Utah Engineers Journal 2021 Issue

62 Adding “Depth” to Civil Designs With 3D Printing ASCE I n the last five years or so, you’ve probably come across a new and exciting technology known as “3D printing.” It might surprise you to learn that 3D printing has existed in some form for around 30 years. Beginning in 2002, some of the earliest 3D printing patents began to expire. With the expiration of these patents and advances in the production of low-cost, easily programmed microcontrollers, 3D printing has exploded in popularity. Hopefully, this article will give you a glimpse of how this exciting technology can add a new “dimension” to our civil engineering designs and provide additional value to our clients and communities. What is “3D Printing”? 3D Printing is a form of additive manufacturing where a three-dimensional object is built up one thin layer at a time. Many different processes and technologies for 3D printing exist. These processes are defined in ISO/ASTM 52900, but some of the most common include: • Material Extrusion (Fused Deposition Modelling (FDM)): Material is selectively dispensed through a nozzle or orifice. • Vat Polymerization (SLA and DLP): Liquid photopolymer in a vat is selectively cured by UV light • Powder Bed Fusion (SLS, DMLS and SLM): A high-energy source selectively fuses powder particles. 1 The most commonly available “consumer” 3D printer models are material extrusion models. If you’ve never seen one of these machines in action, picture a hot glue gun mounted on an old pen plotter. Now imagine that the glue gun “pen” (extruder) draws an object layer by squirting glue onto the paper (build surface). When one layer is drawn, the pen raises up (or paper lowers down) by the thickness of one layer and begins drawing another layer on top of the previous layer. The printer then repeats this process until all the object’s layers have been drawn, resulting in a 3D object. A simple search for “3D printing time-lapse” will reveal hundreds of videos illustrating the process. Here are a couple of videos: • 3D printed Eiffel tower time lapse 2 • Baby Groot - 3D Printing Time Lapse 3 3D CAD Revolution Along with the explosion in 3D printing, the last 10 to 15 years have seen significant advances in the realm of computer-aided design (CAD). With CAD software tools like Autodesk’s Civil 3D and Revit and Bentley’s InRoads and OpenRoads Designer, our industry has seen an increasing shift to 3D design for buildings, roadways, bridges, pipe networks, earthworks and more. It’s not hard to imagine a future where two-dimensional plan sheets — paper or electronic — are obsolete and replaced with 3D interactive models of our designs. In fact, there are organizations such as the Utah Department of Transportation (UDOT) that are actively pursuing initiatives to transition away from 2D deliverables such as paper plan sets. See UDOT’s Digital Delivery Website 4 or refer to UDOT’s March 2017 Intelligent Design and Construction Guidance document. 5 It is one thing to show clients or the public a realistic 3D rendering of your latest design in a video clip or simulation. However, sometimes it helps to sit around a table and point to a physical plan or model to collaborate effectively and communicate design intent or potential concerns. Relatively easily, we can now combine our 3D CAD designs with 3D printing to produce physical models. From 3D CAD to 3D Print Your CAD software handles the conversion from CAD format to a printer spool file that your inkjet or laser printer can print. However, most currently available 3D printers and 3D printing service providers require you to convert a 3D model to a specific type of file called a Stereolithography (STL) file. The STL file is currently the 3D printing industry standard for distributing 3D printable files. 3D Printers and printing service providers take the STL file and run the file through a “slicing” process where the model is broken down into the individual layers that will be printed and combined into the final 3D print. Because every printer handles the actual slicing process slightly differently, we will limit our discussion to how to create an STL file from a 3D CAD model. Also, while several CAD software packages can generate 3D designs, we will focus on using Civil 3D. It is currently the most popular civil design CAD software on the market. Clint Merrell