deskthority

Could someone with more knowledge of ABS or PBT plastics than I have please explain to me why laser etched double shots are a bad idea?

Here is the idea that I have:
- use a laser to not just etch a legend, but to cut clear through a key cap
- use double shot molding to fill the cut area

Now, this would limit font selection as the font would need to be a stencil font. Also perhaps the edges of the cut would be too rough to use. Is there any prior art here?

This does have the advantage of not requiring a whole bunch of per-glyph tooling.

I've read much of Ripsters rants. From what I gather that wouldnt be cost efficent because of the time you'd waste with lasering each cap. Additionally, PBT is more subject to warp and if you tried to 'infill' the lasered out area it probably wouldn't go so well.

Source: Speculation

When you cast something there must always be a pour spout. Almost all keys have pour spouts on the bottom or the back of the key so that you won't see or feel it.

There is already laser-engraved keys with "infill". The infill is of a softer plastic that wears more easily (but not as easily as printed keys), and some variants of it are bumpy.
Cherry's contemporary black POM keys are done that way, but the print is bumpy and you definitely feel it. I think some older type used a smoother infill, but I'm not sure as I've never encountered them myself.

Thanks. I suspect that, as much as anything else, this is a process control issue.

Well, I haven't seen any such keys on the market, so this must be prohibitive for some reason.

Infill is awful. That's the reason.

Matias's'' laser etched legends are better than infill. But still no doubleshots.

not sure if this is of relevance or if you can even see it on my APL set, I'm not sure how old these are and how they were manufactured though:

I think Cherry's black caps are not infilled per se, the plastic has additives that turn into a white "foam" when lasered.
The classic infill is the one on seebart's pics, the laser or engraver cuts a "trench" in the cap and paint is added to make it stand out.

I know infill. This is not what I'm describing.

No, what I propose is to use the laser to cut clear through the plastic, then to fill it from the back with a different color of plastic. This is the same idea as a real double shot key cap. But, instead of using tooling to create the letter (glyph), use the laser to do so.

(If this was not clear let me know and I'll go edit the OP.)

I don't understand why people want PBT doubleshots anyway.. Dyesub is just as good. You really can't tell the difference unless you're right up close to the keycaps.

Colours. You can't dyesub a space cadet set. And you can't dyesub good legends on black keys.

There also something reassuring about seeing the two separate pieces of plastic when you pull a doubleshot and look inside. You can see how deep it really goes.

But yeahs I'm with you. I like pale caps anyway, so dyesub is near ideal for me. Unlimited secondary legends!

Muirium wrote: Colours. You can't dyesub a space cadet set. And you can't dyesub good legends on black keys.

Fair point. The details tend to slip my mind after I've been awake for over 24 hours..

You've got to keep all those Cherry article numbers in there, at all costs! Meanwhile, I can barely remember which letter means hogspritz or sublimeduck.

 Hochdruck Spritzguss and Sublimationsdruck Mu. Your German cracks me up every time. No hogs and no ducks.

Muirium wrote: You've got to keep all those Cherry article numbers in there, at all costs! Meanwhile, I can barely remember which letter means hogspritz or sublimeduck.

HAHAHA that pretty much made my day mate xD .

Muirium wrote: Colours. You can't dyesub a space cadet set. And you can't dyesub good legends on black keys.

There also something reassuring about seeing the two separate pieces of plastic when you pull a doubleshot and look inside. You can see how deep it really goes.

But yeahs I'm with you. I like pale caps anyway, so dyesub is near ideal for me. Unlimited secondary legends!

Well you could , if the whole cap was dye apart form the legend .

Indeed you can.


http://keycapdiy.blogspot.de/2014/12/br ... -caps.html

XMIT wrote: I know infill. This is not what I'm describing.

No, what I propose is to use the laser to cut clear through the plastic, then to fill it from the back with a different color of plastic. This is the same idea as a real double shot key cap. But, instead of using tooling to create the letter (glyph), use the laser to do so.

(If this was not clear let me know and I'll go edit the OP.)

No need, your description was very clear, but the way I see it, there are a few problems.
Lasers cut by literally burning the material away. The focused laser beam gets absorbed by the material and pretty much vaporizes it.
If you have ever seen laser cut wood it is charred along the laser path.
I guess if the outer material was too thin it might deform and char by the heat, likewise if it is too thick, as the feed rate would be slower. I am sure there is a material with the right properties out there but it might not be ideal for molding with it.

I think another solution might be to make the first shot and then "carve" with the laser around the legend so it becomes debossed and then use that with the second shot, essentially eliminating the custom tooling for the first shot.

Any plastic that's merely poured onto the surface will be pretty weak. That's the fundamental problem with infill: it's only skin deep.

Multi shot injection molding is a solved problem. It's still commonly used for other products today, so I've heard. But keyboards are an unfortunate category where cost cutting dominated over quality so hard that we regressed. Going backwards, technologically, so yesterday's processes feel like costly future ones!

You don't notice this so much in things like kitchenware (my Mum's pretty ordinary 1960s mixing bowls and such are much higher quality than you can buy in stores today). But as keyboards are used with technology, by definition, it's amusing and sad how bad things have gotten beneath our displays. Or rather everyone else's…