Some 3d printing services can print ceramics ;)

Services like that exist online, and they're excellent, albeit rather slow. I personally use iMaterialize because they have such a wide range of material options (everything from rubber to titanium) and finishes (for example, 4 different options for silver), but there's lots of others out there, and some are cheaper.

If you've ever played around with 3d modelling, I definitely recommend giving 3d printing a try, even if just a little test piece. :) Note that plastics are a lot cheaper than metals, although metals look the coolest.

And those nerdy kids will grow up playing around with and learning 3d modeling software to be able to make their toys.

This is a good thing.

What sort of 3d prints are you looking at?

Perhaps my expectations of 3d printers are too high because I buy from professional 3d printing services rather than using a low-end home 3d printer. They use high end products and sometimes do post-printing finishing work. But the quality of the stuff you can get is truly excellent, and out of a very wide range of materials.

Isn't that now the limiting factor?

So we have 3d printers in stores. Now we need all of the home devices that could potentially need spare parts printed to be available online, preferably in a unified database. You need manufacturer buy-in. Maybe some sort of certification mark that manufacturers can stick on their devices to show that printable replacement part models are freely available. I could use a new cheese compartment door in my fridge right now, for example. And I live in Iceland where shipping times are long and shipping costs / import duties high, so it'd make time and economic sense to print, too. But while having a 3d printer would be great, if the model isn't available, how does that help me?

Of course some companies, like iRobot, rely on profiting off of selling their spare parts.

It does seem rather weird to treat it as an intractable problem. Are we really talking about something that's AI-Complete here, like natural language understanding? Something not succeptible to a combination of chained rules, physics calculations, and statistical analysis? I seriously doubt it. So different machines can act differently due to wear, etc? Gee, people have never written programs to deal with that before, heavens no. So some things may require a decision from the operator, like whether to restart a defective piece or try to salvage it? Gee, I've never heard of a program asking the user a question during operation before! A piece of "printing" hardware experiencing a jam of some kind and needing manual intervention? Gee, nobody has ever experienced that one before!

I'm not saying that CNC machines and 3d printers are equivalent and that you can just swap a CNC machine in to the sort of role 3d printers are intended for. Of course the task of gouging out steel with power tools is a more intensive one than writing out plastic in layers with a slightly more advanced version of a hot glue gun. But we're not talking about creating superintelligent cyborgs here, we're talking about analyzing physical processes, including their various failure modes, and when a decision or action is required, presenting the user with the information needed to do that.

* This was before the Romans brought chimneys and window glass.

I'm sorry, I'm having trouble hearing you, your horse is too high.

So when do you ride down Electric Avenue on that Harley?

I was going to respond only to your first paragraph, but your last paragraph proves what I'm about to say.

Abstinence education can work, when you encourage critical thinking along with it and do not try to use ignorance to protect innocence. I took what I learned after I was married in Catholic NFP classes, and am using it to teach my special needs son about sex. Being well aware that his body will outpace his mind and critical thinking skills on this issue, I started early with my form of abstinence education- about age 5. Now at 11, he is both protective of his own eyes (hiding during certain scenes in Big Bang Theory, a show he otherwise enjoys) and protective of other people's modesty (necessary, since mommy runs a daycare) . He's already run into homosexuality at school, and handled it by coming to adults with the issue rather than attempting to dissuade a rather aggressive same-age predator on his own.

I have no doubt whatsoever that by high school, he'll be a leader, not a follower, when it comes to sex, and will be armed with the ability to make the correct decision when it comes to abstinence before marriage.

But only because we've talked about it, and because I've been honest.

How much math does it take to use a slingshot?

No it doesn't. Why are you making excuses for the ridiculous state of internet access in the US?

Rural areas of Europe frequently have internet access that make most US cities look terribly slow.

The more you parrot your nonsense argument the longer it will take to fix.

Try again:

"Tesla is new, different, and shaking up the ridiculously old way of doing things."

"... basically says Tesla is going to prevail in every state against ..."

Oh, and in #2, sound insulation would also be very important, both for the compressor (if compressed air is used, rather than bottled oxygen) and for the jet itself (which is basically like a tiny rocket engine). And I guess the filter isn't just about removing any incomplete combustion products from the exhaust, but also any dust or the like.

Even if it ultimately isn't suited for, say, a quiet home office, 3d printing isn't really an home office task, we're more talking about a "garage workshop" sort of thing. I'm just curious whether anyone has pursued such an approach, because at a glance it sure looks to have potential for making a very broadly capable product. I mean, such a system should even be capable of printing electronics, including resistors, capacitors, etc, maybe even some types of batteries (not anything requiring extreme precision, like a CPU, and li-ion batteries would be right out due to the thin, sensitive and rather complex membrane needed, there's no way you could just deposit that, but still..).