AM is luring the designers to work on innovative and new designs without bothering much about the manufacturing aspect. It is a layer-to-layer manufacturing process that uses powder form of material, here metal powder to fabricate parts using various AM methods. AM provides an edge over other forms of the manufacturing processes as it reduces waste and ensures design independence. Though AM can manufacture micro to macro level parts, the precision can only be ensured after accurately setting the employed studies with a proper scale of printing . Today, AM has become a standard and a number of design software and other facilities support AM, which are 3D printable.
The presented research focuses on the feasibility of the manufacturing of the designed battery housing using AM methods, finally choosing the best method. Different parameters are taken into account while judging the viability of the designed component. They can be performance, cost, time, availability of material, platform size and many more. The presented design is process-driven designing and manufacturing that helps in deciding performance aspect and design time. It is not designer driven as they worry about costs and deal with lattices and sometimes present difficulty in handling distorted triangles and complex geometries . AM posits certain manufacturing limitations too, that can be cost, printer size, minimum element size which plays a decisive role in the selection of a proper AM method. There are AM machines of multiple sizes in the market, industries and research laboratories that have a well-defined lower limit over element size. For the manufacturability of the part as large as an electric car battery housing, it is not of much problem. Cost, on the other hand, plays a major factor in choosing parts. The upper limit of cost on re-designing parts may increase, so it is always suggested to cut other costs for compensation. Optimised parts can become costly but customer values in the competitive world are also taken into account, which is specifically mass, i.e., due to the performance aspects. Customers are ready to bear the additional cost for performance enhancement of the parts. Race cars and even new companies are taking this trend into account and looking forward to performance gain and endurance rather than cost rise. Hence, initial cost rise is not a major concern while designing new parts in research laboratories. It can be compensated and thus, not a problematic issue for the presented housing’s study. Cost estimation and build time simulation can be taken into account during re-designing. However, if performance increment is too high, it can be taken into account against cost rise .
4.1 Support Structures
Support structures are an integral component required while fabricating a part using AM machines. The requirement of support structures over a specific location in the design depends on overhang angle of that specific part, i.e., angle of inclination of a part with the vertical axis. Generally, parts having overhang angle greater than the maximum possible angle as per the settings need incorporation of support structures for AM.
Overhang angles and support structures are necessary to deal with when using AM for topological optimisation. The battery housing requires different support structures that are generated using automated computer algorithms taking into consideration overhang angles. Figure 8 depicts the support structures generated for the battery housing considering different part orientations on the platform.
Support structures play an important role in deciding the final orientation of the part. The orientation having minimum percentage volume of the support structures with respect to the battery housing is considered. It helps in minimising the wastage of material, post-processing cost, time and eventually the overall cost and time.
Table 2 compares the amount and percent support structure volume with respect to the battery housing volume. Since orientation 4 has minimum amount and percent support structure than the other orientations, it is chosen as the best feasible orientation for the fabrication of the battery housing.
Table 2. Amount and percentage support structure volume of the battery housing for fabrication
4.2 Different metal AM techniques: advantages and limitations
Different additive manufacturing methods are present that ensure fabrication of the functional parts. The main AM methods that are selected for a specific design depend on factors such as material, resolution, size limit with the associated benefits and drawbacks. The presented research deals with a metal battery housing, specifically AlSi10Mg. The pertinent AM methods that work with metals are powder bed fusion (PBF), directed energy deposition (DED), and sheet lamination. The first two methods deal with bulk metals but the last one is specific to metal tapes and rolls. The most relatable AM methods for this research study are powder bed fusion (PBF) and directed energy deposition (DED).
PBF, containing a diverse group of additive manufacturing methods, i.e., selective laser melting (SLM), direct metal laser melting (DMLM), electron beam melting (EBM), selective laser sintering (SLS), multi-jet fusion (MJF), is a favoured process for metals and alloys, same as the case for battery housing. It makes use of a thin layer of ultra-thin metal powder that are fused inter-layer with the help of layers or binders. SLS and SLM are mostly used for metals and alloys fabrication. Furthermore, this method is greatly applicable in the manufacturing of lightweight structures, aerospace, electronics, and biomedical components. It works for a good resolution range of 80-250 and size limit of , size limit can be larger too. Specific to the battery housing, this method provides a number of benefits starting from fine resolution to high quality manufacturing. There are certain drawbacks too, such as high cost, however it is not a major concern for this study, and slow printing due to the layer-by-layer manufacturing finish of the housing .
