Best STEP File to Use: AP203 vs AP214 vs AP242

20 Apr 2020 by Jimmy Nguyen

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What is a STEP file?

STEP (Standard for the Exchange of Product Data) is a neutral-format 3D CAD file that is interoperable between different CAD programs such as SolidWorks, Creo PTC, Siemens NX, CATIA, Autodesk, and others.

STEP is an ISO-standard (ISO 10303) written using the EXPRESS modeling language.

It is detailed into numerous Application Protocols (APs). In this article we will be addressing 203, 214, and 242.

Why is STEP important?

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As companies move towards model-based definition and away from traditional paper-based workflows, STEP (specifically AP242) is the most popular file format for CAD interoperability downstream with partners, suppliers, departments, and customers.

A STEP AP242 file will also include PMI (product manufacturing information) such as GD&T, BOM, notes etc. to be the single source of truth–data reuse and retention during the entire product lifecycle–for all applications.

For design, this is interoperability between different design systems (CAD to CAD or CAD to CAE).

For manufacturing, this is the transmission of product definition into manufacturing/measurement software (CAD to CAM or CAD to CMM).

Different Versions of STEP AP Files

STEP AP203 

Application protocol: Configuration controlled 3d design of mechanical parts and assemblies.

AP203 defines geometry, topology, and configuration management data of solid models for mechanical parts and assemblies.

Summary of AP203 features:

  • Products as mechanical parts & assemblies
  • Data for configuration control applied to design phase.
  • Data related to documentation of design change process, approval, security classification.
  • Geometrical data as wireframe, surface models, faceted models, manifold surfaces, and solids (BREP). 
  • [Source]

STEP AP214

Application protocol: Core data for automotive mechanical design processes.

AP214 defines everything in AP203 plus colors, layers, GD&T (geometric dimensioning and tolerance) and design intent.

Summary of AP214 features:

  • All from AP203.
  • Colors and layers.
  • Textual annotations associated to the geometry.
  • GD&T with graphical presentations.
  • Validation properties: Global, as volume area, center and Local as Clouds of Points.
  • Construction history in 3D.
  • References to product data represented in another format than STEP.
  • Kinematic structures.
  • Tolerance data and surface conditions.
  • [Source]

STEP AP242

Application protocol: Managed model-based 3D engineering.

AP242 merges STEP AP203 and AP214 to create a single standard for model-based 3D engineering.

Summary of AP242 features:

  1. All of AP203.
  2. All of AP214.
  3. Completions to PMI including surface conditions, PMI in assembly and machining features.
  4. Tessellation: allowing STEP to support light visualization model. 
  5. Composite structures, electrical harness and piping.
  6. Domain of PDM (Business Object Model)
  7. Product data quality (quality criteria and check results).
  8. Mechatronics.
  9. And other topics involved in systems engineering integration.
  10. [Source]

STEP AP 203 vs 214 vs 242: Which one to go with? 

Technically, STEP AP242 is the better format, because it combines both AP203 and AP214, and ISO/TC 184/SC 4 (the governing committee) has withdrawn from doing future work with AP203 and AP214.

It is the the go-to STEP file moving forward for 3D CAD-based applications.

However, because MBD CAD files are still in the early adoption phase, it depends on your current software & version having support for it.

So the best answer is: if you're working only with geometry and don't need MBD data yet, AP214 is the way to go for now.  If you're working with semantic PMI and need MBD data (or want to future-proof), AP242 is the preferred format.

How to Import, Export, and Convert STEP files

CAD System AP203 / AP214 AP242 Notes:
SolidWorks Y Y Exporting to AP242 is an add-on feature and requires its own license. 
Creo Y Y Learn more.
Siemens NX  Y Y Learn more.
CATIA Y Y
Autodesk Y Y Learn more.

As referenced in the table above, the major CAD software vendors can view, import, and export STEP files. MBDVidia is our leading MBD CAD translation tool that converts native CAD files into MBD-ready files like STEP AP242 and others.

How to View & Analyze Your STEP File for Free

The STEP File Analyzer and Viewer is a FREE tool from NIST (National Institute from Standards and Technology) that allows users to open a STEP file and do the following:

  • Generate a spreadsheet or CSV files of all entity and attribute information.
  • Creates a visualization (view) of part geometry, graphical PMI annotations, supplemental geometry, and datum targets that is displayed in a web browser.
  • Analyze any semantic PMI, graphical PMI, and validation properties for conformance to recommended practices.
  • Checks for basic syntax errors.

STEP Alternatives

There are other CAD-neutral file formats to consider. We’ll highlight some popular ones:

QIF

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QIF (Quality Information Framework) is a newer format that solely focuses on MBD, especially semantic PMI for human-&-machine-readable CAD downstream for automation, analytics, and Big Data.

It's a very modern take on MBD with advanced concepts like tolerancing and measurement features, support for assembly-level PMI, and more. Highly prized in the metrology and quality departments.

3D PDF

3D PDF is the most ubiquitous format and easily viewable on every device out there. Great for graphical representation.

IGES

IGES is the oldest neutral format and supports geometry and solids. However, it does not contain PMI.

Resources

Additional Reading


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