2.1. Resilience challenges in modern supply chains and manufacturing

SC is an interlinked network of actors that includes producers, processors, manufacturers, distributors, warehousers, sellers, resellers, and the final consumer (Reference Subramani, Kaliappan, Kumar, Sekar, Poures, De,Patil and RajSubramani et al., 2022). It entails everything from the purchase of raw materials, processing, transforming into valuable products, packaging, distribution, and storage before shipping off to the final consumer (Reference Osei, Asante-Darko and SarkisOsei & Asante-Darko, 2022). The aftermath of the COVID-19 pandemic combined with increasing geopolitical tension across the globe is making the SC network more vulnerable and volatile. For instance, Russia's invasion of Ukraine resulted in hikes to oil and gas prices and the disruption of key trade routes (Reference Bednarski, Roscoe, Blome and SchleperBednarski et al., 2023). Subsequently, parts suppliers, raw material supplies and prices in the automotive industry were greatly affected, with the share prices of many automakers dropping as a result (Reference SilbergSilberg, 2022). Beyond traditional conflicts, trade wars can also cause significant global impacts (Reference ZhaoSchindler et al., 2024; Reference Schindler, Alami, DiCarlo, Jepson, Rolf, Bayirbag, Cyuzuzo, DeBoom, Farahani, Liu, McNicol, Miao, Nock, Teri, VilaSeoane, Ward, Zajontz and ZhaoZhao, 2023). Weather-related disasters such as flooding, hurricane, wildfires and drought can also impact the stability of SC (Reference Tchonkouang, Onyeaka and NkoutchouBurgman et al., 2023; Reference Burgman, Crague, Devery, Healion, Terry, Williams, Henwood, Wescott, Zmood, Champion and ChampionTchonkouang et al., 2024).

2.2. The impact of manufacturing and supply chain on African economies

The pandemic crippled many African countries, revealing their heavy reliance on exported goods as well as poor manufacturing conditions (Reference EnochEnoch, 2023). Many manufacturing industries in Africa use older manufacturing equipment and processes which makes it difficult to adapt to changing SC needs and volatility (Reference NachumNachum, 2023). In global SC, Africa's key role is often the production and supply of raw materials. The continent boasts a vast reserve of critical minerals like aluminum, copper, iron ore, lithium, and manganese (Reference Boafo, Obodai, Stemn and NkrumahBoafo et al., 2024) which are essential for the energy transition (Reference Sterl and ShirleySterl & Shirley, 2024) as well as a wide variety of consumer products (Reference Boafo, Obodai, Stemn and NkrumahBoafo et al., 2024). This highlights a substantial opportunity for the continent to help manufacturers and distributors simplify SC and decrease transportation costs by locally processing the metals into products. This is especially true for relatively low-technology products. However, the continent contributes only 2% of the world's manufacturing output, a decline from slightly more than 3% in the 1970s (Reference YebouaYeboua, 2024). Nearly all African countries have a Manufacturing Environment Index (which indicates the general preparedness of the manufacturing ecosystem) that is below the global average (Reference Rägo, Sabartova and SawyerRägo et al., 2015). The region's growing abundant resource and current state necessitate strategic industrial adaptation (Reference Ndung’u, Shimeles and NguiNdung’u et al., 2022) capable of responding to sudden SC changes and demands.

