This PhD project explored how the use of 3D printing can support design in a circular economy. 3D printing is an emerging technology and is viewed as a promising production process for the circular economy because of its unique additive and digital character. The aim of design in a circular economy is to preserve the value of products and materials through lifetime prolongation or high value reuse and recovery. Product integrity and material integrity are relevant for this, because they represent the quality of products and materials to remain whole and complete over time. In this research, we studied how 3D printing can support product integrity and material integrity in a circular economy. Research through design (RtD) was the main research method. In this method the design process is used to generate knowledge and we used a prototyping process to develop 3D printing in the new context of a circular economy. The main contributions of this research can be summarised as following: •We helped establish of a new research direction by exploring design approaches for product integrity and material integrity in a circular economy. •We developed a circular 3D print process flow for product integrity. This is demonstrated by showing that the digital and additive character of 3D printing can be harnessed to develop reversible connections that enable products to be disassembled and reassembled without loss of quality. We developed reversible joints and demonstrated these with a proof-of-concept of a lamp and vase. •We established a design approach for developing reprintable materials. This was demonstrated by producing reprintable materials from locally available bio-based resources, i.e. ground mussel shells with two different binders (sugar and alginate). We designed a lampshade and hairpin and 3D printed them using these materials. •We contributed to the domain of ‘research through design’ by using the prototyping process for knowledge generation; a less common use. The design goal in the prototyping process was used to obtain relevant information (from other disciplines) for developing technology in a new context. This resulted in an iterative process between experimental prototyping processes and scientific knowledge generation. We would like to conclude by nothing that, in spite of all the optimism about the way the use of 3D printing can accelerate the transition to a circular economy, there are currently few 3D print applications that actually support and enable the circular economy. Our exploration shows that to successfully print for product integrity and material integrity, both in-depth knowledge and understanding of the AM production technique is required. @en

The circular economy requires high-value material recovery to enable multiple product lifecycles. This implies the need for additive manufacturing to focus on the development and use of low-impact materials that, after product use, can be reconstituted to their original properties in terms of printability and functionality. We therefore investigated reprintable materials, made from bio-based resources. In order to equally consider material properties and recovery during development, we took a design approach to material development. In this way, the full material and product life cycle was studied, including multiple recovery steps. We applied this method to the development of a reprintable bio-based composite material for extrusion paste printing. This material is derived from natural and abundant resources, i.e., ground mussel shells and alginate. the alginate in the printing paste is ionically cross-linked after printing to create a water-resistant material. This reaction can be reversed to retain a printable paste. We studied paste composition, printability and material properties and 3D printed a design prototype. Alginate as a binder shows good printing and reprinting behaviour, as well as promising material properties. It thus demonstrates the concept of reprintable materials.

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Additive manufacturing, also known as 3D printing, is acknowledged for its potential to support sustainable design. In this paper, we explore whether the opportunities that additive manufacturing offers for sustainable design are also useful when designing for a circular economy, and to what extent additive manufacturing can support design for a circular economy. We performed a literature review on the sustainability aspects of additive manufacturing and held a series of interviews with designers about their 3D printed design projects to obtain in-depth information. The interviews were analysed using annotated portfolios, a novel analysis method created specifically for this research. This resulted in a visual representation of the outcomes. We found that additive manufacturing supports circular design strategies by creating opportunities to extend a product's lifespan, for instance by enabling repair or upgrades, even if these products were not originally designed for ease of repair or upgrading. However, the use of monolithic structurally complex parts that support design for recyclability may hinder high value product recovery, like repair. Besides this, the current offer of 3D printable materials should be extended with materials developed for durable use, as well as high-value reuse. Concluding, when accounting for these drawbacks, additive manufacturing is able to support multiple product life cycles and can provide valuable contributions to a circular economy.

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The potential of additive manufacturing (AM) for distributed production is often mentioned as an enabler for sustainable manufacturing within a circular economy. Currently, even if manufacturing with AM is distributed, the used materials can rarely be acquired locally and are usually obtained from a centralized location. Addressing this issue, we are developing an approach that supports the search for local materials that are suitable as material input for AM and are recyclable to serve multiple product lifecycles. The approach is an iterative process consisting of four phases; “material in AM context”, “recycling opportunities”, “material property testing”, and “application possibilities”. As an initial example, we present a process to adapt mussel shell waste into AM material. Mussel shells are a voluminous waste stream in the Netherlands. The shells, which mainly exist of calcium carbonate, are ground into a powder and combined with sugar water. Using a modified material extrusion process, 3D objects are created. In this paper, we discuss the iterations through our approach and illustrate the initial 3D printed results. With this project, we intend to demonstrate the potential of using local waste streams for AM processes for a circular economy. This is a first step towards the development of a methodology for linking local material streams to novel AM processes and meaningful applications.@en

This paper explores the use of annotated portfolios as a method to support the qualitative analysis of interview data about design projects. Annotated portfolios have so far been used to support artefacts with text in order to discuss them in the context of ‘research through design’ In this paper, we interpret the five-step method of McCracken and relate it to annotated portfolios to analyse interviews. We use a case study on design projects related to 3D printing and sustainability to illustrate the process. Five designers were interviewed to obtain a deeper understanding of the role of Additive Manufacturing in practice. These interviews were analysed in a visual process with annotated portfolios. The use of annotated portfolios is considered a meaningful approach to analyse interviews, because it leads to a more transparent analysis process: The visuals are rich in information, bring clarity to the data for interpretation and pattern finding and make this stage insightful for discussion with peers. @en

The use of materials derived from waste is one of the prominent ways to contribute to sustainable product design. However, there is a stark gap in literature concerning how people appraise such materials. In this paper, we present our initial attempts to understand the aesthetic appreciation of materials, in particular those derived from discarded raw materials, i.e., revived materials. Two studies were conducted for which we took the aesthetic principle unity-in-variety as the departure point. In the first study, we explored material appraisals by testing whether different visual and tactile qualities interrelate with each other in a similar or contradictory way. Based on these findings, two revived materials were modified and our main assumptions were further explored in Study 2. We outline our findings and show that the aesthetic appreciation of a material can be influenced by the (in)congruity between visual and tactile qualities of the material.

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Circular product design is a relatively new approach to design suitable strategies to realize circular products. Additive manufacturing (AM) is seen as a promising enabling production process. It has digital and additive characteristics, which makes AM different from conventional production techniques. However, it is yet unclear how this technique can contribute to circular product design in practice. In this paper, a literature review is placed in context, i.e. the results of a literature review on sustainability opportunities in AM are compared to five typical design cases in a design review. The outcomes of the literature study reveal the aspects of the digital and additive characteristics of AM, that lead to potential sustainability opportunities. We compared these aspects to the circular design strategies as described by Bakker et al. (2014) and Bocken et al. (2016) in the context of the five selected design projects. Each project is described in terms of circular design strategies and how these were achieved through additive manufacturing. Using design practice to reflect on the outcomes of the literature review resulted in a better understanding of the potential of additive manufacturing for circular product design. The relation between the sustainability aspects of AM and the circular design strategies were made explicit. AM seems to be especially suitable to customize parts to fit existing products and to contribute to new opportunities regarding material recycling. These findings deserve further exploration in order to understand the motives for implementation in circular product design.@en