How To Design a 3D Model for MakerBot Printing with Google SketchUp

By Matthew Braga

Here's how to turn your original creation into a tangible piece of printed plastic art.

Most weeks, our famed MakerBot printouts are culled from a handy website called Thingiverse. It's here that members of the CNC community can submit pre-made models for anyone to print — and if some of our past videos are any indication, there are some very good ones available too. But while it's easy to print someone else's creation, there's something to be said for designing one yourself. There's a sense of accomplishment that you just don't get by mashing "print" on a pre-made design.

Today, we're going to use a free piece of software called Google SketchUp to make a simple 3D model, and show you how to turn your creation into a tangible piece of printed plastic art. There are some caveats, of course — some objects and designs are simply impossible to print — but we'll make sure you come away with something awesome for your effort.

After all, if you make something especially cool, we could print it on a future episode of the MakerBot Mystery Build!

Getting Started

Earlier this week we introduced you to a couple of 3D modelling applications, many of them free. However, this particular guide will focus on Google SketchUp. It's the easiest to acquire and learn, and is available for both Mac and PC. You're free to use competing and more complex suites, of course — such as Blender, Maya or even 3DS Max — but the process will most likely differ.

Things to download:

Choosing a design

The simplest design to start with is a logo or symbol, with parts that can be extruded — or in other words, raised to create an object with three-dimensional depth. Just remember, you only have a single color, so you'll have to find something with distinct or separated edges, and/or easily recognizable features that will stand out when printed.

Once you've settled on an idea or design, you have two options. Simpler designs can simply be imported as a raster image into SketchUp, where you can then trace over lines and shapes to create a digital copy. However, this can take a great deal of time, especially with SketchUp's limited drawing tools, and is entirely impractical for more complex designs. Thus, your second option is to create a vector image using either Adobe Illustrator or the freeware Inkscape, and import your design into SketchUp in a format the software can understand.

Luckily, both Illustrator and Inkscape have built-in tools to convert raster images or bitmaps into vector images for us to work with. In fact, we've even covered the process before. However, you can also trace your own paths over the image manually for more refined or precise results (for those of you new to the pen tool, read this).

For this particular example, we'll use the Blu team logo from Team Fortress 2 (vector image via DeviantART user CartmanPT). This is an image with simple shapes, and a relatively small number of curves, which should make it ideal for 3D printing. As you can see in the above example, we've modified the image so that only the shapes (or faces) we want to extrude are visible.

Finally, we're going to export our finalized vector as a SketchUp-friendly DWG. This is a format that stores 2D and 3D drawing data for use in AutoCAD applications. Simply accept all prompts and default settings, if any.

Moving To SketchUp

The free version Google SketchUp 8 only supports a limited number of formats, and AutoCAD files — such as *.DWGs — aren't included. But there is a workaround. By downloading the previous version of Google SketchUp, Version 7.1, and an additional plug-in from Google, we can get what is now a Pro-only feature for free instead.

Upon opening SketchUp for the first time, feel free to acquaint yourself with some of the tips and tutorial videos until you're comfortable with the software. You don't need to learn much for the purpose of this article, but the basics are useful if you've never used a 3D modelling suite in the past. SketchUp will also ask you to select a template before continuing. For our purposes, "Product Design and Woodworking (millimeters)" is ideal.

After importing your finished vector into SketchUp, we'll need to make a few tweaks. For example, the conversion process has stripped our design of its faces, leaving a wireframe outline that is unfit for printing. We need to get those faces back. Luckily, the restoration process is simple.

First, draw a rectangle that surrounds your entire object, preferably centered. Now select everything on the screen, and navigate to Edit > Entities > Explode. This will ensure the paths of our vector image are cleaned up and ready for extrusion. If the option is greyed out, don't worry — your vector is already fine. Next, with everything still selected, choose Edit > Entities > Intersect With Model. By merging our outline with the rectangle we've just created, we've easily restored our design's missing faces.

This is how our image looks when imported into SketchUp — outlines only.

At this point, you can either delete the rectangle, or retain it as a backing panel — recommended if you have multiple faces/objects that aren't connected to one another, as in our Team Fortress 2 example.

Introducing The Third Dimension

Finally, we're going to extrude our 2D vector image into a 3D model ready for printing. Using the Push/Pull tool from the Tools menu, gently extrude your object's face upwards until you're satisfied with the height. This may be difficult to do for the default perspective, so feel free to change camera angles as required (from the Camera menu).

If you have other faces that also need to be extruded, such as in our example, you can double click on them with the Push/Pull tool, and they will match the first face's height (you can't actually select and extrude multiple faces at once). Finally, if you chose to retain a backing plate, feel free to extrude this by a small amount, relative to your raised faces. This extra depth is necessary to give the MakerBot a base on which to print.

By this point, we should now have a working 3D model with which to print. But we're not quite done yet. We need to export our Google SketchUp model into yet another file format which your MakerBot or CNC machine will understand — specifically, an *.STL. This format isn't natively supported by Google's app, however, so you'll need to install one additional plugin, found here.

You can now export your finished model using the "Export to DXF or STL" option found under the Tools menu — and remember to choose *.STL from the drop-down.

Making MakerBot Magic

You should be left with an .STL file that can be imported into your MakerBot or CNC machine's printing software — in our case, ReplicatorG. This application will take your 3D model, and convert it into something called G-Code, which is essentially a series of coordinates necessary for the printing to take place. It is here that your model is separated into so-called slices, to be printed one layer at a time.

You'll have the chance to see one final 3D rendering of your model before printing begins. This is important, as there's a good chance your model might not be scaled or positioned properly for printing. Feel free to adjust your object's placement as required. At this print, you can finally hit print, cross your fingers, and wait.

It's a long process — we've gone from Illustrator/Inkscape, to SketchUp and now to ReplicatorG — but we promise the end result will be something entirely cool, and totally yours. You can even post your finished creation to Thingiverse for others to use, even if you don't have a MakerBot or CNC machine of your own.

And if it's really impressive, you never know — we might just print it!