Nozzle

A nozzle in concrete printing is the shaped outlet at the end of the print head through which fresh mortar is extruded, defining the width and profile of the deposited filament.

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A nozzle in concrete printing is the shaped outlet at the end of the print head through which fresh mortar is extruded, defining the width and profile of the deposited filament. Round nozzles produce a rounded bead; rectangular or slotted nozzles produce a flatter, more regular layer face. Some print heads carry a trailing trowel or shaping plate immediately behind the outlet to smooth the side of the filament while the material is still soft.

In practice

Nozzle diameters on construction-scale extrusion printers are typically in the range of roughly 20 to 50 mm, with individual machines published over narrower bands; the WASP Crane WASP, for example, is listed by the manufacturer at 25 to 38 mm. A larger nozzle deposits more material per pass and shortens print time, but makes fine detail and tight corners impossible and increases the load on the layers below. Nozzle diameter is normally chosen first, since it constrains both layer height and the minimum feature size the toolpath can contain. Aggregate size has to suit the nozzle: a common rule of thumb keeps the largest grain well below a fifth of the opening to avoid blockages.

Related terms

  • Extrusion — the deposition process the nozzle terminates.
  • Layer height — the vertical step per pass, usually derived from nozzle diameter.
  • Surface finish — the visible result of nozzle shape and shaping tools.

Related

ExtrusionExtrusion is the process of forcing fresh mortar through a nozzle to form a continuous filament, the dominant deposition method in concrete printing.Layer heightLayer height is the vertical thickness of one deposited layer in a print, set by nozzle size, flow rate and how fast the head travels.Surface finish of printed concreteSurface finish is the condition of a printed element's face, from the ribbed as-printed texture to troweled, ground, rendered or coated surfaces.ToolpathA toolpath is the programmed route the print head follows through space, defining the order, direction and speed of every deposited layer.