TheTasTaTur Mark 2 – Resin Casting and Keypods Making

I just poured the first blackened polyurethane resin in the mold of the keyboards case’ bottom part. I’m quite exited. This post’s intended to give a short interim report. What I achieved so far and what to come next. I will not go very deeply in the details of what I have already done. There are mainly two broad topics to mention: resin casting and keypods making.

But, to better draw a picture of what I mean by keypods, I have to describe in more detail the overall design I have chosen for the new keyboard. I criticized the unnatural orientation of the keys on standard keyboards as well as on Mark 1, so I came up with the idea to place the keys exactly as my hands are and naturally move. Also, I had some difficulties mounting the Cherry ML keys in Mark 1, so I had to come up with a better plan for that and alongside acknowledge, that the keys can be placed organically and easily moveable in the assembling phase, allowing for some late configuration. That’s were keypods come into play.

Basically, each key switch is still mounted on the original PCB. I simply cut the PCB in parts, so that each part has one key switch on top. Look at the next picture. You can see parts of the originally Cherry keyboard.

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Under each of those switches with PCB I hot-glued a super magnet using toothpicks as spacer. The bottom part of the cases integrates a steel plate. This way the keys are moveable and at the same time, stick quite strongly to the case. The top cover will be made of two parts. One part is fixed and possesses a big opening. That hole is the area where the keys can be positioned. The second part is a blend, covering the opening and having small openings corresponding to the final key positions.

The next picture shows the master (the bottom part and the top part with the key-area-opening) I constructed from wood, sheets of polystyrene, some plasticine and a little glue.
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From each of those parts I will cast negatives using silicone. For the bottom part I did that already. It worked quite well in the second try. I underestimated the amount of silicone rubber needed and initially bought not enough. It was condensation cure rubber and turned out not that ideal in handling.

The third part of the case, the blend reflecting the key positions, will be cast directly, using the master of the other top part. More on that later. The next picture shows the second silicone negative of the bottom part, I made using additive curing silicone rubber.

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The next picture shows some keypods sticked to a can and the picture there after shows the wired key matrix of keypods sticked to a metal plate.

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And here is a picture of one raw bottom case extracted from the mold. I will wait a few days so that it arrives at its target hardness (Shore-D 75). You can see the steel plate through the unintended bubble holes. I don’t have a vacuum pump and vacuum chamber, so I guess I have to live with the bubbles. I will fill up the big holes and grind everything to an even level. After grinding and polishing all around, it should look quite nice.

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There is one more thing I already did. As I wrote before, I chose Pinguino clones from Olimex. I had to tune them a little to fit in the cases. As the cases should be as flat as possible I had to remove the Olimex typical UEXT and the LiPo connector. I haven’t done any programming so far. I guess it will still take some time. But I will be back soon with in-depth discussions regarding the keypod-making and my resin-casting experiences.

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