Learn SketchUp by Modeling DIY Lego Bricks

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When we got our first 3D printer at Clear Spring School, my students were excited about finding things on Thingiverse and printing out stuff, but after a while that’s about as exciting as watching an inkjet printer. I wanted them to design things of their own, using a basic CAD modeling tool.

As a woodworker, I’d been using SketchUp, so I devised these instructions for making a simple rectangular Lego-compatible brick. All the kids knew about Lego bricks and had played with them, and fitting one Lego to another presented a good test of the final outcome — a measurable result that could be felt in their own fingers, and that was directly related to their own experience.

One of the best things about the project was that the directions had to be followed to a T. Not all students, 5th grade through high school, were successful. Age seemed not to be the crucial factor.

Here are the instructions. They are long and they are hard, but they work. And unlike most learning where assessment is done by third parties, the assessment in this project is directly observed by the student.

Special thanks to my friend David Heim, author of SketchUp Success for Woodworkers, for helping me to clarify and refine these instructions.

Project Steps

Setting Up SketchUp

After opening SketchUp go to Preferences and under Templates, choose 3D Printing — Millimeters. It’s important to use this template because it will start you out with the right units of measure.

Now get to know the tools you will use in SketchUp: Select (Arrow cursor icon), Line (Pencil icon), Tape Measure, Circle, Push/Pull, Orbit, Pan (Hand icon), and Zoom (Magnifying glass icon). The Orbit tool allows you to rotate things for a different view, the Pan tool can drag things into a better view, and Zoom will shrink and enlarge the view as needed.

It is absolutely critical that you use the Measurements box in the lower right-hand corner of the SketchUp drawing environment. Using your keyboard to input the correct measurements is essential; without them, your Lego block will not fit other Lego blocks and will be misshapen and useless!

SketchUp is an X-Y-Z drawing environment and the three directions are represented by red, blue, and green lines. The blue line goes up and down, red runs left to right, and green runs front to back. When you use the Pencil tool to draw along one of these axes, your line will turn red, blue, or green only when it is directly following one of the three axes.

Design Your Brick

After you’ve played a bit in the SketchUp environment and have gotten to know how the tools work, follow these steps exactly:

1. Draw a line from left to right along the red axis and type the measurement 31.8mm to define the length, and press the Return key.

2. Draw a second line from the end of that one along the green axis, type the measurement 15.9mm, and press Return.

3. Draw the next line from the end of that one along the red axis and set distance 31.8 mm.

4. Draw a fourth line from that to finish the rectangle. Enter distance 15.9mm.

Make it 3D

5. Use the Push/Pull tool to pull up and expand the rectangle. Enter the dimension 11.49mm.

6. Now it’s time to put the Tape Measure tool to use. Hook the Tape Measure at one edge of the top rectangle and pull it across the length of the top surface to form a dotted line parallel to the edge. Enter the dimension 15.9mm.

7. Use the tape measure to form dotted lines 3.95mm out from each side of the rectangle.

8. Then use the tape measure to form dotted lines 3.95mm from the dotted line you formed front to back.

9. Erase the dotted line you drew at the center. Now where dotted lines intersect, you’ll have located the spots where the eight round nubs stick up on a standard Lego block.

10. Use the Circle tool to form the round nubs as follows: Put the Circle at the points where the lines cross and pull and click. Then enter the dimension 2.45mm. This will have to be done for all eight nubs.

11. When all the circles have been formed, use the Push/Pull tool to push down on the top of the block and enter the dimension 1.89mm. Voilà! You’ve formed the top of a Lego block.

12. Your measurement lines can now be erased so they don’t confuse the next steps. You can do this using the Eraser tool or by using the edit menu and clicking “delete guides.”

Form the Underside

13. It’s time to form the inside of the block. Use the Orbit tool to click and drag the screen to rotate the block so you can see the underside.

14. Use the tape measure to form dotted lines 1.5mm from each edge.

15. Use the Pencil to follow those dotted lines and connect them where they meet.

16. Use the Tape Measure to form dotted lines 7.95mm from each edge and one that matches the midpoint of the long edges. Where these lines intersect, use the Circle tool to make circles 3.225mm in radius, and then second circles within the first at 2.225mm.

17. Optional for added stability: From the center line that runs front to back, use the tape measure to make a dotted line on either side. Then use the pencil to follow each of those two dotted lines to connect the center cylinder to the sides.

18. At this point, all of the vital underside sections of the Lego block are outlined. Use the eraser to remove the lines where they cross the circles at the center of the block.

19. Now the fun begins again. Use the Push/Pull tool to push down in the various sections on the inside of the block. For each section enter the dimension 8.6mm.

TIP: After using the Push/Pull tool, double click on the next section to get it to conform automatically to the last section. This will eliminate having to type in the dimension each time.

20. Now you’ll want to save your block as a Component, so you can add embellishments and still have access to the base shape.

Conclusion

If you got it all done right, your block can now be 3D printed. You can personalize it by putting your name or logo on it before you export an STL file for printing.

Once you’ve successfully printed this basic model, you can modify it to design all kinds of new bricks, or to design Lego-compatible parts for your other projects — electronics enclosures, robot parts, decorative items, etc. — that will snap into your existing Lego brick systems.