Singapore university 3D prints a bathroom pod in less than a day

After fours years of development, researchers from Nanyang Technological University, Singapore (NTU Singapore) have developed the capability to robotically 3D print an unfurnished bathroom pod in 12 hours or less.

The technique, which uses a 6-axis robotic arm equipped with print nozzle for the special concrete mix, could help firms build prefabricated bathroom units, or PBUs, about 30% more quickly, they say.

PBUs are already required on high-rise residential buildings on Government Land Sale sites in Singapore, but the conventional method for these is concrete casting.

This new method is not only faster, but creates a PBU that is 30% lighter than conventionally cast ones, the university said.

After printing, the bathroom is furnished with toilet fittings, tiles and concealed drains and piping, which takes five days.

Researchers strove for a concrete mix that could harden fast enough to take the next printed layer. They say the final product is as strong as conventional concrete.

See the robot at work in a video below.

The technique was developed by a joint research team led by Assoc Prof Tan Ming Jen from NTU’s Singapore Centre for 3D Printing, in partnership with Sembcorp Design and Construction, and Sembcorp Architects & Engineers.

They will now seek approvals for trials from the Building and Construction Authority of Singapore, and will investigate commercialising the technology through licensing or a spin-off company.

"The complicated shape of a PBU and its walls can be developed and printed at a faster pace to satisfy the needs of individual customers as no formwork or moulds are required, whereas conventional construction of PBUs with concrete or lightweight wall panels always limit the possibilities of design," said Er Lie Liong Tjen, team lead from Sembcorp Design and Construction, and Sembcorp Architects & Engineers.

Mr Lim Tuang Liang, an executive director at the National Research Foundation of Singapore, said: "Singapore’s strength in advanced manufacturing technologies is deepening not only in the area of research, but also in the adoption and deployment of these technologies by our companies."

Researchers said 3D-printing PBUs could help manufacturers halve their production time while lowering transport costs, carbon emissions and materials wastage.

"By being able to print-on-demand, companies can save on their inventory costs as well as manpower costs, as they don’t have to hold as much stock and their workers can be redeployed to do higher-level tasks. This approach improves the safety of the workplace, since robots are doing the construction of the bathroom unit," Prof Tan said.

The printing was carried out in a single build using a 6-axis KUKA Robotic arm, which has a reach of about 6 metres in diameter.

The concrete was fed to mixers and pumped out of a nozzle mounted on the robotic arm, depositing the material layer by layer according to the digital blueprint.

To save material and achieve weight savings of up to 30%, the walls of the PBU were printed in a W-lattice shape, which lent additional strength to the final structure.  

The research team printed and outfitted two PBUs. One measuring 1.62m (L) x 1.5m (W) x 2.8m (H) was printed in nine hours, while the second PBU measuring 2m (L) x 2.6m (W) x 2.8m (H) was printed in 12 hours.

Image: The new method is 30% faster and creates a pod that is 30% lighter than conventionally cast one (NTU Singapore)

Further reading:
How Singapore plans to push its construction industry into the 21st Century

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