# Effect of Filament Material and Printing Temperature on 3D Printing Extrusion Force
## 2 Materials and Methods
### Extrusion Force Measuring Setup  
The measurements were carried out using an FFF Creality CR10-V3 3D printer (Creality 3D Technology Co., Ltd, Shenzhen, China) with a modified extruder with a 1 mm nozzle. A load cell, integrated between the extruder and feeder (Figure 1), measures the force induced by backpressure within the extruder as the filament is driven forward. The load cell is connected to an HX71 amplifier (SparkFun, Boulder, CO, USA), which conditions the signal before transmitting it to an Arduino Uno board (Arduino S.r.l., Arduino Uno, Scarmagno, Italy). The Arduino processes the data and sends it to a PC for real-time monitoring and subsequent analysis. A 500 g weight was used for calibration of HX711 load cell and Arduino measurements. After calibration, a plug-in was installed that logs the Arduino serial output to CSV/Excel file. To effectively monitor the progression of feedback force during 3D printing, it is essential to incorporate a timestamp into the output data from the load cells. This timestamp allows precise identification of the layer and specific region within the layer associated with a given feedback force. A simple Arduino program was employed to zero (tare) the load cell prior to printing and to continuously measure the forces exerted during filament feeding into the hotend. The printer was controlled with OctoPrint software. The OctoLapse \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Formulation Code**} & **PLA** & **Beech** & **TM Beech at 180 \({}^{\circ}\)C** & **TM Beech at 200 \({}^{\circ}\)C** \\  & **(wt\%)** & **(wt\%)** & **(wt\%)** & **(wt\%)** \\ \hline White PLA & 100 & - & - & - \\ PLA & 100 & - & - & - \\ B10 & 90 & 10 & - & - \\ B20 & 80 & 20 & - & - \\ TM\_180\_10 & 90 & - & 10 & - \\ TM\_180\_20 & 80 & - & 20 & - \\ TM\_200\_10 & 90 & - & - & 10 \\ TM\_200\_20 & 80 & - & - & 20 \\ \hline \end{tabular}
\end{table} 
Table 1: Filaments composition and marking. Figure 1: (**a**) Extrusion force measuring setup on modified extruder head on 3D printer—schematic, (**b**) working setup right. plug-in (version 0.4.2) was used to precisely determine the start of each layer. Before the start of each layer, the camera took a photo, and the timestamp of the photo was used to synchronize the force measurements obtained from the load cell and the Arduino board with the start of the layer [21]. Simple cuboid parts measuring (125 \(\times\) 12.7 \(\times\) 3.2) mm were modeled in SolidWorks and saved in STL format. The model was then sliced using CURA Slicer version 5.3.0. The aim of the investigation was to determine the differences in the extrusion forces of the various materials and not the strength of the printed parts. Therefore, the print lines always ran parallel to the length of the sample (unidirectional infill pattern) to ensure long print movements with a uniform/steady flow. In addition, the retraction was limited to the movements of the Z-axis when moving up to the next layer. As a result, the printed parts did not exhibit significant strength as the print lines did not intersect/cross to form a cohesive structure. Printing parameters were determined on the basis of previous experience with the materials used [20,22]. A printing nozzle with a diameter of 1 mm was used to prevent the nozzle from clogging with wood particles in the filament. Three different extrusion temperatures were used: 200, 210, and 220 \({}^{\circ}\)C. The bed temperature was set to 50 \({}^{\circ}\)C. The printing speed was 20 mm/s for all layers. A low printing speed of 20 mm/min was selected based on previous experiments using laboratory-prepared wood-filled filaments. Due to the presence of larger wood particles, a reduced speed was necessary to achieve higher-quality printed samples. In contrast, PLA can be printed at significantly higher speeds, with modern 3D printers capable of reaching 150-200 mm/min. Printing speed also influences backpressure, which could be an important parameter for future research.