# Thermal Layer Design in Fused Filament Fabrication
## 2 Materials and Methods  
The layer deposition temperature is a crucial factor in the layer adhesion quality of FFF components and affects properties such as the UTS, surface roughness, and dimensional tolerances. This effect was investigated by (1) material testing: tensile test specimens were produced and tested to gather data on material properties and measure their corresponding layer temperatures; (2) TLD applied on a component: the layer temperature within a designed part was measured to estimate the strength based on the material testing. The component was then modified by adding mass in thinner sections before the layer temperature was measured and compared to the original component.  
In small components, the layer temperature is primarily affected by the volumetric flow and the layer time. When printing components that increase in size, the volumetric flow becomes a limitation, and other techniques, such as a heated chamber, are necessary to maintain temperatures.  
The process and environmental effect in additive manufacturing majorly impact material properties [12]. Therefore, a high-performance open-source liquid-cooled FFF printer with additional sensors for carefully monitoring the process was used while manufacturing [12]. The work by [PERSON] et al. [12] presents full build instructions in addition to performance benchmarking and results, including both PA6-CF and PEEK-CF. The printer used in this study uses a SuperVolcano HotEnd [13], the top modification available, and a heated chamber that can be adjusted up to 135 \({}^{\circ}\)C. Multiple sensors monitor the chamber temperature and important components of the hardware. Monitoring includes stepper motors, as these may skip and cause artifacts in the print at elevated operating temperatures.  
In addition, essential components, such as the nozzle, are calibrated by external sensors and continuously measured by double thermistors. The setup is made for scientific use, and the result presented by [PERSON] et al. [12] shows that PA6-CF from Polymaker [14] samples on an open-source printer outperforms the Prusa Mk3 by 25% and the datasheet by 15% in the UTS.  
The methods for modifying the layer temperature in additive manufacturing affect both the results and the achievable temperature range. There are several ways to manipulate the layer temperature, e.g., printing speed, chamber temperature, nozzle temperature, and applying additional energy. Due to the specimens' small cross-sections, printing speed was selected as the variable parameter in this study, as it enabled a wide range of layer temperatures. By making printing speed the adjustable parameter, the time to complete each layer will be affected and, in turn, so will the time for heat diffusion to occur before new hot material is deposited. By adjusting the speed of PA6-CF, the yielding temperature will change, as will the material's crystallinity, which affects material bonding, as shown in similar semicrystalline materials [15]. Alternatively, the chamber temperature can be adjusted, but the same effect from the crystalline phase will still occur. Adjusting the chamber temperature also limits the temperature range of the study, as it is challenging to obtain low-temperature test specimens for component comparison. In addition, some minor adjustments can be made, e.g., nozzle temperature and constant layer time, or breaks can be applied that may introduce a warping effect. In this paper, speed is the only adjusted parameter, and all other settings that affect temperature have been fixed to make the comparison as accurate as possible.