Purpose Owing to the operating principle of powder bed fusion processes, selective laser sintering (SLS) requires effective management of the mixture ratio of processed material previously exposed to the high temperatures of processing with new virgin material. Therefore, this paper aims to fully understand the effect that the successive reprocessing has in the powder material and to evaluate its influence on the properties of SLS parts produced at different building orientations. Design/methodology/approach Polyamide 12 material with 0%, 30% and 50% of virgin powder and parts produced from them were studied through five consecutive building cycles and their mass, mechanical, thermal and microstructural properties were evaluated. Then, the experimental data was used to validate a theoretical algorithm of prediction capable to define the minimum amount of virgin powder to be added on the processed material to produce parts without significant loss of properties. Findings Material degradation during SLS influences the mass and mechanical properties of the parts, exhibiting an exponential decay property loss until 50% of the initial values. The theoretical algorithms of reprocessing proved the appropriateness to use a mixture of 30% of virgin with 70% of processed material for the most common purposes. Practical implications This paper validates a methodology to define the minimum amount of virgin material capable to fulfil the operational specifications of SLS parts as a function of the number of building cycles, depending on the requirements of the final application. Originality/value The use of theoretical models of prediction allows to describe the degradation effects of SLS materials during the sintering, ensuring the sustainable management of the processed powder and the economic viability of the process.

Additive manufacturing (AM) is a hot topic nowadays, having a first order in importance in research trends, improving existent technologies and carrying them further. AM can be applied to ceramics, which have importance in current technologies. Their capability to maintain functional properties for long time periods, combined with the easiness to process and the abundance of raw materials, make them a fundamental part of mankind development. Within ceramics, stoneware has a wide range of uses but in some conditions, it can be affected by biofouling. Ti(O)N and Ag-Ti(O)N coatings over 3D printed stoneware, were presented as multifunctional solution, linking aesthetical and antimicrobial properties. Films were developed by reactive direct current (DC) magnetron sputtering and characterized physical, chemical and morphologically, as well as regarding their colour variation. Moreover roughness, wettability, antibacterial and antibiofouling were also evaluated. The results revealed that the Ag doped coatings (with or without oxygen addition) had an enhanced multifunctionality compared to control samples (without Ag). Ag nanoparticles addition created a surface with potential antibacterial and antibiofouling activities, in order to resist outdoors and aqueous environments, making these films able to be applied in architectural pieces as sculptures or other decorative parts, maintaining their properties with good aesthetical properties. implants, soft tissue replacements, drug deliveries, among others [2]; aerospace industry, in reduced volume parts and replacements parts for aircraft with advanced materials as aluminium alloys, titanium alloys, nickel super-alloys and special steels; automotive industry, in the development of some structural and engine parts; and tooling industry, like moulds with complex refrigeration systems enabling better performances and higher life time, [3]. Additive manufacturing, namely with metals and polymers, is no longer the future, it is the unavoidable present, but the additive manufacture of ceramic materials is still far from the desired maturity. Abundance, easy manipulation, low cost, heat resistance and long life time span are the main characteristics of ceramics [4] and across human history, new technologies have enlarged its uses. Chemically, ceramics can be considered as compounds formed between metallic and non-metallic elements with predominant ionic bonding but having a

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Additive Manufacturing (AM) technology has been increasing its penetration not only for the production of prototypes and validation models, but also for final parts. This technology allows producing parts with almost no geometry restrictions, even on a micro-scale. However, the micro-Detail (mD) measurement of complex parts remains an open field of investigation. To be able to develop all the potential that this technology offers, it is necessary to quantify a process’s precision limitations, repeatability, and reproducibility. New design methodologies focus on optimization, designing microstructured parts with a complex material distribution. These methodologies are based on mathematical formulations, whose numerical models assume the model discretization through volumetric unitary elements (voxels) with explicit dimensions and geometries. The accuracy of these models in predicting the behavior of the pieces is influenced by the fidelity of the object’s physical reproduction. Despite that the Material Jetting (MJ) process makes it possible to produce complex parts, it is crucial to experimentally establish the minimum dimensional and geometric limits to produce parts with mDs. This work aims to support designers and engineers in selecting the most appropriate scale to produce parts discretized by hexahedral meshes (cubes). This study evaluated the dimensional and geometric precision of MJ equipment in the production of mDs (cubes) comparing the nominal design dimensions. A Sample Test (ST) with different sizes of mDs was modeled and produced. The dimensional and geometric precision of the mDs were quantified concerning the nominal value and the calculated deviations. From the tests performed, it was possible to conclude that: (i) more than 90% of all analyzed mDs exhibit three dimensions (xyz) higher than the nominal ones; (ii) for micro-details smaller than 423 m, they show a distorted geometry, and below 212 m, printing fails.

The market growing saturation with products similar to the already existent ones or whose adaptation to a user revealed inefficiency, makes relevant the development of projects that effectively bring competitive advantage and consequently contribute to the development and wellbeing of the society and the ecosystem. Therefore, the propose of this research is to elaborate a methodology that enables the development of products, that present solution to the user needs, but considering also the environmental issues. Through an exploratory research and the redesign of a vacuum cleaner as a case study, a new methodology divided into two phases is presented where the: (i) recognition of the real needs of users, as well as problems associated with the product, through research and usability testing (N = 120) and (ii) the environmental impact of the product are addressed. In this way, it was possible to defined the criteria to be incorporated into the product, with the aim of applying measures to improve the usability of the product, that are consistent with ecological solutions and therefore sustainable. POLYM. ENG. SCI., 58:535–544, 2018. © 2017 Society of Plastics Engineers