## 3 DfAM Tools  
AM process allows realising parts with highly complex shapes that are impossible to produce by any other technologies. The complexity and variability of the additive processes require advanced design tools to optimise the product geometry and the settings of the machine parameters.  
The completed design workflow of AM parts requires different kinds of software and the employment of highly skilled users. The specific design tools concern the CAD modelling of the geometrical details, the Finite Element Method (FEM) analysis to simulate the mechanical behaviour of the part after printing, and the FEM simulation of the phases of the 3D printing process, etc. The literature already shows several DfAM tools; however, the 3D printing process's complexity and variability limit the widespread of general purposes tools.  
A completed review of Computer-Aided Engineering (CAE) tools for AM is proposed by [PERSON] and [PERSON] [12]. Their work aims to maximise the vantages of AM technology by presenting the use of specific tools for product development. They analysed engineering and CAD platform tools such as mesostructured design, optimisation software, process management, and simulation solutions. Here, the DfAM tools are classified into seven categories: Design, Topology Optimisation, 3D mesh, Process Simulation, In-service Simulation, and Preprinting Slicing. These seven design tools are employed in five design AM phases: Design, Verification, Slicing, Printing, and Finishing. The most ambitious category concerns the simulation of the 3D printing phases because of the novelty of this manufacturing process. These simulations mostly regard the powder bed fusion processes, allowing geometrical deformations and residual stresses to be calculated. Therefore, the process simulations allow optimising the process parameters to minimise the accumulated tensions and the deformations of the pieces during and after printing. The designer can also use the simulation report to analyse the printing position, select the material, and optimise the support structures.  
While some DfAM tools are well known in the scientific literature and community, others are new and exclusive for specific additive manufacturing phases and processes. For example, [PERSON] and [PERSON] developed a specific DfAM tool for Carbon-Fibers-Reinforced Polymer filament in Fusion Deposition Modeling (FDM) [13]. They implemented a tool-path algorithm to optimise the orientation of the fibres in the FDM process. The main idea was to reinforce fibres aligned with the profile of the high-stress region, which was previously calculated by FEM analysis. This DfAM tool can be classified in Preprinting Slicing, according to the classification described in [12]. Moreover, it can be employed in the phases of Design and Slicing.  
[PERSON] et al. [15] described an example of a design tool for In-service Simulation. They developed a simplified Finite Element Method (FEM) to predict the mechanical behaviour of parts manufactured by fused filament fabrication (FFF) of polymeric pre-structured materials. This paper considers the filament orientation along with the principal stress directions. They also considered the anisotropy of the material related to complex deposition trajectories by introducing specific constants. The simulation confirms that the longitudinal loading direction has the highest yield strength than the transversal one for the FFF process.  
The study of DfAM tools is still an open topic in research. They can be classified by objectives, design phase, materials, or processes; however, they are still so specific that they cannot be applied as general-purpose solutions in AM design. In this context, the literature shows relevant cases of these tools for enhancing their replicability in different applications.