Over the past several releases Model Based Definition or MBD has been enhanced to include more functionality to cover more use cases. If you’re unfamiliar with MBD think of it as a 3D Drawing. You’re able to add Product Manufacturing Information or PMI to a 3D model with dimensions, annotations, notes, and tables in an organized and easy to understand manner. Instead of printing a 2D Drawing you publish a 3D PDF instead. The advantage to 3D PDFs is the ability to rotate the model around to see all sides of the model as opposed to looking at orthogonal views on a 2D drawing. Even though the 2D drawing has an Isometric View it still doesn’t have the impact a 3D model has when it comes to understanding the fit, form and function of the model. For a novice that doesn’t fully understand how to read a 2D drawing a 3D PDF will provide a better means to convey design intent.
MDB is being used more and more in manufacturing especially when CNC machining and fabrication is being used. When a 2D drawing is created every dimensions is needed to fully define the part on the drawing. With MBD you only need to add the critical dimensions that would be used for inspection. The rest of the dimensions are taken directly from the 3D model since its being used to drive the CNC process.
For 2021 sheet metal parts can now have their Bend Table included in the 3D PDF. Bend Tables were introduced to MBD in 2019 but the Bend Table wasn’t included in the 3D PDF which limited its usefulness. Now in 2021 a bend table is created in the PDF and each bend is tagged with an alpha character along with its direction, angle and inner bend radius in the table as shown here in this 3D PDF.
Another MBD enhancement in 2021 is the addition of Datum Targets for GD&T dimensioning. A Datum Target is a line, point or a defined zone on a target with which used in order to establish a Datum plane. In our example of the sheet metal part shown on the PDF above the flat face of the part could be warped or bent a small amount on a local area. That defect could possibly throw off the inspection process enough to reject the part as unusable. If Datum Targets are used to define a plane based on 3 points on the face of the part then that plane is used for inspection purposes. Here’s what the Datum Targets look like when applied to the sheet metal part. The Targets on the left are point targets and on the right a defined circular zone of a 0.25 inch in diameter. The targets are located using dimensions and honor the dimensioning standard set in Document Properties.
Here’s the Property Manager for MBD Datum Targets.
Using Model Based Definition can be a real time saver for downstream manufacturing processes. It also reduces the number of files being managed by PDM or manually. MBD with PMI truly creates the single source of truth: the 3D Model.