Model based definition

Model based definition (MBD) represents a new trend in Computer-aided design (CAD)

Previously, all 3D CAD models had an accompanying 2D drawing, primarily to show high tolerance dimensions, GD&T and annotations. This resulted in a duplication of effort and occasional contradictions between the 3D original and the 2D drawing derivative.

With new advances in CAD architecture we are now able to insert the dimensions, GD&T and annotations directly into the CAD model, thus eliminating the need for drawings.

This simplifies the release process for the designer and reduces costs.

However, the fabricators (Machine Shops, Plastic moulders, Fab houses, Inspectors, Electricians, Plumbers) who were once able to do their work using inexpensive paper blueprints, are now required to purchase and obtain training on proprietary and sometimes costly Low End Viewers (LEVs)or purchase high-end parametric feature based (PFB) CAD systems.

A solution to LEVs and PFB CAD by some vendors is to create 3DMEDs (3D Manufacturing Enhanced Documents) from the source CAD program. Just as a blueprint was able to convey all the manufacturing information needed to make the part or assembly, 3DMEDs are documents (Usually 3D PDFs) that have extracted all the manufacturing information from the source CAD dataset and repackage it in a single PDF that is freely viewable using the Adobe Reader. Companies like Right Hemisphere provide multiple 3DMED's and can also create 2DMED's automatically from CAD based models thus supporting the MBD strategy of modern manufacturers. Companies like SpaceClaim offer next-generation technology that make it practical and affordable for suppliers and the rest of product development to open the native CAD file and work with the geometry as needed and propagate the changes to downstream applications.