Joints and Export

Connect the eyelids with a joint, test the movement and export the parts for 3D printing

Join the eyelids

The two eyelids pivot around the same screw hole. A joint tells Fusion 360 how they’re allowed to move, so you can check they open and close without crashing into each other.

• As-built Joint - Click the ASSEMBLE toolbar menu, then As-built Joint. We use an as-built joint because the parts are already in the right place.
• Select the components - Click the Upper Eyelid, then the Lower Eyelid.
• Set the type - Choose Revolute as the joint type, so the parts can only rotate.
• Pick the axis - Click the edge of the screw hole in the hinge. The pivot is the centre of that hole.
• Click Ok - Click Ok to create the joint.

Test the movement

• Drive Joints - Right-click the joint in the browser (or the timeline) and choose Drive Joints, then type an angle such as -60 to watch the lower eyelid swing open.
• Animate - Right-click the joint again and choose Animate Joint to see it open and close on its own. Press Esc to stop.

If the eyelids hit each other, check the hinge dimensions in lesson 8.

Export the parts

Each eyelid is printed separately.

• Save As Mesh - In the browser, right-click the Upper Eyelid body and choose Save As Mesh.
• Choose STL - Set the format to STL and the refinement to High, then save.
• Repeat - Do the same for the Lower Eyelid.

Open the STL files in your slicer. Print each eyelid with its open side facing up so the dome doesn’t need support, and use an M2 screw (2mm, the size of our screw hole) as the hinge pin.

Check your understanding

Try it yourself

1. Add an eyeball: a 38mm sphere in its own component, centred on the origin, so it sits inside the eyelids.
2. Challenge: design a small arm on the lower eyelid that a servo horn can push, so one servo can blink the eye.

What’s next

• Watch the video at the start of the course to see the full mechanism with its servo
• Design a SMARS Robot in Fusion 360: more Fusion 360 practice
• Introduction to FreeCAD for Beginners: try a free, open-source CAD program

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