Keycaps for mechanical keyboards

dmote-keycap produces a three-dimensional geometry for a keycap: Either a featureless maquette for use in easily rendered previews, or a keycap that you can print and use.

Horizontal keycap size is measured in a traditional unit: The u, where 1 u is 19.05 mm (0.75”) per key mount. A 1 u cap is smaller at about 18.25 mm to allow for space between caps on adjacent mounts. For the same reason, a 2 u cap is more than twice as a wide as a 1 u cap, and so on.

Features

• Supports both ALPS- and MX-style switches.
• A “minimal” style that hugs the body of the switch. This style enables keyboard designs more dense than the traditional 1 u, which can have ergonomic advantages. Dust protection is better than a 0.75 u cap that does not extend down the sides of the switch.
• A “maquette” style for previewing keyboard designs.

dmote-keycap does not provide models of switches and has no support for stabilizers.

Usage

This is both a library for scad-clj applications that draw keyboards, and a CLI utility for drawing printable keycaps that can be used with common mechanical keyboards.

As a library

The dmote-keycap.data namespace exposes various raw data and simple mathematical functions to describe keycaps.

The dmote-keycap.models namespace exposes one function: keycap. It takes a number of parameters, in a flat map, and returns a scad-clj specification:

• :style: One of :minimal (described above) or :maquette (a crude preview).
• :switch-type: One of :alps (ALPS style, including Matias) or :mx (Cherry MX style).
• :unit-size: A 2-tuple of horizontal size measured in u, hence non-linear. On a traditional ISO keyboard, the first value in this tuple (the width) varies from 1 for most keys to about 6 for a space bar. The second value (the depth) is 2 for the Enter key and 1 for all other keys. Please note that a non-rectangular shape, as is typical for the Enter key, is not yet supported by this library.
• :top-size: A 3-tuple describing the finger contact surface, including its thickness in the middle, directly above the stem of the keycap. The first two numbers in this 3-tuple can be omitted by replacing them with nil, in which case :slope (see below) will take precedence. All measurements in mm.
• :slope: A ratio between the top and bottom widths of the keycap. This setting is used only if :top-size is left incomplete.
• :top-rotation: A 3-tuple describing the angle of the finger contact surface, in radians. This would be [0 0 0] for a (row 3 or standard) DSA profile and would have a different non-zero first value for each row of an OEM profile.
• :bowl-radii: A 3-tuple describing the radii of a spheroid used as negative space to carve a bowl out of the top of a non-maquette keycap. If this option is set to nil, no bowl is used.
• :bowl-plate-offset: An optional modification of the vertical distance in mm between the bowl and the top of the keycap.
• :skirt-thickness: The horizontal thickness of material in the outer walls of a minimal cap.
• :skirt-length: The length of material from the top of the stem down toward the switch mounting plate. By default, on a minimal cap, this is 1 mm less than the space available when the switch is pressed.
• :sectioned: If true, the model is cut in half for a sectioned view. This is useful in previews and development.
• :supported: If true, support structures are added underneath the model.
• :nozzle-width: The width of the printer nozzle that will be used to print the cap. This parameter is only used to build supports, which will have the width of the nozzle because this improves print speed and quality.
• :error-stem-positive, :error-stem-negative, :error-body-positive: Printer-dependent measurements of error for different parts of the cap.

Some of these parameters have global default values, while others have default values associated with particular styles, for ease of use. The long-term plan is to model a variety of traditional “families” with just a few parameters.

As a command-line application

Use lein run with command-line arguments corresponding to the parameters listed above. Not all parameters are supported; try lein run --help. The CLI takes an additional parameter for resolution (i.e. level of detail).

The application will generate files of OpenSCAD code under output/scad and, optionally, STL files for slicing and 3D printing.

Printing

Several of the parameters listed above are intended to aid manufacturability. This includes the supported parameter, which is intended to reduce the need for building supports in slicing software.

With single-head FDM printing in a material like PLA, a relatively simple way to get a good result is to print each key in an upright position, with supported. In general, a minimal-style cap with a tall top plate (hence a vaulted ceiling) should not need further support.

Consider the main alternative: Printing each key upside down. This will often give you a cleaner stem and skirt, but with an uneven face (i.e. non-nil bowl-radii), cleaning up the print will be difficult. In particular, even with fairly dense supports added by a slicer, you will probably find tiny cavities behind the face, to such a depth that a really good surface finish is hard to achieve even with a suitable rotary tool. Still, if you intend to paint your prints anyway, or if you have a dual-head printer with a soluble support material, this may ultimately be a better option.

License

Copyright © 2019 Viktor Eikman

This software is distributed under the Eclipse Public License (EPL) v2.0 or any later version thereof. This software may also be made available under the GNU General Public License (GPL), v3.0 or any later version thereof, as a secondary license hereby granted under the terms of the EPL.