Floating idea of a lego style PBT casing

[berserkfan]

OK, I just got this idea, so am throwing it out for public discussion.

I have kids.

Kids have lego.

Kids spend a lot of time building amazing things with lego.

I like PBT.

PBT can't be moulded for large things like keyboard casing because it is too rigid.

I also own some Tipros.

Tipros have modular casings that can accommodate different layouts.

I discussed making modular casings with samwisekoi on geekhack a while back, so that Ron's GH60 and GH144 should share as many parts as possible. Remember that making a PCB is cheap, but making a casing is not.

You can get a great PCB for under $10, but you're still stuck with no casing. But obviously no company is going to make plastic moulds for small production runs of 20 or 40, so we need to stick with smaller, standardized size components. If one keyboard is made of 3 types of 100 parts, lego style, then a production run for 20 people would be nearly 7000 pieces. Then we have some modest economies of scale.

What I am wondering, is whether we can design keyboard casings like that. I can't do it myself, but it would be nice if some interested person took my idea and ran with it. Also I believe a keyboard casing made of many parts would be more resilient to stresses, since it has many parts that can yield a bit when under stressors. If you drop a board and casing breaks apart, you can just put it together like lego. In contrast with a model F XT casing that once came to me broken and can never be fixed again. (F XT casing is super hard, but ultimately it will break and shatter if keyboard is shipped without padding and dropped while shipping, as happened to me.)

[elecplus]

Call me stupid, but why can't small runs of keyboard housings be made from ABS? It melts under 200 degrees F, and is very cheap. Rounded edge things might be difficult, but if you are looking at making casings like Legos, then they would be absolutely square anyways.

On a different track, have you given any thought to re-using a rubberdome case? Most of the ones from Dell are fairly sturdy, and yet have a little flex in them. I see NIB ones at the recycler all the time. I probably have 40+ of the exact model number. They are black, not white, if that is not a problem? Then you would have a controller and USB or PS/2 cord as well. Maybe this will not work; I have never tried to build a keyboard. I can tell you that the Dell and HP rubberdome dimensions are similar to the Cherry mechanical I am typing on now.

[Redmaus]

Does modern ABS yellow? Or is it only beige ABS that does so?

But also keep in mind Cindy that most people are not interested in plastic cases at all. A lot of people like metal(alu) cases for their weight, looks and feel. Most otherwise really great priced boards are ruined by their metal case which drives the price up by twice as much in some cases. My TEX TKL alu case costs more than the keyboard I put it in.

[elecplus]

If I am not mistaken XMIT was thinking about making aluminum cases. But berserkfan specifically asked about plastic.

Black ABS does not yellow. White ABS does not have to yellow; there are chemicals that can be added that prevent the yellowing. We have a plastic manufacturing company here in town, and I talked to them once about making some custom things for me. If you want injection molded, then you pay $10K and up for the forms, but the parts are very cheap. I was pricing new covers (all of the plastic) on an Okidata 320 printer, and IIRC there were 8 separate pieces. Tooling was $10K, but then ALL of the plastic for the entire printer only came to less than $2.50, including anti-yellowing, color matching, and some of the parts were clear instead of opaque.

[berserkfan]

If I am not mistaken XMIT was thinking about making aluminum cases. But berserkfan specifically asked about plastic.

Black ABS does not yellow. White ABS does not have to yellow; there are chemicals that can be added that prevent the yellowing. We have a plastic manufacturing company here in town, and I talked to them once about making some custom things for me. If you want injection molded, then you pay $10K and up for the forms, but the parts are very cheap. I was pricing new covers (all of the plastic) on an Okidata 320 printer, and IIRC there were 8 separate pieces. Tooling was $10K, but then ALL of the plastic for the entire printer only came to less than $2.50, including anti-yellowing, color matching, and some of the parts were clear instead of opaque.

Well, I was just asking about plastic because I figured it was cheaper and easier to handle. But you're right, most geeks like metal keyboards.

But as my discussion here suggests:
https://geekhack.org/index.php?topic=66202.0
Older Tipros used screws. Modern Tipro is held together by tabs that snap.

When you have plastic, they can be made to snap together with some force. That was also the case with Model M casings and Model F AT casings.

If you have metal, it is much harder to use tabs. And the paint would be rubbed off, causing rust to appear at these joints. How do you have a metal casing with modular joints? The only way is to join them, then use rubber or some other substance to cover the joints so that users don't see the rust? And if you used aluminum, wouldn't it be so soft that they start bending at the joints?

[Findecanor]

The cost in injection-moulding is not the materials, but the machines and the moulds. You need to scale up production to make it affordable.
Lego uses a more expensive type of injection-moulding for ABS that heats the plastic in a more controlled manner in order to be able to keep warping to a minimum. This care is necessary to make sure that the Lego bricks will mate properly.
The problem here is that PBT warps more than ABS does... So you would have to use an even more expensive setup for moulding PBT parts that would be able to mate with one-another.

The thing with snaps is that sooner or later, they will break. Snaps are crap. I'll take screws over snaps any day.
The IBM M2 has many snaps to hold it together - and you can't open it and put it back together again without breaking at least one or two.

Only steel rusts. Copper and copper alloys (such as brass) go black, blue or green.
The properties of aluminium depends on which alloy you use. Some alloys of aluminium are harder than some alloys of steel.
Anodizing on aluminium - aluma - is harder than any aluminium alloy.

[berserkfan]

The cost in injection-moulding is not the materials, but the
The properties of aluminium depends on which alloy you use. Some alloys of aluminium are harder than some alloys of steel.
Anodizing on aluminium - aluma - is harder than any aluminium alloy.

Thanks for the technical info Findecanor. When I throw out ideas it is people like you who really make a difference to our speculations.

Just trying to understand - you say anodizing on aluminium is harder than the substrate itself? Are you talking about some kind of coating, or paint on aluminium?

[Findecanor]

No, "anodizing" means that the outer layer of the metal has been oxidized into an aluminium-oxide with the help of an electric current. When an anodized item first comes out of the anodizing bath it is quite porous -- and can be dyed. The dye is then sealed in by boiling it in water.

Most of the time when you see a product made of aluminium these days, it is anodized. For instance, Apple products of aluminium are bead-blasted and then anodized, and without dye, which is why they are grey.

The thickness of the oxidized layer can be varied during production. You can sometimes find an item that has been "anodized clear": I think that the layer is very thin, because these items are quite shiny -- but more so than what raw (not freshly polished) aluminium would be.

There are some other metals that can also be anodized, but I am not as familiar with those.

[Blaise170]

It's not entirely true that only white will yellow - I have a NEC keypad that is dark grey and you can see the yellowing on it.