive industry.
• Lightweight format.

Disadvantages of JT format:

• Less common outside of the Siemens software environment.

4、3D PDF

• File extension: .PDF
• Year Introduced: 2004 Last Updated: 2014 (for CAD)
• Standard: ISO 14739-1:2014
• Representation: Vis-rep (approx.)
• Organization: 3D PDF Alliance

3D PDF files are popular for a reason. It is a ubiquitous format that can be easily viewed on computers, smartphones and tablets. Especially handy for those without a CAD system or viewer.

Advantages of 3D PDF:

• All you need is Adobe Reader to view the file.
• PDF files can be used as containers for other files such as STEP, QIF or other documents.

Disadvantages of 3D PDF:

• Files are huge and performance is slow.
• 3D ergonomics in Adobe are not great.
• The functionality of this file type is severely limited by the Adobe environment.

5、IGES

File Extensions: .IGS, .IGES
Year Introduced: 1980, Last Updated: 1996
Standards: ANSI
Representation: B-rep (exact)
Organization: American National Standards Institute
IGES files are late 1970s/early 1980s The first neutral CAD file invented and deployed.

Although the older standard has been technically superseded by STEP and QIF, it is still used today because it has been around for a long time and has wide support.

Mainly used for surface geometry (although it can support solid models) and design work. It often translates due to gaps between surfaces, missing faces, or even misoriented surfaces. Therefore, it is recommended to use STEP or QIF, or a tool that repairs bad geometry and stitches surfaces.

Advantages of the IGES format:

• This is your grandfather's CAD file.
• General support.

Disadvantages of IGES format:

• IGES can support solids, but it is mainly used for surface geometry.
• Superseded by STEP and QIF.

6、STL

• File extension: .STL
• Year launched: 1987, Last update: None.
• Standard: None.
• Representation: Vis-rep (approx.)
• Organization: 3D Systems

STL files are a general-purpose 3D format that focuses on surface geometry but not color, texture, or other model properties, which is beneficial for rapid prototyping, 3D printing, and some CAM software.

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

STL files can usually only be used with specific software tools that only support STL and use CAD in a more limited way. It's worth noting that even in these cases there can be good STL files and bad STL files, depending on the quality of the mesh.

Advantages of the STL format:

• Widely supported file formats.
• Popular in 3D printing.

Disadvantages of STL format:

• Only describes surface geometry - it's not an exact B-rep.
• Very simple data model - no support for colors, surface grouping, or even user-defined attributes. Its successor format, AMF, supports colors, materials, and constellations.

Related tools: GLB to STL | FBX to STL | OBJ to STL

7、EYES

• File extension: .SAT
• Year launched: 1989 Last updated: 2020
• Standard: None.
• Representation: B-rep (exact) and Vis-rep (approximate)
• Organization: Dassault Systèmes

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

Advantages of ACIS format:

• The internal modeling language used by many modeling software such as AutoCAD, BrisCAD, and Cimatron.

Disadvantages of ACIS format:

• Not a standard data format.
• Usually a custom converter is required to export to ACIS.
• Semantic PMI is not supported in any standard way.

8、PARASOLID

• File extension: *.X_T
• Year launched: 1989 Last updated: 2022
• Standard: None.
• Means: B-rep (exact)
• Organization: Siemens

Parasolid files are used by Siemens' current owned geometric modeling kernels and are used for CAD, CAD exchange, CAM, CAE and product visualization.

Licensed and used in over 350 applications such as NX, SolidWorks, SolidEdge, MasterCAM, Onshape and more.

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

Advantages of the Parasolid format:

• The internal modeling language uses many CAD and downstream software.
• This is a great CAD export option if you use NX or SolidWorks.

Disadvantages of the Parasolid format:

• Not a standard data format.
• Some proprietary mix recipes are used, making some data inaccessible to non-Parasolid modelers.

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Original Link: Top 8 Neutral 3D CAD Formats—BimAnt