Why 2D CAD is still important

3D is modeling, best for design, analysis, and product definition. 2D is drafting, best for fabrication, assembly, and construction. Cost differences are substantial.

For as long as CAD has been a commercial product, there have been both 2D and 3D. But for the last 20 years or so, the marketing messaging coming from most CAD companies and the surrounding technical press would make it seem as if 3D is the only technology that really matters. Autodesk makes no secret of wanting its customers to “move up” from AutoCAD to one of its 3D platforms. By revenue, the top CAD industry vendors all promote 3D design tools either exclusively or primarily.

But let’s set aside marketing buzz and the business models of the largest CAD vendors for a moment. In the real worlds of product development, manufacturing, and construction, there are still many more seats of 2D CAD software in use than 3D CAD. The world’s largest CAD vendor by revenue, Dassault Systemès, estimates that for every seat of 3D CAD software in use at a company, there are anywhere from four to ten seats of 2D CAD software supporting the same mission. The variation is primarily a matter of which industry: aerospace & defense use fewer 2D seats than automotive, which uses fewer 2D seats than construction. (Apparel doesn’t even use CAD, but that’s a discussion for another time.)

3D Seats in use at a typical company	If 4 2D users per 3D user	If 7 2D users per 3D user	If 10 2D users per 3D user
10	40	70	100
40	160	280	400
350	1400	2450	3500

Today’s reality in the CAD industry is a hybrid working arrangement, where 3D tools are for design exploration, simulation/analysis, and visualization; 2D tools are for communicating shop floor requirements, collaborating with suppliers, and supporting the workflow language of construction.

2D or .dwg?

To divide CAD into 2D and 3D is not the most accurate way to speak of capabilities. The de facto format for 2D CAD is .dwg, popularized by Autodesk AutoCAD but now reverse engineered by the Open Design Alliance (and others) with extreme fidelity to Autodesk’s proprietary version, and even extended with new capabilities not provided by Autodesk. .Dwg is capable of storing data in three dimensions, and most applications based on .dwg also offer 3D capabilities. And, from the other direction, 3D CAD products all have 2D drafting tools. A better way to talk about the division of labor in CAD would be to say Modeling (3D) and Drafting (2D). Most modeling occurs in proprietary formats; most drafting is done in the post-proprietary common data format of .dwg. (See also: .dwg is post-proprietary)

Modeling is the language of intent; drafting is the language of action. Generations of designers and craft professionals have agreed upon drafting standards that provide efficient communications to convey maximum information with precision. Everything needed to manufacture an item — from material to fit and tolerance — is efficiently communicated in drawings for internal use and for collaboration with supply chain partners.  

Modeling is an efficient process for creating a great design, especially when combined with simulation and analysis. Executing the design requires communicating more than look and feel and the confidence of having passed a finite element analysis. It requires detailed instructions on how to build the designed object, whether it is a fuel injector or a glass wall.

Any vendor who wants to “upgrade” users to all modeling software needs to have a sound answer for how to replace drawings. There are new tools for model-based definition and PMI (product manufacturing information) but their use requires significant workflow revision that many companies are reluctant to embrace. Interoperability becomes more important than ever in a switch away from drafting software to modeling software. Few engineering environments have only one CAD tool. The 3D model should always be fully accessible, should include 2D read/write, and offer full two-way synchronization.

Cost or cutting edge?

One aspect of the “2D or 3D?” discussion that often gets overlooked is cost. Drafting software is much less expensive than modeling software. Companies who find compelling technical reasons to switch to model-based product development are stopped in their tracks when they calculate the cost of moving. Autodesk AutoCAD LT is the primary CAD tool at many small manufacturers and construction firms. With the rise of sophistication in such products as Bricsys BricsCAD and Graebert Ares — both less expensive to own and maintain than AutoCAD LT — there is a strong pull to stick with a drawing-based engineering workflow.

The ratio of modeling to drafting is not likely to change substantially for many years. It would be more efficient for vendors to help customers find ways to support engineering digitalization without making “pure” modeling environments mandatory. But the vendors who specialize in 3D tools have no economic interest to do this; it is up to small vendors to seize the opportunity and create innovation within the drafting workflow.

Randall S. Newton in Managing Director of Consilia Vektor, and a contributing editor to Digital Engineering, Cadalyst, and AEC Magazine.