Optimal shape design of printing nozzles for extrusion-based additive manufacturing

TL;DR

This paper presents an optimized nozzle design for extrusion-based additive manufacturing that reduces pressure drop and improves flow control, validated through computational simulations and experimental testing.

Contribution

It introduces a combined global optimization and CFD approach to design nozzle geometries tailored for viscoelastic fluids, enhancing printing efficiency and quality.

Findings

Significant reduction in pressure drop (up to 41%)

Improved flow control and material flow rate

Enhanced printing speed and reliability

Abstract

The optimal design seeks the best possible solution(s) for a mechanical structure, device, or system, satisfying a series of requirements and leading to the best performance. In this work, optimized nozzle shapes have been designed for a wide range of polymer melts to be used in extrusion-based additive manufacturing, which aims to minimize pressure drop and allow greater flow control at large extrusion velocities. This is achieved with a twofold approach, combining a global optimization algorithm with computational fluid dynamics for optimizing a contraction geometry for viscoelastic fluids and validating these geometries experimentally. In the optimization process, variable coordinates for the nozzle's contraction section are defined, the objective function is selected, and the optimization algorithm is guided within manufacturing constraints. Comparisons of flow-type and streamline plots reveal that the nozzle shape significantly influences flow patterns. Depending on the rheological properties, the optimized solution either promotes shear or extensional flow, enhancing the material flow rate. Finally, experimental validation of the nozzle performance assessed the actual printing flow, the extrusion force and the overall print control. It is shown that optimizing the nozzle can significantly reduce backflow-related pressure drop, positively impacting total pressure drop (up to 41%) and reducing backflow effects. This work has real-world implications for the additive manufacturing industry, offering opportunities for increased printing speeds, enhanced productivity, and improved printing quality and reliability. Our research contributes to advancing extrusion-based printing processes technology, addressing industry demands and enhancing the field of additive manufacturing.