2.3. Additive manufacturing and casting

Additive manufacturing (AM) involves manufacturing a part by depositing material layer-by-layer until a desired shape is achieved, enabling benefits can be challenging to achieve through TM processes and techniques (Reference Javaid, Haleem, Singh, Suman and RabJavaid et al., 2021). Moreover, AM leaves a strong digital footprint that can drive a variety of machine learning process and integrated directly with quality assurance and control (Reference Wang, Wang, Chen, Cheng, Liu, Niu, Zhao, Zhang and LiuArul Prakash et al., 2020; Baldwin et al., Reference Baldwin, Meisel and McComb2024; J. Chen, Khrenov, et al., Reference Chen, Khrenov, Jin, Narra and McComb2024; J. Chen, Pierce, et al., Reference Chen, Pierce, Williams, Simpson, Meisel, Prabha Narra and McComb2024; Reference Chen, Xu, Baldwin, Nijhuis, van Den Boogaard, Grande Gutiérrez, Prabha Narra and MccombJ. Chen, Xu, et al., 2024; Reference Arul Prakash, Mahan, Williams, Comb, Menold and TuckerQ. Wang et al., 2023). AM also presents opportunities for sustainability (Reference Calignano and MercurioCalignano & Mercurio, 2023). DebRoy et al. (Reference DebRoy, Wei, Zuback, Mukherjee, Elmer, Milewski, Beese, Wilson-Heid, De and Zhang2018) demonstrated that precise material deposition and reduced post-processing in metal AM can significantly cut energy consumption and lower emissions. The current paper focuses on the combination of AM with casting, which can often take two forms: 3D Sand Printing (3DSP) and AM-assisted Investment Casting (IC).

2.3.1. 3D sand printing

Figure 1. 3D printing mold process for sand casting (Reference LiLi, 2021)

In 3DSP, the sand mold itself is directly printed. Recent research has shown that 3DSP allows for an increase in casting complexity, casting quality and weight reduction of finished parts, ensuring shorter manufacturing lead time, minimal product and development delays (Reference DonaldsonDonaldson, 2018). The traditional sand-casting process requires a custom-built pattern and core boxes which may take weeks to months to manufacture. After patterns are manufactured, sand molds can be made in the range of minutes to seconds depending on the level of automation within a foundry. In contrast, 3DSP does not require the production of hard tooling (i.e. pattern, mold and core box). Instead, each individual printed mold is printed in sections, cleaned, and assembled. This process often takes hours to complete (Reference Shah, Patel and PandeShah et al., 2022), but allows for every casting to be tailored. Figure 1 shows how sand printers utilize binder jetting technology to deposit binder resin onto catalyst-infused sand using an inkjet process (Reference Walker, Harris, Lynagh, Beck, Lonardo, Vuksanovich, Thiel, Rogers, Conner and MacDonaldWalker et al., 2018). After each layer is printed, a fresh layer of sand is re-coated over previous layers, and this process repeats until the mold or cores are fully formed (Reference LiLi, 2021). The more complex the tooling that is needed for the job, the longer and costlier the pattern making stage will be. This is the window of opportunity for printed molds which offer a faster way to print and assemble molds and cores.

2.3.2. AM-assisted investment casting

Figure 2. Schematic of IC process (Reference Wang, Sama, Lynch and ManogharanJ. Wang et al., 2019)

AM-assisted IC involves 3D printing a wax investment pattern that can then be covered in a ceramic shell for IC (Reference Tewo, Rutto, Focke, Seodigeng and KoechTewo et al., 2019). In contrast, traditional IC requires high tooling cost for producing the wax patterns, and long process cycle time (Reference Cheah, Chua, Lee, Feng and TotongCheah et al., 2005). AM-assisted IC therefore enables flexibility in the design of customized products, highly complex geometries, process cycle time reduction, quality pattern and cast materials (Reference Shah, Monapara, Chitroda, Karetiya and PatelShah et al., 2023). Figure 2 shows the traditional IC process, which begins with pattern design and wax injection into a die (Reference Wang, Sama, Lynch and ManogharanJ. Wang et al., 2019). Next, wax patterns are assembled onto a wax sprue to form a cluster, then repeatedly coated in a ceramic slurry to build the shell (Reference Pattnaik, Karunakar and JhaPattnaik et al., 2012). After dewaxing through heating, molten metal is poured into the shell, cooled and allowed to solidify (Reference Wang, Sama, Lynch and ManogharanPattnaik et al., 2012; Reference Pattnaik, Karunakar and JhaJ. Wang et al., 2019). Finally, the shell is broken off, and individual castings are separated for post-processing. Although this process does not require expensive and elaborate tooling, it is still considered a costly process due to the high manual labor involved in preparing the wax pattern and slurry (Reference Pattnaik, Karunakar and JhaPattnaik et al., 2012). AM-assisted IC therefore provides cost-effective means of designing complex patterns, decreasing defects and improving its suitability for small batch production (Reference Thymianidis, Achillas and TzetzisShah et al., 2022; Reference Shah, Patel and PandeThymianidis et al., 2013)

