Influence of Print Orientation on Surface Roughness in Fused Deposition Modeling (FDM) Processes

In the present paper, we address the influence of print orientation angle on surface roughnessobtained in lateral walls in fused deposition modelling (FDM) processes. A geometrical model isdefined that considers the shape of the filaments after deposition, in order to define a theoreticalroughness profile, for a certain print orientation angle. Different angles were considered between 5¿and 85¿. Simulated arithmetical mean height of the roughness profile, Ra values, were calculated fromthe simulated profiles. The Ra simulated results were compared to the experimental results, whichwere carried out with cylindrical PLA (polylactic acid) samples. The simulated Ra values were similarto the experimental values, except for high angles above 80¿, where experimental roughness decreasedwhile simulated roughness was still high. Low print orientation angles show regular profiles withrounded peaks and sharp values. At a print orientation angle of 85¿, the shape of the profile changeswith respect to lower angles, showing a gap between adjacent peaks. At 90¿, both simulated andexperimental roughness values would be close to zero, because the measurement direction is parallelto the layer orientation. Other roughness parameters were also measured: maximum height ofprofile, Rz, kurtosis, Rku, skewness, Rsk, and mean width of the profile elements, Rsm. At high printorientation angles, Rz decreases, Rku shifts to positive, Rsk slightly increases, and Rsk decreases,showing the change in the shape of the roughness profiles.Postprint (published version

Influence of infill and nozzle diameter on porosity of FDM printed parts with rectilinear grid pattern

The aim of the paper is to analyze the effect of nozzle diameter and infill on porosity and pore size of FDM printed specimens with rectilinear grid pattern. Two different nozzle diameters (0.2 and 0.4 mm), as well as four different infill values (20 %, 40 %, 60 % and 80 %) were used. Experimental results for pore size agree with theoretical results. On the contrary, low experimental porosity was obtained, especially for high infill values, because printed samples show fewer pores than expected. The higher infill, the lower porosity and pore size. Higher nozzle diameter implies higher pore size but similar porosity.Postprint (published version

Influence of structure support printing parameters on surface finish of PLA hemispherical cups for emulation of ceramic hip prostheses

Hemispherical hip ceramic prostheses require certain degree of porosity on their external surface so as to fix them by means of osteointegration. This can be achieved with porous mesostructures. In contrast, internal surface needs to be smooth in order to assure appropriate sliding of femoral head. Such specific shapes can be obtained by means of 3D printing. However, in certain printing processes, structure supports are required when overhang exceeds a certain angle. In this case, once supports are removed, joints between supports and prostheses will produce irregularities which will increase roughness on the internal surface of the prostheses. In the future, bimaterial prostheses are to be printed in ceramic with plastic structure supports, which are cheaper than ceramic ones. For doing this, double head printing machines will be used. In the present work, as a first step of research, both prostheses and supports were printed in plastic material. Specifically, PLA, which is a biocompatible polymer, was used. Influence of printing variables for supports on surface finish of internal surface of hemispherical cups after removing supports was studied. Prostheses were obtained by means of Fused Deposition Modelling (FDM) technology. Full factorial design of experiments was performed, with three printing variables: Support Pillar Resolution, Horizontal Offset from Part and part, and Dense Infill Percentage. Regression analysis was carried out. Results showed that Support Pillar Resolution and Horizontal Offset from Part are main parameters factors influencing roughness parameters Ra and Rz. In order to obtain low roughness values, high Support Pillar Resolution should be selected. In case low Support Pillar Resolution was necessary, then high Horizontal Offset from Part would be recommended. In the future, research presented in the present work will help selecting proper values for printing parameters in order to obtain smooth internal surfaces of ceramic hemispherical hip prostheses. This will reduce or even avoid subsequent polishing time of the internal surface of the prostheses.Postprint (published version

Linear modelling of water potential and supply for decentralized Energy-Water-Food systems - case Study St. Rupert Mayer, Zimbabwe

