These fast and rough 3d printers were critical to the early building activities in Moon Town. Powder regolith is sieved through screens into a hopper, which spreads thin flat layers of it over a giant crude printing bed. Then linear Fresnel lenses run along the bed, focusing sunlight to a very thin line across its width and melting the powder there into a glassy material. A set of motorized shutters block out portions of the lens, moving around as the lens travels the length of the bed. This allows simple flat shapes to be defined. Then the hopper spreads another layer of powder and the process is repeated. Successive layers allow simple objects to be built up to a depth of about 50 cm.
The rails that the lens runs along can also accommodate other simple robotic equipment. In the SketchFab viewer below, a supplementary round Fresnel lens is shown. It can be used to heat spots in the piece being worked on for the purpose of bending, punching, or stamping it. When not doing that, this lens can be used to keep a pot of regolith molten, that can then be used to join pieces together. Perhaps a cutter tool could be added to the rails, that slices pieces when they have solidified just enough for that to work, thus aiding in making folds or cleaner edges. Screens of insulation could be deployed to slow cooling.
This system is only really effective for about 10 of the 15 days of sunlight during each month, when the sun is high enough. Optionally, that could be extended by using a microwave emitter to melt regolith in the bed at other times. Note that the scale of the printer is, like many things in the town, as large as was practical when it was created. The effective printing area of the bed is 14 m wide and 59 m long. The Fresnel lenses focus the energy of 70 square meters of sun onto a line the width of a spaghetti noodle.
If you click the arrow in the image below, you can then click on the numbers that appear and take a tour of the concept.
The construction materials provided by this process tend to have a lot of flaws, but this can be compensated for by being generous with the amount of material used and building hefty things. In many cases that’s good enough. These were used to create the massive arches across the glazing of the atriums, for instance. Panels were created, then bent and joined into boxes, which were filled with a gravel and molten regolith mixture. Series of such boxes were then assembled to create each arch, including cables that run through grooves and channels, to pull the arch down against the pressure of the atmosphere in the habitat below. They were also used to create the columns and arches of the factory buildings outside, the walls and floors of the underground pressurized habs, and many elements of the gallery hab roofs. They continue to be used to fabricate the tiny homes of town residents, and furniture, kiosks and such.
There is a channel on our Discord server for discussion of the design of this equipment. Come join if there is anything you’d like to comment on or ask – https://discord.gg/B2pQuFRJny
Also see the Projects page for general guidance on designing for Moonwards – materials, infrastructure, transport, practices, and main reference works.