Model-Based Definition (MBD) is the process of documenting the information necessary to manufacture and inspect a part or an assembly in the 3D Computer Aided Design (CAD) model as opposed to a traditional 2D production drawing. The component’s product manufacturing information (PMI) – dimensions, geometric tolerances, notes, symbols, surface finishes, and more – are captured as 3D annotations. The model geometry and surfaces that pertain to the annotations are stored as semantic references, which means that manufacturing and inspection programs and machines can read them.
With every version of Creo, more functionality has been added to make MBD easier and bring the implementation in line with the latest ASME and ISO standards. Let’s take a look at advancements in MBD in the last six versions of Creo.
Full Semantic Definition. Dimensions, Datum Feature Symbols, Geometric Tolerances, and Datum Targets can have surfaces, planes, and axes added as semantic references.
Streamlined Workflows. The workflows for creating dimensions, Datum Feature Symbols, and Geometric Tolerances were made more intuitive. Datum Feature Symbols and Geometric Tolerances can be created as Annotation Elements without an Annotation Feature.
Semantic PMI with STEP Application Protocol (AP) 242. The STEP file format is one of the most common methods for exchanging CAD files in a neutral format. Creo 4 introduced support for exporting and importing 3D annotations in STEP files.
GD&T Advisor. Developed by Sigmetrix, the GD&T Advisor guides you through the process of defining Geometric Tolerances. It validates that your model complies with ASME and ISO standards, and your geometry is fully constrained.
Semantic Query. In accordance with ASME and ISO standards, selecting an Annotation Element highlights its semantic references.
Conversion of Legacy Annotations. This tool helps users convert the old set datums into the modern Datum Feature Symbols for GD&T while maintaining associativity to existing geometric tolerances.
Improved Annotation User Experience. Creo 5 introduced Mini Toolbars for annotations, Undo and Redo support, and better failure notifications.
Modernized Annotation Continuation. Notes received an overhaul to improve workflows for creation and editing. They can also store semantic references.
Improved Annotation Features. Annotation Elements can be easily moved from one Annotation Feature to another without having to edit the Annotation Feature.
Increased Annotation Support. During creation, Data Sharing features like Copy Geometry can more easily propagate stacked Annotation Elements. ModelCHECK added checks for annotations, references, and combined states.
Updated ISO and ASME Standards Compliance. You can select between 2 ISO and 2 ASME standards for syntax checking the tolerances in a model or drawing.
Modernized Tolerance Analysis. Creo EZ Tolerance Analysis replaced the Tolerance Analysis Extension for creating and managing multiple 1D tolerance stackups.
Symbol Modernization. New, more intuitive ribbon tabs were added for the placement and editing of custom symbols. The symbols are selected from a new gallery layout. Symbols are customized in a single detachable panel.
Advanced surface collection methods for semantic references. Some 3D Annotations pertain to numerous surfaces in a model. Previously, these had to be selected one-by-one. In Creo 8, advanced surface collection methods like loop surfaces, seed and boundary, and intent surfaces can be used to define surface sets for semantic references, greatly speeding up the process.
GD&T Advisor. This application now works on assemblies in addition to parts. The Matched Annotations tool allows you to review, apply, and skip updates to annotations identified by GD&T Advisor.
Surface Finish Modernization. Like symbols in Creo 8, surface finishes have new tabs for placement and editing; a gallery for selection; and a detachable panel for configuring all surface finish options and variable text.
Standard Compliant Surface Finish Symbols. Three new surface finish symbols have been added for compliance with standards: ASME Y14.36-2018, ISO 1302:2002, and ISO 25178:2016.
Symbol Parameters. Parameter names can be pre-defined in a symbol’s definition. The parameters are created automatically when the symbol is instanced. These parameters can be designated so that they are passed to Windchill when the object is checked in. This functionality has been leveraged in weld symbols so that designated parameters are available in Windchill MPMLink.
MBD is a work in progress. What enhancements would you like to see? Did you know that you can submit your ideas for product improvement and new functionality at the PTC Community site? Your peers can vote on which ideas they would like to see. The submissions are reviewed by the PTC product managers for consideration in future software releases.
For more information about MBD in Creo, visit www.ptc.com/mbd.
Dave Martin is a Creo, Windchill, and PTC Mathcad instructor and consultant. He is the author of the books “Top Down Design in Creo Parametric,” “Design Intent in Creo Parametric,” and “Configuring Creo Parametric,” all available at amazon.com. He can be reached at email@example.com.
Dave currently works as the configuration manager for Elroy Air, which develops autonomous aerial vehicles for middle-mile delivery. Previous employers include Blue Origin, Amazon Prime Air, Amazon Lab126, and PTC. He holds a degree in Mechanical Engineering from MIT and is a former armor officer in the United States Army Reserves.