## 2 Materials and Methods
### Experiment Plan and Set Parameters of the FFF Process  
Main parameters of the FFF process (in addition to the type of building material) affecting process time and model quality are the height of the material layer to be applied,the distance between individual material paths, the head feed rate, the diameter of the material extrusion nozzle, the degree to which the model is filled with material (fill rate), the shape of the fill, the temperature of the material extrusion, and in some devices also the table temperature and the speed of the fan cooling the work zone. The orientation of the product on the work platform as well as the method the CAD model is processed into the STL batch file (including chord height, angle control, and step size) are also important. When creating models in additive processes, it is important to know the relationship of the various process parameters and their impact on the quality indicators of the product. It should also be noted that changing the value of the parameters also affects the time consumption of the process and, as a result, its cost. The most important advantages of the FFF method are the low cost of the model and the relatively short time to produce it, and it is most often because of these features that users decide to use the FFF method. However, these features can be achieved through a kind of compromise between the pursuit of high technological quality of the product and the process time determining its efficiency and cost. In the described research, the influence of two key parameters of the FFF process on selected indicators of model technological quality was studied. These were layer height and percentage fill rate. The selected parameters are easily controllable and significantly affect both the technological quality of the model as well as the process execution time, so examining their impact allows for making informed decisions regarding the aforementioned compromise. By layer height, we mean the amount of material extruded during one pass in the \(Z\) axis. The layer height is always smaller than the diameter of the material extrusion head; in this case, the diameter is 0.4 mm. A smaller layer height results in a higher resolution of the manufactured product and, by definition, a better reproduction of the set geometry. Reducing the layer height also results in increased process time. During the conducted tests, samples were prepared at three values of layer height: 0.12 mm, 0.16 mm, and 0.20 mm. The density of the filament fill of the manufactured product has a direct impact on its mechanical and geometric properties. The more material inside the fills, the more durable the finished product will be. Similarly, a higher percentage of fill will result in a longer process time. Due to the nature of the process and the stresses present in the material, the finished product may have deformations or deviations in size and shape [11]. During the conducted tests, models were produced with fill rates of 30%, 50%, and 70%. Nine specimens produced with different parameters of the FFF process were prepared during the conducted research. Table 1 shows the experiment plan, according to which the models for the measurements were manufactured. Table 1 also provides information on the estimated manufacturing time of each model.