## 1 Introduction  
Traditional manufacturing processes involve the realization of components through the succession of two phases: an initial phase of coarse forming (by casting, forging, extrusion, rolling, etc. ), followed by a final finishing phase (by cutting, turning, milling, drilling, grinding, etc.). In the first phase, solid parts are created and then modeled through subtractive processes of materials [1]. Alongside these well-established traditional processing technologies, the use of unconventional innovative techniques [2], valid in both phases, has become increasingly widespread. These technologies allow one to carry out processes such as cutting, milling, drilling, etc. through the use of innovative processes including lasers [3], plasma [4], water jets [5], and electro-erosion [6]. The push towards the research and industrialization of innovative, unconventional processing technologies is linked to the most important disadvantages of traditional ones [7]. In fact, although the vast majority of objects are still today made using traditional techniques, production based on material removal processes requires auxiliary support systems (such as electricity, water, air compressed, steam, waste water, purification), often large workspaces, and conspicuous natural and energy resources [8]. Production is centralized, taking place in large industrial systems with huge storage warehouses downstream, from which the finished product is distributed to the customer. Traditional manufacturing, therefore, proves to be little oriented towards environmental, energy, and economic sustainability, leading to the need to research and optimize innovative and more sustainable production processes [9]. In this context, the role of 3D printing or additive manufacturing (AM) processes, born and developed initially to meet the needs of rapid prototyping, is crucial [10]. These processes involve the manufacture of artifacts by overlapping multiple layers of material, starting from a 3D model of the object to be created. The layers are compacted by melting the material, which then solidifies into the desired geometry [11]. The starting 3D model can be either the result of a CAD design or a 3D scan of a real object. The software that governs the 3D printers, divides the digital model of the object into superimposed layers (slicing), and then controls the deposition of the material. Additive manufacturing processes allow one to work with different materials such as plastic polymers [12], metals [13], ceramics [14], and composites [15]. Technological evolution has led to the possibility of using materials with industrial characteristics capable of withstanding high temperatures and significant mechanical stress [16]. Today, the use of 3D printing proves to be an optimal technology for small series productions or where great flexibility and a high level of customization of the finished product are needed [17]. Compared to traditional subtractive manufacturing, additive manufacturing technology offers several advantages such as the possibility of creating, in a single piece, shapes with complex geometries, avoiding traditional assemblies [18]; the reduction of processing waste; the possibility of using alternative and innovative materials [19]; the reduction of production costs associated with the fabrication of objects in small series; great ease of customization of an object [20] compared to a basic model, with very low costs to manage production variations, and not requiring intervention on the machine equipment; the significant reduction of the \"time to market\", thanks to the possibility of producing small batches to be placed on the market, for an initial evaluation of the product response, and only then activating a large-scale production; and the possibility of producing components \"on-site\", thus also reducing warehouse stocks [21]. However, the spread of 3D printing in mass production is still limited by several factors, the most significant of which is low productivity, linked to the current limited 3D printing speeds [22].