# Enhancing Design for Additive Manufacturing Workflow: Optimization, Design and Simulation Tools
## 1 Introduction  
According to ISO/ ASTM standards, additive manufacturing (AM) is defined as the process of joining materials, generally by layer-by-layer approach, to produce parts starting from digital representations [1]. Continuous development of metal AM technologies, such as directed energy deposition (DED) or laser powder bed fusion (LPBF), yield new industrial design perspectives due to several technology benefits. Indeed, the main AM advantages include: the possibility to manufacture complex internal part-functionalities like cooling channels in turbine blades [2], lattice and gyroids structures in medical implants [3, 4]; low buy-to-fly ratio [5]; consolidate part assemblies into fewer components [6]; achieve mechanical properties as tensile and yield strength comparable to bulk materials [7]; and high part-customization. Consequently, AM becomes an economically suitable technology where low-production volumes or customizable production on-demand are required [8]. However, there are still drawbacks related to the complex thermo-physical phenomena involved: repeated cycles of rapid cooling of the melted pool generate anisotropy depending on building direction [9]; control of printing parameters is required to prevent physical problems of balling, key-hole formation and lack of fusion [10]; residual porosity affects end-parts mechanical properties [11]; energy consumption is high to melt or sinter the metal powder [12]; and low surface quality occurs due to layer-by-layer deposition [13], thus reducing fatigue life [9]. Moreover, volumetric restrictions on part size [14], time-consuming jobs and lack of standard certifications for certain industries as aerospace, are still considered limitation factors [15]. In the traditional design for manufacturing (DFM) process, it is required to find a design solution that minimizes manufacturing, assembly and logistic costs [16]. To take into consideration these objectives with the unique AM technology capabilities (e.g., partconsolidation, design freedom and highly part-customization), the design for additive manufacturing (DfAM) allows rethinking the whole design process from the digital database to the final printed part. In addition, to take into consideration the geometric printing technology limitations, DfAM guidelines are provided, based on empirical analysis depending on the material, printing parameters and manufacturing technology. Namely, it's possible to recognize [17]: critical angle of self-supported faces, minimum diameters for unsupported holes, optimal position on the building plate, maximum allowable aspect ratio of thin columns, minimum printable wall thickness and minimum feature size. To reduce manufacturing costs related to energy consumption, printing time and post-processing, parts should be designed with minimum support generation. Indeed, supports are usually required for overhanging sections, to prevent collapse during building. However, for metal AM, supports are crucial and cannot be removed at all due to the high-stress gradient generated during printing. In this case, supports act as heat transfer structures preventing excessive distortions and residual stresses. Initially, the guided-design process performs post-processing checks, while recent advancements on software platforms allow predicting thermal effects and mechanical performance in earlier design phases. However, the physical and manufacturing limitations mentioned above mean that the DfAM process workflow involves several stages to maximize printing capabilities and ensure correct manufacturability. In addition, the process is considered a challenging task to perform, since computer-aided design (CAD), computer-aided engineering (CAE), and computer-aided manufacturing (CAM) must be evaluated at different abstraction levels requiring full design, simulation and manufacturing knowledge.