Imported from GitHub: MabezDev/mkey · commit ad1fd74 · license Apache-2.0

Description

A mechanical keyboard based on an ESP32-S3

README

mKey Case — 3D Printing Build Guide

Prerequisites

• OpenSCAD (CLI must be in $PATH)

Quick Start

Export print-ready STLs for 3D printing:

cd 3d/case
./build_stl.sh

This produces mkey_tray.stl and mkey_overlay.stl in the current directory, oriented for optimal printing (overlay flipped cosmetic-face-down, tray bottom-down). Add supports in your slicer (Lychee, ChiTuBox, etc.).

[!NOTE] Run ./build_stl.sh after every parameter or geometry change. The build verifies that all assertions pass and that CGAL produces a valid mesh at production $fn. A clean OpenSCAD preview at low $fn does not guarantee a clean export — some CGAL errors only surface at $fn=128.

Build Options

Flag	Description
--piece tray|overlay|both	Which piece(s) to export (default: both)
--fn N	Circle resolution override (default: 128; file preview default is 48)
--outdir DIR	Output directory (default: .)

Print Orientation

The build script sets PRINT_MODE=true, which transforms the parts for optimal 3D printing:

• Overlay: The 5-degree wedge tilt is removed so the part lies perfectly flat. The cosmetic face (key openings / display window) is flipped down toward the build plate — this gives the best surface finish on both SLA resin and FDM.

• Tray: Printed bottom-down (the bottom is already flat at Z=0). Add supports in the slicer — place them on outer walls and bottom only, not inside the cavity.

Design Parameters (case.scad)

The main toggles in case.scad control which features are included:

Toggle	Default	Purpose
SHOW_TRAY	true	Render the tray (bottom + walls)
SHOW_OVERLAY	true	Render the overlay (top surface)
PRINT_MODE	false	Re-orient pieces for 3D print export
ENABLE_OVERLAY_RABBET	true	Locating tongue/recess for X/Y registration
ENABLE_MAGNET_POCKETS	true	Blind magnet pockets for overlay hold-down
ENABLE_SCREW_INSERTS	false	M1.4 bolt + glued hex nut overlay retention (mutually exclusive with magnets)
ENABLE_DECORATIVE_TRIMS	true	Debossed logos, pinstripe, initials

JLC3DP SLA submission notes

[!IMPORTANT] X-AXIS SCALE COMPENSATION IS A HARD BUILD GATE. Do not upload the STLs unless you have pasted the full order-note block below into the JLC3DP manufacturer-instructions field AND confirmed on the pre-build screenshot that JLC3DP applied the compensation on both pieces. Skipping this does not produce a looser fit — it produces parts that physically cannot assemble. The plate PCB is fabricated and frozen at its true size; the printed case without X-scale comp drifts up to ±1.09 mm over the 363 mm case length, which blows past every outer tolerance budget in the design (slot play, USB cheek, magnet margins).

The geometry has belt-and-braces room for ±0.3 mm of residual post- compensation drift, not the raw ±1.09 mm uncompensated drift.

Paste the following instructions into the JLC3DP order-note / manufacturer- instructions field when uploading mkey_tray.stl and mkey_overlay.stl. Missing any of these will compromise fit or finish.

Two-piece keyboard case, SLA standard resin.

MANDATORY — X-AXIS SCALE COMPENSATION ON BOTH PIECES: Apply JLC3DP's per-batch X-axis scale compensation on BOTH mkey_tray.stl and mkey_overlay.stl. The case is 363 mm long and mates to a pre-fabricated FR4 PCB at tab positions spanning the full length; any asymmetric or uncompensated shrinkage will prevent assembly. Please confirm the compensation in your pre-build screenshots.

TRAY (mkey_tray.stl):

• Orient bottom-face DOWN on the build plate (the flat ~363 × 111 mm face). Walls up, cavity open upward.
• Factory supports on the outer side walls and outer bottom are acceptable. Do not add factory supports inside the cavity.
• The outer back wall carries a debossed "mKey" logo centred horizontally, vertically between the bottom chamfer and the wall top (~43 × 9 mm footprint). Please keep factory support contact points clear of that debossed region if possible.

OVERLAY (mkey_overlay.stl):

• Orient cosmetic-face DOWN on the build plate (the face with the key openings and display window). The underside, which carries the magnet pockets (or hex nut pockets if using screw retention), faces up.
• Place factory supports only on the outer vertical side walls. No point supports on the downward-facing cosmetic face (key openings, display window rim, pinstripe groove) and no supports inside the magnet pockets, hex nut pockets, or display pocket on the up-facing underside. A raft under the cosmetic face is acceptable provided the pinstripe groove and key openings drain during post-processing (we IPA-flush these on our end).
• RAFT KEEP-OUT under the display window: Please keep the raft contact area clear of the ~32 × 38 mm region centred on the display window cutout on the down-facing cosmetic face. The picture-frame around the window is a 1.0 × 1.5 mm cross-grain rib — raft peel forces can fracture it during support removal. An island of bare build-plate under the window (with supports only on the surrounding slab) is preferred.

