The original note, as written at the time
With 3D printing complexity is basically free. Imagine 3D printing with drones. And this we can birth something known as intelligent 3D printing.
Ongoing development
With 3D printing, complexity is basically free. So imagine 3D printing with drones — and out of that, something that could be called intelligent 3D printing.
Complexity being free is the premise, and it is under-exploited because a printer is a box. A gantry machine can only build what fits within its frame, at the scale of the frame, in the order the head can reach. That constraint is not about material; it is about the machine being bigger than the object.
Drones remove the frame. Several of them, cooperating, deposit material in free space at a scale limited by the site rather than the workshop. The object is built by a swarm that knows the shape and its own position within it.
The word intelligent is doing real work. A drone printer has to know what has already been printed and how it is curing, because unlike a gantry it cannot assume the substrate is where it left it. That means sensing, and it means the plan is revised continuously rather than executed.
The plausible first use is not a house. It is repair — a crack in a dam, a spall on a chimney, a patch on a silo, all of which are places where scaffolding costs more than the material. A drone that can build a small structure in a place a person cannot stand is already valuable.
The objections are wind, accuracy and cost, and none of them are fatal at the scale of a repair.
The frame is the limitation. Remove it and the site becomes the printer.