Design, Development and Characterization of a 3D Printed Fixed and Variable Orifice Flowmeter

Accurate flow measurement is essential in various applications, including spirometry and mechanical ventilation. In recent years, technological advancements have enabled the development of novel types of flowmeters beyond conventional designs. In particular, Fused Deposition Modeling (FDM) 3D printing offers new opportunities for customization and rapid prototyping. Nevertheless, the use of FDM in the field of flow measurement remains relatively unexplored, and existing solutions are typically limited to the fabrication of the external duct, excluding the sensing element itself. This study focuses on the design and fabrication of a fully 3D-printed flowmeter incorporating both fixed (FO) and variable orifice (VO) configurations. The conduit was segmented into multiple components to ensure modularity and interchangeability, especially regarding orifice replacement. Experimental results demonstrate that, even in a fully printed system, the FO made of polylactic acid (PLA) exhibits a characteristic parabolic differential pressure-flow relationship, while the VO made of thermoplastic polyurethane (TPU) successfully linearizes the output across all tested thicknesses (0. 4 m m, 0. 8 m m, and 1 m m). Different sensitivity values were obtained depending on the orifice thickness, with a maximum value of 18.5 Pa/L. min-1 recorded for the 1 mm VO. These findings highlight how the advantages of FDM can be leveraged to easily tailor orifice thickness, enabling a trade-off between pneumatic resistance and sensitivity, allowing the sensor to be adapted to different operational scenarios.