Hey guys the past few weekends we´ve been experimenting a bit with Jesmonite and figured we´d share our findings and results with you.
Disclaimer: We hoped to be the first ones to introduce a jesmonite project, but Brazen/Ian was a little faster, so make sure to check out his “Mason60” project as well :)
All disclaimers aside, let's get going :)
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What´s Jesmonite?
I´m going to borrow that one straight from the horse's mouth:
“Jesmonite is a composite material used in fine arts, crafts, and construction. It consists of a gypsum-based material in an acrylic resin.“
Why Jesmonite?
One day I stumbled upon this video https://www.youtube.com/watch?v=GGpN61XvLtU&t=10s (https://www.youtube.com/watch?v=GGpN61XvLtU&t=10s) of Alexandre Chappel on Youtube and saw what he was doing with Jesmonite.
At some point this came to mind while we were building some of our boards at Teleport and I figured, why not try it on a small scale proto for a board. The Material is quite unique, as it can be colored with pretty much any color (pigments), or other additives (such as metal powder), to give it a different look each time.
Workability:
Jesmonite comes as a powder with an additional liquid and is mixed in a 2:1 ratio, then cast into a mold to hold its shape. After a few minutes an exothermic reaction takes place and that stuff dries quickly, as we learned the hard way (who reads instructions anyways, right..?)
To sum this up: It looked different and seemed to be somewhat of a workable material.
Initial Concerns - Weight, Haptic and Sturdiness:
As we are all somewhat used to metal boards, we were concerned mostly about the above mentioned points. We will go over these points later in detail, however, we did not want to have something light (plastic like) and were concerned that haptics would be very similar to classical plaster.
All concerns aside, here are our first experiments in chronological order:
- 60% board poured into a 3d-printed mold
Not gonna spend too much time on this one. A 3d printed mold for our model was a bad idea in the first place and we had no idea how fast that stuff would react. So we ended up with a puddle of half hardened jesmonite, before we could even cast. We figured to add the picture for the laughs :)
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Picture: Maybe read instructions next time...
- Testing the waters
No idea how that stuff reacts to water, so we used some of the scraps and let them soak in water for a whole week. Didn't do much to it, but better safe than sorry :)
- Numpad with silicone mold
As we needed a somewhat smaller mold, which didn't require two halfs to be printed and we had some numpad PCBs lying around, we figured we'd keep on going with that first, before moving on to bigger casts. So we designed a 3d model of a NumPad with a rough idea of the mounting in mind, printed it and created a silicone mold out of the 3d print.
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Picture: 3d printed Model
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Picture: Silicone mold of 3d model
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Picture: 2nd pour, this time according to the instructions
This turned out way better than expected and our second pour gave us the proof of concept we were looking for. We applied some clear coat finish as well, just to make sure there won't be any changes in color over time.
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Picture: 2nd pour released out of the mold, sanded and coated
The small thing weighs in at 290 grams. The haptic is hard to describe, the best thing I can come up with is a mix of plaster and acrylic. It's super smooth, smaller irregularities can be sanded and it's much sturdier than expected. We mixed White and Yellow, certainly not everyones cup of tea, we however think it has a unique and pretty look to it.
- Figuring out the Mounting
As this stuff needs to be casted, we figured it would be a good idea to stick to a 1-piece design and not overcomplicate things. So we went with a simple tray mount for our NumPad. We tried several ways to get the mounting pins sturdy enough to hold a pcb + mounting plate.
We first tried to simply embed pcb spacers into the bottom of the case with glue. It worked, but we didn't think it was sturdy enough to hold the spacers.
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Picture: Glued Spacers as mounting pins
We tried adding additional material around the spacer, but that just looked clunky, and made casting it more difficult than it needed to be. We didn't even bother gluing pins in, but here´s a picture.
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Picture: Additional material for the glued mounting pins (ignore the air bubbles, this was just a quick pour of the bottom to test different mountings)
The other option was to cast M2 screws upside down into the bottom of the board, so only the thread would be visible and the screw head would stabilize it. Then add a PCB spacer to mount the PCB and mounting plate. This worked well, the threads are solid, don´t move a bit and everything can be mounted on them, with enough space for pcb, switches and stabs.
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Picture: M2 screw upside down as base for the mounting pin
Overall, we are happy with the Mounting, especially for a NumPad, which isn't under heavy typing fire all the time, it works out just fine. We were experimenting with additional O-Rings, but due to little space between the switches and stabs, they would squeeze against the switch housing and we didn't really like that. Also it seemed overkill for a NumPad, we´re going to revisit that, in case we make an actual keyboard out of this one day :)
- From Experiment to a Prototype we felt was worth sharing
After we decided on how to mount everything, we added a few design elements in the bottom of the case and agreed on a final look of the NumPad.
Again, 3d printed it, this time added some filler and sanded the 3d model to make it overall smoother, casted a mold with silicone and then poured in the Jesmonite.
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Picture: Hardened NumPad before sanding with brass mounting plate
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Picture: Numpad after sanding with some Cherry MX Silent Red (they matched the red, okay…?)
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Picture: Numpad with some white keycaps
Next Steps:
We are not yet 100% happy with the pouring results, as with all casting materials, air bubbles build up while mixing the liquid. We are looking into different ways to reduce that. Our best bet at this point is either a vibration plate or a pressure chamber. Vacuum doesn't seem to be a great alternative, as the stuff hardens relatively quickly and vacuuming bubbles takes quite a while. If you have other good ideas, let us know. We´ll keep you updated.
We´re still unsure whether or not we will put it up for sale in our shop. Clearly, this is also dependent on your guys' feedback, so let us know what you think and if you'd like to have something like this on your desk and if you think it's worth investing more time in. Colors are up for debate, pretty much anything is possible.
PS: Still unsure of the project name, feel free to share any ideas ;)
We hope you enjoyed the read, thanks for taking your time and greetings from Germany!
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