Looking behind the hype, what is left ? A new tool.
And - as it is with every tool - there are hobbyists fiddling around with it and there are others using it to the extremes. An - well known - example: a solder iron is a versatile tool. You can even use it to make pictures on wood. In the expert's hands it can be used to produce the most complicated and advanced electronics. (Though you might choose more sophisticated soldering tools :) )
And one of the latest 3D printers in the - extended - hobbyist budget is a real photolithographic printer: no longer fiddling with thermoplasts. - - - Time will show how these tools are developing. I'd expect new applications to be found.
BTW: in the far, far past there have been some "unorthodox" plotters having wheels instead of some kind of flatbed. Applying this principle on 3D printers would - to some extend - overcome the current object size limitations.
On the other hand the "subtractive tools" (vulgo: CNC lathes and milling machines) are becoming more and more affordable too. Though currently this is not in the public focus.
I think the 3D printing has brought the manufactruing to home just like the desktops brought the computing to home some 30 years ago. So tomorrows kids will not just assemble the DIY kits from the blocks provided but will have the freedom to create their own building blocks. 3D printing is a good tool for prototype building and also a tool to build small actual objects. I have seen a news where there is a plan to construct a full size house using a special 3D printer. So what 3D printers will do in the near future is best left to one's imagination. The only hitch is the material handling !
I absolutely agree that 3D printing won't let machines reproduce. (That may happen, but not because of 3D printing.) The most impressive use I've seen to date was by a heart-surgeon who transformed a CAT scan into a 3-D model of the heart upon which he planned to operate. It enable him to see exactly what he would find inside the heart itself in a way that a 2D image just can't do. At that point, I started believing a lot of what I'd previously dismissed as hype.
This is a very interesting topic. I suppose one awkward point for 3D printing is what happens if a particular piece got botched in the middle. I suppose it would have to be scrapped? Otherwise, you'd have to pick up exactly where you left off. Wouldn't that automatically generate a flawed interface (like a defect) between the previous and restarted printing portions?
I agree with most of what you've said. It has always bugged me when people comment on how a 3d printer can print itself. Especially when you're talking about additive plastics. The most important parts of the machine are the hot nozzle(extruder) and the stepper motors. Neither of which can be printed as a functional unit right now.
I was amused by the following statement though.
"Also, in the general case a machine that could print itself could only make smaller copies of itself -- just as a mother makes a baby. I am excluding special topological cases, such as a donut-shaped machine that could extrude a sausage-shaped daughter-machine designed to then curl up to form a full-sized repeat of the mother-machine."
This only holds true if you also require that machine to assemble the product. I own a 3d printer and have actually printed several things that, when assembled, are of a larger volume than the printer itself.
There are companies that print in metal right now! They tend to use a different method than the typical "hot glue" style printer you see right now. Look at Shapeways for example, you can choose for your item to be printed in a variety of plastics as well as stainless steel, silver, and ceramic.