The Ultimate Glossary of Model-Based Engineering

Companies use MBD (model-based definition) to create, organize, and manage a fully defined 3D model that captures design intent and serves as the master product definition for the extended enterprise.* If you’re new to model-based definition and engineering, bookmark this list of terms to familiarize yourself with the language of MBD.

3D PDF. A file format that supports 3D geometry. Using a viewer (such as Adobe Reader), anyone can zoom, pan, measure, and section a 3D model in a 3D PDF file. In the same way a 2D PDF file won't allow users to modify the source document, a 3D PDF prevents them from making significant changes to the geometry.

Annotation. An element that describes a model or a feature of a model. An annotation might be a dimension, a note, a symbol, a datum feature symbol, a surface finish symbol, a weld symbol, etc.

Annotation Plane. A datum plane or flat surface used in Creo to define the orientation of annotations.

ASME/ISO Standards. Major standards used for model-based engineering, specifically, ASME Y14.5 & ASME Y14.41 and ISO 1101 & ISO 16792.

Combination State. A collection of display settings used in Creo to control the visibility of objects in a model. This is helpful for model-based definition as you can create a combination state to show annotations and geometry.

Coordinate Measuring Machine (CMM). A device that measures the geometry of physical objects. Used in manufacturing, CMM can be programmed in minutes using MBD (compared to hours using 2D drawings). It provides an example of how downstream processes benefit from 3D annotated models.

Control Characteristics (also known as key characteristics). Control characteristics capture and communicate the design intent and critical product information required for manufacturing. Not only can you use these control characteristics to find and reuse model data, you can also use them in the planning stage. You can access information for the manufacturing decisions without having to open the models in the Creo application or other CAD systems to verify the model data. In Creo, you can designate annotation elements as control characteristics.

Datum Feature Symbol. A type of annotation that represents a datum. A datum is, according to ISO standards, an exact geometric feature used to locate or orient tolerance zones for tolerance features of virtual conditions.

Datum Target. The designated points or areas that are used in establishing a datum.

Datum Reference Frame (DRF). A set of three mutually perpendicular planes that constitutes a reference frame for dimensioning and tolerancing.

Geometric Dimensioning and Tolerancing (GD&T). A system for defining and communicating engineering tolerances. It uses a symbolic language on engineering drawings and CAD models that explicitly describes nominal geometry and its allowable variation.

Geometrical Product Specifications (GPS). The ISO term for GD&T, GPS is a symbolic language for communicating workpiece requirements on engineering drawings and CAD models.

GD&T Advisor. An extension to Creo that provides expert guidance on the application of GD&T and validation that it has been done correctly. GD&T Advisor ensures models comply with the relevant standard and are fully constrained.

JT (Jupiter Tessellation). A neutral 3D file format used for product visualization. It can contain faceted data, boundary representation surfaces, product and manufacturing information, and text attributes either exported from the native CAD system or inserted by a PDM system.

Model-Based Definition (MBD). The practice of specifying product information, such as materials and geometric dimensioning and tolerancing, from within a 3D CAD model.

Product Data Management (PDM). A type of software that stores, organizes, and secures data across teams. PDM systems may also include sharing and reviewing capabilities to make engineering data more consumable for non-engineering teams. 

Product and Manufacturing Information (PMI). The non-geometric attributes in 3D CAD systems needed to manufacture product components and assemblies. PMI may include GD&T, 3D annotations, surface finishes, and material specifications.

STEP AP242. A widely used and shared neutral CAD format used to represent 3D objects and related information, such as PMI.

Technical Data Package (TDP). The complete technical product information including annotated 3D geometry, PMI, and metadata. The TDP is typically sent to suppliers, manufacturers, or customers.

Tolerance. The total amount a specified dimension is permitted to vary. The tolerance is the difference between the maximum and minimum limits.

Tolerance Analysis. A calculation to determine the effect of the accumulation of tolerances on product requirements.

Where to Find More

Adopting a model-based enterprise means changing some familiar processes and getting familiar with new terms. But you’ll soon reap rewards as you eliminate redundant 2D drawings and create a reliable source of truth that can be used throughout the extended enterprise—from design to manufacturing to quality assurance.
For more GD&T terms, visit the Glossary found in Creo Online Help (free website). To learn more about how reusing rich 3D models can give your team a competitive edge, download the free Model-Based Definition e-book.

*Madhavi Ramesh, Model-Based Definition e-book