Accuracy of 3D printing of the samples in the prototyping of cavity-based metamaterials

Recent developments in designing cavity-based metamaterials require advanced methods for prototyping measurement samples, such as 3D printing techniques, which allow for the manufacture of complicated shapes unavailable for other technologies. However, the imperfections of the printouts, which vary for different printing technologies and printer settings, may cause differences between the designed and measured acoustic performance of the samples. This paper presents a complex study of the influence of printing details on the resulting sound absorption coefficient of a simple cavity-based metamaterial consisting of a coiled-up Helmholtz resonator. A general approach for manufacturing measurement samples is discussed. It is shown that the samples should be printed in one whenever possible, and joining the parts results in the formation of microslits and leads to mismatching of the sample impedance. Different printing technologies were also compared (SLS, DLP, FDM), and it was shown that for the studied geometry, the differences obtained for different printers are negligible from a practical point of view. The settings of the FDM printer were also studied for comparison with previous works by other authors. It was shown that the printer settings and the choice of filament are less important than random printing errors, which may occur regardless of the printer settings.