I've watched a ton of MBD, DimXpert videos over the years from respected sources such as Trimech, GoEngineer, SolidWorks, etc. and they all have one thing in common: They present the practice of creating 3D annotations as
(re)creating what one would expect on a typical 2D drawing, i.e. a fully dimensioned part. In this day and age when most companies have been exchanging 3D models for many years (and therefore have the ability to query the model), it confounds me a little to see this.
Assume you have embraced (or at least bro-hugged ;-) MBD/3D annotations, you are faced with a choice: fully dimension the model and generate a PDF or drawing, or minimally dimension, relying on established standards (both industry-wide and company-specific) in a way that clearly defines those characteristics of the model that are not covered and defined by other standards. I have a list of requirements to support minimal dims (none of this is radical or even innovative necessarily, just my thoughts:
1. Establish default dimensional tolerances
2. Establish Profile of Surface default value
3. Establish default dimension place values
4. Define primary datums [A, B, C]
5. State clearly that the model is the truth!
As an example, consider the following (admittedly simple) part, fully dimensioned using DimXpert:
If I apply the proper standards, such as this:
ALL DIMENSIONS ARE INCHES UNLESS OTHERWISE SPECIFIED
DIMENSIONING AND TOLERANCING PER ASME Y14.5 - 2009
FEATURES WITH NO GEOMETRIC TOLERANCE INDICATED SHALL HAVE A PROFILE TOLERANCE ZONE OF .010 APPLIED
FEATURES WITH NO LOCATIONAL TOLERANCE INDICATED SHALL HAVE A TOLERANCE OF +/- .020 APPLIED WITH RESPECT TO THE PRIMARY DATUMS [A, B, C] OF THE 3D SOLID MODEL
FEATURES WITH EXPLICIT ANNOTATIONS SHALL HAVE THE FOLLOWING TOLERANCES UNLESS OTHERWISE SPECIFIED:
.XX = +/- .01
.XXX = +/- .005
ANGLES = +/- 1 Deg.
The result, I submit, would be this:
By the way, the output media on this is irrelevant; it could be a 2D drawing, or a 3D PDF, or just the model.
So... is this viable as an approach to MBD/3D annotations? I'd like to get feedback on this from everyone, but especially from those on the manufacturing end.
Sorry for the long post, but I wanted to lay the discussion out clearly.