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3D Printing in the Civil Space

Have you ever wanted to use Civil 3D to create 3D prints? Maybe you want to print out a physical representation of your proposal for the City? With Civil 3D and a 3D printer, you can bring your projects to life.

Some Civil 3D users may not know this, but Civil 3D has a 3D Modeling mode within it. This is used to turn your simple surface into a solid that you can print from, however, to get to this step, there are a few things you need to do first.

Note: I am using Meshmixer, a free Autodesk program highly recommended for all aspects of 3D printing. This tool can help us fix holes or do any extra 3D modeling to the print.

Prepare for Printing Inside Civil 3D

For this example, I am using a basic Surface, which was added to a pyramid created from grading tools. This is only done to add definition to the surface.

To make the curbs on the road more defined for the print, I exaggerate the Surface. If you use the default, the curbs will be almost flat when printed.

To exaggerate a Surface, simply right click on the Surface that will be created into a solid and Edit Surface Style inside your prospector tab.

Next, click on the Triangles tab and change Triangle display mode from “Use surface elevation” to “Exaggerate Elevation”. This helps bring out the curb details of the road to give it more volume and make it visible on the print. Experiment with this setting to get the desired definition for your print.

Keep in mind: Since I have a Pyramid to add definition, some pieces will be exaggerated. If this is not something you want, separate it from your surface and use a different setting for that piece.

Surface to Solid

When you find a good exaggeration for your model, (If needed; If no curbs are shown in your 3D model print, exaggeration may not be needed) it’s time to make a solid out of your surface. There are different ways this can be done. One method is exporting your Surface to LandXML format, and then opening that in 3DS Max. Not everyone has 3DS Max, so let’s discuss a workflow that uses only Civil 3D and Meshmixer.

To begin Select the surface that you want to 3d Print (Will need to select each surface individually if you have multiple surfaces) and on the ribbon you will have an option to “Extract from Surface” then “Extract Solids from Surface.”

Once in the Extract Solid from Surface dialog box, you MUST ad in vertical definition for your print to have thickness to it. Otherwise, it will not print correctly. I have found that a Depth of 5 works well for me.

Since I included an Exaggeration for the triangles in my solid, the solid will be sitting above my surface in Civil 3D. If done correctly, you should have something that looks like this in your drawing.

After turning your Surface into a solid, save this solid as an “.stl” format:

Click the big C in the top left, hover over Export and click “Other Formats”

A “Save As” dialog box will pop up.

Save as format: Lithography (.stl)  

Note: .stl format is what a 3D printer reads to print.

Then, it will ask you to select your solids. Window select over the surfaces you have made into a solid and hit Enter.

After selected and named appropriately, hit save. Now we move on to Meshmixer.

Inside MeshMixer

If you are confident your Civil 3D solid is 100% watertight, MeshMixer may not be needed. However, if your Solid that is imported from Civil 3D is not watertight, it may contain holes from combining multiple surfaces. MeshMixer finds and helps you repair those holes for a successful print.

Bonus: You can also add objects, smooth, and clean up your 3D model with Meshmixer.

Now, let’s quickly check our 3D model to ensure it is solid and watertight.

Open MeshMixer and select import, then, import the .STL file you created inside Civil 3D.

After importing, left click on “Analysis” then “Inspector”

I tend to use Minimal Fill with Small Thresh and hit Auto Repair All. Any minor holes in your solid should now be fixed.

From here, Export this newly-created model as STL Binary Format (.stl), then, import this STL into your favorite 3D print Slicer.

The 3D print Slicer has many settings that are specific to the type of print, which is too much to discuss in this blog. As a 3D printer enthusiast, I recommend the free program Ultimaker Cura, however, there are many options to choose from. If you are unsure, search for videos on 3D printer Slicer programs, or consult with ATG and we can help you make the right decision.

Conclusion

3D printing is still a new concept. At first it may seem a little pricey and difficult to learn, however, presenting a visual of a full site is impactful to a client. The ability to bring a 3D printed concept to a meeting can elevate your pitch and give you a selling point you need.

This blog is written by Technical Specialist Patrick Smith.

Behind the Blog: Meet Patrick Smith

Patrick has over three years AutoCAD/Civil 3D drafting experience. After high school, Patrick joined the military which landed him in Washington State.

He has a strong passion for the technology industry as a whole, an even greater love for the AEC industry, and is eager to help clients find the best solutions to their engineering needs.

In his spare time, Patrick enjoys building computers and solving general IT issues for friends and family.

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