Vittoria Laghi; Michele Palermo; Giada Gasparini; Valentina Alena Girelli; Tomaso Trombetti
Abstract
In the last decades Additive Manufacturing has gained fundamental importance in the development of digital fabrication for the automotive, aerospace, biomedical and only lately civil engineering field. In particular, the technology of Wire-and-Arc Additive Manufacturing, based on a welding process adopted ...
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In the last decades Additive Manufacturing has gained fundamental importance in the development of digital fabrication for the automotive, aerospace, biomedical and only lately civil engineering field. In particular, the technology of Wire-and-Arc Additive Manufacturing, based on a welding process adopted on a robotic arm, is the most suitable to realize structural elements which usually requires large dimensions of the printed outcome, with still a good mechanical response of the printed metal material. The authors have been part of a pioneering work which provides the first insight into the material and geometrical properties relevant to characterize 308LSi stainless steel elements to realize the first 3D-printed steel footbridge to be held in Amsterdam by 2020 and manufactured by the Dutch company MX3D. In detail, the work presents the first results of an intense geometrical study to characterize the intrinsic irregularities of the printed outcome, by means of hand measurements and high-precision 3D scan acquisition of different element types. Copyright © VBRI Press.
Hong-Cheol Kim; Da-Yeong Kim; Ji-Eun Lee; Keun Park
Abstract
According to recent advancements in additive manufacturing (AM) technology, also known as 3d printing, the role of AM has changed from the conventional rapid prototyping (RP) to direct fabrication of functional parts. The AM technology based on layer-by-layer manufacturing has a limitation in its poor ...
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According to recent advancements in additive manufacturing (AM) technology, also known as 3d printing, the role of AM has changed from the conventional rapid prototyping (RP) to direct fabrication of functional parts. The AM technology based on layer-by-layer manufacturing has a limitation in its poor surface finish and mechanical strength, especially along the thickness direction. This study proposes a new post-processing method for thermoplastic AM products with the goal of improving surface finish and mechanical strength. The proposed method, called constrained remelting, uses a metal mould with a negative shape that surrounds the printed polymer part. This mould is heated near the melting temperature of the polymer material so that the printed sample is melted and reshaped inside the mould. To evaluate changes in surface finish and mechanical strength, tensile specimens were printed and tested with various build directions; the tensile test revealed that the Z-directionally printed specimen had much lower mechanical strength than the specimens built along X- or Y- directions. Remelting experiments were then performed for the Z-directionally printed specimen under various remelting conditions (remelting temperature and initial thickness), and the resulting changes in surface finish and tensile strength were investigated. Among these remelting conditions, the 160°C remelting temperature and 4.0 mm thickness condition provided the best result where surface finish and tensile strength were improved significantly so as to be comparable to those of injection-moulded products.
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