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Q-Bot·2020–21

SAWS: Spray Applied Wall Gantry System

3D scan to tool path for an intelligent gantry that renders and insulates walls: window detection, wall segmentation, surface and texture analysis, then tool paths for extruding, smoothing and scratching.

Problem

Rendering and externally insulating a wall by hand is slow, skilled and weather-dependent. The Spray Applied Wall Gantry System (SAWS) does it automatically, but a gantry only knows where to move if something turns the wall in front of it into tool paths.

What I did

We scanned each wall with a Leica laser scanner. I developed the pipeline from that 3D scan to control action: it detects window panels, segments the wall and its properties, measures surface variation and texture, and extracts the geometry features needed to generate tool paths for each operation: extruding material onto the wall, smoothing it and scratching it.

Result

The gantry was at an early stage, and our initial workflow prototype showed promising results on both real and simulated data. Simulation confirmed the gantry could follow the generated trajectories, and the real rig then went from scan to tool path to render on the wall. The apparatus is covered by a US patent application on which I am a co-inventor.

simulation to wall

3 steps

  1. 01

    Simulate

    Before anything touched a wall, the generated trajectory ran in simulation against the scanned geometry. The end effector is tool-agnostic, so the question was whether the gantry could follow the path: covering the wall in passes, working around the window opening, and using the 4th and 5th axes to stay square to each face without colliding with the frame. It could.

    Simulation · passes around the window
    Simulation · top-down, following the wall profile
  2. 02

    Apply

    The same trajectory, exported as G-code, drives the real gantry. With the nozzle on, it lays render onto the wall bead by bead, including around the window frame.

    Real wall · extruding
  3. 03

    Smooth

    Swap the tool and run a smoothing pass. The compliance module keeps the smoothing tool pressed into the wet render as it works the surface flat.

    Real wall · smoothing

figures

click to enlarge

fig. 01Leica scan of the test wall, window opening and all, loaded into the planning UI.Q-Bot film by Duckrabbit
fig. 02Generated extrusion tool path, exported as G-code and previewed in the gantry controller.Q-Bot film by Duckrabbit
fig. 03Extruding render onto the wall along the planned path.Q-Bot film by Duckrabbit
fig. 04The SAWS gantry working the test wall.Q-Bot film by Duckrabbit
fig. 05Gantry that moves the tool arm along a path over freshly applied render.US 2024/0181489 A1, fig. 1
fig. 06Tool head on a compliance module that keeps the tool pressed into the wet coating.US 2024/0181489 A1, figs. 2–3
fig. 07The apparatus working render applied to a building.US 2024/0181489 A1, figs. 9–11
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