## 2 Materials and Methods
### Geometry of the Reference Component and Measured Quantities  
To conduct experimental studies, a special geometry of the reference component was developed to indicate differences in the technological quality of the shaped product caused by changes in the FFF process setpoints. Figure 1 shows a 3D CAD model of the component along with its dimensions. The geometry of the CAD model was developed with the following assumptions:  
* The overall dimensions of the model must not exceed the dimensions of the working zone of the FFF machine. * The model should have typical geometric features found in machine parts, such as cylindrical protrusions (external cylindrical surfaces), cylindrical openings (internal cylindrical surfaces), perpendicular protrusions, and perpendicular niches. * The model should allow measurement of lateral surface roughness (perpendicular to the base plane). * The model should allow measurement of dimensional and shape accuracy of geometric features using coordinate measuring techniques in \(X\) (width), \(Y\) (depth), and \(Z\) (height) axes. * The model should be characterized by dimensional variation of geometric features in at least two axes (\(X\) and \(Y\)). To compare the technological quality of the various models produced, measurements of surface roughness as well as dimensional and shape accuracy were carried out. The measurement of the roughness profile of the test samples was carried out using a Mitutoyo SJ-210 stylus profilometer (Mitutoyo Corporation, Kawasaki, Japan) described in Section 2.6. The measurement was performed on the lateral surface to map the ar  
Figure 1: An isometric view of the 3D CAD model of the reference component (**a**) and a view of the example physical model produced (**b**). rangement of layers formed in the FFF additive manufacturing process. The measurement was obtained at a length of 2.4 mm, with a stylus feed rate of 0.5 mm/s and a sampling resolution of 2.5 \(\upmu\)m. The lateral surface area obtained as a result of overlapping layers was measured, so the effect of layer height on the roughness of the shaped model surface could be determined. There are about 100 parameters by which the roughness of a measured profile can be defined; however, the following set of parameters was described and used in this paper:  
* The \(Ra\) parameter is the average deviation of the peaks and valleys on the measured surface. The greater the difference between high points and depressions, the greater the value of the \(Ra\) parameter. It is used as a basic indicator for determining surface roughness because of its simplicity. * The parameter \(Rq\) is the mean square deviation of the profile. This parameter is used to eliminate the influence of random impurities or scratches on the surface. * The \(Rz\) parameter is the average value of the height of the largest peaks and valleys in the five measurement sections. This value represents the characteristics of the average deviation between peaks and valleys. Dimensional and shape accuracy is defined by the degree of reproduction of the designed product relative to that obtained in the manufacturing process. In many applications it is allowed to reproduce the product with a certain deviation, i.e., the obtained dimension differs from the one specified in the design, to ensure the tolerance of the parts or due to the production process used and its limitations. The dimensional and shape accuracy of the model produced by the FFF method is particularly dependent on the set process parameters and the accuracy of the guides and positioning system responsible for the precise positioning of the material extrusion nozzle in the working space of the device. In the case of the described tests, the characteristic dimensions of cylindrical openings and protrusions of various sizes, as well as parallelograms and niches in the material presented in Figure 1a, were measured.