3.1. East African region

East Africa, a region consisting of 18 countries, is bordered with the Sahara Desert to the north, the Indian Ocean to the east, and the southern and central regions of Africa to its west and south. It is the fastest growing region of the continent with GDP increases of 1.5% in 2023, 5.1% in 2024, and a projected increase of 5.7% in 2025 (AfDB, 2024). This growth is largely centralized to the Rwandan, Kenyan, Tanzanian, Ethiopian, and Ugandan economies, and most prominent in sectors such as transportation and logistics, manufacturing, technology and innovation, and urban development (AfDB, 2023). In addition to abundant natural resources, each state has established Special Economic Zones (SEZs) to incentivize investment and industrialization (Reference Otiende and NiskanenDiop et al., 2012; Reference Diop, Marotta and MeloOtiende & Niskanen, 2021). Significant manufacturing outputs include agro-processing, textiles, clothing, and leather. The transportation and logistics sectors in this region are improving significantly through e-mobility initiatives, enhanced public transport, digital integration, and upgraded air and road infrastructure. This progress is facilitated by strategic ports along the Northern Corridor (Port Mombasa, Kenya) and Central Corridor (Port Dar es Salaam, Tanzania) connecting landlocked nations.

3.2. North African region

North African consists of 7 countries (Algeria, Morocco, Tunisia, Sudan, Egypt, Libya and Western Sahara) and is positioned strategically between the Mediterranean Sea and Sahara Desert, with access to European and Middle Eastern markets. The region generates one third of the continent's total GDP, with the manufacturing sector contributing 18% to that share (Reference YebouaYeboua, 2024), making it the continent’s largest and most industrialized region. Primary industries of the region include textiles, automotive, and food production. North Africa dominates the African automobile manufacturing market. The top players in this region are Morocco, Algeria, Tunisia and Egypt, with Morocco recently toppling South Africa as the leading car manufacturer in Africa. Interestingly, Morocco is fast becoming a prime supplier of European manufacturers' components such as seat kits, and wiring harnesses, particular for car interiors (Reference SmithSmith, 2020). This reveals the region's high manufacturing potential in automobile manufacturing especially with OEMs (Original Equipment Manufacturers) like Volkswagen, Renault-Nissan, Toyota, Mercedes-Benz and Toyota investing heavily in the region.

3.3. West African region

West African, consisting of 16 countries, sits between North Africa, the Sahara Desert, and the Atlantic Ocean. Important economies in the region include Ghana, Ivory Coast, Nigeria, and Senegal (Reference SemanouAdegbite, 2021; Reference AdegbiteSemanou, 2022). Major manufacturing sectors include fuels, food and beverages, textiles, and apparel, with the region being the sixth-largest cotton manufacturer globally. Nigeria, the continent’s leading oil and gas producer, significantly influences regional trade and manufacturing activities as Africa's fourth-largest economy (Reference Dobbs, Strube, Rassey, Mischke, Remes, Roxburgh, George, O’Halloran and RamaswamyAdegbite, 2021; Reference AdegbiteDobbs et al., 2012). The region’s connectivity is supported by active ports, road networks, and air routes, mainly trading with the European Union.

