The Modern Digital Workplace
With fabricators continuing to push the limits of digital manufacturing, it was inevitable that classic drafting documentation would eventually become obsolete. For quite a while it has been possible to manufacture a finished part solely based upon the information taken directly from the digital 3D design. Feeding a CNC machine G-code derived from the original 3D model is now common place across the manufacturing discipline.
But what about the machine parts and assemblies that still require a skilled machinist and fabricators? How do we deliver machining tolerances and assembly instructions to our manufacturing division without proper 2D documentation? The answer is found in a relatively new process called Model Based Definition.
Model Based Definition is the process of adding all necessary fabrication instruction information directly to the 3D model. The model is then transmitted directly to manufacturing for assembly or fabrication. Because this process eliminates the entire drafting step, it is far more efficient than any traditional “paper-based” workflows.
Going Beyond Paperless
Many of us remember the “paperless initiatives” pursued by countless organizations during the early years of the digital manufacturing era. Based upon the idea that there were reliable 2D digital formats like PDF and DWF, printing and producing paper drawings was almost completely eliminated. With Model Based Definition, it is now possible to not only go truly paperless, but to eliminate the classic drafting documentation step altogether. The same portable tablets used to view the 2D drawings can now be utilized to display the full 3D model complete with tolerances and assembly instructions.
Model Based Definition for Parts and Assemblies
With the introduction of Autodesk Inventor 2018.1 we now have the ability to add 3D annotations to parts and assemblies, placing the product manufacturing information directly into the 3D model. Commands for adding this information are now located on the Annotation tab available in the part and assembly modeling environments. The Annotate tab provides complete support for Geometric Dimensioning and Tolerancing in way of part design. The built in Tolerance Advisor can assist you in GD&T validation. The Tolerance Advisor guides you through creating a fully constrained design. When you create tolerance features, the advisor displays informational messages or warnings about potential issues in the Tolerance Advisor browser pane.
The 2018.1 subscription release of Inventor now offers the ability to add 3D annotations to assemblies. The simple difference between the assembly and part annotations environment is the understandable absence of the GD&T tools which are only valid in part fabrication instructions. Dimensions, Hole Notes, Surface Texture, Leaders, and General Notes are available to include as 3D part, and assembly annotations.
Organizing your 3D Annotations with Design Views
The 3D Annotations you add to your models are all stored in the Annotations folder located in the model browser. You typically create individual Design Views for the classic Front, Top, Right, and Isometric viewpoints. 3D Annotations are automatically visible in each design view and can be manually hidden in specific views where they don’t apply. Each Design View remembers the visibility state for all 3D Annotations. There are also options to hide 3D Annotations and Component Annotations on the Object Visibility command located on the View Tab.
Pitfalls and Considerations
As with all emerging workflows and design features, there are a few drawbacks and incomplete functionality that need to be considered. It is important to note that this is the initial release of Model Based Definition in Autodesk Inventor and there are still major gaps in design documentation that need to be addressed. Overall the current functionality is a fine first step toward the goal of a completely annotated 3D design, but there is still a way to go. Below you will find some the pitfalls I have initially found with this workflow. You should certainly begin utilizing 3D Annotations now, but consider these points before full adoption.
Pitfall #1 - Sharing your Design to Mobile Platforms
At this point the only reliable method of sharing the 3D model to portable tablets utilizes the 3D PDF export feature available on the Annotate tab. This means that your collaborators or fabricators will have to install an app that supports and displays 3D PDF files. It is foreseeable that Autodesk will eventually include the display of 3D annotations in a DWF or A360 viewer, but as of the time of this article, 3DPDF is the only viable option.
Pitfall #2 - Missing Annotation Types
A classic 2D drawing contains other annotations beyond the standard dimensions, tolerances, and leader notes. There are no current 3D annotation support for the following.
- Bill of Materials / Parts List
- Custom Symbols
Pitfall #3 - Everything in the One File
The current workflow puts all 3D Annotation in the main assembly or part file. While keeping everything together seems to have some organizational advantage, it can quickly clutter the file with useful but distracting visual data. The data management cycle for versioning these types of files will be greater because of the nature of updating and tweaking annotations. It would be nice to see a dedicated annotation file, like an Inventor Presentation file which holds all manufacturing information but does not impact the actual 3D model.
I will be the first person to sound off and cry that “you will never take my 2D drawings!”, but the future is coming whether you like it or not. 3D Model Annotations and Model Based Definitions have already been adopted by many companies including high end defense contractors. If there is a silver lining to the passing of traditional 2D drawings, it’s that the same care and attention to detail are required to produce the modern 3D equivalent. So, jump in and begin experimenting with this new workflow. Chances are you will be utilizing it sooner than you think.