**3.1 Fused deposition modelling**

Fused deposition modelling (FDM) or known as fused filament fabrication (FFF) is a manufacturing technology in which objects are created by extruding polymer filament onto a built platform through a heated nozzle. There are numerous versions of FDM printers with various price ranges. In this research, Prusa i3 MK3 is used as a low-cost FDM printer where the platform moves in the Y-axis and the nozzle in the X- and Z-axes. When one layer is done, the nozzle will move up vertically to allow a new layer to be applied to the previous one. The thickness of the layer (slice) depends on the print parameters, and in the case of the used Prusa printer, the slices are between 0.05 and 0.30 mm thick [29]. Prior to the AM process, the constructed CAD model must be exported in a compatible file format, such as STL. Such a model is then cut into horizontal slices in a software package (so-called slicer). The paths of the platform and the nozzle are calculated by the software according to the parameters set by the user. In addition to the mentioned layer thickness, which significantly affects the accuracy, some of the other variable parameters are the number of layers in the outer wall and the number of layers at the bottom and top of the part, the percentage and structure of the filling, extrusion speed, and others. Because the next printing layer prints on top of the last one, supporting structures are required to print large overhangs or holes. They are printed together with the part and removed after printing is done. In general, overhangs should be avoided by proper orientation of the part or by using angled overhangs where possible. The most common materials used in FDM technology are ABS, PLA, PC, ASA, PPSF/PPSU, ULTEM, PH-HD. PE-LD, PET, TPU, and others. **Figure4** shows a working principle of the FDM technology.

### *3.1.1 Continuous fibre fabrication*

In addition to classic FDM technology, devices that can produce parts from composite materials using FDM processes are known as continuous fibre fabrication (CFF). In this paper, Markforged Onyx Pro is used, in which the platform moves in the Z-axis and the nozzle in the X- and Y-axes. Compared to the Prusa printer, it is a much more expensive device but allows 3D printing of composite materials made of plastic matrix and inlaid

*Framework for Design and Additive Manufacturing of Specialised Multirotor UAV Parts DOI: http://dx.doi.org/10.5772/intechopen.102781*

**Figure 5.** *Fibre reinforcement layout—CFF technology [30].*

fibreglass fibres for better mechanical properties and increased lifetime, compared to plastic alone. The strength and stiffness of a fibre-reinforced part can be comparable to aluminium. The software package allows adjustment of the classic print parameters and further adjustment of the composite reinforcements parameters as shown in **Figure 5**.
