Bendy SAO

Once the components were attached to the boards, the two layers of boards had to be sandwiched together with the spring contacts pressing against the circular solder pads. 

A push rivet goes through the corresponding holes in the two layers to align them and allow them to pivot. The push rivet needs to be the correct height to hold the layers against each other firmly so they don't separate, but aren't too close either. A buffer layer sits in the middle of the opposing PCBs so that the spring contacts aren't crushed. The working height of the spring contacts is about 1.8 mm, so I used 1.6mm laser cut acrylic to create a buffer layer in a shape that doesn't overlap the components. In addition, male header pins hold opposing components together, so I needed to find male header pins with an insulation layer no more than 1.6 mm thick. I found these at DIgiKey.

Prototype boards came back from JLC, The side-emitting LEDs have tiny solder pads, so I ordered stencils along with the boards for the first time. Amazingly, the solder paste stenciling and SMT soldering worked quite well for the first few boards, and I seem to have routed all the connections correctly. I haven't used these specific LEDs before, but I like the way the attached lens diffuses the light.

Submitted prototype (and possibly final as I doubt there will be enough time for iteration) designs to JLC PCB for 6 different boards (front base, front middle, front top, back base, back middle, back top) to comprise a bendy assembly. Working under a time crunch, I'm focusing on keeping things as simple as possible, so I added pads to mount a XIAO 2040 (only $3!) on the front base, to easily program patterns on the LEDs in CircuitPython. The image below shows two columns of boards, with front layer on left and back layer on right. Each column contains one base, two middle and one top board.