30,639 research outputs found
An application- and market-oriented review on large format additive manufacturing, focusing on polymer pellet-based 3D printing
No full textSince this advent, additive manufacturing (AM) has grown steadily and found applications across all types of sectors. While the great development of such technologies has improved the quality of prints and expanded the availability of materials, AM still has some limitations regarding its physical scaling. This paper will briefly present the state-of-the-art of large-scale additive manufacturing and subsequently greater attention will be given to extrusion-based 3D printing. Specifically, we will discuss about large format additive manufacturing (LFAM) or big area additive manufacturing (BAAM), a technology based on material extrusion born a few years ago. These systems are characterized by higher deposition rate and lower costs of the material compared to fused filament fabrication (FFF) printers; moreover, they allow to obtain parts with better properties (e.g., adding carbon or glass fibers). The world of research has shown great interest in large-scale material extrusion technologies, which appear to be quite competitive with conventional manufacturing processes and which will find increasing application in the industrial field. With the aim of developing a tool for orienting researchers and technicians in this complex field, the present paper presents a systematic review of the actual market of machines, the research in extrudable materials and related applications concerning large-scale 3D printing, and in particular the LFAM
Quantitative analysis of a chemical treatment to reduce roughness of parts fabricated using fused deposition modeling
No full textThe diffusion of Additive Manufacturing technologies is leading to new needs in industrial research and development sectors. In particular, mating additive manufactured parts is not a simple task, due to the poor accuracy of several additive technologies, such as Fused Deposition Modeling (FDM). Several papers are focused on studies of how FDM accuracy is affected by process parameters. In this paper the authors report a study of the influence of working parameters on FDM dimensional accuracy, paying particular attention to variables that can affect axial symmetric mating between parts, and how these parameters can be set to improve the mating process
3D Digitization of Curves on Human Bodies by Means of Digital Close Range Photogrammetry
No full textThe realization of custom made clothes implies continuous tests, long times of delivery and often prohibitive costs. In this field, one of the most interesting challenges is to automate some parts of the process to obtain a competitive product.The first step to be completed to automate the realization of customized garment apparels is the 3D Digitization of customers. In the present research the authors present a properly designed low cost offline 3D body digitizer, based on Digital Close Range Photogrammetry. The results are satisfactory for tailoring applications that do not require high accuracy. Furthermore, essays on Dense Surface Models are described
Validation study of an analytical model of FDM accuracy
No full textThe diffusion of Additive Manufacturing technologies is leading to new needs in industrial research and development sectors. In particular, mating additive manufactured parts is not a simple task, due to the poor accuracy of several additive technologies, such as Fused Deposition Modeling (FDM). Several papers are focused on studies of how FDM accuracy is affected by process parameters. In this paper the authors report a study of the influence of working parameters on FDM dimensional accuracy, paying particular attention to variables that can affect axial symmetric mating between parts, and how these parameters can be set to improve the mating proces
Analytical model to predict the extrusion force as a function of the layer height, in extrusion based 3D printing
No full textFused Filament Fabrication is the most widespread 3D printing process, and issues such as improving accuracy and speed are significant areas of research. To better understand and foresee the process, accurate models would be very useful. Several analytical models have been proposed in the literature; however, while the behavior inside the print core has been investigated, to the best of the authors’ knowledge, no studies are reported on the behavior of the melt filament downstream of the nozzle. This lack of research is very important, since the behavior downstream of the nozzle is influenced by the counterpressure generated by the deposited material. Qualitatively, the lower the layer height, the higher the counterpressure should be, while the higher the printing speed, the lower the counterpressure. No such models are available in the literature that take these phenomena into account, and such a model would help in managing the printing process when low layer height is required for improving the accuracy and roughness of the part. In the present study, a new analytical model was developed to compute the minimum force necessary to push the filament into the extruder according to given values of printing process parameters. The model considers both the contribution of the extrusion force and of the deposition force, allowing the prediction of the variation of the required pushing force when variations of the layer height occur and can be a useful tool in the design of process parameters when very accurate components are needed in the process of additive manufacturing (AM)
