Thermal enhancement of hollow-Core 3DP through nozzle design customization

This is the authors' abstract. We don't add key points for this paper.

On the architectural scale, material extrusion (ME) or Big Area Additive Manufacturing (BAAM) have been fabrication methods for polymer-based components explored as an alternative to injection molding, over the past 20 years. These Additive Manufacturing (AM) techniques face long printing hours, slow material cooling rates, and high material usage when scaling towards building-size components. Hollow-core 3D printing (HC3DP) is an novel fabrication method that addresses these limitations by extruding tubular beads, thereby saving time and materials. A key advantage of HC3DP is its insulating properties due to the air chambers within the prints. This technique has significant potential for large-scale facade fabrication while providing essential thermal insulation. However, initial research indicates that deploying HC3DP at an architectural scale, while meeting building insulation standards, requires using a double pane with an internal infill structure. This reduces its ability to optimize time and material efficiency. The full potential of this technology rather relies on its application for the fabrication of single-pane mono-material façade elements. Therefore, as a first step, this research aims to explore the different insulating properties of various HC wall configurations from more complex to infill-less wall typologies. As a second step, thermally optimized bespoke die-end extrusion nozzles are designed for HC3DP of façade panels to achieve higher material, time, and thermal efficiency. Through bespoke nozzle customization, different levels of thermal insulation improvement could be achieved, reaching an U-Value of 0.998 W/m2K on a HC3DP single-pane panel, improving by two the insulating capacity of basic single pane circular-sectioned HC, and complying with the nearly zero-energy building (NZEB) standards (1). All of this while reducing printing time, material usage and cost up to half compared to an insulating-equivalent HC3DP wall typology. • Expanded overview of different HC3DP wall typologies and their thermal transmittances. • Novel approach to thermally tune HC3DPF based on the design of bespoke nozzles. • Thermal transmittance of HC reduced by up to 50% with a 5-cavity nozzle compared to a HC nozzle with no internal subdivision.