Large Format Additive Manufacturing (LFAM) enables the rapid fabrication of large-scale components but is limited in resolution due to the size of deposited strands. As a result, integrating functional features necessary for component assembly often requires manual post-processing steps such as drilling or milling. These secondary processes are not only labor-intensive but can also compromise the structural integrity of the printed parts. To overcome these limitations, this study explores the functionalization of LFAM structures through robotized, mobile injection molding. The central approach involves the local overmolding of 3D printed components to directly integrate functional elements. A series of investigations were carried out, beginning with the identification of compatible material pairings for additive and injection molding processes. Custom specimens were developed and manufactured to evaluate joint performance. Load-bearing tests were conducted to assess the mechanical integrity of the overmolded joints, while computed tomography (CT) was used for detailed structural and quality analysis of the joining zones. The results demonstrate a high level of joint performance, underscoring the viability of mobile injection molding as a complementary technology to enhance the functionality and application range of LFAM structures.