Limited water accessibility threatens the development of communities, especially where agriculture is the main income source.  The implementation of decentralized Energy-Water-Food systems is a promising approach to improve the situation in these communities, creating synergies and improving the profitability of the system. The model urbs optimizes Energy-Water-Food systems to generate the highest revenues, considering the local conditions and sustainability limits. This work improves the hydrogeological part of urbs in order to model the water potential of a given community, establishing interrelations of the water sector with the energy and food sectors, and maximizing the long-term benefits within the sustainability limits. The proposed method was applied to the rural community of St. Rupert Mayer in Zimbabwe. In order to analyse the impact of data uncertainty on the model results, the sensitivity of the main input parameters is analysed. The results indicate that it is important to implement reliable input data for dimensioning the proper system configuration, as otherwise the whole system would not be sustainable.&nbs

Effect of printing parameters on dimensional error and surface roughness obtained in direct ink writing (DIW) processes

Prostheses made from ceramic materials have the advantages of producing little debris and having good durability, compared with those made from metal and plastic. For example, hip prostheses require a porous external area that allows their fixation by means of osseointegration and a solid internal area that will be in contact with the femoral head. The manufacturing of complex ceramic shapes, by means of machining processes, for example, is complicated and can lead to breakage of the parts because of their fragility. The direct ink writing (DIW) process allows the printing of ceramic pastes into complex shapes that achieve their final strength after a heat treatment operation. This paper studies both the dimensional error and surface finish of porous zirconia prismatic parts prior to sintering. The variables considered are infill, layer height, printing speed, extrusion multiplier and bed temperature. The responses are the dimensional error of the lateral walls of the samples and an areal roughness parameter, the arithmetical mean height, Sa. Mathematical models are found for each response, and multiobjective optimization is carried out by means of the desirability function. The dimensional error depends mainly on the interaction between layer height and infill, while the roughness on the interaction between infill and printing speed. Thus, infill is an important factor for both responses. In the future, the behavior of compact printed parts will be addressed.Postprint (published version

Effect of grain size and density of abrasive on surface roughness, material removal rate and acoustic emission signal in rough honing processes

Honing processes provide a special cross-hatch pattern to the internal surface of cylinders that favors oil flow. However, along honing operation the abrasive grains wear out and lose their ability to cut material. The honing chips mixed with oil fill the pores of the abrasives and they start cutting in an incorrect way, leading to clogging. In the present paper, honing experiments were carried out according to a 32 factorial design, with different grain size and density of abrasive grains. Roughness, material removal rate, and tool wear were determined. Acoustic emissions were also measured and the chirplet concept was applied in order to detect differences between correct and incorrect cutting operations. As a general trend roughness and material removal rate increase with grain size and with density of abrasive. However, when clogging occurs roughness and material removal rate decrease, because the abrasive grains tend to deform the material instead of cutting it. When the honing process is working appropriately, the chirplet diagram of the harmonic part of the signal shows constant marks. On the contrary, when it does not work properly, marks disappear with time and their frequencies decrease. The results of the present paper will allow monitoring the honing process in order to change the abrasives when they are not working properly.Peer ReviewedPostprint (published version

Evaluation of porosity in 3D printed trabecular bone structures for prostheses

Hip prostheses require an external porous area in order to fix them by means of osseointegration. Different structures can be printed in order to favour bone fixation, such as octet-truss or trabecular, among others. In the present paper, bone-like structures are printed in cubic shapes, by means of fused filament fabrication (FFF). Three design parameters of the structures were varied: the number of joining points per unit volume, the area scale and the offset that is given to the different struts of the structure. Both the theoretical and the measured porosity of the samples is evaluated, from the drawing of the structures and by means of weight measurements respectively. As expected, the structures having fewer union points per unit volume are more porous than the structures having more points. When low number of points generating struts of the structure were employed, measured porosity is lower than the theoretical one, while when high number of points is considered, the opposite situation is found. The present work will help to obtain porous structures to be used in prostheses, by means of extrusion 3D printing processesPeer ReviewedPostprint (published version

Impact of the mobility alteration on air pollution over different cities: A vision for citizen awareness

