## 4 Design: CAD & CAE
### CAE Analysis  
Once all components are modelled on a CAD software, it is possible to develop on a CAE software (as Autodesk Inventor) a finite element analysis to evaluate the parts subject to greater mechanical stress. The finite element analysis is a mathematical technique designed to analyze and simulate the behavior of organs subjected to efforts, which was born in the 60s. The term 'efforts' refers to mechanical, electrical, or thermal stresses. This type of analysis breaks the structure under examination into smaller substructures, called finite elements. The finite elements and their interactions are converted into an equation and solved mathematically. Among the advantages in the adoption of numerical simulation systems it is possible to find: behavior prediction, raw material reduction, early validation, 'what-if' scenario analysis.  
Let us now analyze some components. The FEA analysis was developed in the Autodesk Inventor environment. The material used for all components is the Nylon PA 12, introduced by HP, whose yield strength Rp is 48 MPa and it has a density of 1.01 g/cm\({}^{3}\).  
Figure 11: Concept design and initial sketches to executive project.  
Support: The support is the most stressed component. In fact, it is required to consider the weight of all the components and apply a force on this support and analyze the deformations. Now we evaluate the weights of the pieces given by CAE software:  
Body: 0.196 Kg  
Engine (from catalog): 0.303 Kg  
Fan: 0.014 Kg  
Grill: 0.041 Kg  
Cap: 0.010 Kg  
The total weight on that lies on the support will be given by the sum of these.  
Weight = 0.564 kg. The weight force is obtained as W = 0.564 \(\times\) 9.8 m/s\({}^{2}\) = 5.53 N. Now we apply this force on the surface of interest. The following results are obtained (Figure 12):  
By applying the gravitational force and the load, and after fixing the constraints of the support, it is possible to notice that the area subjected to the greatest effort is the part highlighted in red. However, the maximum effort recorded is 3.778 MPa, while the yield strength of PA12 is 48 MPa. Therefore, we are still in the elastic field, far from the breaking load. In addition to the Von Mises factor, displacement must also be considered. Since both the structure and the material are very elastic, an important displacement can be noticed in the area furthest from the vertical support. A displacement of 8 mm has been registered, allowing a spring effect.  
Body: The body is the most fragile and difficult part to analyze. The'spider' supports of the motor housing are thin and risk breaking if subjected to high mechanical stress. In the FEA analysis of this component, both the thrust force of the fan and the motor weight force were calculated. The engine's torque is neglected (Figure 13).  
MPa. In this case, unlike the support, the displacements along the horizontal axis are of the order of microns and considering the application of the component (domestic use), they can be neglected [4].  
Fan: A FEA analysis was also performed for the fan. In conditions of absence of friction and lack of resistance of the fluid, the component is put in rotation at 1500 RPM to evaluate its consequences. Displacements in the order of microns and stress of 0.19 MPa are highlighted (Figure 14).