PRODUZIONE E SUPERFICIE FINITURA DEI COMPONENTI PRODOTTO DA ADDITIVE TECNOLOGIA DI PRODUZIONE - RAFFINARE

Additive manufacturing (AM), or 3D printing, is an emerging technology that has profoundly transformed the industrial production landscape thanks to its high flexibility and its ability to create components with complex geometries. These geometries, which are often difficult or even impossible to produce with traditional manufacturing methods, make AM an innovative solution for industries such as aerospace, biomedical, and automotive. However, despite the advantages offered by AM, one of its main drawbacks is the poor quality of the surface finish of the produced parts, which often fails to meet the precision requirements needed for advanced applications. This leads to the need for post-processing treatments to improve surface roughness and ensure compliance with the high-performance and safety standards. AM technologies allow the production of metallic or polymeric components, either finished or semi finished, through the progressive layering of material. In metal AM processes, the material is typically in powder form, whereas in polymers, other forms may be used. Once the layering process is complete, the component undergoes a densification treatment using an external source, which can be a laser for metals or a UV source for polymers. The surface roughness of the components produced depends on several process parameters, including the minimum deposition layer thickness, which in turn is a function of powder granulometry, heat treatment duration, and the quality and type of the metal alloy used. Despite the precision achievable through these techniques, the surface finish is still of lower quality compared to that obtained with traditional subtractive processes, such as chip removal. Consequently, additional post production treatments are required to improve surface quality, aiming to achieve specific roughness values quickly, in order to preserve the production speed advantages offered by AM. This thesis thoroughly analyzes the factors that influence surface finish quality in various AM processes, such as selective laser sintering (SLS), fused deposition modeling (FDM), and laser powder bed fusion (LPBF). To this end, an experimental study was conducted on the key process parameters, including layer thickness, part orientation during printing, deposition speed, and laser power, correlating these factors with surface roughness and other mechanical properties of the final part. The ultimate goal is to understand how optimizing these parameters can enhance the surface and structural characteristics of the manufactured parts. Currently, the finishing technologies used in industry to improve the surface quality of AM components are often based on traditional grinding machines that employ abrasive wheels and discs. However, these techniques can be inefficient, especially when dealing with complex geometries or small production batches, as they require high reconfiguration costs and long setup times. In recent years, the manufacturing industry has increasingly experimented with more flexible and modern solutions, such as fluidized bed technologies, which offer an eco-friendly and more efficient alternative. In these processes, the component is immersed in an abrasive fluid bed inside a fluidization column, where the abrasive particles suspended in a gas or liquid flow behave like a fluid, capable of perfectly following the contours, even complex ones, of the part. This technology offers numerous advantages, including better surface finish quality, reduced treatment times compared to conventional techniques, and greater effectiveness in processing internal or intricate surfaces. Additionally, reconfiguration costs are practically zero, making this technology highly advantageous even for small production batches. The thesis analyses the effectiveness of the Abrasive Fluidized Bed (AFB) process through an experimental activity carried out on samples made of PA12 using Selective Laser Sintering technology. It evaluates the influence of key parameters such as abrasive particle size and type, fluid flow rate, and treatment duration, aiming to identify optimal combinations for achieving high-quality surface finishes. Through a series of experiments, the AFB process was shown to significantly reduce the surface roughness of AM components without compromising their static dimensional or mechanical properties. In contrast, a notable improvement was observed in the dynamic mechanical properties, particularly in the fatigue life of the treated components. The results highlight that, compared to other post-processing techniques, AFB allows the creation of smooth and uniform surfaces, even on complex geometries. Furthermore, the process proves to be highly scalable and sustainable, making it a promising solution for a wide range of industrial applications. In conclusion, the integration of Abrasive Fluidized Bed technology into additive manufacturing represents a highly effective strategy for improving the surface quality of parts, helping to overcome one of the main limitations of AM technology and opening up new prospects for its large-scale adoption