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Desktop 3D printers work by moving a tiny nozzle across a tiny and rigid, precisely engineered level plate. Said nozzle extrudes a thermoplastic that can be tra

Desktop 3D printers work by moving a tiny nozzle across a tiny and rigid, precisely engineered level plate. Said nozzle extrudes a thermoplastic that can be transported to the nozzle in solid form, quickly melted and then solidified again. Building-grade 3D printers work by moving a giant and heavy nozzle across a wobbly giant frame, set on whatever uneven ground that happens to be at the building site. Said nozzle extrudes a concrete mix that can only be transported to the nozzle in liquid form, and one must wait for the layers to solidify before the next one can be laid down. Also, said concrete must not be liquid enough, that it flows off the print surface (like regular concrete), but must be liquid enough to be pumped around the machine. Clearing clogs must be a nightmare. Also, concrete sucks in tension, which is why steel bars are inserted into it, to pre tension it, which is not possible with this technology. For all the engineering reasons desktop 3D printers make sense, building grade ones don't.

ben_w 3y ago
Given the first I heard of a concrete building printer was some random person doing it at home to give their daughter a small fantasy castle to play in, I think you might possibly be overstating the difficulty of the challenge from the point of view of domain experts. https://hackaday.com/2014/09/01/update-3d-printed-concrete-castle-completed/ https://hackaday.com/2014/09/01/update-3d-printed-concrete-c...
- torginus 3y ago
  Sorry not seeing how this disproves anything in my post. "Some guy did it so it can't be that hard" is not a solid line of reasoning. And as someone who has 3d printed stuff, there is a distinct lack of (hard to print) overhangs in this structure. By the way, imo one of the hallmarks of impractical technology is stagnation, dude did it a decade ago, and 3d printed structures have the same problems today.
  - serf 3y ago
    >By the way, imo one of the hallmarks of impractical technology is stagnation, dude did it a decade ago, and 3d printed structures have the same problems today. no, they don't have the same problems today. Building houses on planar lines with concrete extrusion doesn't represent the cutting edge, it represents the technology that has been vetted and approved enough for public ownership and land endorsement. multi-axis extruders with large DoF and non-planar routing is approaching the state of the art, and overhangs are well dealt with. 3d printing in general is one of the least stagnant industries I can think of right now. It's being adopted en masse by the largest groups and is generally receiving a lot of intellectual attention.
    - torginus 3y ago
      I'm sorry, I raised a bunch of technical concerns, and you hand waved them away with the vague notion that technological progress has solved them. I still don't see how you can build tensioned reinforced concrete structures with this tech, and overhang bridging is not possible due to fundamentally different material properties than say, PLA. To be clear I'm not saying the technology doesn't work, just that it's not better than anything we have now, because of the problems I outlined, and thus is relegated to niches.
      - ben_w 3y ago
        Your technical concerns clearly aren't showstoppers because the professional building exists now, and because random person did it DIY a decade ago. There's one overhang solution in my previous link, the more recent videos about printed houses with windows use a different, traditional, solution: lintels. As for reinforcement, I can't say I really deeply understand the Wikipedia page "Reinforcement in concrete 3D printing", but it is quite sizeable and lists many things: https://en.wikipedia.org/wiki/Reinforcement_in_concrete_3D_printing https://en.wikipedia.org/wiki/Reinforcement_in_concrete_3D_p... To be clear, I also think 3D printed concrete is a case of throwing buzzwords at problems rather than a good idea, but not because it doesn't work, rather because it produces a merely OK result for what is the single cheapest part of the construction process — I can get a prefab shell of a house built here in Germany for €100k, but that turns into €550k when you add the land, preparation of the land, connecting utilities, wiring and plumbing, and interior plastering.

ben_w 3y ago

Given the first I heard of a concrete building printer was some random person doing it at home to give their daughter a small fantasy castle to play in, I think you might possibly be overstating the difficulty of the challenge from the point of view of domain experts. https://hackaday.com/2014/09/01/update-3d-printed-concrete-castle-completed/ https://hackaday.com/2014/09/01/update-3d-printed-concrete-c...

torginus 3y ago
Sorry not seeing how this disproves anything in my post. "Some guy did it so it can't be that hard" is not a solid line of reasoning. And as someone who has 3d printed stuff, there is a distinct lack of (hard to print) overhangs in this structure. By the way, imo one of the hallmarks of impractical technology is stagnation, dude did it a decade ago, and 3d printed structures have the same problems today.
- serf 3y ago
  >By the way, imo one of the hallmarks of impractical technology is stagnation, dude did it a decade ago, and 3d printed structures have the same problems today. no, they don't have the same problems today. Building houses on planar lines with concrete extrusion doesn't represent the cutting edge, it represents the technology that has been vetted and approved enough for public ownership and land endorsement. multi-axis extruders with large DoF and non-planar routing is approaching the state of the art, and overhangs are well dealt with. 3d printing in general is one of the least stagnant industries I can think of right now. It's being adopted en masse by the largest groups and is generally receiving a lot of intellectual attention.
  - torginus 3y ago
    I'm sorry, I raised a bunch of technical concerns, and you hand waved them away with the vague notion that technological progress has solved them. I still don't see how you can build tensioned reinforced concrete structures with this tech, and overhang bridging is not possible due to fundamentally different material properties than say, PLA. To be clear I'm not saying the technology doesn't work, just that it's not better than anything we have now, because of the problems I outlined, and thus is relegated to niches.
    - ben_w 3y ago
      Your technical concerns clearly aren't showstoppers because the professional building exists now, and because random person did it DIY a decade ago. There's one overhang solution in my previous link, the more recent videos about printed houses with windows use a different, traditional, solution: lintels. As for reinforcement, I can't say I really deeply understand the Wikipedia page "Reinforcement in concrete 3D printing", but it is quite sizeable and lists many things: https://en.wikipedia.org/wiki/Reinforcement_in_concrete_3D_printing https://en.wikipedia.org/wiki/Reinforcement_in_concrete_3D_p... To be clear, I also think 3D printed concrete is a case of throwing buzzwords at problems rather than a good idea, but not because it doesn't work, rather because it produces a merely OK result for what is the single cheapest part of the construction process — I can get a prefab shell of a house built here in Germany for €100k, but that turns into €550k when you add the land, preparation of the land, connecting utilities, wiring and plumbing, and interior plastering.