The new 3D printers are pretty cool. We use them for prototyping at my company. The 3D components can be assembled and actually function. I hear that the next step is using powered metals to produce components. I can't wait to test these out.
Dassault Systèmes proposes a free design tool called 3DVIA Shape (http://www.3dvia.com/products/3dvia-shape/), directly connected to 3DVIA.com where 3D designs and prototypes can be stored, used in 3D experiences and/or sent to 3D print. It's pretty much a 3-clicks process. Your feedback would be most welcome.
Printing a house is pretty cool. We did a story on Design News about KOR EcoLogic, a company using 3D printing to produce a prototype of a car. I'm sure there are mounting examples of 3D printing used in ways unimaginable before.
I too have seen a lot of this 3D printing lately. I read an article about a larger unit that could "print" a house, well sort of. Just Google "print-a-house", it is a project at USC supported by Caterpillar. I am thinking that as the cost of the printers comes down various services will proliferate that will print the design for you if you don't have your own printer as you mentioned. The advent of readily available and easy to use software for designing the items will accelerate this tend even more.
I have used Google sketchup but it has been a long time since I worked with the more upscale tools. If someone links a free adn easy to use tool like sketchup to a 3D printing service it will definitely be a boost in this trend. I can see this being combined with other prototyping tools like the Arduino tools to be able to create much better working designs and prototypes.
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