Pendant Membrane Switch Graphic

[bkukowski]

The only idea I have is those iron-on t-shirt transfers. Not sure how that would work..or look. If you reversed the image and put it on the back....maybe?

[ShayArnett]

I have a DIY idea, that might be easier than trying to figure out the conductive printable formable plastic part.

Basically a spring loaded normally closed group of buttons all connected to a ground plane through the springs. They make contact with a pcb flipped copper down forced closed by the springs. A small nub sticking through a via in the pcb is able to be pressed to open that switch.

I'll see if I can work up a drawing to better explain this, tools are limited here at work.

[JavaDog]

I went digging in my Pile O' Stuff and I found a control panel that has an overlay that is EXACTLY what you are looking for. So, I took it off and scanned it for you...


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The top feels like thick vinyl, possibly screen-printed, however I think heavyweight adhesive vinyl (sign shop) would work as well.


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Now, the underside has the printed conductive-ink traces - which you said you can't do (at least, not easily or low-cost).

Looking at this, and thinking of how I would low-tech it - I may have come up with a solution that might work for you.


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Basically you would have a Circuit Board with Microswitches mounted to the back of your control surface. The control surface would have holes drilled in the locations of the switches that would allow them (switches) to be flush with the top of the control surface. Then your Adhesive Vinyl Overlay Graphic would go on the top of the control surface. Bada-Bing, inexpensive and fairly simple "professional" membrane interface!

[vacpress]

javadog.

Thanks for the detailed reply. That is actually EXACTLY what I have tried thus far. The problem was the printed transparency sheet on the thin white plastic sheet were too hard to press reliably. multiple buttons got pressed.

It is actually possible to silkprint conductable ink, and it is actually easy to silkprint onto plastic sheet that is then vacuum formed (i know all about these 2 processes, vacuum forming and silkprinting)...

unfortunately making a silkprint stencil is quite alot of work, and my design is... 4 colors.. ugh. that puts the cost for the first panels printout around $40, at least, for silkscreen, emulsion, ink, etc...

an ideal solution though, could use silkprinting. i have silkprinting equipment.. i just would MUCH prefer to inkjet print.. I would imagine I may make about 20 of these..maybe 50... silkprinting multiple-colors is just not economical at those low volumes...

One thing i maybe could have done that would work is to just heat a 1/2" steel rod and use it to make little divits in the plastic..

If you search the web you can find another solution used in industry.. Basically little metal 'doodads'... sort of a third sphere, with clearance for a trace to come out under it, and when you press down it has a tactile response.. you solder these right to a pcb, and then glue the plastic overlay with similarly molded 'button' dimples vacuum formed in...

this is just 3 layers.. pcb, metal thingies, graphics...

the real question is how these pro shops produce their prototype graphics..

any ideas? tell me more about these adhesive vinyl stickers... if i am thinking of the same thing, they can be inkjet printed... but they canot be molded..

[vacpress]

incidently.. inkjet printing onto the 'just barely too thick' thermal-plastic ive got resulted in a very smeary mess. i cannot tell if it was because the material was too thick, or if it was the surface...

someone out there MAY make a product that is like inkjet transparencies - slightly textured - but for thermal forming... i couldnt find it though...


another idea is water-slip decals.. but something tells me they dont hold-up

[fkaCarel]

Hi, I think this is what you want "in the metal". I chose separate keys because those membrame boards aren't durable and tactile. Every key has it's own bore to prevent accidental dual keying. This construction is what farmers hammer away on, they didn't destruct anything yet. It's covered by a laminated print, the thinnest variety of heat laminate.
Carel

[ShayArnett]

You should contact some sign-makers in your area and see if they have a wide format solvent printer or thermal printer, they would be able to print to a vinyl substrate that wouldn't make a smeary mess when you tried vaccum forming.

[vacpress]

carel,

that looks nearly identical to what i had worked up at 3am last week.. minus the LCD screen...

I couldnt get a reliable or satisfying feel with any material i covered the thing with...

im not sure about forminy vinyl.. we always used this white HDPE sheet (if i remember correctly. someone else did ordering, i built the vaccuum forming equipment and designed some of the products... cant remember what we ended up with in stock though. it was 3 years ago)


shay,
we silkprinted onto plastic with great results, really fantastic, using the t-shirt printing ink.. My theory is that the heat from the vacuum former melted the little vinyl globules in the ink, or whatever, and fused it to the plastic. the result was very nice..

however, silkprinting multiple colors is a last-case scenario for me on this project...

grrrr. another issue with forming printed materials is distortion. but i think the really slight relief of the buttons should have little effect...

thanks!

[fkaCarel]

Well, what is called "ABS" in Europe will do the job. They make suitcases, bumpers etc. from it. Google showed LEGO is made from the stuff. It can be formed and the most important: it is cheap. About multi-color, it's industrial thus B&W.

Carel

[vacpress]

sure. ABS.. i beleive we usually call it ABS or styrene in the states.

it till needs to be printed on. this is the hard part!

also, i would imagine one can get ABS formulated to most any color. its maybe the most common plastic for injection molded parts?

[JavaDog]

incidently.. inkjet printing onto the 'just barely too thick' thermal-plastic ive got resulted in a very smeary mess. i cannot tell if it was because the material was too thick, or if it was the surface...

What brand printer? HP's ink is water-based, and will always smear on plastic (not on their coated transparencies though). Epson has printers with a pigment based ink system that will not smear, well - might not smear.

You should contact some sign-makers in your area and see if they have a wide format solvent printer or thermal printer, they would be able to print to a vinyl substrate that wouldn't make a smeary mess when you tried vaccum forming.

That is exactly what I was talking about when I was mentioning 'adhesive vinyl'. I was talking about the heavyweight vinyl material with the self-adhesive backing that would make it easier to put onto your control surface.

The solvent based plotters (would not go thermal) are waterproof, and the low-heat that it will take to put the little 'bubbles' for the buttons shouldn't mess up the printing at all. Call your local signshops, tell them what you are doing, see if you can get a sample overlay printed to "test" before you order.

Personally, I don't really see the need to vaccum form the overlay - but I understand what you are going for...

[lwill]

Java, I did a control panel for a test fixure simalar to the way you described. The over lay was screen printed on very thin polycarbonate, regular vinyl will wear pretty quick unless laminate with somthing.
It worked ok, but the spacing has to be just right or it feels weird.
There might be a way to make one like the one you scanned. What about the silver conductive "circut repair pens" to make the traces on the flexable part? I have used them to fix connections on a dart board that used the same type of swithces in the score board. Just sort of "draw" your own circuit board on some mylar or thin lexan. The only problem I see is how to connect it to the outside world. The conections on that type of thing are usualy some type of "edge" connector or has pins crimped to it. (this was the problem with the dart board, the connection to the pins was loose/corroded so I used the pen to bridge them back to the traces)

A side note, I have a 54" SolJet printer that can print on almost anything you can fit in it that will take the ink. Being solvent based it wears very well and could all so be laminated over or stuck to something. Much better than plain old ink jet. If some one wants to try something like this I could print them very reasonably on a material to be determined. (if it is on vinyl, it can also conture cut the shape/windows in it)
PM me if interested.
ED: By the way Vacpress, I am also in the Chicago area.(Melrose Park/Aurora)