Please confirm orientations AND the X-axis scale compensation in the pre-build screenshots before starting the build.

Why X-scale compensation is mandatory: JLC3DP SLA has ±0.3% length tolerance above 100 mm. At the 363 mm case X-axis that's ±1.09 mm worst case, which would exceed the 0.6 mm slot tolerance on the outermost plate tabs and shift the USB cutout off the receptacle body. With compensation, residual drift is expected to stay inside the designed tolerances.

Hand-finishing (post-delivery)

Order of operations when the parts arrive from JLC3DP:

1. Inspect and photograph factory support locations before removing anything — useful if a part has to be reordered.
2. IPA-flush the resin-trap zones with isopropanol and a soft brush before the final UV cure, if the factory hasn't already. These are recesses that sat against the build plate and may hold uncured resin:
   • Tray bottom underside: the SM / 2026 owner-initials deboss.
   • Overlay cosmetic face: the pinstripe groove and (if enabled) the DECO_LOGO_TOP deboss.
3. Snap off factory supports from the tray bottom raft, tray outer walls, and overlay outer vertical walls. Expect witness nubbins — sand flat.
4. Flush-sand the tray bottom (raft side) with 120 → 240 → 400 grit, checking SM / 2026 deboss legibility under raking light. Stop when legible; the 1.0 mm deboss depth tolerates ~0.3 mm of surface removal before legibility degrades.
5. Light-sand the overlay outer vertical walls (400 grit) to clean support nubbins. The cosmetic face should need only 800–1200 grit touch-up where any micro-support witness remains.
6. Break the window edge on the overlay with a fine file: the 1.0 mm shelf_frame_x on the display window long edges is at the brittle- fracture boundary under direct fingernail pressure during cleaning. A 0.2–0.3 mm edge break at all four window corners and edges multiplies its real-world durability.

Fabrication Methods

SLA resin (recommended) — JLC3DP or equivalent. All tolerances and minimum feature sizes are tuned for SLA's +/-0.2 mm accuracy. Add supports in your slicer.

MJF/SLS nylon — NOT recommended. Loses the 1.0 mm shelf_frame_x display window detail.

FDM — NOT suitable. Layer lines destroy the display cut tolerance and the 1.0 mm shelf frame sits below FDM's 1.6 mm wall minimum.

Hand-cut hardwood — Disable print-specific features:

# In case.scad or via -D flags:
ENABLE_DECORATIVE_TRIMS = false;
PRINT_MODE = false;

Assembly

Gasket install order

The plate is gasket-mounted: each of the 9 tabs is sandwiched between two gasket strips inside its wall slot. Order matters — the plate cannot be seated if the top gaskets are placed first.

1. Bottom gaskets first. Press a gasket strip into the bottom of each of the 9 slots before the plate goes in. These rest at the bottom of each slot, below where the tab will sit.
2. Drop the plate in, front-first. With 9 tabs engaging 9 slots simultaneously, a pure vertical descent is harder than a two-stage descent. Engage the 4 front tabs first (lower end of the tilted case), then lower the plate straight down — the 3 back tabs and 2 side tabs drop into their slots simultaneously. Do NOT pivot about the front tabs: a rotational descent swings the side tabs through ~3 mm of Z and can bind them against the wall top, which has only 1.5 mm of open-top margin. The 0.6 mm per-side slot tolerance accommodates the straight-down motion.
3. Top gaskets second. Press a second gasket strip onto the top of each tab, filling the remaining slot height.
4. Overlay caps the stack. Seating the overlay on the wall tops closes the open-top slots and compresses the top gaskets against the tabs, which compresses the tabs against the bottom gaskets.

Magnet polarity

The overlay is held to the tray by six Ø2×1 mm N52 disc magnet pairs — one per tray pocket and one per matching overlay pocket. Each pair must attract, not repel, or the overlay will kick itself off the seat.

