3D printing (3DP) is an additive manufacturing (AM) technology that builds objects by adding successive layers of material, offering flexibility in design and prototyping through digital modeling and parametric design. Unlike traditional subtractive manufacturing methods, 3DP promotes environmental sustainability by minimizing waste, reducing energy consumption, and using only the necessary materials for production. This technology has the potential to revolutionize the fashion and apparel industry by enabling personalized, small-batch production with less waste. However, the adoption of 3DP in textiles is still in its infancy, as current tools and materials lack the functionality, comfort, and breathability required for wide-scale application in clothing. Despite these limitations, 3DP shows promise in specific areas such as functional prostheses, sportswear, and garment assembly, reducing the need for traditional sewing processes. Earlier studies have explored 3D and 4D printing onto textiles, but the sustainability and circularity of these polymer-textile composites remain to be fully assessed. This research proposes a new methodology and tools to support fashion designers in utilizing 3DP for personalized fashion, addressing current limitations in design practices and 3D printing technology. Through a research-through-design approach, the study presents a case study showcasing how 3DP can promote sustainability and inclusivity in fashion, focusing on eco-design solutions that facilitate garment assembly and disassembly. By enabling human-machine collaboration and providing tools for generative and parametric design, this research aims to empower designers and transition the fashion industry toward a greener, more inclusive future aligned with Industry 4.0 and 5.0.