# Effect of Filament Material and Printing Temperature on 3D Printing Extrusion Force
## 4 Conclusions  
This research presents a method that determines the feed force required to feed filaments into the hotend and extrude material. It detects variations in the feed force (between 1 and 8 N) and distinguishes between materials with and without wood particles and at different printing temperatures. Detecting extrusion forces can serve as a valuable method for optimizing the printing process, as high feed forces indicate the risk of filament slipping in the feed rollers, leading to uneven extrusion or possible nozzle clogging. Corrective action can be taken to address these issues, such as cleaning the nozzle, adjusting the process parameters (e.g., reducing the print speed, increasing the extrusion temperature, and changing feeding acceleration),  
Figure 9: Extrusion force—printing on previous layer vs. printing in air (ratio between forces) for different materials and printing temperatures. or using a larger-diameter nozzle. Conversely, if the extrusion forces are low, the force can be increased to an optimum level by increasing the printing speed, thus ensuring a stable material flow and increasing productivity at the same time. This study provides valuable insights by measuring the extrusion forces in wood-polymer composites with different wood contents and different modification methods. By analyzing these parameters, this study contributes to a deeper understanding of wood-polymer extrusion behavior, complements existing monitoring techniques, and enhances process optimization to improve material performance. This study found that between tested materials, white PLA filament requires the highest average extrusion force at the lowest extrusion temperature (200 \({}^{\circ}\)C). This higher force is probably due to the high content of titanium dioxide (TiO\({}_{2}\)) in white filaments, which is usually between 5 and 20 percent by weight. Compared to pure PLA filament, almost twice the extrusion force was required for white PLA, which may partly be due to differences in the PLA base polymer type. A higher extrusion temperature generally reduced the polymer viscosity, which lowered the extrusion forces. This trend was observed for white PLA, pure PLA, PLA with untreated beech wood particles (10%), and TMB180. However, it was less consistent for filaments with TMB200 wood particles, likely due to nozzle clogging during the printing process, which affected accurate force measurements. The literature indicates that a higher wood particle content generally increases the viscosity of wood-plastic composites, although this was not observed in the average forces measured, which unexpectedly decreased at higher particle loads. Filaments with untreated beech wood required lower extrusion forces than those with thermally modified (TM) wood. This discrepancy could be due to differences in the particle size and distribution, as previous research has shown that TM wood particles are smaller and more uniform because they have become more brittle due to exposure to 150-200 \({}^{\circ}\)C. The smaller size and larger surface area of the TM wood particles probably contribute to these differences. When printing on a previous layer or the print bed, the back pressure increases the extrusion forces, especially for filaments with wood particles. For wood-containing filaments, greater differences were observed between extrusion in air and extrusion on the previous layer, likely due to backpressure causing uneven flow and possible nozzle clogging. Despite these results, the significant variability of the measurements indicates that the method needs to be further optimized. Future improvements should focus on real-time force measurement and analysis during printing. Modern technologies such as computer vision, machine learning, and artificial intelligence [7] could detect nozzle clogging and dynamically adjust printing parameters inline to ensure a consistent print quality.