Adaptable design is a product development approach that allows companies to be more responsive to changes in the requirements of users or other stakeholders. A product development process usually results in a technical description or design that guides the manufacture of a solution or product. In consequence, Gu et al (2004) distinguish two types of adaptability: design adaptability and product adaptability. Design adaptability is the capacity of a technical description to accept modifications in order to guide the fabrication of updated versions of existing products or new members of a family of products. Depending on whether these modifications respond to expected or unexpected changes in the requirements of users or other stakeholders, Gu et al (2004) characterize design adaptability as specific (SDA) or general (GDA). Design adaptability is usually of relevance to the producer because it allows the reuse of design knowledge and the reduction of manufacture and post-sale service costs.
On the other hand, product adaptability is the capacity that a physical solution has for accepting modifications that improve its performance or that allow it to perform new functions. Again, depending on whether these modifications derive from expected or unexpected  changes in the requirements of users or other stakeholders, product adaptability can be specific (SPA) or general (GPA). Product adaptability is usually of relevance to users because it allows them to upgrade and/or customize a product in accordance to changes in their needs. Product adaptability usually implies the replacement of parts or the incorporation of attachments. For closed-architecture products, part replacement and the development and instalment of attachments are conduct only by the original equipment manufacturer (OEM). For open-architecture products, these activities are conduct also by other manufacturing companies, specialised contractors and even the users themselves.Â
While there is no standard process for the development of adaptable products, Gu et al (2009) have proposed a general workflow. The first stage of this process consists in modelling the functional requirements (FRs) of the product. To do so, designers can use methods such as tree-based design modelling, AND-OR graph-based design modelling, axiomatic design, FBS, etc. If designers can anticipate upcoming changes in current requirements and/or the emergence of new requirements, they may include them into the FRs model as additional functional requirements (AFRs). Usually, designers include these changes only when the cost of adapting an existing product is less than the cost of developing a new one. Thus, the flexibility of a manufacturing system is a relevant variable for the development of adaptable products. To estimate and compare the costs of adapting an existing product and developing a new one, designers can use methods such as the SPA evaluation method, etc. Next, designers have to group components with functional, technological or structural similarities into modules, and explore several alternatives for assembling these modules (Jiao et al, 2007). When doing so, they need to take into consideration the flows of material, energy and information between the modules and the interfaces that will enable their assemblage. According to Ulrich and Tung (1991), three types of interfaces are of relevance for configuring a product’s architecture in a modular way. The first is the slot interface, which can accept only a specific module. The second is the bus interface, which can accept any module of a certain kind. The third is the sectional interface, which can accept any kind of module. In order to determine which modular arrangement to use, designers can evaluate different alternatives using fuzzy mathematics, genetic algorithms (GAs) and simulated annealing. Alternatively, they can use evaluation methods such as modularity, commonality, and customizability or methods that consider other stages of product life cycle such as maintenance, repair, remanufacturing, and upgrading/downgrading. Once designers select a modular arrangement and the technical description is completed, the manufacturing phase will begin.
