The objective of the collaboration in the new CRC/Transregio is to conduct interdisciplinary and trans-locational research into additive manufacturing for the construction industry. In additive manufacturing, also known as 3D printing, objects are produced in layered structures. As a result, geometric shapes and the structure itself can be individually designed. In the construction industry, this technology additionally offers the possibility of a more efficient production of components, resulting in lower energy and material consumption. In the sub-project “Structural timber by individual layer fabrication (ILF)”, Dr. Frauke Bunzel from the Fraunhofer WKI and Dr. Klaudius Henke from the TU Munich are addressing the question as to how additive manufacturing can be used in order to produce resilient and resource-saving components from renewable raw materials.

Conventional methods of additive manufacturing involving the binding of wood particles with an adhesive generally require large quantities of binding agents. Moreover, the products produced in this way have mechanical properties which are not suitable for structural applications. Dr. Bunzel and Dr. Henke are therefore pursuing a new approach: They want to construct components by laminating individual layers of wood composites. To achieve this, they are implementing the innovative “individual layer fabrication” (ILF) process. The shape of the individual layers is to be achieved through the selective binding of particles. This distinguishes the ILF process from the single-layer process “laminated object manufacturing” (LOM), in which each layer to be laminated is subtractively shaped through contour cutting. Furthermore, the layers are to be produced using the ILF process under the application of mechanical pressure. This enables the mechanical properties necessary for construction applications to be achieved and the required amount of binder to be reduced.

A further advantage of this process is that it can be organized as a continuous process, thereby helping to increase the construction speed. Another new feature of this project is the production of elements with unfilled, closed cavities, which cannot be created using other methods of selective binding.

“With our research project, we can introduce the renewable raw material wood, whether as fresh wood or from the remnants of the wood-processing industry, into large-scale additive manufacturing. We are delighted to be able to contribute our expertise in all aspects of this versatile material and are proud to be part of the Collaborative Research Centre,” says Dr. Bunzel.  

Since December 2018, Dr. Bunzel has headed the “Surface Technology” department at the Fraunhofer WKI. She and her team develop paints and adhesives on the basis of vegetable oils, sugar, lignin and waste materials. The researchers develop solutions for business customers along the entire value chain of wood coatings and adhesives, including the synthesis of binders and the formulation and application of coatings. Method development of weather-related ageing processes, standard tests and damage analysis round off the profile.

The DFG Collaborative Research Centres are long-term university-based research institutions and have a duration of up to twelve years. They enable the execution of innovative, challenging and complex research projects. Within the CRC/Transregio program variant, several universities are working together trans-locationally. The DFG-funded CRC/Transregio “Additive Manufacturing in Construction” (TRR 277) will begin in January 2020 with an initial duration of four years.

Background

Sustainability through the utilization of renewable raw materials has formed the focus at the Fraunhofer WKI for more than 70 years. The institute, with locations in Braunschweig, Hanover and Wolfsburg, specializes in process engineering, natural-fiber composites, wood and emission protection, quality assurance of wood products, material and product testing, recycling procedures and the utilization of organic building materials and wood in construction. Virtually all the procedures and materials resulting from the research activities are applied industrially.