Arup has found a way to overcome cost, quality and regulation issues related to conventional 3D printed metal structural components by using 3D-printed sand moulds.

In a manufacturing process that uses 3D printed sand moulds, the firm can rapidly produce complex steel structural components that meet current certification standards.

Developed in collaboration with 3D printing specialist 3Dealise, the fabrication method builds on Arup’s previous work focused on the production of 1,600 intricate steel ‘nodes’ for a tensile street lighting scheme in the Hague.

Under that project, generative design software was used to optimize the volume and shape of the nodes to support loads in the structure.

The nodes were then 3D printed using direct laser sintering (see our previous story on the project).

Arup demonstrated that the technology would be structurally feasible, but the project uncovered issues: production time using currently available metal printers would be relatively slow for 1,600 pieces, costs were 10 to 20 times higher than for traditional methods, and above all, construction safety standards do not yet allow for 3D metal printed parts in critical positions.

The new approach aims to fuse the benefits of 3D printing with traditional technology to provide both freedom of design and feasible production.

3Dealise used its gigantic sand 3D printer, the S-Max, to 3D print a mould for one of the nodes and then worked with a foundry to produce a traditional casting.

The hybrid approach proved technically and economically feasible. Generative design achieved a weight reduction of 75%, compared to traditional design methods. Sand printing was faster than metal 3D printing, the materials could be reused, costs were lower and large items could be produced with regulatory pre-approval.

Salomé Galjaard, senior designer at Arup, said: ‘An interesting shift is taking place. Whereas the focus initially has been on printing final products, 3D-printing is being applied in an earlier phase in the production process. The aim is to make the most of the freedom-of-form opportunities of 3D-printing without the limitations which are now still [associated] with production.’