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Goings on at the Because We Cannery

Revit to CNC process recap

So we get designers asking us sometimes about how we work with Revit and CNC tools together. Or they say that they tried doing it, and didn't have it really work out very efficiently. They wonder what special tool or bit of software we're using that makes it work.

Well, it's not about technology or tools. It's about people and process. We here at BWC have worked out a process that allows us to quickly and efficiently go from a BIM model in Revit to CNC-produced physical elements.

The thing that most designers don't understand about a CNC workflow is the CAM software, isolation of elements for export, and general fabrication and modeling methods and limitations. It's all about the process in how you use these tools, and how you link them together, than in the tools themselves.

Having decent CAM software is a big part of this being successful. We use something called Aspire from Vectric, and we love it. It's great for three-axis work, which is what our CNC router is. We're not simply dumping out whole messes of models and feeding it to the CNC machine directly as if it was a 3D printer, we're exporting discrete elements from Revit, importing them into the CAM software, setting up the jobs within the CAM software, and then running those jobs on the CNC.

So we model things in Revit in a way where we can easily separate out all the bits. Good families, view templates, sections in families, lots of isolated 3D views, and more go a long ways to making this work. By exporting clean 2D sections of flat parts as DWG/DXFs, or 3D solids as DWG/DXF/SAT files, you can import those parts into CAM software for proper toolpathing.

We also at times use Revit families as a placeholder for a more complex model, or sometimes have a simpler representation in Revit of something we know we'll add more details to in the CAM software. For example, we might start with a solid in Revit, export that to Blender, manipulate it further, and then bring that into the CAM software. Or we might simply have two solids overlap in Revit, and within the CAM software we'll insert in the vectors requred for toolpathing the proper joint.

The final thing really is that we know how things go together. We know fabrication and construction, and a lot of Architects and designers simply don't really know how to build things. A huge part of making the CNC work is the actual craft of the thing, understanding tolerances and material strengths and weights and joinery details.

So it's really a whole process, not just a single tool or bit of software that makes it work. I'll be talking about this at the upcoming TAP pre-AIA conference, and I'm hoping to talk more about this at AU this year. With an actual demo of making something via a CNC or laser cutter on the spot if they will let me!

Also, if you are an Architect or Designer looking to go from Revit BIM models to CAM software and CNC production, well, give us a call. We love to help people out, and we're fast and reasonably priced, as well as being fun to work with! We've helped a number of designers as CNC consultants with modeling, toolpathing, and actual production and fabrication of their ideas, and we've got a proven track record of using BIM and CNC together.

Jeffrey McGrew