3.4. Southern Africa region

Southern Africa includes Angola, Botswana, Lesotho, Malawi, Mozambique, Namibia, South Africa, Eswatini (formerly Swaziland), Zambia, and Zimbabwe. The region's coastline stretches from the desert border with Namibia with the Indian ocean in the east and the Atlantic Ocean to its west. Primary industries include textiles and clothing, automotive manufacturing, metals, chemicals, plastics, and wood products. South Africa, the continent’s largest economy, is a prominent manufacturing hub, especially in the automotive, iron/steel sectors (South African Government, 2017).Mining significantly contributes to the economy, exporting mainly gold, platinum, cars, and diamonds, supported by extensive trade partnerships with global powers such as China, US, EU, Germany, India, and Japan.

3.5. Commonalities

Across all regions, the agriculture/agro-processing and automotive sectors emerged as critical sectors for potential high-impact growth. These two sectors have also been identified African Continental Free Trade Area (AFCTA) in strategic plans for priority development in the continent (Reference Signé and MunyatiSigné & Munyati, 2024). Transportation, logistics, and pharmaceutical industries were also identified as key development areas. Agricultural and agro processing contributes approximately 35% to Africa's GDP and significantly exceeds the global average in economic contribution (Reference Munyati and SignéMunyati & Signé, 2023). Moreover, 70% of Africa's population rely on agriculture as their primary source of livelihood, making agriculture the backbone of its economy (Reference Woldemichael, Salami, Mukasa, Simpasa and ShimelesWoldemichael et al., 2017). Undeniably, agriculture and agro-processing sector has great potential to spur economic growth and create sustainable employment through forward and backward linkages (Reference ThindisaThindisa, 2022). Investment and restructuring of this sector's infrastructure is therefore crucial for productivity and economic growth (Reference Gajigo and LukomaGajigo & Lukoma, 2011). Likewise, the automotive industry has also rapidly expanded, positioning Africa as an emerging global automotive hub. AfCFTA’s strategy involves scaling production to 4–5 million vehicles by 2035, emphasizing electric vehicle (EV) production and sustainable farming technologies (Reference Signé and MunyatiSigné & Munyati, 2024). This expansion includes significant investments in assembly, maintenance, and component production (Reference Agarwal, Black, Lemma, Mkhabela and StuartAgarwal et al., 2022).

4.1. Applications of AM-augmented casting in Africa

AM allows for the rapid creation of prototypes, enabling faster design iterations and reducing wait times. In the automotive industry, production of custom tools, jigs, suspension components, fixtures, structural parts, and engine components can be produced faster and with more flexible design iteration using AM-augmented casting. Traditionally, sandcasting is usually used to produce engine blocks, an important component in the automotive industry. The engine block is the largest and main casting part in engine parts which produces space for cylinders, allows passage of coolant, exhaust, and in-take gases over the engine, and houses the crankcase and camshafts (Reference LiLi, 2021). Integration of AM with sand casting in this part of the automotive industry provides the benefit of improving the quality of engine blocks by allowing better cooling channel design, more complex geometries, and reduced defects. A key example is Volkswagen leveraging AM to manufacture complex vehicles structures (V., 2021). Notably, South Africa has been at the forefront of using AM-augmented casting to produce high quality commercialized complex components like hydraulic press for the automotive industry (Reference Gao, Li, Wang, Ma, Li and LiuGao et al., 2022). Similarly, AM-augmented casting benefits the agricultural and agro-processing industry by enhancing the production of agricultural machineries, parts and planting facilities (Reference Bourell, Kruth, Leu, Levy, Rosen, Beese and ClareBourell et al., 2017). Applications include gear boxes and engine components for tractors, harvesters and threshers for harvesting, plows and rototiller tines for soil cultivation, and pumps and valve parts for irrigation systems. Additionally, South Africa's agro-processing sector has demonstrated AM-augmented casting's potential in producing high-quality, customized components for food processing/packaging machinery, improving productivity and efficiency (International Trade Administration Commission of South Africa, 2016). AM-augmented casting extends to smart agriculture, enabling integration of AI and IoT (Reference Lu, Xu, Leng, Liu, Xu, Ding, Zhou and CuiLu et al., 2024). Notably, Liu et al. (Reference Liu, Chen, Chiu, Hsu, Chen, Pai, Peng and Chiang2018), built a flexible grasping claw module, integrating it with a robotic arm for automated fruits and vegetables handling using machine vision and grasp control. These applications showcase the vast potential for African Manufacturers to compete globally. Sustained investment in research, innovation and infrastructure is essential to realize the full benefits of AM-augmented casting in Africa.