DED, containing laser metal deposition (LMD), laser additive manufacturing, wire arc additive manufacturing (WAAM), electron beam additive manufacturing (EBAM), on the other hand, has a coarse resolution of ~250 and size limit of within enclosed chamber or outside. This method requires a dense support structure, thus increasing the overall material of the battery housing for processing. It is difficult to use this method when dealing with complex shapes and structures. Surface quality is also compromised with. This method deals with metals and alloys in the powder or wire form, reducing time and cost of fabrication, that is not the scope of this research study. Furthermore, it finds use mostly during cladding, retrofitting and repairing the aerospace and biomedical components .
4.3 Finalised AM method
Based on the critical analysis of the feasible AM methods for the fabrication of battery housing, selective laser melting (SLM) is finalised. As the material used in designing the battery housing is AlSi10Mg, the mechanical properties of the SLM manufactured AlSi10Mg is comparable or better than cast AlSi10Mg due to the formation of Al and Si near eutectic composition . This method melts the top layer of the powder bed according to the 3D presented CAD data so as to ensure fully dense structure. SLM, being a sub-group of selective laser sintering (SLS) helps in achieving higher yield strength than casted AlSi10Mg and hence useful for the battery housing fabrication .
Since the bounding box of the re-designed battery housing is , a 3D printer of platform size as large as is required to manufacture the battery housing as a whole. A number of highly efficient 3D printers are available in the industries and research laboratories today that deal with such large-sized components. The idea of welding the small manufactured parts of the battery housing is quite tempting but it will compromise with the mechanical properties of the re-designed battery housing. Welding is a process that is hard to simulate and validate the veracity of. It mostly depends on the efficiency of the worker in case of manual welding or robots in automated welding. However, some promising results are obtained by Nahmany et al.  where sound weld metal porosity and no typical heat affected zones (HAZ) occurred, so minimal deterioration of joint properties, when electron beam welding (EBW) of AM parts is carried out. Contrary to this, significant heat affected zones (HAZ) and less porosity is observed when electron beam welding (EBW) of cast parts is carried out. In that case, size of SLM can be as large as 1 m and quadra lasers can be used in SLM. Even conventional battery housings are achieved after welding the extruded Aluminium parts. Speed welding is required there for minimising the degradation of the metal properties and not compromising with the performance of the parts. Kang et al.  proposed an inherent strain method that quantifies the welding deformation when friction stir welding (FSW) is applied to weld the aluminium parts of the battery housings. These welding deformations affect the performance and the properties of the components due to gap formation, spattering, and high temperature cracks. It results in rough surfaces and residual stresses occur within the housing. Arc welding gives even larger amount of deformations.
4.4 Feasibility index
The viability of fabrication using AM methods depends majorly on three factors - Performance of complex features part, Cost and Time. Feasibility index provides a good overview of the viability of fabrication as demonstrated by the practical feasibility model proposed by Ahtiluoto et al. . The model contains performance, part production volume, design cost, manufacturing cost, design time, manufacturing time of AM and CM with the respective weighting factors as input. Higher the index value, more suitable the part is for AM. It completely depends on market demands which factor is of more importance, so designers estimate accordingly the weighting factor for the feasibility index. Since, cost and time of the electric vehicle battery housing are not of utmost importance in the presented research study, the weighting factor for performance is very large than the weighting factors for cost and time. The re-designed battery housing due to the aspiration of increased performance, thus increased performance weighting factor and overall increased feasibility index is a completely feasible design for the fabrication using AM methods as per the results of Ahtiluoto et al. .
Part performance, being one of the major factors for the feasibility of fabrication study of the re-designed battery housing depends on ease of use, assemble/disassemble time, flow resistance, friction resistance, damping and many more. However, when cost becomes one of the leading factors for the feasibility index, CAD integrated cost estimation solution is a must . One can also turn to cost estimation in macros addon API tool of Solidworks, though some ambiguity will be there due to lack of specification data, compatibility, and analysis of theoretical model. Cost can be minimised by decreasing build height and lessening the support structures which is the favourable cost minimisation method in the presented battery housing’s study.