Model Based Definition (MBD)
Definition of Model Based Definition Initiative
Model Based Definition (MBD) is a mechanical engineering initiative where a 3D model with Product Manufacturing Information (PMI) augments or replaces a 2D engineering drawing as design documentation.
Product and Manufacturing Information (PMI) is composed of non-geometric information that describes a design, including Geometric Dimensioning and Tolerancing (GD&T), surface finish, material information and more. Geometric Dimensioning and Tolerancing (GD&T) is an approach to defining tolerances that uses a symbolic language.
Design documentation refers to the deliverables that engineering releases to downstream functional organizations such as manufacturing, procurement, suppliers, service and much more.
MBD deliverables are created and consumed with Mechanical Computer Aided Design software or 3D Visualization software. Such deliverables can be managed with Product Data Management software or Product Lifecycle Management software.
Why Pursue a Model Based Definition Initiative?
There are a few reasons an organization would pursue this initiative, including:
- Contractual Obligations: A number of today’s Department of Defense contracts include terms and conditions requiring the delivery of 3D models with PMI. For some, their pursuit of this initiative is primarily driven by contractual obligation.
- Reducing Efforts to Create and Amend Design Documentation: Theoretically, embedding PMI onto a 3D model should take less time than detailing a complete 2D engineering drawing, promising some benefit from this initiative. Furthermore, 3D models with PMI is often clearer in communicating manufacturing intent, allowing engineers to avoid the creation of amending documentation to clarify 2D engineering drawings. Findings from Lifecycle Insights’ The Model Based Enterprise Research Report validated this claim.
Clarifying Points on Model Based Definition
- MBD Initiatives ≠ Paperless Initiatives: Some organizations are pursuing paperless initiatives, where documentation is delivered electronically instead of on physical, hardcopy prints. While an MBD initiative may also be paperless, it does not have to be paperless. MBD deliverables can be printed on paper and distributed in physical, hardcopy forms.
- MBD Initiatives ≠ Drawlingless Initiatives: Some organizations are pursing drawingless initiatives, where a 3D model and PMI is delivered instead of a 2D engineering drawing. While MBD deliverables can enable such efforts, it is not required. Some organizations that have pursued MBD initiatives use 3D models and PMI alongside 2D engineering drawings.
Model Based Definition Standards
For years, professional organizations published standards that defined how drawings should be documented. As some manufacturers considered the vision behind MBD, those professional organizations developed and published new standards that defined how PMI should be documented in 3D models.
- ASME Y14.41 3D Digital Product Definition (Wikipedia entry)
- ISO 16792 Digital Product Definition Data Practices
- JEITA 3D Annotated Model Guidelines