scott wrote:
>> I'm presuming a mould with a fake-leather texture to it has gotta be 
>> pretty expensive to make...
> 
> You mean like the one you have on the dashboard in your car?

Yeah, like that.

Or in fact, just now I was looking at a cheap knife. The blade is a lump 
of metal that's just about sharp enough to cut bread, and the handle is 
a blob of black plastic that looks like it's injection-moulded. (It has 
a fetling line on it.) But then I noticed, the plastic has a rough 
texture to it. (To enhance grip?) How do they do that?

I wonder if they use something like the acid on "frosted" glass...

>> Yeah, I guess if you want to see how strong it is, you need to use the 
>> real material that the final product will use.
> 
> Or if you 
> want to check it still works after you drop it on the floor etc, that 
> sort of thing.

Yeah, well, that's a function of far more than the plastic shell. Gotta 
assemble the whole thing for that! ;-)

>> Reading Wikipedia, it appears that "most" plastic items are 
>> thermoplastics rather than thermosetting. Is that true? Does that mean 
>> there's a possibility of reusing your prototypes once you're done with 
>> them?
> 
> I don't think so, the cost of reprocessing the parts into something the 
> plastics maker could use would be too high.

Apparently by dad spent some time working in a plast where they do 
"vacuum forming", and each time you do that, you have to cut a bunch of 
wasted plastic off the edges. He says they sent it back to the suppliers 
and they got a discount. (But then, how hard can reprocessing a flat 
sheet of plastic be?)

>> Suddenly I'm wondering what the tolerances are for those *tiny* little 
>> screws they have on things like spectacles. ;-) Man, the thread on 
>> those is tiny!
> 
> Yeh, imagine the tolerance on the thread pitch of those :-)  Something 
> insane like 0.02 +/- 0.005 mm !

Hee... must be expensive! ;-)

>> You might even know this one... What is the total travel on the 
>> buttons of a mobile phone?
> 
> Don't know, but usually there are just tiny rubber "poppers" underneath, 
> a bit like those toys you used to have as a kid that were like a thick 
> hemisphere shell of rubber, you turned them inside out and set them 
> down, then after a few seconds they jumped up in the air.  The click you 
> feel on the keys is when the rubber "snaps" in and out of shape.

Right.

And that brings us back to my question about components which are 
supposed to "snap together". I guess it depends on how deformable the 
plastic is? (And that surely must depend on shape...)

>> Damn. So after some guy designs what the final thing is even meant to 
>> look like, some other dude has to figure out what seperate bits to 
>> make and how to slot them together, and then yet another guy has to 
>> figure out how the **** to build something to make stuff that shape! o_O
> 
> Exactly - and you begin to realise how expensive, how many people, and 
> how much time it takes to design something apparently simple like a 
> mobile phone.  Then imagine designing something like a car, or a plane! 
> It's just not possible to imagine how much work goes into such a product.

I wouldn't have called a mobile phone "simple", but yeah. I was thinking 
more something like a pen. (They usually have that click-action that 
allows you to retract the tip. And a lid that needs to fit properly. And 
the tip is usually metal, not plastic. And you need to fill it with ink 
somehow...)

It kinda makes you wonder how anything ever gets made in the first place!

>> Heh. Damn... I wonder how they cut the mould to exactly the right shape?
> 
> You can get milling machines that are controlled by very accurate 
> stepper motors, a computer sends a list of commands to the machine and 
> it moves the cutting bit around.

Heh, and I bet that's even *more* damed expensive again... not to 
mention the quality hardened steel you need for it to mill...

I wonder... do companies buy all this stuff themselves? Or just 
subcontract it out?

I also wonder... Today we have machines that make components of machines 
that are used to make machines for making machines. Some of this stuff 
is made to absurd tolerances - stuff no human could ever make by hand. 
So... how the **** did we make it in the first place?!

Dude, HOW DO YOU BOOTSTRAP CIVILISATION?! O_O

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