The free STEP File Analyzer and Viewer (SFA) opens a STEP (ISO 10303 –STandard for Exchange of Product model data) Part 21 file (.stp or .step or .p21 file extension) and generates a spreadsheet or CSV files. 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 files are also used for long-term archiving and retrieval of product data (LOTAR).
A spreadsheet simplifies analyzing information from the STEP file at an entity and attribute level. Typical STEP file viewers show a 3D view of the part or model represented by the STEP file. The viewers usually have a high-level hierarchical display of the information in the STEP file where the user can drill down to individual attributes of parts. However, there is no way to analyze all of the actual STEP entities and their attributes at once. The STEP File Analyzer and Viewer provides the analysis capability by creating a spreadsheet from the STEP file.
- STEP-File-Analyzer_stp.xlsx - Spreadsheet generated from an AP203 (STEP 203) file. Validation Properties are report is on the property_definition entity. PMI Presentation is reported on the annotation_occurrence entity.
- STEP-File-Analyzer-PMI-Representation_stp.xlsx - Spreadsheet generated from an AP242 (STEP 242) file. Detailed PMI Representation reports (see explanation below) are on various entities indicated on the Summary worksheet. There are also PMI Representation Summary and Coverage Analysis worksheets. The Summary and Coverage Analysis worksheets are color-coded by the number of expected PMI annotations and elements in the NIST CAD models.
- STEP-File-Analyzer-Coverage.xlsx - Spreadsheet generated when processing Multiple STEP 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.
STEP File Viewer
The software can also open a STEP file to view boundary representation part geometry, tessellated part geometry, PMI for geometric dimensioning and tolerancing (GD&T), supplemental geometry, and finite element models. The viewer uses x3dom that can be displayed in any web browser. Other general-purpose STEP file viewers might not display PMI, tessellated part geometry, and finite element models. However, those viewers are usually better at viewing and measuring b-rep geometry than the STEP File Analyzer and Viewer.
- Boundary representation (b-rep) geometry and graphical PMI annotations
- AP242 (STEP 242) tessellated part geometry
- AP209 finite element analysis models
Testing STEP Implementations
The CAx Implementor Forum (CAx-IF) tests software implementations of AP242 (STEP 242) and tested AP203 (STEP 203) and AP214 (STEP 214) in the past. The CAE Implementor Forum (CAE-IF) tests software implementations of AP209. The objective of the CAx-IF is to advance CAx (mainly Computer-Aided Design and Engineering) software system STEP translator development and to ensure that user requirements for interoperability are satisfied. The CAx-IF and CAE-IF are joint testings effort between PDES, Inc., prostep ivip, and AFNeT. prostep and AFNeT have published AP242 benchmark tests.
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 due to how some PMI was modeled in the CAD system or how the PMI was exported to the STEP file.
The STEP File Analyzer and Viewer generates reports for PMI Representation, PMI Presentation, and Validation Properties based on Recommended Practices defined by the CAx Implementor Forum. Examples of the spreadsheet reports are shown above.
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.
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. The PMI Representation spreadsheet report includes information related to GD&T such as Dimensional Tolerances, Geometric Tolerances, and Datum Features. PMI Representation is typically found in AP242 files.
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. The PMI Presentation spreadsheet report includes the type of the PMI and geometry entities such as polylines that make up the PMI Presentation. Associated geometry, PMI Representation, and Saved Views are also reported.
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 spreadsheet report include geometric, PMI, assembly, annotation, attribute, and tessellated validation properties.
Coverage Analysis worksheets for PMI Representation and PMI Presentation are also generated when processing single or multiple STEP Files. Coverage is based on characteristics of PMI defined in the Recommended Practices. If a STEP AP242 file from a NIST CAD model is processed, then the PMI found in the STEP file is checked against the expected PMI in the corresponding NIST test case. The coverage analysis worksheets are color-coded by the expected PMI in each test case.