**2.1 Manufacturing machines**

To manufacture the different layers, some machines must be used. A few possible ones are explained in the following paragraphs.

## *2.1.1 Plotter/cutter laser*

This kind of machines use lasers to mill, cut, and drill substrates. Lasers are usually conical, so that the incidence angle is not 90°, but slightly lower, being necessary to minimize this effect as it will be explained in section 4.3. Laser machines are slower than mechanical milling machines, but they have a higher precision. In **Figure 1**, an example of these machines can be seen.

#### *2.1.2 Milling machine*

These machines use different mechanical drilling tools to mill, cut, and drill. The main downsides are the precision in comparison with laser ones and corner inner cuts, which are rounded because of the cylindrical shape of this tools. Although milling machines are very useful, they have some limitations: First, milling drills sizes vary from 0.2 mm to 3 mm, and their intermediates' values depend on the commercial drilling tools. In **Figure 2**, an example of these machines can be seen.

Both laser and milling machines can work independently or combined, given that mechanical machines are much faster than laser ones, especially in the drilling processes; being good enough for those kind of prototypes or parts in which drilling accuracy is not crucial. The combination of both machines decreases hugely the total production time without decreasing the accuracy, and it is highly recommended for prototypes with rigorous requirements. Resolutions of high-performance machines shift from 0.1 μm to 2 μm, and their repeatability oscillates from 0.1 μm to 2 μm; it depends on the machine. Theoretically, both machines can reach similar resolutions; however, drilling tools tend to be slightly bigger/smaller reducing resolution till 100 μm.
