# Assessing Energy Efficiency in Desktop-Size FFF 3D Printers
## 2 Materials and Methods  
The study employed a single-factor experimental design to analyze the energy consumption characteristics of various FFF 3D printers under controlled and standardized operating conditions. The primary variable under investigation was the type of 3D printer, with 12 different machine models representing distinct levels of the independent variable. To ensure consistency and eliminate confounding factors, a single test element was printed in each process on each machine, using identical material and as standardized a set of process parameters as the devices allowed. This methodology enabled the evaluation of energy efficiency differences attributable solely to the variation in printer models. Key aspects of the experimental setup are outlined below. To obtain comparable and reliable results regarding the energy consumption of the FFF process, it is essential to print identical elements on different devices. The selected product should have a relatively simple structure, be made from the same material in all cases, and be manufactured using the parameters recommended for each specific device [4]. Wherever possible, the following technological guidelines were applied to the additive manufacturing process to ensure consistency and comparability: a layer thickness of 0.2 mm, a path width of 120% of the nozzle diameter, three contours in each layer, three solid top and bottom layers, a material deposition speed of 50 mm/s, a build plate temperature of 50 \({}^{\circ}\)C, and a nozzle temperature of 215 \({}^{\circ}\)C. The infill density was set to 25% using a rectilinear pattern, and no supports or additional technological features were included. Simplify3D (v. 4.1.2) and Z-SUITE (v. 3.5.0.0) software were used for generating NC codes for FFF 3D printers. Not all technological parameters can be standardized across devices. For example, Zortrax machines lack fine control over layer thickness, and the recommended temperature range for the same material class is significantly broader than on other machines. Additionally, the raft cannot be disabled on Zortrax machines (Zortrax, Olsztyn, Poland), leading to extended production times and increased material consumption, which should be considered post-production waste. For Ender 3 machines, the same control code was used for versions 1 and 2. However, for version 3, the NC code was generated using a different engine while maintaining the same production parameters. Consequently, a lower production speed than recommended was employed for version 3, resulting in an estimated production time consistent with versions 1 and 2. For other machines, the most comparable and acceptable technological parameters were applied in alignment with each machine's control software. The position and orientation of the product on the worktable were standardized across devices, with the product centered and its largest dimension facing the front of each machine. A simple snap hook (carabiner) was selected as the test product, as shown in Figure 1. The geometry of this element has a volume of 7.82 cm\({}^{3}\) after tessellation to the STL format. The selected geometry of the test product was deliberately chosen to deviate from standard test specimens or simple geometries such as cubes. The intent was not to associate the results with specific products, geometries, topologies, or the structural properties of a particular object. Instead, the geometry was designed to provide a more general representation of the additive manufacturing process and its capabilities. This approach facilitated a more objective evaluation on different devices by reducing the influence of the characteristics of standardized test samples or specific product-oriented requirements. The quality of the samples--and indirectly the manufacturing process--was assessed in a binary manner: the samples were evaluated as either correctly or incorrectly manufactured.