# Sustainable Transformation: A Case Study of an Engineering-to-Order Additive Manufacturing Firm
## 4 Literature Overview  
### Additive Manufacturing (AM)  
AM, an alternative to traditional CNC machining, is one of the most important technologies [54] enabling reduction of material waste, labour, transport cost [10; 55; 56], time [17], transaction cost [57], machine space [58], and storage space [55; 56]. At first, the main advantage of AM lied in on-demand part availability and swift delivery [59; 60]. Initially used for prototyping, AM is now employed for medium- and high-volume production [61]. AM offers various technologies tailored to various customer needs, from prototyping to part production, currently evolving to an alternative manufacturing technique with a focus on low to medium product quantities [6] and batches [25; 62]. Batch production allows a larger number of parts to be produced quickly and less costly, enabling AM to achieve economies of scale when the proper collaborative planning is performed [13; 61]. Table 1 outlines the available AM technologies used for industrial purposes. Additionally, the table presents the authors' attempts to evaluate the sustainability of the AM technique and its suitability for batch production. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Technique/Material/ Method** & **Description** & **Industry** & **Part Properties** & **Efforts towards Sustainable Evaluation in the Literature** & **Batch Production** & **Reference** \\ \hline Fused deposition modelling //Material extrusion & Parts are formed by melting and depositing plastic & Aerospace, automotive, robotics, and electronics & High-performance and industrial strength & Analysis of FDM processes and their societal impact, environment and economic analysis of FDM & [23; 62; 63] \\ Stereolithography (SLA)/Polymers/Vatt & Plants are made by using a reservoir, converting it into 3D solid plastics layer through & Jewellery, dental equipment, layer through & High accuracy, watertight & Keying accuracy, watertight & Yes & [7; 62] \\ Photography/materials & Photography & Photography & Parts are made by projecting & & & \\ Digital light processing & ultravicket (UV) light from a digital projector onto the 3D photopoply/mersion & Dental appliances, medical devices & Isotropic, highly accurate parts & Evaluation of the process sustainability with a focus on process time and waste & Yes & [62; 64] \\ Photoply/mersion & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Additive manufacturing techniques used for industry purposes. Challenges in Achieving Sustainability in AM Operations  
The industry and society are being reorganised to enable complete industrial digitisation with an emphasis on sustainability objectives [71]. AM, due to its characteristics (more sustainable than traditional CNC manufacturing, human-centric, resilient supply chain), is an essential ingredient in the new era of the Industry 5.0 [2; 47]. Therefore, it is becoming even more critical for AM manufacturers to embrace sustainable business practices as pressure increases from all market dimensions, including employee needs, shareholder expectations, and regulatory requirements [2]. Sustainable AM necessitates maintaining various elements of a sustainable process. These include economic viability, ensuring profitability, environmental protection by conserving energy and optimising the use of natural resources, and social equity, ensuring the safety of employees and the local community [56; 72]. However, the current literature highlights that AM does not exhibit superior sustainability compared to conventional manufacturing (CM) in batch production scenarios [5; 6; 7] due to factors such as: high production costs, elevated energy consumption, costly material inputs, expensive machinery, material wastage, and adverse environmental impacts [5]. Notably, AM demonstrates lower environmental impacts than traditional techniques only in cases of very limited production quantities [11; 12].