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STEP File Analyzer and Viewer

NIST STEP File Viewer screenshot

The free STEP File Viewer supports parts and assemblies, dimensions and tolerances, supplemental geometry, datum targets, and point clouds. The Analyzer generates a spreadsheet of all entity and attribute information; reports and analyzes any semantic PMI, graphical PMI, and validation properties for conformance to recommended practices; and checks for basic STEP file format errors.

What is STEP?

STEP (ISO 10303 –STandard for Exchange of Product model data) files are also known as Part 21 files with a file extension of .stp, .step, or .p21. STEP files are used to represent parts, assemblies, and Product and Manufacturing Information (PMI) that is used for data exchange and interoperability between Computer-Aided Design (CAD), Manufacturing (CAM), Analysis (CAE), and Inspection (CMM) software. PMI consists of annotations and attributes that define product geometry and product specifications including annotations to specify Geometric Dimensioning and Tolerancing (GD&T).

NIST has been involved with the development of STEP since the 1980's.

STEP AP242, AP203, AP214 and others are supported. See Uses below. Compare the differences between STEP AP203 vs AP214 vs AP242.

STEP File Viewer

The STEP File Viewer displays many features of a STEP file in a web browser.  Click on the links for examples.

STL to STEP Converter

The viewer can also be used convert STL files, that are used for additive manufacturing and 3D printing, into STEP AP242 tessellated part geometry.  This research compares STEP, STL, and other 3D printing formats.

Spreadsheets and Reports

A spreadsheet simplifies analyzing information from the STEP file at an entity and attribute level. In a spreadsheet, each entity type is a worksheet and each row is an entity instance where the columns are the entity attributes.  Reports can be generated for PMI Representation, PMI Presentation, and Validation Properties based on Recommended Practices defined by the CAx Implementor Group.  A Bill of Materials (BOM) of part and assembly information can also be generated.

  • STEP-File-Analyzer-PMI-Representation-sfa.xlsx - This spreadsheet was generated from an AP242 file with PMI Representation (also known as semantic PMI) reports for dimensional tolerances, geometric tolerances, and datum features. PMI Representation is computer-interpretable to facilitate automated consumption by downstream applications for manufacturing, measurement, inspection, and other processes. Results are color-coded based on one of the NIST CAD models.
  • STEP-File-Analyzer-sfa.xlsx - This spreadsheet was generated from an AP203 file that contains Validation Properties and PMI Presentation (also known as graphical PMI). Validation properties are quantities related to features of a CAD model that are computed by the native CAD software used to validate the import of those quantities. PMI Presentation is not intended to be computer-interpretable and does not carry any representation information, although it can be linked to its corresponding PMI Representation.
  • STEP-File-Analyzer-Coverage.xlsx - This spreadsheet was generated when processing multiple STEP AP242 files. The File Summary worksheet shows the distribution of STEP entities across all of the files. The Coverage Analysis worksheet shows coverage of PMI Representation concepts from the STEP file and CAx-IF Recommended Practices.
  • Bill-of-Materials.xlsx - This spreadsheet has a worksheet for a Bill of Materials (BOM) for a bracket assembly.  The BOM lists the quantities of parts and assemblies in two tables.  The assemblies also show their components which are parts or other assemblies.

Syntax Checker

The software includes a syntax checker that checks for basic syntax errors and warnings in the STEP file related to missing or extra attributes, incompatible and unresolved entity references, select value types, illegal and unexpected characters, and other problems with attributes. Syntax checking might help you diagnose errors when importing STEP files into CAD software. STEP file errors should be fixed to ensure that the file conforms to the STEP schema and can interoperate with other software.

Testing STEP Implementations

The CAx Interoperability Forum (CAx-IF) tests software implementations of AP242 and previously tested AP203 and AP214. The CAx-IF is a joint testing activity between PDES, Inc. (U.S.), prostep ivip (Germany), and  AFNeT (France).  The ASD Strategic Standardisation Group has also done AP242 Benchmark Testing.

Sample Screenshots

STEP File Analyzer and Viewer user interface
Created December 7, 2012, Updated September 13, 2022