This work presents an analytical solution to the transient heat conduction developing during filament deposition in Fused Deposition Techniques (FDT), which is coupled to a routine that activates or deactivates all relevant local boundary conditions depending on part geometry, operating conditions and deposition strategy. Boundary conditions include contact between filament segments, between filament segments and the support, as well as heat transfer with the environment. The resulting MatLab code comprises an adhesion criterion that is used to estimate whether contiguous filament segments will adhere adequately to each other prior to solidification. Predicted and experimental data for the filament surface temperature showed very good agreement. Also, adhesion predictions were in accordance with the results of real peel-like tests. The practical potential of this calculation tool is demonstrated by an application example.

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.

Fused filament fabrication (FFF) is an additive manufacturing technique that is used to produce prototypes and a gradually more important processing route to obtain final products. Due to the layer-by-layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed, which strongly depends on the temperature development of the filaments during the deposition sequence. This study reports experimental measurements of filament temperature during deposition. These temperature profiles were compared to the predictions made by a previously developed model. The two sets of data showed good agreement, particularly concerning the occurrence of reheating peaks when new filaments are deposited onto previously deposited ones. The developed experimental technique is shown to demonstrate its sensitivity to changing operating conditions, namely platform temperature and deposition velocity. The data generated can be valuable to predict more accurately the bond quality achieved in FFF parts.

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Purpose The performance of the parts obtained by fused filament fabrication (FFF) is strongly dependent on the extent of bonding between adjacent filaments developing during the deposition stage. Bonding depends on the properties of the polymer material and is controlled by the temperature of the filaments when they come into contact, as well as by the time required for molecular diffusion. In turn, the temperature of the filaments is influenced by the set of operating conditions being used for printing. This paper aims at predicting the degree of bonding of realistic 3D printed parts, taking into consideration the various contacts arising during its fabrication, and the printing conditions selected. Design/methodology/approach A computational thermal model of filament cooling and bonding that was previously developed by the authors is extended here, to be able to predict the influence of the build orientation of 3D printed parts on bonding. The quality of a part taken as a case study is then assessed in terms of the degree of bonding, i.e. the percentage of volume exhibiting satisfactory bonding between contiguous filaments. Findings The complexity of the heat transfer arising from the changes in the thermal boundary conditions during deposition and cooling is well demonstrated for a case study involving a realistic 3D part. Both extrusion and build chamber temperature are major process parameters. Originality/value The results obtained can be used as practical guidance towards defining printing strategies for 3D printing using FFF. Also, the model developed could be directly applied for the selection of adequate printing conditions.

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The increasing use of learning videos in Higher Education (HE) have revolutionizing the traditional teaching environment. b-Mat@plicada is a b-Learning Mathematics course mainly composed of educational videos that the HE students of a Portuguese Institution can used for their study as a complement of the face-to-face lectures. In a previous research, an experiment was performed in the classroom context, where 49 HE students watched the b-Mat@plicada video on Matrix Multiplication as replacement of the traditional face-to-face explanation. Then, they were asked to solve individually an exercise, and respond to a survey assessing attitudes, perception, and satisfaction. In the present study, 63 HE students participated to a similar experiment with the b-Mat@plicada video on the Laplace Expansion Theorem, where a specific didactical approach is used. Beyond the comparison between the results of the two experiments, the findings of this study revealed that most students achieved the leaning objectives and appreciated the quality of the video in terms of image, sound, clarity and useless. The necessity of video contents in teaching was also expressed, mainly to clarify doubts and remember contents. However, all students considered that videos cannot replace traditional face-to-face classrooms, mainly due to the importance of the Teacher-Student dialogue.