# Topology Optimisation in Structural Steel Design for Additive Manufacturing
## 7 Designing for Additive Manufacturing with Topology Optimisation
Table 7 summarises some selected recent developments, which add to the advances in TO depicted in the previous chapters. \begin{table}
\begin{tabular}{c c} \hline \hline
**Development** & **Reference** \\ \hline Multi-Material Topology Optimisation (MMTO) by generalising the single-material Pareto tracing method. & [553] \\ Guidelines for integrating TO and AM to restrain support structures. & [246] \\ A TO approach to minimising support material by optimising an allowable self-supporting angle. & [554] \\ A TO approach to designing self-supporting structures. & [555] \\ Guidelines for TO regarding AM process parameters. & [556] \\ Guidelines for enabling AM newcomers to produce better quality designs. The proposed worksheet has a useful \"pass-or-fail\" arrangement. & [557] \\ A method for topologically optimised infills in additively manufactured parts. By fostering non-uniform infills, better results have been attained. & [558] \\ TO for AM with EBM (or PBF-EB). & [559] \\ AM-fabricated Materials with Site-Specific Properties (MSP). This design approach allows designing materials with heterogeneous properties, where local material enhancement is possible without requiring an increasing fabrication time and cost for the whole element. & [560] \\ TO approach to minimise overhangs, assisted by its sensitivity analysis. & [561] \\ TO approach to minimise overhangs and generating self-supporting structures. & [562] \\ TO approach to minimise support structures and thin features. & [563] \\ Optimisation of support structures design for AM. & [564] \\ A multi-objective TO approach to minimise supports material consumption and removal time and cost, while minimising parts deformation. For such an end, a repulsion index (RI) is used. & [565] \\ A design method for additively manufacturable free-form periodic metasurfaces. & [566] \\ A multiscale method which includes both TO macro-scale optimisation and AM layers mesoscale. & [567] \\ A new version for the MMC method based on AM data. & [568] \\ A TO model to account for thermal residual stresses and deformations due to the AM processes. & [569] \\ TO approach to minimise overhangs in compliant mechanisms, using the Smallest Univalue Segment Assimilating Nucleus algorithm. & [570] \\ TO approach to minimise overhangs and assure a minimum length scale, both for enhanced printability. Application to a tensegrity connection. & [547] \\ TO for AM with SLM (or PBF-L). & [571] \\ A Non-Probabilistic Reliability-Based Topology Optimisation (NRBTO) method to account for additively manufactured materials’ properties uncertainty. & [572] \\ A TO method to account for AM cost and fabrication time. & [183] \\ A TO density-based approach with one field for design parameters and another field for support layout optimisation. & [573] \\ A TO approach for designing and re-designing additively manufacturable parts. & [574] \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Recent research on design techniques for AM. The path between a topologically optimised model and a manufacturing input can pose significant obstacles, even if the smoothing of TO model boundaries has already been accomplished [588]. Not only several fabrication parameters must be accounted, but also data transfer can be a complex task. The TO model must be exported to a CAD three-dimensional format, suited to the manufacturing process and sliced into thin layers [423]. Moreover, many available approaches have not been broadly and satisfactorily tested for manufacturability [589]. Regarding this issue, one may refer to the work by [PERSON] and [PERSON] [97], yielding TOPSlicer, a MATLAB code for transforming matrices or arrays with density values into additively manufacturable digital outputs. Furthermore, ontologies databases may assist designers in enhancing DfAM. Within this domain, [PERSON] and [PERSON] [590] contributed to systematise a knowledge base, and to infer the design rules using the Web Ontology Language (OWL)/Resource Description Framework (RDF) Protege tool must be highlighted.