Fabrication Parts for Revit MEP - 4 Years In
In the Fall of 2011 I was already a long-time Autodesk® Revit® MEP user, promoter, teacher, etc. I was working for a HVAC contractor using Revit MEP to design and engineer projects, as well as using it as the platform for BIM coordination. To support fabrication we were using a complicated, labor-intensive, error-prone process. This included exporting to expensive additional software, some converted model re-use along with a significant amount of model re-creation, and much manual review to ensure the fabrication model was both faithful to the coordinated Revit model and that the data sent to manufacture was accurate as modeled in the fabrication software.
That being said, I was elated to receive the email on October 20, 2011 that announced that Autodesk had acquired MAP Software, the makers of CADduct. My immediate assumption was that within five years, Autodesk would be able to roll MAP Software’s full functionality into Revit MEP. Here is the list of functionality that I expected out of the fabrication features.
- Maintaining the Revit style of modeling
- Full engineering support
- The same ease of documentation
- The ability to create a complete model
- Spool drawings
- Direct CNC sheet metal download interface to fabrication equipment
- Support for robotic field point layout
Here is my personal review of the first public release of the fabrication software within Revit. For the sake of brevity and specificity, I’m limiting the review to duct, but most of it also applies to the electrical and piping features. I’m also limiting the review to the Revit platform. Revit is superior for whole building modeling and users would benefit from having to become skilled in only one software platform.
Revit’s Style of Modeling
As you can see from the brief demo video on Autodesk’s Revit features web page (currently at http://www.autodesk.com/products/revit-family/features/all/gallery-view), fabrication parts are not modeled in Revit in the same fashion as family MEP elements. The modeling method for standard Revit MEP elements is strongly based on the straights, allowing the system family settings to insert transitions and bends for you. The new fabrication features require specifically picking and placing all components.
For instance here is the process to create a run of duct 15 feet long, reduce it’s size, run 3 more feet, turn and run another 15 feet. This list includes every required action (see Figure 1).
Figure 1
Standard Revit MEP duct:
- Start the duct command
- Select the needed size in the Options Bar
- Pick a start point
- Pick an end point (or type a distance and press enter)
- Change the duct size
- Click a new endpoint parallel to the previous run (the duct command stayed active)
- Click a new endpoint perpendicular to the previous runs
New fabrication features:
- Select “Straight” from the MEP Fabrication Parts palette
- Select the needed duct size in the Properties palette (Options Bar remains empty)
- Pick a start point
- Pick again to place another straight at the end of the previous
- Pick again for another straight
- Select the “Transition” fitting from the Fab palette
- In the Properties palette, change the “Secondary End” to the desired duct size
- Pick to place the transition on the end of the run
- Select “Straight” from the Fab palette
- Pick to place the straight
- Cancel the straight command
- Select the duct segment just placed (it does not remain selected after placement)
- To shorten that segment to 3 feet, either drag the endpoint grip in the Drawing Area or in the Properties palette, change “Length Option” to “Value” and type 3 in the Length property
- Select your desired elbow from the Fab palette
- Pick to place the elbow
- Select “Straight” from the Fab palette
- Pick to place the duct segment
- Pick again to place the duct segment
- Pick a final time for the last piece
A huge portion of the Revit modeling method relates to the modify tools. Unfortunately the most useful of these do not work at all with fabrication parts. Trim, Extend, and Offset don’t recognize Fabrication parts at all. Figure 2 shows the Extend tool working as expected for a standard duct to extend to a detail line. Figure 3 shows that the Fabrication part doesn’t recognize that command. There is also no remote snapping function for Fabrication parts aligning with distant model elements as you drag them around—this includes even aligning with other distant Fabrication parts. The align tool does work. However, this takes us way back to old hand drafting and AutoCAD style of editing, which made extensive use of temporary sketched lines for layout.
Figure 2
Figure 3
Full Engineering Support
The primary features related to supporting the design process I'm referring to are systems (i.e., duct supply air versus return air) and tracking flow along a run of duct or pipe. Systems and flow are a bit finicky and require effort to maintain in standard Revit duct and pipe layouts, but they do indeed work. Both of these features are entirely excluded from Fabrication Parts. If you would like a deeper discussion on doing this in Revit and you are an AUGI Professional Member, you can review the previous article in the January 2012 issue, “Plumbing Systems for Well-Documented Flow.”
Since the default Fabrication configuration files do not have any air terminals (grilles/diffusers), it would seem that the intention is for users to continue to use standard Revit family air terminals. This would still allow you to perform airflow calculations with Revit spaces with no change from the Fabrication features. As mentioned before, the flow defined by the Air Terminal will not propagate in the Fabrication part duct run.
Ease of Documentation
Full engineering and construction documentation can be genuinely beautiful when generated from Revit. Model elements and annotation elements blend well and all of this can be done much easier and more quickly than what I remember from my now distant AutoCAD days.
Is this ease of documentation still available with Fabrication parts? In a word, no.
