Expandable Collapsible Ball

A fun project that simply snaps together to create a ball (based on dodecahedron geometry) that will smoothly expand and collapse in a mesmerizing way. Enjoyable to use in your hands, and strong enough to even toss around.

All parts are designed so that they can be printed without supports or brim, and you'll need to print 60 arms, 20 three-way connectors, and 12 five-way connectors to assemble. The version shown in the pictures uses the 6 cm arms, which creates an expanded shape around 25 cm. But, additional arm lengths are also provided if you'd like a larger version.

Assembly Tips:

It took me about 30 minutes to assemble, and there are likely many ways to do it - but here's what I did:

#1: The top/bottom connector pieces are designed with a small snap-together locking mechanism, and therefore you simply need to place the arm pieces and then firmly squeeze the top and bottom piece together.

#2: Assemble all 20 sets of arms using the three-way connectors independently.

#3: Connect 5 of the assembled three-way sets together using a five-way connector. Importantly make sure that the five-way connector is facing in the opposite direction as the three-way connectors (i.e. if the smooth side of the three-way connectors are facing down, then the smooth side of the five-way connector should be facing up).

If you did it correctly, the full set of 15 arms should be able to fold together like is shown in the second picture below.

#4: Now the fun part! Work around the ball linking in the remaining three-way sets using the five-way connectors (making sure that the smooth-side of the five-way connectors are always facing towards the center of the ball). Although it may at first look complicated, really you're just creating a bunch of triangles - and so you'll find there's only one obvious way to join together each five-way joint.

I did the assembly with just my two hands, but it certainly may be easier if you can recruit a second set. You can work in any order, but here's a picture of what it look liked for me when I was part way through: