Using Titanium for Push Button Switches

[KuKu427]

Can titanium made thin enough or designed a certain way to be used as a cover for a push botton switch?
Such as the one made from plastic in the flashlight below.

http://www.photonlight.com/PhotoDetails.asp?ShowDESC=N&ProductCode=P1-keychain-LED-flashlight

The titanium would cover the momentary switch and flex when depressed to activate the switch.

Thanks for any help.

 

[Danger]

Welcome to PF, Kuku.
Is there any particular reason that you have to use titanium? It seems inappropriate for the purpose. Plastic or aluminum would work better, unless there's some environmental reason that they wouldn't survive.

 

[KuKu427]

Thank you Danger

Titanium was choosen for it elastic properties, corrosion resistance, resistance to wear, colorability, and also its inherent "cool" factor. I would also like to keep the number of parts as low as possible so I would like to machine the cover as part of the switch housing.

Plastic would not be an improvement over the original item. Water resistance should also be improved if I were to keep the cover and housing in one piece as there are less surfaces to seal.

As for aluminum, does it have the flexibility necessary for such an application?

Edit: Titanium is pretty much set as far as material selection goes.

 

[Danger]

Okay, I think that I see where you're coming from. You want the membrane to be an integral part of the housing, rather than something that's glued on top of it. I didn't get that from your original post.
As a pure amateur (who I have pointed out in the past never graduated high school), I am now out of my depth. Several of the professional engineers on PF have awesome materials knowledge. I now step aside in wait for them.

 

[KuKu427]

Lack of formal education does not always mean lack of knowledge.

 

[Danger]

True. But, alas, in this particular instance it does.

 

[MATLABdude]

I'm not a mechanical engineer (so I probably come at this from a weaker position than Danger does, given that I also don't have his experience).

Could you turn the entire top surface into a membrane tactile switch and design the casing such that it seals watertight like a (good) wristwatch? You could make it out of sheet titanium, but it'd have to be thicker around the outside rim (or case hardened, or something like that--not sure if you can do it to titanium) so as not to deform.

Unfortunately, all of the above is going to be expensive. And the thing you link to is designed to be cheap, and a throw-in on something that costs $5 (or at least they were when I went on eBay to buy a UV flashlight!)

 

[KuKu427]

The original plan was to do just that. Turn the top into a membrane switch with a thick rim for screw attachments and o-ring seals.

But how thin does it need to be? What contour should the membrane be? Dome, flat, convex, or "corrugated"?

This is a personal project and cost doesn't really enter into the equation.

 

[FredGarvin]

You can stamp and draw titanium, but I am pretty sure it has to be with no alloying elements to prevent tears and cracks. I can't say I have ever seen it done, but after doing some quick looking around I found this which looks pretty impressive.

http://www.okayind.com/Its_A_Stamping2.htm

You may just want to examine your cost-to-product numbers to see if going from plastic to titanium doesn't blow your ideas out of the water.

 

[KuKu427]

I can't see the volume needed for stamping to be cost effective in this product. However it would be a very interesting way of manufacturing this design if there ever was that kind of volume.

Right now I am looking more at CNC prototyping for the actual manufacturing process.

Has anyone actually used Ti for a membrane switch?

 

[Bob S]

I suggest you go to:
http://www.espi-metals.com/metals/cattitanium.htm
and get some thin titanium foil of thicknesses 0.001, 0.002, 0.003, etc. Punch some discs out of it using a Rotex punch, and put a small dimple in them to give a tactile feel when it flexes. If the titanium is too expensive, start with some stainless foil available from McMaster-Carr
http://www.mcmaster.com/#stainless-steel-foil/=2f2rsz

 

[Topher925]

+1 for what Bob S said. Machining something like this is not possible or practical. Also, keep in mind that probability of your titanium membrane failing within 100ish cycles is probably pretty high. Unless your going to be using this thing in an extremely harsh and corrosive environment, I don't see any reason to use titanium for such an application.

 

[KuKu427]

Buying Ti foil for the switch cover will make this into two parts and not a one piece unit.

OK, so basically Ti is not flexible enough to be made thick enough to be used as a cover for an electrical switch?

 

[daveg360]

How about constructing it to allow a very small amount of deformation and then attaching a strain gauge on the inside? it would unfortunately require some electronics but might make it possible.

 

[KuKu427]

How about constructing it to allow a very small amount of deformation and then attaching a strain gauge on the inside? it would unfortunately require some electronics but might make it possible.

Good idea! But unfortunately, there is no room for more electronics.

 

[Danger]

I'm assuming (yeah, dumb thing to do) that this membrane impinges upon a microswitch inside the housing. If so, could you replace the microswitch with a capacitance sensor and just etch a switch-shaped design in the titanium housing over it? That way, you'd just have to touch the proper area without actually depressing it.