[EN] Every year the concern from environmental pollution increases as it affects human health. In the current paper, it is analyzed the evolution of the air quality in different cities on international level related to the reduction in mobility trend due to the emergence of the pandemic. The air pollution is studied in order to achieve healthier cities in the future and create an awareness for the citizens. The COVID-19 pandemic situation was declared during the first months of 2020 and has shown (indirectly) the effects that restrictions on human activity and road traffic have on atmospheric pollutant values. This pandemic condition derived, in most cases, in mobility restrictions in order to decrease the spread of the virus through the density of population in different places and, as a result of these restrictions, pollutant presence decreased equally. This article analyzes some of the largest cities around the world, such as Tsuen Wan district in Hong Kong (China), Los Angeles (USA), London (UK), Sao Paulo (Brazil), Bangalore (India), Johannesburg (South Africa), and Sydney (Australia) in order to check the different mobility restriction policies established in each location, and how those restrictions led to decrease the levels of some pollutant particles such as NO2 in the atmosphere. This should serve as a focus of awareness of the city and political interests of how it affects human activity, and those measures should be taken to reduce pollutants.The authors are grateful for the support of the Institute of Materials Technology of the Universitat Politecnica de Valencia (Spain)Cárcel-Carrasco, J.; Martínez-Corral, A.; Aparicio Fernandez, CS.; Kaur, J. (2022). Impact of the mobility alteration on air pollution over different cities: A vision for citizen awareness. Environmental Science and Pollution Research. 29(53):81048-81062. https://doi.org/10.1007/s11356-022-21326-38104881062295

Analysis for the Heritage Consideration of Historic Spanish Railway Stations (1848¿1929)

[EN] This article presents the study carried out on the main Spanish historic railway stations to obtain a joint and comparative view of the current state of its heritage conservation. The temporal scope is limited to the construction period of the Spanish historic stations. A motivated selection of a series of extrinsic and intrinsic variables is proposed, checking heritage variables to evaluate the degree of adequate heritage protection. The conclusions of the study show the antithesis between what is to be protected (the railway station) and what is really saved (the passenger building), making it necessary to change the legal protection status from monuments to landscapes. Thus, various interventions can be observed on the disaffected land with no heritage connection. The material and technological valorisation of unique components such as the large platform and track roofs is ignored. It is also observed that the maintenance of railway use is essential and that global interventions lead to a more significant loss of significance than those carried out for maintenance purposes. This leads to the conclusion that preventive conservation is more effective in protecting this heritage than global interventions.This work was carried out at the Universitat Politècnica de València in the framework of CONDEREFF project (Ref. PGI05560-CONDEREFF). This work has been carried out within the framework of the PREDILAB research group, as part of the research carried out at the University of Castilla La Mancha and entitled Methodology and systems for improving maintenance and energy efficiency in the rehabilitation and reuse of industrial heritage. Phase 2.Martínez-Corral, A.; Cárcel-Carrasco, J.; Carnero, MC.; Aparicio Fernandez, CS. (2022). Analysis for the Heritage Consideration of Historic Spanish Railway Stations (1848¿1929). Buildings. 12(2):1-17. https://doi.org/10.3390/buildings1202020611712

The Medical Oncology resident mentor: situation and workload

Oncologia mèdica; Mentor resident; Càrrega de treballOncología médica; Mentor residente; Carga de trabajoMedical oncology; Resident mentor; WorkloadPurpose: The Spanish Society for Medical Oncology (SEOM, for its acronym in Spanish) and the National Commission for the Specialty of Medical Oncology seek to highlight the important workload and unrecognized dedication entailed in working as a Medical Oncology (MO) resident mentor, as well as its relevance for the quality of teaching units and the future of the specialty. Materials and methods: The current situation and opinion regarding the activity of MO resident mentors was analyzed by reviewing the standing national and autonomic community regulations and via an online survey targeting mentors, residents, and physicians who are not MO mentors. The project was supervised by a specially designated group that agreed on a proposal containing recommendations for improvement. Results: Of the MO mentors, 90% stated that they did not have enough time to perform their mentoring duties. An estimated 172 h/year on average was dedicated to mentoring, which represents 10.1% of the total time. MO mentors dedicate an average of 6.9 h/month to these duties outside their workday. Forty-five percent of the mentors feel that their role is scantly recognized, if at all. Conclusions: The study reveals the substantial dedication and growing complexity of MO resident mentoring. A series of recommendations are issued to improve the conditions in which it is carried out, including the design of systems that adapt to the professional activity in those departments that have time set aside for mentoring tasks.This study was funded as an unrestricted grant by Servier. Servier did not have any intervention in the discussion and outcomes of this report