Methods and apparatus for computer-assisted spray foam fabrication
In exemplary implementations of this invention, a nozzle sprays foam, layer by layer, to fabricate a fabricated object according to a CAD model, and a subtractive fabrication tool removes material from the fabricated object according to a CAD model. The fabricated object comprises a mold or an interior form. The foam may be low-density, high strength and fast-curing. The foam may be used for large-scale 3D printing. For example, the foam may be used to 3D print molds for walls of homes. The foam molds may be left in place, after casting concrete in the molds, to serve as insulation. Or for example, the foam may be used to 3D print on site an internal form for a large wind turbine blade. The wind turbine blade may then be produced on site by depositing fiberglass on the outside of the internal form.
1. A method comprising, in combination:
(a) spraying foam from a nozzle, layer by layer, to fabricate walls of a mold according to a CAD model, which walls are configured to contain a casting material within the walls while the casting material cures; and
(b) removing material from the mold walls using a subtractive fabrication tool,
wherein a fabricator arm:
(i) supports a tool module, which tool module comprises the nozzle and the subtractive fabrication tool, the nozzle and the subtractive fabrication tool being positioned at different locations within the tool module, and
(ii) actuates movement of the tool module to position the nozzle and subtractive fabrication tool appropriately for the spraying and removing steps.
2. The method of claim 1 , wherein:
the foam cures after being sprayed; and
the mold is insulative and is left in place after the foam cures.
3. The method of claim 1 , wherein the foam is chemically setting.
4. The method of claim 1 , wherein at least one material property of the foam that comprises the mold varies spatially within the mold.
5. The method of claim 1 , wherein the spraying causes an exterior surface of the mold to be doubly-curved.
6. The method of claim 1 , wherein the removing causes an exterior surface of the mold to become smoother immediately after the removing than immediately before the removing.
7. The method of claim 1 , wherein the method further comprises embedding structural elements in the walls.
8. The method of claim 7 , wherein the structural elements are ties.
9. The method of claim 8 , wherein the ties are configured to hold rebar in position.
10. The method of claim 1 , wherein, for each respective wall, the only solid surface that touches and is external to the respective wall, during the spraying, is positioned beneath the respective wall.
11. The method of claim 1 , wherein:
the foam is sag-resistant; and
the spraying is during a multi-cure period in which a span of a wall of the mold is formed, which span is, during the spraying, an unsupported span.
12. The method of claim 1 , wherein:
the foam spraying from the nozzle is in a flat fan pattern spray; and
rotating the nozzle varies width and thickness of a layer being deposited.
13. The method of claim 1 , wherein the foam is sprayed upward from the nozzle and then adheres to a wall of the mold being fabricated.
14. The method of claim 1 , wherein:
the foam undergoes curing after being sprayed from the nozzle; and
during the curing, the foam expands.