Comparative evaluation of vat photopolymerization and steel tool molds on the performance of injection molded and overmolded tensile specimens

This study explores the use of vat polymerization stereolithography (SLA) for fabricating mold tooling, subsequently utilized in injection molding (IM) and overmolding of tensile specimens and directly compared to those produced using metal molds. The results first find the manufacturing time for an SLA-fabricated mold is remarkably short, approximately 6 h, presenting a substantial improvement over traditional methods. Mechanical testing revealed that the tensile specimens from the SLA-fabricated molds exhibited the highest tensile strength among all overmolding batches. This performance was consistent with the tensile bars produced using metal molds, demonstrating the viability of SLA-fabricated molds for overmolding applications and highlighting the potential of FDM to customize the properties of final products. However, variations in mold types impacted the dimensional tolerance and tensile strength of the final specimens. Metal mold-fabricated tensile bars exhibited superior dimensional accuracy and maximum tensile strength (50.6–61.7 MPa) compared to those produced with SLA-fabricated molds (46.9–55.9 MPa). These differences are attributed to the rougher surface finish inherent to the layer-by-layer construction of SLA and the internal stresses and defects resulting from lower thermal conductivity and uneven cooling. In conclusion, this study underscores the promising future applications of SLA-fabricated molds in overmolding, offering reduced manufacturing costs and enhanced design freedom. The findings support the potential of SLA to revolutionize mold fabrication, thereby extending its utility and optimizing the production of polymer components with customized properties. Highlights: SLA molds compared to metal molds for direct injection molding and overmolding. FFF preforms with varied geometries were overmolded to finalize the specimens. Joint configurations in overmolding improved tensile performance. Overmolding showed better dimensional accuracy than FFF specimens. SLA mold preparation significantly reduced manufacturing costs.