Figure 3. AM-augmented casting supply chain with AM regional hubs

4.2. Strategic approaches for AM-augmented casting adoption in Africa

It is envisioned that once the foundries receive their casting order and decide on their manufacturing mode, they order the IC or sand molds and cores from AM hubs as shown in Figure 3. The figure is inspired by the hybrid metal-AM SC in US diagram in (Reference Strong, Kay, Conner, Wakefield and ManogharanStrong et al., 2019), showing how AM-augmented casting integrated SC factors in the costs for potential part failure or scrap. Traditional manufacturers receive low-production-run orders from customers and send CAD models to an AM hub. The hub produces near-net metal parts and ships them to heat treatment facilities. Upon treatment, parts are sent to traditional manufacturers for hybrid post-processing before final delivery to customers using existing methods. The strategic placement of AM hubs across African regions, in specific countries like South Africa, Nigeria and Ethiopia is based on their economic attractiveness such as existing industrial infrastructure like foundries, proximity to raw materials, skilled labor and local market demand. Beyond these economic considerations, AM-augmented casting regional hubs adoption also drive sustainability (Reference Calignano and MercurioCalignano & Mercurio, 2023). Attaran (Reference Attaran2017) emphasized that in regions where reliance on complex imported tool poses logistical and financial challenges, localized manufacturing with AM-augmented casting can reduce cost while shortening SC and cutting transportation related emissions.

Hub locations are the main drivers for the allocation decisions. Alumur & Kara (Reference Alumur and Kara2008) discussed a review of several hub location and allocation problems such as hub with fixed cost, hub centering, and hub covering using both single and multiple allocations. Campbell et al. (Reference Campbell, Kelly, Campbell and Kelly2018) presented a survey on hub location literature where they discuss the evolution of the hub location problem (HLP), evaluating from the origin to its current state. Daskin & Dean (Reference Daskin and Dean2004) discussed the importance of facility location models where poorly located facilities or too many or too few facilities will increase expenses and diminish customer service. According to L. Chen et al. (Reference Chen, Olhager and Tang2014), optimally located sites can improve operational performance and help gain competitive advantages in both the short term and long term. Moreover, the location of facilities with respect to their competitors as well as customers has a significant impact on a firm’s ability to run and deliver efficiently (Reference DaskinDaskin, 2013).

Over time, several research works have highlighted the need and the advantages of integrating AM and machining processes (Reference Xiong, Zhang and WangHur et al., 2002; Reference Hur, Lee, Zhu-Hu and KimXiong et al., 2009). Such hybrid strategies have been developed for the environment where additive and subtractive operations are repeated in a cycle until the final part is created (Reference Xiong, Zhang and WangKarunakaran et al., 2010; Reference Karunakaran, Suryakumar, Pushpa and Akula Xiong et al., 2009). Others contend that hybrid manufacturing has the potential to improve the capabilities of TM by integrating AM where traditional machining would post-process the AM metal parts (Reference Strong, Sirichakwal, Manogharan and WakefieldStrong et al., 2017). Other researchers recognize that existing manufacturers with heterogeneous bills-of-material may develop AM capabilities to isolate disruptive, low-volume production from scalable mass production (Reference Sasson and JohnsonSasson & Johnson, 2016).