The advantages of 3D printing of formwork are proven once again

voxeljet AG prints complex molds for "intelligent" concrete ceiling at DFAB (NEST)

Using 3D printing, voxeljet AG created the highly-complex formwork for the research project DFAB House (digitally-manufactured house) in the NEST project (Next Evolution in Sustainable Building Technologies) of the EMPA (Swiss Federal Laboratories for Materials Science and Technology). This involved a 78 m2 lightweight concrete slab as a structurally-optimised and functionally-integrated ceiling slab with a performative complex design. 3D printing using the Powder-Binder-Jetting process once again proved valuable in such a Project.

At NEST in Zurich, voxeljet has once again proven how useful 3D printing is for the creation of highly-complex formworks. For the DFAB House project (digitally-manufactured house), a research project from ETH Zurich as part of the Digital Fabrication Swiss National Centre of Competence in Research (NCCR DFAB), 136 formwork elements were created using the Powder-Binder-Jetting process.   The specific process used was the Furan-Direct-Binding (FDB) process from voxeljet. A 3d printing technology in which silica sand layers are selectively bound together with an organic binder (furan resin) through polymerisation.

3D printing saves time, material and money

The intelligent slab is one of the core elements of the DFAB House, which is designed, planned and built in the NEST of the EMPA by the research group Digital Building Technologies (DBT) at ETH Zurich under the direction of Prof. Dr. Benjamin Dillenburger. The formwork system for this large-scale project was designed by the team of DBT. The objective of the project was, to demonstrate how 3D printing, based on optimised CAD data, can save resources on construction sites. Compared to columns, slabs require much more concrete – actually up to 80% of the total weight of a building can be accounted to slabs only. The saving potential is correspondingly significant. And the objective was achieved: At the DFAB House, the slab has been realized only as heavy as statically required at each point. Therefore, over 60% of concrete have been saved, compared to conventional construction methods. 3D printing using the Powder-Binder-Jetting process was the ideal solution for these highly-complex and three-dimensional curved formwork elements. "Smart Slab" is intended to help the construction industry to build more compact and material-saving structures in the future, as additional functions such as lamp sockets, drill holes or openings for sprinkler systems can already be integrated in the data set for 3D printing.

Flexible and economical formwork methods for complex shapes

For this demanding project, many factors spoke in favour of 3D printing of the individual formwork elements. Project manager Dr. Mania Aghaei Meibodi on the main benefits of this method: “Through a parametric model, adjustments can be made at any time, without additional costs. If a three-dimensional shape is changed, the 3D data and the 3D printing can be easily adjusted. This allowed us to adapt the geometry of the slab exactly to the 3D scan of the load-bearing wall. In addition, very complex geometries can now be produced, which were previously not achievable”.

With the VX4000 from voxeljet - the world’s largest 3D printing system for sand molds - formwork elements of 4.00 x 2.00 x 1.00 m can be printed. When post-processed accordingly, each of these elements can withstand concrete casting pressures of 100 kN/m². The 136 elements printed by voxeljet for the DFAB House had a total volume of over 6,000 litres. The largest element had a volume of approx. 70 litres. The 3D-printed elements were prefabricated by voxeljet and infiltrated with polyester resin by the ETH Zurich. Subsequently the elements were assembled into 7 meter long formwork for the slab elements and coated with a release-agent. Prior to the actual concrete casting, a thin layer of fibre-reinforced shotcrete was applied. Finally, a laser-cut timber formwork was used for the struts and the concrete cast. Therefore, immediately after stripping, the finished elements were transported directly to the construction site and assembled there.

Conclusion: 3D printing using Powder-Binder-Jetting saves time, material and money. In the long term, the use of 3D-printed formworks will revolutionise concrete construction in a wide range of applications (formworks, formwork skins, facades, etc) and provide companies a decisive market advantage with novel designs never seen before.

What is Powder-Binder-Jetting?

Powder-Binder-Jetting is an additive manufacturing process, which uses particle material, such as sand or plastic. voxeljet 3d printing systems apply thin layers (150-300 µm) of the powder material to a building platform with the so-called recoater. Subsequently, a high-performance print head applies a binder wherever the desired component is to be built. This selectively bonds the material to form the part. Then the building platform is lowered by one layer thickness and powder and binder are applied again. This process is repeated until the desired component is complete. The only prerequisite for 3D printing: Printable 3D data must be available. Afterwards, 3D-printed formworks can be used in the same way as conventional concrete formworks.

3D printing for architecture

voxeljet offers various 3D-printing applications for the architecture and construction industry. These include: the printing of detailed and extremely realistic architectural models for a perfect and accurate impression of future buildings. In addition, 3D-printed replications can be used as exact models for sculpting or the preservation of historical monuments. One of the most innovative applications is the 3D printing of 21 mm thick formwork skins for concrete casting which can be combined with traditional wooden formwork. Digital data from the CAD model is used as the input. voxeljet is one of the world’s leading companies offering this process.

Digital Building Technologies / DFAB HOUSE

The research group Digital Building Technologies (www.dbt.arch.ethz.ch) at the ETH Zurich investigates the strong interplay of digital design and digital fabrication, which is demonstrated in the project Smart Slab (www.dfabhouse.ch/smart-slab) within the DFAB HOUSE. The DFAB HOUSE is a collaborative demonstrator of the Swiss National Centre of Competence in Research (NCCR) Digital Fabrication on the NEST building of Empa and Eawag. As part of the full-featured building project, researchers from eight ETH Zurich professorships have come together with industry experts and planning professionals in a unique way to explore and test how digital fabrication can change the way we design and build.