Any report about the digital exchange of computer-aided drafting to computer-aided manufacturing must begin with a review of building information modeling and its role in the process.

In the late 1980s, when computer-aided design software arrived on the market, many North American sheet metal contractors adopted it quickly and were soon using it to perform what they referred to as “collision checking,” “3-D modeling,” “3-D spatial coordination” and “CAD/CAM direct downloading.”

Around 2005, European construction professionals introduced the concept of “building information modeling” to North America. The practices it delineated were well known within the sheet metal industry: they’d been working that way for years.

Top-tier sheet metal contractors have created virtual CAD models of HVAC systems and downloaded these fabrication-readied models directly to a CAM software application. This practice is a building information modeling-compliant exchange of digital data. Because this exchange eliminates redrawing or re-inputting data, every step adds value, which is a core tenet of BIM. In the same way, contractors who use a 3-D HVAC model to coordinate with other trades are also engaging in a BIM-compliant exchange. Both forms of data exchange, the basis of many firms’ workflows, demonstrate the commitment and degree of participation that these contractors have long brought to projects, practices that are now called BIM.  

Yet many outside the HVAC industry don’t see it that way. An alternative view is that there is only one BIM-compliant workflow, and it originates and finishes inside an architectural-based software tool named Revit MEP. Some stakeholders go so far as to say that if a project is not modeled, coordinated and fabricated in Revit, it is not BIM compliant. That is a questionable assertion, yet many believe it to be true. Many BIM managers find that the tool-focused view of BIM reflects a lack of knowledge about what adds value to the sheet metal process and what does and does not contribute to an efficient workflow. 

Not an app, not a tool

BIM is neither a software application nor a specific software tool. BIM is a mindset, a method for eliminating waste that requires collaboration between project stakeholders. BIM uses many tools and many different processes that include any form of data exchange. What is important is that software tools and construction practices focus on efficiencies to deliver real value.

The speed at which new technologies are entering the industry is accelerating. Recently, a new direct-download option has been introduced into the market and runs as a plug-in inside Revit MEP. As early adopters engage, test and implement this tool (and perhaps other Revit MEP CAD-to-CAM direct-download tools that are expected to be released soon) they each should judge these tools on their capabilities, return on investment, efficiencies gained and value provided.  Each CAD-to-CAM tool should be evaluated on the merits of what it offers, not on the platform it runs on.  

BIM managers offered great insight into how BIM is used and perceived in the sheet metal industry. The point that emerged was the common belief that although each company uses a different software publisher for its CAD and CAM work and direct download, they achieve similar results. Several other common observations emerged from the interviews.

First, these professionals represent a domain that must deliver a finished product.  As of spring 2014, many felt that Revit MEP does not support the basic requirements of an HVAC contractor. They do believe that the chasm that exists today between the MEP design team software and the contractor’s software is moving in the right direction. In order to complete contract obligations, they require CAD-to-CAM products that provide an interoperable, efficient and effective workflow from their duct-design CAD to CAM manufacturing and installation.


This is the criterion by which the industry should judge a Revit-only MEP workflow. This is also the reason why these contractors continue to rely on the software they’ve been using for the past 25 years. They do not believe they have other options, but as mentioned earlier, new technologies are entering the market every month.   

The BIM managers interviewed all download and use their models for spatial coordination in companies that have been practicing direct download for more than 25 years. There remain many contractors that do not download CAD model data to their CAM software for their cutting tables, preferring instead to re-input the data from their virtual model. Eventually though, these contractors will not be able to keep up with their competitors, who use direct downloading to be more efficient and less expensive.  

Similar to the connectivity between duct design and the manufacturing phase of a project, sheet metal contractors continue to hope for the same connectivity between the duct-design tools and their estimating software. There are a number of duct-design products used such as PractiCAD, QuickPen, Autodesk and EastCoast that connect to either their own or some other software publisher’s estimating product, each providing varied levels of integration and success.

These top-tier firms, which have completely different approaches and software tools, believe that they achieve the same results regardless of which software tools they use. What makes the difference is having the right person in charge, someone who accepts change and does whatever it takes to make the tool work within the process flow.  Another important factor is the willingness of every team member (CAD and CAM operators) to wholeheartedly participate in making the change and becoming competent users of both software types.  

BIM pushes more expense and cost to the front of the construction project than it did in years past. However, those costs are recovered when a firm engages in pre-fabrication and direct downloading to the shop and the CAM operator, particularly because of the savings from pre-fabrication and just-in-time delivery of materials to the site. 


Everyone on the team must pay attention and be willing to speak with senior management when it becomes apparent that the project is not being managed properly; avoiding a free-for-all is critical. Success often comes down to the experience of both the construction manager and the BIM manager, who are responsible for how well — or how poorly — a BIM construction project is managed.

Order of precedence needs to be established, especially when adding a new software project management tool. For example, adding a tool such as Autodesk’s BIM 360 Glue into the mix and failing to define and set rules and order of precedence creates havoc and disorder. 

When BIM is implemented properly, owners and all project participants really like it. All four managers interviewed would choose to work within a BIM-managed project because of the greater potential for success. In keeping with the basic practices of a BIM project, all would like access to the MEP design model much earlier in the cycle than is currently the case on most projects. When the design model is available before coordination begins, these managers report a higher degree of project success. 

Lastly, to be successful with BIM, sheet metal contractors need to be prepared to invest heavily in resources and expertise. Firms need to ensure that their key CAD and CAM professionals become experts at the software they use. Nothing is more important.

David E. Quigley is the author of Achieving Spatial Coordination Through BIM: A Guide for Specialty Contractors and is managing director of Emerson Research and Construction Services. Contact him at or (603) 672-7880. Article contributors included Andy C. Roy of R.F. Knox Co. Inc., Sean Lauck of HPE Inc., Steve Hunt of Dee Cramer Inc., and Bill Parent from Bonland Industries.