WARNING: CHOKING HAZARD - SMALL PARTS!

NOTE _ This model is for reference ONLY - Please use updated version: https://www.printables.com/model/1129004-3-ring-hoberman-sphere-v20 - The instructions are the same for the newer model, the parts just look a bit different.

This is 100% PRINTABLE - NO glue, screws, or pieces of filament used as hinging.  The four-way connectors simply snap together, which in hindsight can be troublesome if you messed up and you need to pull them apart (it can be done with difficulty and minimal damage to the parts if you're careful).  It helps to ‘dry fit’ the segments before you snap them together.  Check twice, snap once.

The finished product is a bit fragile - it does work, but I recommend not fully opening it as it can be a bit difficult to close.  You can expand by pulling the opposing squares apart and contract if you separate the sets of squares on opposite sides and push gently together.  With PLA it seems to move better after a while playing with it.

I used different colors for the different link types mostly to make assembling easier, and because it looks cooler.

SLICING / PRINTING

You will need to print:

Qty. 48: Big+Link(F)

Qty. 24: Big+Link(M-L)

Qty. 24: Big+Link(M-R+Stopper)

Qty. 36: Square_Base

Qty. 36: Square_Cap

Layer Height: 0.1mm
First Layer Height: 0.15mm
Perimeters: 6
Solid layers (top and bottom): 5
Infill: 100%
Infill pattern: Rectilinear
Skirt/Brim/Raft: No
Generate Support Material: Yes
Support Material Style: Grid
Auto Generate Supports: No
First Layer Expansion: 1.0mm (brim around support material)
Patience Level: Extreme

I printed in PLA, 'cause that's all I have, but if you have PETG or something stronger, I'd use that.

The links will need to be printed on edge with custom supports - if they are printed flat, the support material roughs up the sides and it will not move easily.  See the pic above on how to support it, or just use the provided 3mf or bgcode.  I do recommend printing 3 or 4 extra of each link, as some parts may break during assembly (*EDIT* the newer V2.0 model is much stronger, but includes extra parts just in case).  The square connectors/caps can be printed flat with no brim or support.

ASSEMBLY

Start by assembling sections comprised of 4 links: two Big+Link(F), one Big+Link(M-L) and one Big+Link(M-R+Stopper), as shown in the above pic.  Assemble the sphere as shown - each section is then connected with TWO square connectors and caps - one on the top and one on the bottom.  The outer square lid is facing out, the inner square lid is facing in (see pics).  Insert the link pins fully in the square, then place the cap on top and squeeze together with pliers.

I hope that this is as satisfying for you as it is for me.  If anyone has improvements on this, by all means share them.  I am proud to share this with the 3d printing community free of charge, but please drop a like to boost my Prusameters!

I will edit this as needed.  Best of luck!  Have fun!

From the cave,

TroggPrinter