1. Pick a reference magnet from the bag and mark one face (dab of paint, sharpie dot). Set it aside.
2. Tray magnets — install every magnet with the same face up as the reference. Before each press-fit, hold the magnet face-up next to the reference: if they repel, flip it.
3. Overlay magnets — install with the opposite face up. When the overlay is flipped onto the tray, each overlay magnet then presents the attracting pole downward toward its tray mate. Test by holding the magnet with its eventual-up face touching the reference's marked face: it should attract.
4. Glue each magnet FLUSH with the pocket mouth (critical). The pockets are 2.0 mm deep for 1.0 mm magnets — if a magnet sinks to the pocket floor, the 1 mm recess on each side creates a 2 mm air gap that reduces holding force by ~90%. Place a flat reference plate (glass, steel straightedge) over the pocket mouth during CA cure so the magnet cures at the surface, not the bottom.
5. Retain with thin CA glue (mandatory, not optional). The 1.25 mm nominal cheek between pocket and outer wall (1.05 mm worst-case after SLA shrink) is too thin to rely on press-fit alone — any walk-out during thermal cycling or drop shock can chip the cheek. Use gel-type CA so it doesn't wick into the pocket and onto the seam, and press a strip of painter's tape across the pocket mouths during cure to prevent lift.

Test before any glue cures. With all 12 magnets placed but still removable, lower the overlay onto the tray dry (no gaskets, no plate). All six pairs should click together. If any pair repels, pop that magnet out and flip it — catching this before the CA sets is much cheaper than after.

Screw + nut retention (alternative to magnets)

When ENABLE_SCREW_INSERTS=true (and ENABLE_MAGNET_POCKETS=false), the overlay is secured by four M1.4 bolts threading up from inside the tray into hex nuts glued into the overlay. Nothing is visible externally — bolt heads sit in pockets on the tray underside (hidden against the desk), and the overlay top surface is flush.

Hardware (4 of each)

Qty	Part	Specification	Key dimensions
4	Hex nut	M1.4 DIN 934	3.0 mm across-flats, 1.2 mm thick
4	Socket head cap screw	M1.4 × 14 mm	2.6 mm head dia, 1.4 mm head height

Same bolt length at all 4 positions. The bolt threads up from the tray underside through the wall column and into the overlay nut. The through- hole is a 4-segment stepped bore — no post-print drilling required:

• Pocket (3.4 mm dia, from tray bottom upward): bolt head sits here
• Mid (2.0 mm dia, intermediate): head catches on pocket→mid step
• Lower clearance (2.5 mm dia, 5.2 mm): wider pass-through
• Upper clearance (2.0 mm dia, 2.0 mm from wall top): shaft alignment

Bolt length note: M1.4 × 14 mm. The overlay nut pocket is 1.4 mm deep — the 1.2 mm nut sits flush with the overlay underside (0.2 mm tolerance headroom). 14 mm is the only standard M1.4 SHCS length that simultaneously satisfies the mid-bore and back-pocket 3× depth rules; 12 mm fails the back pocket and 16 mm fails the mid bore.

Each segment stays within JLC3DP SLA depth limits (max 3× diameter) even under worst-case ±0.3 mm hole-tolerance shrink. At the back corners, the 10 mm chamfer removes the tray bottom; the pocket starts from the chamfer face (deboss).

Nut installation

1. Dry-fit first. Drop each nut into its hex pocket on the overlay underside and confirm it sits flush with the surface. The pocket is only 0.2 mm deeper than the nut, so the nut should sit essentially flush by geometry. The hex shape should prevent rotation by hand. If a nut is tight, ream the pocket lightly with a needle file — do not force it.
2. Glue with gel-type CA. Apply a thin ring of gel CA around the pocket wall, press the nut in, and hold for 10 seconds. Wipe any squeeze-out immediately — excess CA on the overlay seating face will prevent the overlay from sitting flat on the tray.
3. Do not use heat-set inserts. SLA resin warps under soldering-iron temperatures. Glued hex nuts are the correct fastener for this process.

Final assembly

1. Complete the gasket + plate install (see above).
2. Seat the overlay on the tray wall tops (nuts face down, aligning with the clearance holes in the tray walls).
3. Flip the assembled case upside-down.
4. Insert the M1.4 × 14 mm bolts into all 4 pocket holes from below and tighten into the overlay nuts with a 1.25 mm hex key. Finger- tight plus a quarter turn is sufficient. Hand-torque only — do NOT use a torque driver or electric screwdriver. The bolt head bears on a 0.3 mm radial annulus between the Ø3.4 mm pocket and Ø2.0 mm mid segments (~2.2 mm² contact area); over-tightening will crush that step into the SLA resin and wander the pocket, which is not serviceable. If an overlay feels loose after the quarter turn, STOP and inspect — you will not fix it by tightening harder.
5. Flip the case back upright. The bolt heads sit in the pocket recesses on the tray underside, hidden against the desk.