Economic and Energy Consumption Aspects of Additive Manufacturing
* PhD Thesis: Economic aspects of additive manufacturing: benefits, costs and energy consumption. Martin Baumers. Doctor of Philosophy of Loughborough University, 2012.
"Additive Manufacturing (AM) refers to the use of a group of technologies capable of combining material layer-by-layer to manufacture geometrically complex products in a single digitally controlled process step, entirely without moulds, dies or other tooling. AM is a parallel manufacturing approach, allowing the contemporaneous production of multiple, potentially unrelated, components or products. This thesis contributes to the understanding of the economic aspects of additive technology usage through an analysis of the effect of AM s parallel nature on economic and environmental performance measurement. Further, this work assesses AM s ability to efficiently create complex components or products.
To do so, this thesis applies a methodology for the quantitative analysis of the shape complexity of AM output. Moreover, this thesis develops and applies a methodology for the combined estimation of build time, process energy flows and financial costs. A key challenge met by this estimation technique is that results are derived on the basis of technically efficient AM operation.
Results indicate that, at least for the technology variant Electron Beam Melting, shape complexity may be realised at zero marginal energy consumption and cost. Further, the combined estimator of build time, energy consumption and cost suggests that AM process efficiency is independent of production volume. Rather, this thesis argues that the key to efficient AM operation lies in the user s ability to exhaust the available build space." (https://dspace.lboro.ac.uk/dspace-jspui/handle/2134/10768)
From the conclusion:
" Tuck et al. (2008) suggests that AM possesses two advantages over other, more conventional manufacturing techniques. Firstly, AM is able to efficiently generate geometrically complex components; and secondly, the technology is able to produce very small production quantities at a relatively low average cost.
This research has demonstrated a methodology for the quantification of measures associated with complexity. Using a measure reflecting shape complexity, as proposed by Psarra and Grajewski (2001), it has been shown that the energy inputs to the AM variant EBM do not correlate with the complexity found in the layers of a test part. This gives reason to believe that in some AM processes, such as EBM, the financial production cost will also be independent of product complexity. As noted by Hague et al. (2003), this is a novel feature for manufacturing processes and is unlike most conventional processes.
Contributing to the on-going debate on AM‟s ability to efficiently manufacture products in low volumes (down to a single unit), this research has discussed the determinants of energy consumption and financial production cost. In terms of pure process energy consumption, it is demonstrated that the degree of capacity utilisation is highly important for summary metrics of energy consumption on some platforms. The presented evidence reveals that especially powder bed fusion AM technology, such as LS, SLM, DMLS and EBM are subject to severe economic penalties if the available build volume capacity is not fully used. On the other hand, the economics of the FDM process appear to be relatively independent of the degree of build volume capacity utilisation.
However, unlike some previous models of manufacturing cost, this thesis argues that is not possible to infer a relationship between manufacturing unit cost and production quantity. The reason for this is that the underlying behaviour would not be rational. In reality, empty capacity is avoided by the users of AM systems (Ruffo and Hague, 2007). This can be achieved by postponing builds, selling excess capacity to external demanders or adopting a smaller AM system.
Thus, this thesis suggests that the AM users‟ ability to fill the available machine capacity is the linchpin for favourable manufacturing economics on most AM platforms, apparently with the exception of FDM.
Motivated by the need to reduce the energy consumption associated with the manufacture and use of durable goods, there is an increased tendency to take into account the whole life cycle in engineering design.
This thesis appreciates that the environmental impact of durable goods is not restricted to the production processes. It extends „upstream‟ to the raw material generation process and „downstream‟ to the 229 product‟s use-phase and to its disposal. Here, the adoption of AM may be beneficial in two ways: due to its ability to create complex products in a single step the wastage of raw material is minimised. Moreover, its ability to fully differentiate products to the function they will perform during their use phase should ultimately result in highly effective and functional products. These gains may be large enough to compensate for disadvantages in terms of manufacturing cost or manufacturing energy consumption.
According to Stoneman (1995), an important research puzzle deals with the issue of whether environmentally benign technologies may be privately profitable. The evidence presented in this thesis, especially the outcomes of the combined energy consumption and cost model, points to the conclusion that the minimum cost configuration in AM is also the configuration that minimises the energy inputs during the manufacturing stage.
Hence, from an ecological standpoint, AM adoption may come with the side-effect of correcting production configurations with non-minimal energy inputs. This aspect may be an important prerequisite for energy efficiency gains in manufacturing (Lovins, 1996). Moreover, a corrective of this kind is perhaps also a hallmark of a particular class of technology described as „Mumfordian biotechnics‟. It has been argued that these technologies may in the distant future replace conventional mass production by a more benign, scalable and product performance oriented manufacturing approach (Mumford, 1971). Aspects of AM that support this classification are the qualitative richness of products enabled by AM (Hollington, 2008) and the freedom from quantitative pressures associated with the absence of sunk tooling costs present in traditional mass production (Ruffo et al., 2006b)." (https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/10768/3/Thesis-2012-Baumers.pdf)