Multi-step approach for automated scaling of photogrammetric micro-measurements
No full textPhotogrammetry can be used for the measurement of small objects with micro-features, with good results, low costs, and the possible addition of texture information to the 3D models. The performance of this technique is strongly affected by the scaling method, since it retrieves a model that must be scaled after its elaboration. In this paper, a fully automated multi-step scaling system is presented, which is based on machine vision algorithms for retrieving blurred areas. This method allows researchers to find the correct scale factor for a photogrammetric micro model and is experimentally compared to the existing manual method basing on the German guideline VDI/VDE 2634, Part 3. The experimental tests are performed on millimeter-sized certified workpieces, finding micrometric errors, when referred to reference measurements. As a consequence, the method is candidate to be used for measurements of micro-features. The proposed tool improves the performance of the manual method by eliminating operator-dependent procedures. The software tool is available online as supplementary material and represents a powerful tool to face scaling issues of micro-photogrammetric activities
A simple photogrammetric system for automatic capture and measurement of facial soft tissues during movement
No full textA proper diagnostic classification of developmental disharmonies, congenital or acquired
malformations is essential for assessing spontaneous or induced rehabilitation of facial soft tissue and skullfacial structures, and for monitoring the changes induced by surgical, esthetic and functional treatment
methodologies. In this work the authors describe a digital close-range photogrammetric system developed to acquire the spatial coordinates of facial landmark points and track their movements. The obtained results allow biometric measurements and tests to be made to evaluate the clinical and functional characteristics of a subject. The system produces a 3D animated model (wireframe, tasseled and textured surfaces), which accurately reproduces the subject's facial movements during opening and closure of the mouth. Recognition and tracking of facial landmarks were achieved by automated procedures that required minor human intervention
Single or high-dose bolus trifiban and sirolimus eluting stent versus abicixamab and bare metal stent in acute myocardial infarction (STRATEGY Study)
No full textAim to asses whether in patients with STEMI the combination of SES with a single high dose bolus tirofiban regime results in similar incidence of death and MI but in a lower rate of TVR after six months
Tirofiban, administered at high dose bolus during coronary angioplasty is highly effective in preventing periprocedural ischemic complications in diabetic patients. Insights into the ADVANCE trial.
No full textPlatelet reactivity is pivotal in the pathogenesis of complications after coronary angioplasty. ADVANCE trial sought to determine whether tirofiban, administered with the high-dose bolus is able to reduce ischemic events in diabetic patients referred for elective or urgent PCI
Erratum to: Effect of moderate red wine intake on cardiac prognosis after recent acute myocardial infarction of subjects with Type 2 diabetes mellitus (Diabetic Medicine, (2006), 23, 9, (974-981), 10.1111/j.1464-5491.2006.01886.x)
No full textIn an article by Marfella et al, the author name C. Saron is incorrect and should be listed as C. Sardu. Therefore the correct author list is: R. Marfella, F. Cacciapuoti, M. Siniscalchi, F. C. Sasso, F. Marchese, F. Cinone, E. Musacchio, M. A. Marfella, L. Ruggiero, G. Chiorazzo, D. Liberti, G. Chiorazzo, G. F. Nicoletti, C. Sardu, F. D'Andrea, C. Ammendola, M. Verza and L. Coppola.In an article by Marfella et al, the author name C. Saron is incorrect and should be listed as C. Sardu. Therefore the correct author list is: R. Marfella, F. Cacciapuoti, M. Siniscalchi, F. C. Sasso, F. Marchese, F. Cinone, E. Musacchio, M. A. Marfella, L. Ruggiero, G. Chiorazzo, D. Liberti, G. Chiorazzo, G. F. Nicoletti, C. Sardu, F. D'Andrea, C. Ammendola, M. Verza and L. Coppola
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