C128 keyboard plungers

I needed a bunch of keyboard plungers to fix up an old “flat” Commodore 128, so I went looking for something suitable.  Turns out there are at least TWO variations of the “flat” C128 keyboard assembly.

While searching, I found these two projects:

https://www.printables.com/model/934528-commodore-128-keyboard-plungers

https://www.thingiverse.com/thing:5173434

However, both have minor printability issues, and they could be a bit higher-resolution.  Plus I wasn't sure what goes to what.  So since I have both keyboard variants, I decided to rip both apart and make my own!  

One variation has white plungers for the top row of keys, and green plungers of a slightly different design for the rest of the keys.  On my keyboard, there really aren't any identifying marks on the back/outside, but on the top/inside of the PCB is the legend “Mitsumi C-128 56 3090”.

The other variation has blue plungers with slightly longer stems for the top row, and black, longer plungers for the rest of the keys.  On mine, one identifier might be the small amount of PCB that's missing from each front corner.  There are allso a few ceramic capacitors on the back/outside, in the 10-key area.  On the top/inside of the PCB is the legend “Mitsumi C-128F 56 7565” next to the hole for the Caps-lock key, and the legend “TW-15 94HB” over by the 10-key pad.

As far as I can tell, they need to be paired blue with black, and green with white, otherwise you may end up with some keys having different resting heights from the others.

You will of course need to salvage the conductive rubber bit from the plungers you're replacing.  They just twist on/off with tweezers, but gentle, they're round about 30 years old now.

Use 0.1 mm layer height, set your perimeter line width to 0.4 mm, and enable “thin wall” or “single wall” mode in your slicer.  You will need decent bridging performance, a well-calibrated first layer position/Z offset/height, and most importantly, well-calibrated flow and positioning since these are high precision parts.

0.4 mm nozzle or smaller, no supports required.

Filaments used:  Atomic PETG in black, white, RepRap Green, and Baby Blue.

Notes:

These plungers are meant to fit fairly tight.  If you find you can't push the keycap in at all, check that you aren't over-extruding, and check that the keycap's little stem on the underside isn't all mangled.  

Also, regarding the descriptions/“part numbers” above, I had to guess at things a bit, so cannot guarantee that that info holds true for every keyboard out there.  When in doubt, defer to the plungers' colors.

Credits:

I do not consider this project to be a derivative of either of the ones linked above, as I had to redo everything from scratch, apart from taking a handful of measurements and positioning references from those models.  Still, you can call this one… “inspired" by those two.