Combine, cut, and hollow out solids to turn raw blocks into finished enclosures.
Intermediate~10 min
1Experience
2Reflect
3Theorize
4Apply
Boolean Operations - Add, Remove, Intersect
When you create a new 3D feature on top of an existing solid, CAD asks: what should happen where they overlap? That answer is the boolean operation.
The Three Booleans
Join (Union)
Fuses two bodies into one. The classic "add material" operation - extrude a boss onto a plate and join.
Cut (Subtract)
Removes the overlapping volume. Every hole, pocket, and slot in CAD is a cut.
Intersect
Keeps ONLY the overlapping volume. Handy for carving a complex shape out of a simpler one.
Watch the preview: Most CAD programs show a color hint before you click OK - a plus symbol for join, a minus for cut. If it doesn't look right, switch operations before confirming.
Shell - Make It Hollow
The Shell tool takes a solid part and hollows it out to a given wall thickness. It's how every electronics enclosure, bottle cap, and robot housing gets made.
Shell Basics
Thickness: 1.5-2.5 mm is typical for 3D-printed enclosures.
Open faces: Select the face(s) you want to remove so the interior is accessible.
Inside vs outside: The wall can grow inward (keeps outside shape) or outward (grows the overall size).
Shell + Boolean Workflow
1
Build the Outer Form
Extrude, revolve, or loft the outside shape of your enclosure.
2
Shell It
Remove the top (or bottom) face and shell to 2 mm. Do this before fillets and chamfers.
3
Cut Holes & Slots
Add boolean cuts for ports, screw holes, and cable exits.
4
Join Internal Bosses
Extrude and join cylindrical bosses inside so screws have something to bite into.
Order of Operations
Boolean operations and shells are order sensitive. Doing them in the wrong sequence can ruin a model.
Golden Sequence
Build the base solid (extrude / revolve / loft)
Shell it
Use boolean cuts for holes and ports
Use boolean joins to add bosses, ribs, and clips
Pattern / mirror as needed
Fillets and chamfers last
Common mistake: Filleting internal corners before you shell. The shell operation follows those round corners inward and the walls get weirdly thin. Shell first, then fillet.
Pause and Reflect
✓ Your reflections are saved automatically
Apply What You Learned
Turn a solid block into a 3D-printable battery enclosure.
Start with a solid rectangular block sized for your battery
Use the Shell tool with the top face removed, 2 mm walls