The problem is the usual: a single material isn't enough to make anything but the simple constructs. Almost everything is complex these days. Materials Science hasn't been a science for a century for nothing.
EDIT: They also show visual demonstrations of techniques as to HOW this would be accomplished.
It may be true that fixtures could be set into place in an automated way. Its not true that they can be connected. And certainly no existing fixture is ready to be installed this way.
Housing construction depends upon massive efficiencies of scale. All the new fixtures for these imaginary houses would be designed differently (for robotic installation, not hand-installation). They will start out at a price many multiples of existing fixtures. They will go down ONLY if this process becomes very, very common.
So, maybe this could be used to make novelty houses for the rich. That's about it. The video makes grand claims about cheap housing for the masses. That is preposterous. Folks in India are not suffering from expensive housing because construction is a dangerous occupation. Its land and materials that are expensive. Labor is the cheapest part of their equation I think.
I think they may be aiming for something like Katrina homes. Or any other refugee situation. See some more refugees crossing the border, squirt a few extra refugee houses where they fit. Prefab is probably still cheaper.
Even imagine the robot exists: how exactly does it just 'plug in' the plumbinb and electrical systems? Currently it takes a person to scramble all over the house, drilling and fitting and connecting.
There is nothing being solved here. Just a blue-sky story about an imaginary printer.
The real breakthroughs will come when people stop fixating on "printing" (extrusion) and realize it's the 3-d (4-d, 5-d, etc.) gantry that's the super-useful part. Fitted with different tools, such as painting, gluing and sanding tools, a 3-d gantry can be extremely useful.
There will however continue to be a "last mile" problem in Computer-Assisted Manufacturing (CAM) applications. These are the details, such as stripping wires, screwing in electrical boxes, etc. where the robot to perform these tasks is prohibitively expensive. The breakthrough is the 3-d gantry form, due largely to the reduction in prices of microcontrollers and power transistors, but it does not extend to all robotics, such as detail work.
For example, I've been watching videos on building guitars. I would love to see a 3-d printer friend explain to me how it's going to build a guitar from scratch. The economy of 3-d printing doesn't extend to the large number of distinct tasks, requiring different tools, techniques, process and forces in most objects that are useful in the real world.
This entropic mixture of difficult processes, I would argue, is the very reason WHY particular artifacts, such as a guitar, television set, couch, etc. are valuable in the first place. It is because no quantity of single, unskilled process (like shoveling coal) can produce them.
I don't make guitars but I am guessing you could 3-d print most of a factory to make guitars. All the jigs and fixtures ready for use accurate to a 1/1000th.
What I do know about, and am interested in, is 3-d printing foundry patterns. Its harder to make a foundry pattern than you'd think, not just the obvious stuff like bulk material shrinkage and draft angles, but its really hard to handle differential shrinkage (warping, essentially). Its a complicated fine woodworking skill (assuming you're using wood foundry patterns). So you can't 3-d print a cast iron pan or an engine block, but you can print a pattern to be rammed in a sand mold and then cast some iron in the mold and ta-da a perfectly flat pan or perfectly straight engine block or whatever. This isn't a magic tool that'll make any idiot able to do foundry work, but it does mean that any idiot on the planet would be able to share world class pattern designs.
I would be happy to be able to print some holding fixtures for my metal lathe. You can't make crazy deep hogging cuts with flimsy PLA holding the work to the mill table, but you could do "something" at least.
I think people who expect 3-d printers to be magic star trek replicators are going to be very disappointed, although indirectly via one or two levels of indirection they will probably play a huge role in everything, soon enough.
Its just positive machining. Much as people don't use my negative machining traditional lathe and mill, I don't think joe 6 pack is going to be using a 3d printer on a regular basis, although much like negative machining revolutionized the world behind the scenes, sorta, positive machining will also revolutionize the world, again, behind the scenes sorta.
http://www.kurzweilai.net/the-worlds-first-3d-printed-guitar
edit - and a video of a 3d printed violin http://www.youtube.com/watch?v=XU3AZmf6O7I
I think that 3D printing will win when it starts making things that couldn't be made before. How about an instrument with complex echo chambers impossible to reproduce with wood and glue?
Could you watch the video? He already addresses these issues, and they are clearly researching how to do this. This is just a giant pick-and-place machine working with larger components. They already show that some human effort will be required in the assembly process, but hopefully will be much safer than what is done today.
Lays them in as it builds presumably. Pick and place is easy with a big h-crane robot.
Also, you can lay down multiple materials by making the head swappable. I would also say plumbing and electrics are nowhere near as complex as they used to be. Everything is available as clip-on fittings these days, which is perfect for automation.
Why do you think one or more significantly smaller printers couldn't be used as an on-site prefab factory? That seems like a much more reasonable way to approach this problem.
But your point still stands. A master plumber might not be required for every part of every job today.
I do tech/IT by day, but have a welding certification as well. Its extremely easy to braize copper tubing together for plumbing once you've practiced, but feels like its work that isn't necessary when there are easier ways to do it (ie the pex pipe you suggested).
Coincidently, I'm replacing two toilets in my home tonight. Wish me luck!
Off topic: They actually advertise the toilet as being unclogable and demonstrate it by flushing a bucket of golf balls down it. Brilliant.