  Fused deposition modeling (FDM) using mobile robots instead of the
gantry-based 3D printer enables additive manufacturing at a larger scale with
higher speed. This introduces challenges including accurate localization,
control of the printhead, and design of a stable mobile manipulator with low
vibrations and proper degrees of freedom. We proposed and developed a low-cost
non-holonomic mobile 3D printing system guided by a projector via
learning-based visual servo-ing. It requires almost no manual calibration of
the system parameters. Using a regular top-down projector without any expensive
external localization device for pose feedback, this system enabled mobile
robots to accurately follow pre-designed millimeter-level printing trajectories
with speed control. We evaluate the system in terms of its trajectory accuracy
and printing quality compared with original 3D designs. We further demonstrated
the potential of this system using two such mobile robots to collaboratively
print a 3D object with dimensions of 80cm x 30cm size, which exceeds the
limitation of common desktop FDM 3D printers.
