Binder Jetting Wood

Abstract

Repurposing waste materials is essential to reduce our dependency on raw materials. Binder jet 3D printing shows potential for cost-effective freeform production from wood waste due to its high material compatibility. This thesis uses a granulated wood powder and optimizes process parameters through a structured Design of Experiments followed by Bayesian Optimization to maximize the bending strength of as-printed structures. The resulting parameter set yields a modulus of rupture of 1.85 MPa. A dedicated test artifact is 3D-scanned to characterize design insights and dimensional accuracy. While the in-plane accuracy is within 1.2%, the part height along the build direction can exceed its nominal height by 8.6% due to the compressibility of the powder, depending on the positioning in the print box. Drying-induced fractures are inherent to the process and are the main limitation for scaling up to large print sizes.



The characteristic porosity of as-printed structures makes the material a promising candidate for sustainable sound absorption. The porosity is evaluated through micro-CT scanning, and non-acoustical (Johnson-Champoux-Allard-Lafarge) parameters are inversely characterized on impedance tube measurements. Building on these results, a poro-acoustic metastructure is proposed in accordance with the identified design insights and evaluated numerically using the identified non-acoustical parameters. The structure outperforms printed bulk material below 1200 Hz and the impervious reference structure above 1400 Hz. The results demonstrate the potential of wood-based binder jetting and the possible application in sustainable acoustic attenuation.