This research into developing large-scale 3D printing of polymers has been in continuous development since 2015. The lab has made pioneering contributions to the development of large-scale polymer printing and its application to architecture and building construction. This research includes developing approaches to 3D printing recycled plastics and developing circular economy approaches.

RECYCLED PLASTICS

We have developed strategies for printing recycled plastics, with particular expertise in printing recycled PETG. RMIT has invested in a facility for shredding large plastic components (including our own prints and prototypes) to create stock that can either be batch processed into new pellets or used directly in our robot mounted extruder. Several of our projects, including Composite Bioforms and Unclear Cloud, have been printed with recycled plastic.

Within the lab, we have developed techniques for large-scale plastic deposition using industrial robots. This Fused Deposition Modeling (FDM) technique employs a 6-axis Kuka KR150 industrial robot (mounted on a 4m linear track) with a polymer extruding end-effector to directly deposit the plastic through a layer-by-layer operation. This technique enables a significant increase of scale from the FDM 3D printing which S. Scott Crump initially developed in the 1980’s and was commercialized by Stratasys in 1990. The extruder melts pelletized plastic that is fed through its nozzle by a variable speed screw. The layers typically vary in height from 1mm to 3mm and width from 4mm to 8mm, with a build envelope established at RMIT University of 5m x 2.5m x 2m.

HIGH TEMPERATURE PLASTICS

The lab has developed approaches to printing a variety of plastics including PETG, PLA, ABS, HDPE and Polycarbonate, The high temperature required for the extrusion of polycarbonate makes it a difficult material to 3D print; in an uncontrolled environment shrinkage can cause warping in the material as it cools. We have developed a process of stabilizing the cooling of printed parts through controlling radiant heat and conduction through the base-plate. Despite these complexities polycarbonate is an excellent building material as it is crystal clear, UV stable and has excellent mechanical properties. Polycarbonate parts printed at RMIT have recently passed the necessary lab testing to adhere to Australian fire codes enabling it to be used in building construction.

Polymer printing is an easily scalable process that becomes increasingly efficient with an increase in size. An important limiting factor on the speed of deposition is the setting time between depositing layers, a factor that becomes less relevant as the tool path of each layer becomes larger and the parts increase in scale. Large-scale 3D printing enables the construction of complex and intricate geometries, however each printing process has its own set of limitations. The primary limitation of this polycarbonate printing technique is its draft angle – the prints are limited to 40 degree overhangs.

PUBLICATIONS

• Snooks, Roland. Harper, Laura. "Printed Assemblages". In Fabricate 2020, edited by Jane Burry, Jenny Sabin, Bob Sheil, Marilena Skavara, 202-209. London: UCL Press, 2020.

• Snooks, R. 2018, 'Sacrificial Formation', in Towards a Robotic Architecture, ORO Applied Research + Design, New York, United States, pp. 104-117 ISBN: 9781939621634