As mentioned earlier, systems and flow do not exist for Fabrication parts—both of these are frequently part of my documentation. There is no tag for Fabrication Parts in the default content. When you apply duct or pipe insulation, there is no separate visibility control for the insulation, making it impossible to properly document.
The biggest offender, though, is the lack of hidden-line support. Figure 4 shows the outline of the duct below broken and with a lighter lineweight. Figure 5 shows the same situation with Fabrication Parts. Here, the lower element is completely removed. Even in this simple example you can see that the duct transition is completely lost, not allowing good documentation.
Figure 4
Figure 5
A Complete Model?
When talking about Revit, one of the more common statements is that the key to success is good content. Even though this is the first release of Fabrication in Revit, there does seem to be plenty of content to use. However, if there are some minor modifications needed, there is no fabrication configuration editor. You can download the default configuration from Autodesk or receive a configuration from a current CADmep user. One example of this is that the default configuration file doesn’t include duct or pipe insulation. Since Fab parts are not standard Revit system families, you cannot use standard Revit insulation. This means that with the software and default configuration files currently released, in addition to Revit MEP you would have to buy CADmep or CAMduct before you can simply add insulation to your model.
One of most useful things in Revit is the family editor—both standalone and in the context of a project for in-place families. There are some times when the parts needed are completely custom. Imagine a duct fitting that can only be built by hand in the corner of the shop by the old school tin knocker. This fitting may not be in the pre-created list of Fab parts. Since Fabrication Parts are not Revit families, they can’t be customized or built from scratch in any version of the family editor.
Fabrication Parts are not Revit families, which significantly limits their customizability.
Spool Drawings
A spool drawing is one step between a contractor’s building scale shop drawings and the purchased part list/fabrication cut & bend drawings. Usually it represents a handful of parts that are going to be assembled in the shop and shipped to the job site. This might be a pre-assembled handful of duct fittings or welded pipe and fittings (see Figure 6). This has been supported for some time by the Revit platform feature “Assemblies.” However, it will be important for the final use to be careful that individual parts are identified by the same parameter throughout the manufacturing and assembling process. For instance, if the “Mark” parameter is used to tag piece numbers, you will have your fabricator confirm that that ID is also visible in his software and will translate to a physical label on the part.
Figure 6
Some information about Fabrication parts is not available for use in Revit schedules (i.e. duct connection types). This will again require additional care with regard to coordinating between information rich sources such as the exported fabrication file .maj and somewhat poorer sources such as Revit schedules and tags.
● Direct CNC sheet metal download interface export to fabrication equipment.
Modeling with fabrication ready elements would be nearly pointless if we couldn’t plug that information directly into CAMduct for use in cutting and folding the sheet metal. Surprisingly, this function is not included in the default installation of Revit MEP, but is available for free on the Autodesk Exchange (apps.exchange.autodesk.com). The Revit Extension for Fabrication will allow you to directly export to the .maj file format.
What about indirect exports? Many installing contractors own their own fabrication equipment, but others buy fabricated parts from multiple sources. The best way to do this may be with the same .maj file, but if the supplier uses different software to drive their equipment, a different method may be needed. The lowest common denominator is a simple list of parts with enough data to get the correct size and shape. As mentioned above, this data is lacking the required fields available to be scheduled with Revit Fabrication parts.
Support for Robotic Field Point Layout
Using a robotic field layout tool is the best way to translate your carefully BIM coordinated layout to actual locations in the building. The one common method for accomplishing this in Revit is to add a nested “point” family to your various hanger families (see the blue highlighted elements in Figure 7). As already covered, Fabrication parts are not Revit families. This being the case, some other more manual method of identifying and exporting hanger location will have to be devised.
Figure 7
Summary
I struggle to see how the new 2016 features will advance the day-to-day use of these two products (Revit and CADmep). The process of modeling Fabrication Parts is so limited in Revit that it will take Autodesk additional development before attracting users to adopt the use of ITM in a Revit modeling workflow. In my view, the 2016 release of Fabrication Parts in Revit should have been introduced in Labs for 2016 and not for production.
The Future
I was very surprised that Autodesk has taken this path after acquiring MAP Software. My expectation would have been that MAP’s fabrication experience would be used by Revit developers to build on to the existing core Revit MEP functionality and that resellers of MAP Software products would continue to push forward with the AutoCAD platform.
Instead Autodesk has bolted the legacy CADmep .itm file format onto the outside of Revit’s core functions, similar to just inserting a CAD file plus a little additional functionality. All the while SysQue has decided to dive head first into creating native Revit families supplemented with the Revit API. Given my Revit experience I feel that SysQue is far closer to what I’d hoped for from the union of Autodesk and MAP.
Competition between the players helps drive the whole industry forward. I’m looking forward to seeing how both Autodesk and SysQue continue to work on providing tools to address design to construction workflow in on single Revit platform.
I’m confident that we’ll eventually have a single platform with a unified workflow that will unite the various engineers and contractors. Autodesk and the Revit development team in particular have always actively sought and listened to user comments. After all, there is still about a year to go before my imagined five year deadline.
