Making LEGO Assemblies in Fusion 360

Hello, my name is Chase Kahn and I am an industrial design student at Rochester Institute of Technology.

Here is the assembly I made for a LEGO sewing machine. I modeled the bricks and turned them into a complete assembly in Fusion 360.

This tutorial is written to help you assemble bricks you already have modeled. To model bricks, you can measure physical pieces by hand using calipers and then create them individually using Fusion 360, or you can make one brick that can change width, length, and height using parameters, and create many bricks using that one file as the base. Here is a useful tutorial for modeling a parametric LEGO brick.

Regardless of how you model your bricks, it is important the you use the shell command to shell the bottom face of your brick to an inside thickness of 1.6mm. This will give you small circular indents on the underside of your brick face, which are important for the following steps.

You will need to apply this step to each of your individual brick files before we begin the assembly.

Click Create Sketch in the Fusion 360 Solid Modeling menu.

When prompted to pick a plane to put the sketch on, select the bottom edge face of the brick.

From within your sketch, hit the P Key, or expand the Create Menu to activate the Project Command.

Select all of the circles on the underside of the brick. Make sure not to click the face by accident! If you do it correctly, the bottom right corner of your screen should say "x edges." If you have selected a point or face by mistake, it will say "multiple selections" instead. The number of circles or "edges" you select depends on the size of your brick. In the screenshot, I have 8 because I am using a 2x4 brick.

After selecting the circles, click OK in the projection command, and then click Finish Sketch. You should now see your circles projected onto the bottom plane of your brick. Save your file.

Repeat steps 2 and 3 for all of your bricks before continuing to step 4.

If a piece doesn't have studs to project circles from (eg, a flat tile), you can sketch the correctly placed circles manually using the following dimensions:

• Circle Diameter: 2.4mm
• Circle Distance from Inner Wall: 2.7mm
• Circle Distance from Each Other: 8mm center to center

Before beginning your assembly, it is a good idea to know what you want your final LEGO build to look like. You can do this by physically assembling LEGO bricks you own, or by using a program like Stud.io to mock it up virtually using their library of parts. Here is the Stud.io mock up I made of a sewing machine.

Go to File > New Design. Save your new file and name it.

Go to your file viewer, and right click on the first piece you want to insert, then select Insert Into Current Design. The Move/Copy menu will appear, select OK.

You need to Ground this component so it will not move as you build your assembly on top of it. Click the arrow in the browser to expand the features of your inserted piece. Right click on component and select Ground. While you have this menu open, it is a good idea to turn off the origin of the piece using the eyeball icon next to the word origin.

Use the insert command as described in Step 5 to add the next piece of your build to the assembly. Before clicking OK, use the arrows and dials on the piece to rotate it into roughly the orientation you want it to be and move it out of the space of the previous bricks. Then I recommend turning off the origin of your components as soon as you insert them to avoid confusion.

If you have more than one piece in your first layer, you need to attach them together using a rigid joint.

Select the one of faces you want to become adjacent, then while holding the Shift key, select the other face.

Click the Joint Icon in the Assemble menu.

Repeat this process until all of your first layer of bricks have been joined face-to-face.

Now we get to the exciting part! We will begin adding the second layer of bricks to your assembly. From this point forward, we are no longer using joints between faces. We will instead join between specific edges to achieve the snap-fit that LEGO is known for.

Use the insert command to add your next piece to the assembly.

Select the edge at the base of the stud you want to join from Component A, then while holding Shift, select the projected circle from Component B that you want to meet the stud.

Click the Joint Icon in the Assemble menu.

After joining a component to the component under it, I recommend expanding the component menu in the browser and turning off both the Origin and the Sketches, to keep them from blocking your view as you continue to add more pieces that all have their own Origins and Sketches.

Continue using the combination of one base edge of the stud and one projected circle to join your bricks directly to the bricks underneath them. You can even get fancy and use circle and irregular tiles, as long as they have the circles on the bottom plane (see Step 4).

You can use this joint technique to make all kinds of LEGO assemblies using Fusion 360! Feel free to comment assemblies you've made using this method! Maybe in my next Instructable, I'll cover moving joints :D