Large scale 3D printing
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Large scale printing will be needed for any number of useful things, the challenge is useful materials and resolution.
Resolution on this machine could be improved by using a laser or electron beam in conjunction with the air blower. The blower would be used to fuse large internal volumes, and the laser would allow the exterior to be much finer, while saving much time over a pure laser system. Electron beam, if it works, would be more resilient than the laser.
I was looking at a .250″ nozzle for an FDM machine. The ideal machine would have a sub-.010″ nozzle for detail work, perhaps an intermediate one of .050-.100″, and would use them together–the larger nozzles would rapidly fill internal volume, while the smaller ones would allow precise dimensions on the finished outside of the part. You might end up with a four or six nozzle machine, with a set for your support material.
I was looking at a makerbot vs reprap vs kludging my own, but the DIY area seems to be lacking on support material support. Something I plan to look into is using a still to extract the newer water soluble materials for reuse. This would go with having a grinder and extruder to make your own filament. Plastic is cheaper in pellet bulk. I think a large nozzle like a quarter inch might need to be pellet fed directly anyway.