An approach to design reconfigurable manufacturing tools to manage product variability: the mass customisation of eyewear

In Mass Customisation (MC), products are intrinsically variable, because they aim at satisfying end-users' requests. Modular design and flexible manufacturing technologies are useful strategies to guarantee a wide product variability. However, in the eyewear field, the current strategies are not easily implementable, due to some eyewear peculiarities (e.g., the large variability of the frame geometry and material, and the necessity to use specific manufacturing phases). For example, acetate spectacle frames are bent through a thermoforming process. This particular phase requires dedicated moulds, whose geometry strictly depends on the frame model to be bent; consequently, changes of the frame geometry continuously require new moulds, which have to be designed, manufactured, used, and finally stored. The purpose of this paper is to propose a new strategy to transform a dedicated tool (i.e., a thermoforming mould) into a reconfigurable one, to optimise the tool design, manufacturing and use. First, how the frame features influence the mould geometry has been investigated, creating a map of relations. On the basis of this map, the conventional monolithic-metallic mould was divided into standard (re-usable) and special (ad-hoc) modules, where the special ones are in charge of managing the variability of the product geometry. The mapped relations were formalised as mathematical equations and then, implemented into a Knowledge Based Engineering (KBE) system, to automatically design the special modules and guarantee the mould assemblability. This paper provides an original example of how a reconfigurable thermoforming mould can be conceived and how a KBE system can be used to this aim.