3D Printing Method “Eggshell” Revolutionizes Engineering

In collaboration with the German engineering firm Basler & Hofmann, researchers from ETH Zurich, Switzerland built a “future tree” using an eggshell-like concrete 3D printing process in the courtyard of the company’s headquarters.

Concrete is indeed the most-used building material in the world and can be shaped into almost any form, at least in theory. But mostly concrete is shaped into orthogonal structures because the material’s cost for non-standard elements is rather expensive. This is mainly due to the concrete transition from a fluid material into solid for which it has been supported by a framework. 

A Huge Potential for Mass Customization and Structural Optimization

The Zurich team developed another approach and combined a 3D printing method with casting methods that enables a material-efficient production of complex structures like concrete sculptures. A large-scale robotic Fused Deposition Modeling (FDM), 3D printing and the simultaneous pouring of fast-setting concrete, as well as set on-demand, lead to completely new possibilities in the engineering field. The eggshell method has therefore a huge potential for mass customization and structural optimization.
The researchers declared:

“This novel fabrication process, known as “eggshell”, allows for the fabrication of non-standard, structurally optimized concrete structures, whilst being able to integrate standard reinforcement and minimize formwork waste.” 




Concrete as Thin as an Eggshell

The shell of a chicken egg has a thickness of less than 0.5mm but the 3D printed concrete even falls below this with 1.5mm thickness. How is that even possible? 


With the combination of the large-scale robotic FDM 3D printing with the set-on-demand digital casting system. During the fabrication, the structure doesn’t need to be moved. This is ensured by simultaneous 3D printing and filling of the formwork.
The concrete was mixed for a total of eight hours and could be short-term activated with a custom-accelerator mix. Afterward, the robotic arm was controlled by a custom-developed Python interface and constructed the columns of the future tree based on pre-programmed files. 


During the experimentation with a range of solutions to support the concrete columns, the researchers of the Zurich team found out that the combination of these approaches (the large-scale robotic FDM 3D printing with the set-on-demand digital casting system) is necessary for the optimum results. 


The Future Tree

With the project “the future tree”, the German engineering firm Basler & Hofmann and the researchers from ETH Zurich combined their eggshell process and timer elements that acted as a reciprocal frame. The 1,152 square feet roof consists of 380 acetylated timber elements that are supported by the tree’s concrete stem. The tree’s designers clarify:

“Here, motivated by the frame’s structural behavior, the honeycomb pattern gradually transforms between a hexagonal and a triangular in order to achieve varying levels of flexural rigidity in different areas of the frame.” 


At the moment, the researchers are working on the sustainability and financial viability of this project by automating the process and using more recyclable materials. Nevertheless, the Zurich researchers agree on the construction applications in a broad spectrum:

“As research progresses and the process is stabilized and streamlined, the range of building components produced could extend to beams, floor slabs, or connecting and transitional elements, paving the way toward sustainable mass customization in concrete architecture.” 


The innovative “eggshell” method has begun to garner attention from companies and researchers around the world. In the U.S., concrete specialists have partnered up for concrete buildings. In the future, it will be used to build homes for people on a low income and for disaster relief organizations. We are curious how this technology will develop in the future!