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Concurrent Engineering Blog

What is Model Based Definition?

Posted by Concurrent Engineering on 03-Nov-2022 09:30:00

MBD is an essential part of the design process, and if you’re a Creo user, you’re in the best place to get it right. Let’s find out more.


Model-Based Definition (or MBD) is the way designers document all the necessary data to manufacture a part or assembly in a 3D CAD (Computer Aided Design) model. It captures all the part’s product manufacturing information (PMI), including:

  • Dimensions
  • Geometric tolerances
  • Symbols
  • Notes
  • Surface finishes


Each piece of data is expressed as a 3D annotation, while the model geometry and surfaces related to annotations are captured as semantic references. Manufacturing and inspection programs are able to read this data. MBD represents a considerable step from traditional 2D production drawing.


Creo, PTC’s 3D CAD solution, has had MBD functionality since Creo 4 in 2016. As the Creo solution has evolved, so have its MBD-related features. Today in 2022, Creo 9 makes MBD easier than ever, bringing MBD implementation into compliance with the latest ISO and ASME regulations. This article will look at how MBD inside Creo has changed through the years with every new feature added. Let’s get started.


2016 - Creo 4


Full semantic definition - This feature enables dimensions, datum targets and feature symbols, and geometric tolerances to have surfaces, axes and planes added as semantic references.


GD&T Advisor - Your guide to defining geometric tolerances. It confirms that your geometry is fully constrained and that your model complies with ISO and ASME standards.


Semantic PMI including STEP Application Protocol (AP) - For the first time, Creo 4 introduced the ability to export and import 3D annotations as STEP files, one of the most popular ways to transfer CAD files in a neutral format.


Workflow enhancements - Creo 4 also streamlined workflows for creating:

  • Dimensions
  • Datum feature symbols
  • Geometric tolerances


This includes the ability to create annotation elements without the need for an annotation feature.


2018 - Creo 5


Conversion of legacy annotations - This new tool, introduced in Creo 5, helps users transfer legacy set datums into current Datum Feature Symbols for GD&T, with access to existing geometric tolerances maintained.


Annotation enhancements - Creo 5 improved the user experience for annotations, with:

  • Mini toolbars
  • Undo and redo
  • Enhanced failure notifications


Semantic query - To comply with ISO and ASME standards, semantic references are highlighted when a user selects an annotation element.


2019 - Creo 6


Enhancements to annotation features - With Creo 6, users could now move annotation elements from one annotation feature to another without needing to edit the entire annotation feature.


Improved annotation support - Creo 6 allowed data-sharing features (e.g. Copy geometry) to propagate stacked annotation elements more easily. ModelCHECK added checks for:

  • Annotations
  • Combined states
  • References


Upgraded annotation continuation - Creo 6 gave users an overhauled Notes feature, including improvements to creation and editing workflows, with storage for semantic references.


2020 - Creo 7 


Enhanced tolerance analysis – In Creo 7, the new Creo EZ tolerance analysis replaces the old tolerance analysis extension for creating and managing tolerance stack-ups.


Upgraded ASME and ISO standards compliance – Creo 7 lets users select between 2 ISO and 2 ASME standards to check the syntax in tolerances.


2021 – Creo 8


Enhanced surface collection for semantic references – In previous Creo versions, 3D annotations related to multiple surfaces in a model had to be selected individually. In Creo 8, you can define semantic references fast, employing methods including:

  • Loop surfaces
  • Seed and boundary
  • Intent surfaces


Enhanced symbols – Place and edit custom symbols more intuitively with ribbon tabs, a new layout for the gallery and a detachable panel for customisation.


GD&T advisor – Upgrades to this feature mean that it now works on assemblies as well as parts. In addition, with the matched annotations tool, you can review, apply and skip updates to annotations through GD&T Advisor.


2022 – Creo 9


Enhanced surface finish – Workflow for surface finish upgraded to include new placement and editing tabs, a new selection gallery and a configuration panel.


Surface finish symbols compliant with standards – Three new symbols have been added to comply with standards:

  • ASME Y14.36-2018
  • ISO 1302:2022
  • ISO 25178:2016


Symbol parameters – Users can now pre-define parameter names in symbol definitions, automatically created when a user instances a symbol. You can designate parameters to pass to Windchill on check-in. 


Looking to the future


Over the years, MBD has become one of Creo's most significant aspects. However, PTC’s team are not ready to stop yet. They are always in touch with the Creo user base to get feedback and suggestions for new ideas.


Stay tuned for more great MBD enhancements.


Find out more