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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, sketch and supplemental geometry, and datum targets.  The STEP File 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.

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 part geometry 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.

STEP File Viewer

The free STEP File Viewer supports part shape, graphical annotations for geometric dimensions and tolerances (GD&T), sketch geometry, supplemental geometry, datum targets, and finite element models that is displayed in a web browser.  Nested assemblies are supported where one STEP file contains the assembly structure with external file references to individual assembly components that contain part geometry.  STEP part geometry is converted to X3D for the viewer with the open source NIST STEP to X3D Translator.

Spreadsheets and Reports

A spreadsheet simplifies analyzing information from the STEP file at an entity and attribute level.  In the spreadsheet, each entity type is a worksheet, 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.

PMI (Product and Manufacturing Information) consists of annotations and attributes that define product geometry and product specifications. PMI includes annotations to specify Geometric Dimensioning and Tolerancing (GD&T), as well as non-geometric data such as surface texture specifications, finish requirements, process notes, material specifications, and welding symbols. GD&T is a symbolic language used to communicate tolerances on manufactured parts.

  • STEP-File-Analyzer-PMI-Representation-sfa.xlsx - The spreadsheet was generated from an AP242 file with detailed PMI Representation reports for dimensional tolerances, geometric tolerances, and datum features as indicated on the Summary worksheet. There are also PMI Representation Summary and Coverage Analysis worksheets.  PMI Representation (also known as semantic PMI) includes all information necessary to represent GD&T without any graphical presentation elements. PMI Representation is associated with CAD model geometry and 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 - The spreadsheet was generated from an AP203 file that contains Validation Properties and PMI Presentation. 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. The validation properties report (property_definition worksheet) can include geometric, PMI, assembly, annotation, attribute, and tessellated validation properties.  PMI Presentation (also known as graphical PMI) consists of geometric elements such as lines and arcs preserving the exact appearance (color, shape, positioning) of the GD&T annotations. 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.  PMI Presentation is reported on the annotation_occurrence worksheet.
  • STEP-File-Analyzer-Coverage.xlsx - The 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.  Results are color-coded based on one of the NIST CAD models.

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.  Any STEP file errors might help you diagnose errors importing STEP files into CAD software.  There should not be any of these types of errors in a STEP file.  Errors should be fixed to ensure that the STEP file conforms to the STEP schema and can interoperate with other software.  There are other validation rules defined by STEP schemas (where, uniqueness, and global rules, inverses, derived attributes, and aggregates) that are not checked.

Testing STEP Implementations

The CAx Interoperability Forum (CAx-IF) tests software implementations of AP242 and tested AP203 and AP214 in the past.  The CAE Interoperability Forum (CAE-IF) tests software implementations of AP209.  The CAx-IF and CAE-IF are joint testing activities between PDES, Inc., prostep ivip, and  AFNeT.

To test how well your CAD system implements STEP AP242 PMI, download the NIST PMI CAD models, open one of the models, export an AP242 file with PMI, and process it with the STEP File Analyzer and Viewer.  In the resulting spreadsheet, the PMI Representation Summary worksheet will indicate how well the AP242 PMI matches the expected PMI in the NIST PMI CAD model test case definitions.  Differences might be due to how some PMI was modeled in the CAD system or how the PMI was exported to the STEP file.

Uses

The software supports all commonly used STEP file formats, also known as Application Protocols (AP), including those listed below. An AP is the implementable part of ISO 10303 on which translators are based on in a particular engineering domain.

Some other EXPRESS schemas are also supported.

Contact

Created December 7, 2012, Updated November 10, 2020