Keycap Stems

Every PolyKybd key needs a 3D-printed stem that carries its display and clicks into a transparent relegendable keycap cover. A full Split72 build takes 72 stems — 58× 1U and 14× 1.25U.

Tip

Resin (SLA) printing is strongly recommended. The stem’s MX cross and the pocket the display sits in are small features that FDM struggles to hold to tolerance.

Choosing a profile

The stems come in three profiles. They are interchangeable — the keyboard, plate and PCB are identical either way — so this is purely about how the keys feel under your fingers.

Flat

Every row identical: the R3 plates, 58× 1U and 14× 1.25U. The simplest to print and the simplest to source, since there is only one plate design per width.

Stepped

Rows are tilted rather than curved. Works best if the keyboard itself is inclined by 5 degrees or more — see tenting legs. There are two variations:

Sculpted (pictured above) — S1 on the front row, S5 on the back row, S on the three rows between:

Plate	1.25U	1U
S1 (front row)	4	10
S (middle three rows)	8	36
S5 (back row)	2	12

Uniform — the S plates everywhere, 58× 1U and 14× 1.25U:

A flatter feel, and like the flat profile it is a single plate design per width.

Curved

A different stem per row, R1 at the front through R5 at the back, so the rows follow a curve the way a sculpted keycap set does:

Plate	1.25U	1U
R1 (front row)	4	10
R2	4	12
R3	2	12
R4	2	12
R5 (back row)	2	12

Which files to print

The plates live in parts/export/keycap_stem/ in the hardware repo, named:

keycap_stem_revAlpha_<width>_<profile>_10p.stl

where width is 1U or 1U25 and profile is one of R1–R5, S1, S, S5. Each plate holds ten pieces, so divide a count from the tables above by ten and round up to know how many copies of that plate to print — e.g. curved needs one ..._1U25_R1_10p.stl plate (4 of its 10 pieces) and one ..._1U_R1_10p.stl plate.

Note

Always take the latest revision. revAlpha is current at the time of writing; the revision is engraved into every piece, so you can tell printed stems apart later.

Making your own profile

The stems are generated from OpenSCAD, not hand-modelled. The shape lives in one shared library, parts/keycap_stem/keycap_stem.scad, and each plate is a small file in parts/keycap_stem/variants/ that sets the two parameters that define a profile — the tilt angle and the extra_len that lifts the row:

include <../keycap_stem.scad>
ten_connected_pieces_1U(angle = 10, extra_len = 4, txt = str("5    ", revision));

So a new profile is a new file in that directory. Then:

parts/keycap_stem/build_stems.sh          # export every variant
parts/keycap_stem/build_stems.sh 1U_R2    # or just the ones matching

The script walks the variants directory and needs no editing. parts/README.md covers the rest, including the Noto font the engraved revision needs.