How would you do this button?

[jason harris]

I need to make some custom keypad buttons with symbols on them that I cannot get off the shelf.

So, I would be starting off with ~12mm square (1/2") grey buttons which go on to a small keyboard.

I would like to try and use the laser for them but I am wondering if there is a better technique than I might have thought up. The two things that are of most importance is that the text is legible and that it will not come off after a long time of use. If I had a third, it would be the ability to backlight it but that could complicate it.

I am looking for white text on grey keys.

My immediate thoughts are to engrave the text and fill in with *something*? white that will stay there almost indefinitely. Second is to get some adhesive white material I could attach to the keys then cut out the letters and remove the excess. Only question is how long would it stick?

I am posting because there is no doubt, some well know, or super secret method that I dont know :)

Thanks!
Jason

[Michael Hunter]

I expect that the keytops will be made from ABS : don't expect great results engraving this stuff (but worth a try).

For large-scale keyboard production from blank keys there are two main methods -

1 Engrave with a YAG laser. Unlike a CO2, it does not remove material but turns the ABS white.
2 Pad- or screen-print with a UV curing ink.

[Conrad Fiore]

Jason,
We mechanically engrave and fill thousands of keycaps by cutting to a depth of .003-.005" and fill with Keeler & Long Hi-Temp Wipe-in Filler. The filler is mfg. by PPG and costs about $250.00 a quart, expensive but there is nothing that can touch it. It is the next best way to mark a key to injection molding.

[Richard Rumancik]

Jason, are you making the keys yourself from sheet? If so there will be limitations on what processes will work. eg. if injection molded, you can get plastics that will turn color when lasered (but usually UV laser is required). Commerical keys are sometimes sublimated (in your case if you could mold white polyester they could be sublimated with gray background). But sublimation requires compatible subtrates. So I think you are probably limited to pad printing or color filling. Conrad is mechanically engraving, but you should be able to laser engrave and color fill.

Conrad, can you provide a part number of the PPG material you are using? I tried a bit of searching but no luck.

[Conrad Fiore]

Richard,
The paint is KEELER & LONG PPG Architectural Finishes P/N 2386 Hi Temp White Wipe-In.

[Richard Rumancik]

Hi Conrad

Thanks for looking this up. It might be good stuff but PPG seem to be hiding it on the web. I could not locate it at the PPG site and Google could not seem to come up with anything. (It did find an old post of yours where you recommended it to someone else in another thread.)

[Conrad Fiore]

Richard,
You won't find it on the web, you would have to call for info. We have been buying and using it for over 45 years, watching the price go from $35.00/qt (we thought that was expensive then), to about $285.00/qt now.
We used to buy it from Keeler & Long in Watertown, CT, makers of industrial coatings for the nuclear industry. Now PPG has taken them over, but the Wipe-In remains one of their products. There was a time when they made it in a half dozen standard colors, plus black and white. I don't know if they do today, now we only buy the black and white.

[jason harris]

Thanks guys, I too did a search the other day and nothing came up. I am in New Zealand so I am not sure how easy it would be to get it but at that price and the small number of keys I may do it may be too expensive.

I am using off the shelf grey key caps for small tactile switches.

I have been playing around over the last day but I don't yet have a result I am completely happy with. I have been engraving with a laser with masking tape on top, then filling in with paint. The hard part is taking off the masking tape. Take it off too early and risk smearing which is hard to wipe off without removing the paint from the lettering. Take it off too late and some of the paint for the lettering can be lifted with the masking tape.

I am now thinking of something a bit more of a filler but easy to get in like paint. This way I can engrave a bit deeper and running some 1200 grit sandpaper over the front smooths it out nicely.

The plastic does not engrave too well, it is melting but doing an acceptable job if I get fill it in ok.

Thanks again,
Jason