SELECTIVE BINDER CURING: A NOVEL HYBRID 3D PRINTING TECHNIQUE TESTING, DESIGN AND ASSEMBLY OF A PROTOTYPE

The thesis relates to the work done in order to develop a new hybrid 3D printing technique for metal parts. Starting from the operating schemes and the structures of binder jetting printers and vat photopolymerization systems, it was decided to build a system capable of making use of some of the key elements of both techniques. In fact, the idea was to use a low-viscosity photopolymerizable resin and metal powder to create a homogeneous mixture and to spread it over the building platform, making the layers needed for the fabrication. Differently from binder jetting, the extremely precise but slow jetting mechanism is not required, and the accurate creation of the desired shape is obtained through the selective photopolymerization of the binder. This is possible thanks to the use of a DLP projector, which also replaces the heating system present in conventional binder jetting. Related to this, one of the greatest advantages of this new system must be highlighted: the possibility of obtaining rapid curing in an efficient and modular way. The technique, in fact, was meant to be applied to large-area printers, where our system could be simply installed multiple times until all the building platform is covered by the projection. After the creation of the desired components through the repetition of the process layer-by-layer, the post-process activities, typical of binder jetting have to be followed in order to get a fully sintered part. Following this concept, a prototype has been realized. The first steps were focused on the effective design of the system. At the same time, manual experiments were performed in order to assess the actual feasibility of the manufacturing process, particularly for what concerns the curability of the binder when mixed with metal powder and exposed to UV light. The same tests were performed after a DLP projector was purchased. The design was continuously refined, considering all the manufacturing constraints, as well as the characteristic of the component that we had to purchase from external supplier. A final Bill of Material was created, selecting among all the considered parts the cheapest that satisfied our needs. All the components were bought or created using the equipment available at the MSU machine shop, the prototype was assembled, optimized and run, thanks to a code created with the NI LabVIEW software. In the end, the results are discussed and compared to the initial expectations.