3D knitting for upholstery: guidelines to design at the interface of sustainable fashion and furniture.

Textile products, a synthesis of the complex relationship between physical and sensory characteristics, have always played a fundamental role in the culture of furniture design projects. Like many other production sectors, the furniture one in recent years has been called to meet the growing demand for conversion to sustainability both in terms of processes and raw materials, since most of the time disassembly is very difficult and the padding material is generally difficult to reuse, recycle, or recover when furniture pieces are dismissed. 3D knitting allows reducing the productive steps, consequently, i.e. reducing the supply chain. Moreover, it allows the development of local and on-demand production systems and, lends itself to the use of recycled materials. Finally, at the end of life of furniture pieces, the above-mentioned technology facilitates the recycling of yarns and drastically reduces the possibilities of exploitation of labor. In addition, the use of this process in furniture design has the potential to answer to the strong demand for circularity that the furniture sector is asking for. This research focuses on the relationship between innovative textile technological processes and furniture design (upholstered sofas and armchairs in particular). This study aims to investigate how the 3D knitting process, can contribute in terms of sustainable production in the furniture sector. The technological transfer has been studied either in literature and with direct dialogue with industrial 3D knitting experts. Through this research, it has been possible to demonstrate that the process is not limited to reducing production waste but also to bringing environmental, economic, and social benefits. In fact, 3D knitting allows companies to reduce the size of the product during transport, meeting the trend of flat packaging, allowing the replacement of polyurethane foams in upholstery with recycled and recyclable materials and ultimately leading to a different conception of the furniture product. 3D knitting brings the designer to conceive furniture in a completely new and different way, simple and easy to disassemble, factors that are fundamental principles of circularity design. To provide an output that was not only illustrative but also functional to the designer, in the second part of the research, some specific design guidelines for 3D knitted upholstery have been defined. The guidelines have been established through an overview of the basics of knitwear, the explanation of the machines and their operations, case studies and samples collection, and interactions with 3D knitting industries. Thanks to these guidelines it is possible to guide the designer in the early stages of the development of a 3D knitted product. A final case study on the guidelines application is also provided. This research has allowed to shed light on a process still little known in the world of product design, identifying the potential for the creation of circular products, especially in the furniture sector, and helping designers approach this technology.