Direct metal laser sintering (DMLS) is a powder bed fusion (PBF) process commonly used within the medical device and aerospace industries to fabricate high value, complex components. Powder material used in the DMLS process can be costly and it is rare for a single build to require a full batch of powder. The un-melted powder, which differs in particle size and morphology from virgin powder, is often recycled for further builds. This work presents a study of the effects that recycling a stainless steel metal powder used in the DMLS process has on finished parts. Hence in this paper, powder material characteristics, such as particle size, particle morphology and bulk chemical composition have been monitored throughout the recycling process. An analysis of parts manufactured via DMLS on an EOS M280 demonstrate the negative effect of powder recycling on part quality in terms of surface roughness, part density, hardness and dimensional accuracy. Results from this research provides an insight to the effect that recycling AM powders has on the powder characteristics and on the quality of the parts produced.

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Information, digital and academic literacy skills are more important than ever as the nature of global information streams becomes more complex and increasingly online. New methods are needed to ensure that students are taught to identify, use and critically evaluate this complex information myriad during their education and in their future careers. Peer assisted learning is one method that has been shown to help, and previous research in the field of peer support has indicated that the interaction between students at different levels enhances a first-year student’s successful transition into higher education (HE).  In 2016, a peer support scheme was introduced at the Institute of Technology Tallaght (ITT Dublin) as a collaboration between the Department of Mechanical Engineering and the library. Initial evaluation of the programme showed that some students respond positively to the inclusion of peer support within an academic module. We also found that peer tutors have a critical role in the support of a first-year student’s learning and their transition into higher education. They act as role models and guides and can help students form the essential linkages between the different resources they will need to be successful in higher education and beyond. An attractive social strand to the programme can act as a critical motivator for students. Further research is needed to identify the essential elements required.

Metal additive manufacturing (AM) processes, viz laser powder bed fusion (L-PBF), are becoming an increasingly popular manufacturing tool for a range of industries. The powder material used in L-PBF is costly, and it is rare for a single batch of powder to be used in a single L-PBF build. The un-melted powder material can be sieved and recycled for further builds, significantly increasing its utilisation. Previous studies conducted by the authors have tracked the effect of both powder recycling and powder rejuvenation processes on the powder characteristics and L-PBF part properties. This paper investigates the use of multiple linear regression to build empirical models to predict the part density and surface roughness of 316L stainless steel parts manufactured using recycled and rejuvenated powder based on the powder characteristics. The developed models built on the understanding of the effect of powder characteristics on the part properties. The developed models were found to be capable of predicting the part density and surface roughness to within ±0.02% and ±0.5 Ra, respectively. The models developed enable L-PBF operators to input powder characteristics and predict the expected part density and surface roughness.

Laser-based powder bed fusion (L-PBF) of AlSi10Mg is used to fabricate complex, light-weight structures with high thermal conductivity. Much effort has gone into investigating the mechanical behavior of L-PBF components; however few studies investigated their thermal properties. This investigation characterizes the effect of process parameters on the relative density of AlSi10Mg components fabricated by L-PBF to understand how these parameters contribute to thermal conductivity. Exposure time, laser power, pointwise distance, and build orientation were examined. Results show that these parameters affect the effective thermal conductivity of printed parts by up to 22%. Pointwise distance had the most impact on melt pool size and on effective thermal conductivity compared with other parameters. As the pointwise distance increased, both the conductivity and the melt pool width decreased, whereas the laser power had a negligible effect on both. The effect of exposure time was mainly dependent on the pointwise distance. We show that thermal conductivity is not only related to the relative density of the samples, but the number of the melt pool boundaries in the microstructure also plays a significant role in interrupting the heat flow. A new factor which accounts for the number of melt pool boundaries per unit length in the direction of heat flow is introduced to quantify the phonon scattering associated with the microstructure evolution induced by the process parameter changes. This helps explain the variation in thermal conductivity for samples manufactured with high energy densities which had negligible difference in relative density.