How to Use the Shell Command in Fusion 360 (The Right Way)

The Shell command in Fusion 360 is incredibly powerful. Whether you're designing complex shapes or creating custom holders for components, it gives you the ability to hollow out solid bodies quickly. But there are some key gotchas and features you should be aware of—especially when it comes to face selection and shell types.

Let’s break it all down so you can avoid the common pitfalls and unlock the full potential of this tool.

🔧 Where to Find the Shell Command

You’ll find the Shell command by going to the Modify menu and selecting Shell from the dropdown. You can also click it directly in the toolbar.

The first thing to know is that what you select first really matters.

🧱 Basic Use: Shelling a Body

If you don’t select any faces on the model but instead select the entire body from the browser, Fusion 360 will hollow out the model with the default thickness you specify.

• ✅ You can check the result in the timeline and confirm it using Section Analysis.
• ✅ The default behavior leaves all faces intact and removes material from the inside.

✂️ Removing Faces While Shelling

If you select one or more faces before running the Shell command, Fusion 360 will remove those faces and then shell the body from that opening using the thickness you’ve defined.

Example: Select the top face of a cube, set the shell thickness to 2mm, and the result is a hollow cube with an open top and 2mm wall thickness.

↕️ Shell Options: Inside, Outside, and Both

1. Inside Shell

• The outer dimensions of the part remain unchanged.
• The thickness is applied inward.
• Example: A 100mm cube shelled with 10mm retains its outer 100mm size.

2. Outside Shell

• Expands the object outward by the thickness value.
• Adds material externally to the original faces.

3. Both Sides

• Adds material both inside and outside.
• Example: 10mm added inside and 30mm outside creates a thick-walled design.

🎯 Bonus: Rounded Shells

When using the outside shell, you can enable Rounded Shell to automatically add fillets to the outer edges.

Great for smoothing out all the exposed corners in a single step. Fillets are only applied to faces that are not removed.

🌀 Multi-Step Shells for Advanced Geometry

You can break your shell operations into multiple steps to create more interesting and controlled designs.

1. Shell one section at 5mm.
2. Repeat the shell command and shell additional faces.

This gives you more flexibility than shelling everything all at once.

Tip: Changing the sequence of shelling steps will give you different results and can help build frame-like geometries or internal supports.

🧱 Post-Shell Edits with Press Pull

Although the Shell command applies a uniform thickness, you can override individual faces later using the Q (Press Pull) command.

• Be careful with the Offset setting—choose New Offset for best control.
• This is helpful when you want to reinforce a particular area of your design without affecting the rest of the geometry.

🛠️ Creating Custom Holders with Shell

Another powerful use case is creating holders or secondary components by copying and shelling a body.

In this example, we copy a camera body, paste it as a new body, and use it as the base for a custom-fit holder:

• Change the material appearance to help visualize parts.
• Use Split Face with a curved sketch to divide the body and isolate regions to shell.

👇 Pro Tip: Precision Selection

When selecting faces to remove, be sure to turn off Tangent Chain if you want finer control over face selection. This allows you to grab only what you need—like the top of a body—without accidentally grabbing surrounding geometry.

🧩 Designing a Pegboard Camera Mount

Using the split and shell technique, we can:

1. Split the copied camera body with a curvy sketch.
2. Shell only the upper faces to be removed.
3. Shell the bottom faces outward with a 2mm thickness to create a snug-fitting mount.

This ensures that your camera can drop into the holder with proper fit, accounting for any 3D print shrinkage.

✅ Final Thoughts

The Shell Command in Fusion 360 can do much more than just hollowing out cubes. When used well, it becomes a modeling superpower for creating enclosures, holders, and efficient internal structures.

Remember:

• Selecting faces changes everything.
• The order of operations matters.
• Use inside, outside, and both options to your advantage.
• Post-process thicknesses with Press Pull for extra control.