build a membrane keyboard: possible with hobby tools?

[DiTBho]

Pre#1: assuming you can create a PCB with key-conductive-traces that don't oxidize or wear out quickly
Pre#2having access to

• a 3D printer, to print the grid as shown in the figure
• metal adhesive tape (easy to cut into round shape with scissors)
• very thin sheets of polycarbonate (very flexible)

I wonder if: it is possible to create a small membrane QWERTY keyboard, about half the size of a keyboard used in a laptop 

[Whales]

That design doesn't have mechanical hysteresis, so the keys will feel mushy.

I think you can buy little rubber domes just for this purpose.  You glue each of them to the pcb and they have a graphite pad underneath.  If you want to fully construct yourself: I'd suggest trying to 3d print them in TPU and working out a way of making their underside conductive.

It's probably wise to print and test 1 key at a time, not a whole pad, as it will take you a few iterations to get something nice.

[Skashkash]

Perhaps dome switches under your plastic layers. One spacer layer with cutouts, top flexible layer with printing.

https://www.snaptron.com/products/standard-domes/

Snaptron is very helpful with samples.

But (IMHO) membrane style keyboards are typically terrible for any lengthy data entry. Okay for control panels.

 

[abeyer]

Polycarbonate (even if thin enough to be flexible enough) seems like it wouldn't be a very nice surface for a membrane. I'd maybe consider vinyl. That has the advantage of also being sublimation printable for your legends. Maybe even a clear protective layer over the printed layer for durability.

Also I suspect that 3d printing the grid might work if you use dome switches or something, but would probably be too thick otherwise. I'd consider cutting the grid out of some sort of sheet material for a thinner layer if you don't use the domes.

TPU printing was also mentioned... which I'd lean towards more for a rubber dome style pad like a calculator, but might be interesting to try printing a monolithic TPU membrane and grid as a single unit.

[DiTBho]

Also I suspect that 3d printing the grid might work if you use dome switches or something, but would probably be too thick otherwise. I'd consider cutting the grid out of some sort of sheet material for a thinner layer if you don't use the domes.

cutting Polycarbonate for the grid, and using Vinyl for the top membrane layer?

[abeyer]

cutting Polycarbonate for the grid, and using Vinyl for the top membrane layer?

Yeah, something along those lines seems like what I'd try, at least. Depending on what tools you have on hand, might be easier to try something besides polycarbonate, too: acrylic could be laser cut, or perhaps styrene if you're doing it by hand.

[DiTBho]

acrylic could be laser cut, or perhaps styrene if you're doing it by hand.

I don't have a numerically controlled laser-cutter, but I might buy one for this project.

Still, I have to find the proper one, and allocate the proper budget (<= 1000 euro)

I have a low-entry 3D printer, many cutters, files and hacksaws, marketed for model making, so designed for cutting wood, balsa, and some soft types of plastic.

[abeyer]

I don't have a numerically controlled laser-cutter, but I might buy one for this project.

Still, I have to find the proper one, and allocate the proper budget (<= 1000 euro)

I have a low-entry 3D printer, many cutters, files and hacksaws, marketed for model making, so designed for cutting wood, balsa, and some soft types of plastic.

Seems like a big investment for this... though maybe it's a good excuse if you want one anyway. 

I just suggested as it seemed like it might be a lot of work to do by hand in polycarbonate. But the materials there don't really make much difference for the grid layer, I wouldn't think, it's more just about finding something easy enough to work with the tools at hand.