*Metal 3D-Printing of Waveguide Components and Antennas: Guidelines and New Perspectives DOI: http://dx.doi.org/10.5772/intechopen.106690*

The set of guidelines is indeed very broad, since it goes from the initial RF design of geometry to the type of machine parameters used to fabricate the part. This section will only cover the ones concerning the RF designer, since the rest will change depending on many considerations, ranging from the type of machine to productivity. In any case, and as it will be demonstrated in this chapter (which contains many examples from different authors and therefore different manufacturers), the basic RF guidelines are enough to produce very good performance regardless of the 3D printer, alloy, or manufacturer.

Concerning RF design, the most basic consideration when 3D printing RF devices is the orientation that the piece will have in the 3D printer. Such orientation determines the manufacturing tolerances, the degree of symmetry of the printed component, the eventual need of supports if the printer finds surfaces that are hanging, and the number of parts that one can print in the same platform. In order to attain both high precision and high symmetry, the piece should be oriented in a way that either the main waveguide propagation axis is parallel to the building direction (vertical printing) or the main waveguide propagation axis is perpendicular to the building direction (horizontal printing).

The remaining of the subsection discusses the basic guidelines that a designer may follow to adapt a waveguide device to vertical or horizontal printing.

### **2.1 Overhanging faces**

Overhanging faces are those that are perpendicular to the printing direction and facing down, as illustrated in **Figure 1(a)**. As part of the design process, such overhanging faces should be modified, since they can suffer strong deformation or even collapse if they are too big. The recommended design practice is to chamfer or tilt the face with an angle of 45<sup>∘</sup> or larger. As it will be shown later, this technique can be applied to corrugations, irises, cavities, posts, etc.

#### **2.2 Wall thickness**

In certain microwave devices, thin walls are needed as part of the RF design (e.g., septums in orthomode transducers, irises in filters, inner walls in power dividers, etc). To the best knowledge of these authors, the lowest wall thickness that can be 3D-printed nowadays with a good reliability is 0.5 mm. In certain

#### **Figure 1.**

*Nonfeasible overhanging face (a) and feasible inclined overhanging face (b). The orange arrow indicates the printing direction.*

**Figure 2.**

*In order to successfully print very thin walls, it is important that they are supported by adjacent thicker walls. The orange arrow indicates the printing direction.*

occasions, it can be possible to achieve thicknesses of 0.3 mm, although only for very short walls and supported by thicker adjacent walls, as illustrated in **Figure 2**.
