# Geometric Benchmarking of Metal Material Extrusion Technology: A Preliminary Study
## 1 Introduction
Indeed, these artifacts are meant to be compared with design specifications to provide information on geometric dimensioning and tolerancing (GD&T) characteristics, dimensional accuracy, minimum feature size, repeatability, and surface finish [24]. After a critical review of existing works on the topic of tolerancing, it was observed that different studies already investigated, to different extents, both the geometric and dimensional tolerances of metal products realized through PBF processes [25; 26; 27], as well as parts obtained by traditional MEX of plastic filaments [28; 29; 30]. [PERSON] et al. [25] designed a benchmarking artifact with mating components to study the geometric and assemblability tolerancing of laser powder bed fusion (LPBF) using both the random field theory and thermo-mechanical simulations. The method proposed by the authors was then used to extract standardized GD&T quantifiers. [PERSON] et al. [26] proposed a methodology for designing geometrical benchmarks for metal LPBF systems based on the designers' needs. A simple test artifact was created to experimentally validate the proposed methodology and outline an uncertainty map for relevant geometric characteristics using a relative coordinates system. [PERSON] et al. [27] conducted an extensive benchmarking activity on several LPBF machines to understand the influence of the individual machine on the final quality of predesigned specimens and to assess the capabilities and limitations of the technology. Specifically, the performances of five machines operated by their respective manufacturers and two machines operated by end users were compared to investigate different aspects, including feature dimension, surface roughness, and repeatability. [PERSON] et al. [28] used the design of the experiment to investigate the effects of layer thickness, printing speed, and number of contours on five geometric tolerances and the printing time of the MEX of the PLA plastic filament. Based on the results, the authors proposed a strategy to optimize process parameters to improve the accuracy and printing time of the MEX technology. [PERSON] et al. [29] proposed the combination of a simplified geometrical model with a modal representation of geometrical defects to predict the surface roughness and dimensional deviations of the MEX process. The working principle of this model was illustrated through a case study considering a simplified test artifact printed in PLA. The authors also proposed a geometrical simulation tool combining a Monte Carlo simulation and an optimization algorithm to assess the impacts of the geometrical deviations on an assembly. [PERSON] et al. [30] proposed a methodology based on IT grades to improve the dimensional accuracy of parts printed through the MEX technique. Several hole and shaft assemblies were modeled as the arithmetic mean of the minimum and maximum diameter allowed by each tolerance zone between IT9 and IT14. The dimensions of the specimens were then evaluated through a noncontact measurement procedure, and the resulting roundness tolerances were determined. To the best of the authors' knowledge, no study available in literature has ever been conducted to provide a geometrical or dimensional characterization of the metal-MEX technology. This paper addresses the existing gap in knowledge by initiating a comprehensive geometrical characterization study, with the primary goals of mitigating product design uncertainties and improving the technical feasibility of the metal-MEX process. A preliminary investigation was thus conducted by printing geometrical artifacts using a composite filament comprising 316L stainless steel powder to reproduce a variety of simple primitive shapes with varying dimensions. The analyzed features were then used to investigate the achievable geometrical tolerances with metal-MEX and concurrently determine the lower technological thresholds of the technology.