# Computer-Aided Design and Additive Manufacturing for Automotive Prototypes: A Review
## 1 Introduction  
In a wide range of opportunities to improve technologies in the field of automotive manufacturing, prototyping production is revolutionized using smart manufacturing technologies [1], such as Cyber-Physical Systems (CPS) and the Internet of Things (IoT), whichenhance manufacturing capabilities and support informed decision-making for smart manufacturing systems [2; 3]. Computer-aided design (CAD) and additive manufacturing (AM) are emerging as enabling technologies for production platforms in the automotive industry, offering new prototype design possibilities [4; 5]. Both technologies, combined in an integrated solution beyond their original roles, are being used to attain new possibilities in automotive prototype fabrication, allowing for the economic and low-volume production of prototypes and enabling the development of functional components and conceptual models [6; 7; 8]. This integration has changed paradigms in the traditional manufacturing landscape by combining manufacturing process flexibility and precision in part assembly [9; 10; 11]. Through smart manufacturing technologies, CAD and AM are vital forces reshaping automotive prototype production, allowing flexibility, reduced development time, speeding up processes, weight optimization, cost-effectiveness, and the ability to respond to the market [12; 13]. According to the academic literature, integrating CAD and AM in prototype production, particularly in the metal-mechanical sector, reflects a transformative improvement in manufacturing and design processes [14; 15]. In [16], the authors developed a methodology that integrated AM with topology optimization for innovative product design, highlighting the potential for innovative product design and improved material efficiency. In [17], the authors propose a methodology to improve products by utilizing AM opportunities and introduce a \"functional improvement rate\" to quantify the improvements of optimized systems based on Design for Additive Manufacturing (DfAM). In [18; 19], the authors highlighted the need for practical CAD tools for topology optimization in AM processes. The work in [20] demonstrated the integration of CAD and computational fluid dynamics (CFD) simulations for rapid prototyping, thereby enhancing the development of industrial components. The authors proposed a method to assess CAD tools for additive topology optimization, focusing on automotive components. The work in [21] highlighted the integration of CAD and AM by using advanced design strategies. In [22], the authors showcase generative design and AM integration in automotive manufacturing, emphasizing improved design capabilities and manufacturing efficiency. In [23], the authors detailed a sustainable hybrid manufacturing approach for creating an AlSi5 alloy turbine blade prototype, combining robotic direct energy layered deposition (wire arc additive manufacturing--WAAM) with subsequent milling. This method integrates the layer-by-layer material deposition capabilities of WAAM with the precision and surface finish enhancement of milling. The combination offers several advantages, including an enhanced surface finish, improved dimensional accuracy, material efficiency, and design flexibility. This approach demonstrates the broader adoption of hybrid manufacturing methods in industrial applications, particularly for producing complex components with high precision and quality. The work performed in [24] enhanced the application of CAD in the design and optimization of 3D-printed jigs by integrating thermomechanical properties. Despite the wealth of literature on CAD and AM, a significant gap exists in the exploration of the specific integration of these systems for automotive-part prototypes. This study fills this gap by providing a comprehensive understanding of how the integration of CAD and AM can revolutionize the prototyping manufacturing environment and reshape traditional manufacturing paradigms in the automotive sector.