• Keyplate tray parameter tuning

    Kelvin Chow • 11/18/2023 at 05:08 • 0 comments


    The keyplate is where the key switches snap-fit onto into and provide some support.  For the type of key stabilizers I purchased, they also snap fit onto the keyplate.  For the 3 key tester, I made one that fit 2x 1U keys (standard) and 1X 2U key  that was double in width and required a set of stabilizers.

    Keyplate Material

    Originally, I had set out to make an all-wood mechanical structure, meaning my first attempt at making a keyplate was using wood veneer.   It probably should have been obvious that snap-fit parts onto thin wood was not going to work out. I tried anyway and of course it didn't work. Acrylic's a pretty common choice. 

    Keyplate Thickness

    The thickness was 1/16" (or 1.5mm), which is pretty typical for mechanical key switches.  For the stabilizers used here, the thickness required as stated here was 1.2mm.  In the picture above (and in the DXF file), there is a rectangular etch that is made around the perimeter of the stabilizer cutout.  That etch was made so the thickness around the stabilizer was 1.2mm. 

    Keyswitch Cutout and Spacing

    The keys I purchased required a 14mm square cutout.  A standard keyboard spacing is defined in units of U (=19.05mm).  The cutouts and spacing in the test keyplate are made to these parameters. 

    Using this sample for tuning laser cutter settings

    The dxf files attached work for my laser cutter setup, but might be machine dependent and require kerf adjustments.  I used this test to determine my laser cutter parameters to 

    • snap-fit the key switches
    • snap-fit the stabilizers
    • find the power settings to etch the plate down to a thickness of 1.2mm around the stabilizers

    After a few attempts, the parameters that gave me nice-fitting parts was used and applied to the full-scale keyboard CAD files.

  • Troubleshooting with 3 key tester

    Kelvin Chow • 11/13/2023 at 03:19 • 0 comments

    Making a small scale test for feasibility.  Ignore the defect on the left key, I was using scrap wood.

    Before jumping straight into a full-scale keyboard, I made a small scale version of the parts that required some troubleshooting.  This smaller test had 3 sets of key switches/keycaps and a set of keyboard stabilizers for the wide key.  

    Exploded view of 3-key tester. 3 key switches and 1 set of stabilizers snap into keyplate tray.

    For creating the custom parts, my design process was:
    • Create a complete 3D CAD model of the full keyboard
    • Based on the 3D CAD model, create 2D DXF files for the individual laser cut parts.
    • Cut parts with laser cutter
    • Tune laser cutter parameters and use hand tools to match 3D CAD model.  Tuning parameters are necessary for anything that is snap fit.  Hand tools are used to remove burn marks from the laser cutter.   
    Because of this process, the DXF files and STEP files in the project files won't match. The differences are either due to laser cutter kerf adjustments or purposely made bigger so there is material to finish with hand tools. 
     A zip file is added in the project logs that contains a STEP file of the entire assembly and individual DXF files for 3 of the parts that were laser cut.  The following few logs will detail the making of this 3 key tester.

  • Finding the right key

    Kelvin Chow • 11/06/2023 at 19:59 • 0 comments

    The biggest challenge of this project is the wooden keycap set.  Before I did anything else, I needed to know if it was feasible for me to create a wooden keycap on a key switch repeatedly.  My initial attempt was to keep things simple: square keys with flat tops and no tapered sides.  This need for simplicity was due to the tools I had at my disposable: just a laser cutter.  I've seen people make keycaps using a CNC mill to give them a more standard key switch shape.  However, 1) I don't have a CNC mill and 2) one of my main goals was making a keycap set with grain continuity between keys.  The amount of waste from a CNC mill (although it probably could have been optimized better) wasn't something I liked.   A laser cutter with a smaller kerf was better for visualizing this grain continuity. 

    Typical Mechanical Key switches/keycaps


    Looking at the Cherry key switch and compatible keycaps, there is a pretty aggressive taper and a small stem.  Typical injection molded plastic keycaps have these thin tapered walls (maybe 1-1.5mm thick), which I thought would have been difficult to replicate with wood.  I thought making the tapered walls was difficult and structurally, I would want thicker walls.   Briefly thinking about trying to design around a tapered key switch, I thought against it and looked for an alternative.

    Cherry MX switch (left) and compatible keycap dimensions (right)

    My Choice: Redragon Low Profile Switch

    What I ended up deciding on was this nice and square ( and cheap) low profile key switch from Redragon.  This would allow me to make simple, square, thick-walled keycaps.  The low profile nature was advantageous too, as I planned to etch away the inner shell using a laser cutter.   I ended up buying 300 of these switches and hoped it would work out. 

    Redragon key
    Redragon key

    If I were to try again: Kailh Choc Low Profile Switch

    The Redragon key wasn't the best choice for a key switch, as I intend to discuss later on.  Initialy, I cared about the square, untapered shape of the Redragon key.  What I didn't think about was the key switch stem design.  If I were to make this decision again, I would try with the Kailh Choc low profile switches.  I had a lot of trouble with the keycap stems with my first attempt, and the Kailh switch seems more willing to accept a larger, simpler mating feature.

    Kailh Choc key switch