The performance of parts produced by Free Form Extrusion (FFE), an increasingly popular additive manufacturing technique, depends mainly on their dimensional accuracy, surface quality and mechanical performance. These attributes are strongly influenced by the evolution of the filament temperature and deformation during deposition and solidification. Consequently, the availability of adequate process modelling software would offer a powerful tool to support efficient process set-up and optimisation. This work examines the contribution to the overall heat transfer of various thermal phenomena developing during the manufacturing sequence, including convection and radiation with the environment, conduction with support and between adjacent filaments, radiation between adjacent filaments and convection with entrapped air. The magnitude of the mechanical deformation is also studied. Once this exercise is completed, it is possible to select the material properties, process variables and thermal phenomena that should be taken in for effective numerical modelling of FFE.

Additive Manufacturing Techniques such as Fused Filament Fabrication (FFF) produce 3D parts with complex geometries directly from a computer model without the need of using molds and tools, by gradually depositing material(s), usually in layers. Due to the rapid growth of these techniques, researchers have been increasingly interested in the availability of strategies, models or data that may assist process optimization. In fact, 3D printed parts often exhibit limited mechanical performance, which is usually the result of poor bonding between adjacent filaments. In turn, the latter is influenced by the temperature field history during deposition. This study aims at evaluating the influence of the phase change from the melt to the solid state undergone by semi-crystalline polymers such as Polylactic Acid (PLA), on the heat transfer during the deposition stage. The energy equation considering solidification is solved analytically and then inserted into a MatLab^® code to model cooling in FFF. The deposition and cooling of simple geometries is studied first, in order to assess the differences in cooling of amorphous and semi-crystalline polymers. Acrylonitrile Butadiene Styrene (ABS) was taken as representing an amorphous material. Then, the deposition and cooling of a realistic 3D part is investigated, and the influence of the build orientation is discussed.

Coronavirus pandemic has impacted the whole education system. Suddenly, presential classrooms are replaced by online learning, leaving students and teachers to deal with various problems without any specific preparation. This research study examines the perceptions of 78 students from a Portuguese Higher Education (HE) institution towards online learning during the Coronavirus disease 19 (COVID-19) pandemic. Two months after the implementation of the online learning, they responded to a survey whose responses were analyzed by using descriptive statistics and independent Chi-squared tests. The findings of this study reveal the difficulties that the students encountered, like the lack of familiar/spatial conditions at home, the failures of Internet connection, and the fear of clarifying doubts in this context. The preference for face-to-face classes was also expressed. However, the selected platform used for the online classes, the appropriate development of the explanations and the digital contents made available by the teachers were appreciated by the students. The present research also investigates the factors that affected the study motivation of the students and the future plans regarding their studies.