it’s a macro photographie, so all defaults look bigger than they are in reality…it’s my first test, now the material just need to be a bit colored…
but that’s a good start!!!
the material used is called “fimo liquid”, the mold are done with a special silicone that support high temperature (the material need to go to an oven)…all this material are a bit expensive, so i will only do other test if people are interested by such parts..
i’ve to do some more calculation for the price but i think i can keep my money back selling the caps for 0.5 Euros/part…it’s a bit expensive but i’ve to pay the “research and dev” section of my multinational company!
hum…finaly, this product appear to be less soft two hours after getting it out from the oven, i will try to warm it less than this first time…it’s still soft , but not enough in my opinion for doing mpc style pads..using directly the RTV silicone will be better for this purpose (i’ve already do test that lead to great result, the only thing that stop me is that i can’t find appr. mold - if someone own some square plastic box that can be used for that…).
the advantage of this product is that you can do transparent soft button, to be used with a backlight LED…
finaly, my little cap is really harder than expected (i’ve let it dry one more day and it become harder, so now you really have to push on it hardly to see that is “rubber”, so in fact only the “touch” is slightly different from the resin caps
it’s not enough “rubber” in my opinion… as i’ve paid 8 Euros for 50ml of this material, i won’t be abble to do a lot of other test…grrrr…i will look for a more appropriate material (for the while ,i’ve found a that a clear silicone exist, but it’s impossible to mold it in my silicone mold (fusion)…
…still on the fight
btw: i’ve tested a mpc style pad done with my standart silicone with some tact switch, but the result is not good (you “feel” the tact switch through the pad).
so i’ve un-mounted my MV8000 drum machine to see how are done the pad: it’s done with a conductive “serigraphy” engraved on a pcb and the back side of the pad hold a part of conductive material…i don’t know if it’s easy to do such a thing…
i’ve tested to warm the “fimo liquid” only 10 minutes, then only 5 minutes (instead of 20 minutes): same result, this product is too hard in all case
then i’ve tested with colored material:
i don’t find the result really beautiful…
then i’ve tested to backlight it, and here too the result is bad, the light don’t go trough the material when it’s colored, and when using a clear cap, you can see the source of the light…
so: it’s finaly not the appr. material to do rubber caps…
I wouldn’t give up just yet, i’m sure there’s an application for something like this. Maybe you need to have the silicon be less transparent, maybe by mixing some fine powder. That way it will diffuse the light. How about adding glitter for a glam effect?
I was actually thinking about this, if you wanted to make small buttons, I imagine that you could use silicon sealant for bathrooms etc. It’s not all that durable, but it’s nicely translucent for illuminating. The trick would be releasing it from the moulds.
in fact the problem is that you feel the “click” of the tact switch too…
it’s a way the pads are done on MPC and others:
finding a conductive material to put back side the pad won’t be a problem i suppose, and maybe the pcb can be done with standart method ?
… mostly used is a graphite as the conductive material on the bottom of the buttons.
Graphite powder (about 20%) is also mixed into thermoplasts, to make make it conductive (ever wondered how plastic encoder knobs of digital mixers can be touch sesitive? )
You could try to mix about 80% graphite powder with 20% of some silicone glue and smear it over the bottom of your buttons, to make it conductive.
The big challenge will be the construction shape to receive a nice tactile feel. You have to design some kind of silicone dome which snaps when you push the button.
Exactly, if all it costs is time then definitely keep going (if you can spare it of course!). I’m certainly interested. I’m pretty sure that silicon sealant will adhere to your silicon moulds i’m afraid, unless you have some sort of release agent.
I was thinking of how i’d mould the buttons for my menu using some silicon.
I could get a smallish piece of steel or alu, around 1/4" deep and thick into which I’d drill a series of holes around 7mm deep and 7mm across. I’d then spray the steel with something like WD-40 or wipe it with some light grease, and then fill the holes with silicon and also cover the top to give some purchase for pulling them out when set.
I’m hoping that the result would be similar to a membrane keyboard, with the individual buttons attached to a common flat base. They can either be used like that or cut off.
finaly, my little cap is really harder than expected (i’ve let it dry one more day and it become harder, so now you really have to push on it hardly to see that is “rubber”, so in fact only the “touch” is slightly different from the resin caps 
