Fidget Toy | Natalie Lin

I designed a print-in-place fidget toy in Fusion with two ways to interact: rotating a gear and pushing a slider. Both engage flexible springs to create tactile feedback.

Final design

The final version in use.

Top view of the final red fidget toy, showing the gear, slider, and springs — Top: the gear, slider, and springs.

Side view of the final red fidget toy — Side.

Underside of the final red fidget toy, showing the slider along the edge — Bottom: the revised slider and slot.

The slider teeth and slot are on the bottom side, so the teeth print directly from the build plate. That makes them cleaner and more robust than in Version 10, and the slider is easier to push.

Design iterations

Numbered prototypes arranged in order, from the first gear mechanisms to the final gear-and-slider toy — The full sequence of prototypes, arranged by version.

Versions 1–3: freeing the gear

In the first two versions, the 0.3 mm clearance between the gear and its central support was too small: the parts fused during printing. Adding chamfers in Version 2, shown in yellow, opened the gap slightly but still did not let the gear rotate.

After consulting a TA, I increased the clearance to 0.5 mm and widened the frame so it creates less pressure on the gear and spring since the corners are further from the center. Version 3 could rotate, but its small teeth barely deflected the spring.

Blue and yellow early prototypes viewed from above — Versions 1 and 2: the gear fused to its support.

Angled view of the blue and yellow prototypes, showing their gears and frames — Chamfers in Version 2 did not provide enough clearance.

Version 3 gear-and-spring prototypes with wider clearance — Version 3: the gear could turn, but contact with the spring was weak.

Version 4: bigger teeth

I enlarged the gear teeth and the spaces between them so that each tooth made better contact with the spring. This produced a louder click and a more distinct feel when turning the gear.

Three gear-and-spring prototypes, including Version 4 with larger gear teeth — Version 4: larger teeth with wider gaps between them.

Compare the gear–spring interaction in Versions 3 and 4

Version 3: rotation with limited spring deflection.

Version 4: a louder click.

The mechanism worked, but it still needed a larger redesign:

The gear could come off its support too easily.
The gear was too small to be satisfying.
Most of the toy was outer frame, so holding it and turning the gear was less comfortable.
The narrow spring was difficult to print cleanly; its first-layer lines could come loose.

Versions 5–6: big gear, big spring

I redesigned the toy around a larger gear and spring. In Version 5, I accidentally extruded the spring to the back-frame face instead of the gear face, so it was stuck. Its tip was also a bit too small. In Version 6 I fixed the extrusion and enlarged the tip, but too much: it was now so close to the gear and the outer frame that the gear wouldn’t move.

Version 5 with a larger gear and spring — Version 5: a larger mechanism, but the spring was stuck at the wrong extrusion depth.

Blue Version 6 prototype with an oversized spring tip — Version 6: the depth was corrected, but the oversized tip blocked the gear.

Versions 7–9: making room for the spring to flex

Reducing the spring tip in Version 7 helped, but the spring still hit the frame as the gear turned. Widening the frame to 20 mm in Version 8 made counterclockwise rotation smoother. Clockwise still caught. At 22 mm, in Version 9, both directions were smooth, though counterclockwise remained easier because of the spring’s orientation.

Orange Version 7 prototype with a smaller spring tip beneath the gear — Version 7: the smaller tip still needed more room to move inside the frame.

Compare spring movement in Versions 7, 8, and 9

Version 7: the spring catches on the frame.

Version 8: smoother counterclockwise rotation.

Version 9: smooth rotation in both directions.

Version 10: adding a slider

To add a second interaction, I introduced a toothed slider that engaged another spring. In Version 10, the teeth started partway up the print with nothing underneath them, so they came out messy and the slider was hard to push.

Fusion side view showing Version 10 slider teeth suspended above the build plane — Version 10's slider in Fusion: the teeth float in mid-air.

Version 10: the first combined gear-and-slider prototype.

What I learned

Getting the gear to turn and getting it to click were separate problems. Increasing clearance freed the gear, but tooth size and spring geometry determined the feedback. The spring also needed clearance throughout its motion, not just in its resting position.

The slider taught me that a part can look workable in CAD and still be hard to print.