Combining aesthetics and engineering specifications for fashion-driven product design: A case study on spectacle frames

The successful combination of aesthetic and engineering specifications is a long-standing issue. The literature reports some examples where this problem was achieved developing tools to support the automatic generation of new product shapes, embedding and linking predefined rule-sets. Notwithstanding, these kinds of tools are effective if and only if the relations among these specifications are known. Other complementary strategies act upstream by building a common ground: they aid in the formalisation of these specifications, fostering the use of a shared language and the same level of detail. This paper lies in between the previous approaches since its purpose is the description of a strategy to formalise the relations among aesthetic and engineering specifications and whose validities are not affected by the product variability. Indeed, fashion-driven products are subject to continuous innovations and changes. Therefore the identification of these predefined rule-sets is challenging. In detail, the paper objective is to build a high-level and long-lasting formalisation of these relations, based on topological and functional rules. To demonstrate the effectiveness of this approach, we developed a case study in the eyewear industry. We started considering the spectacle-frame functionality and derived the high-level formulation linking aesthetic and engineering specifications. We used this formulation to generate an abstraction of the frame geometry, i.e., an archetype, to be used as a reference for the design of new collections. We implemented the archetype through a MATLAB script, and we translated it into a design tool, to wit an Excel spreadsheet. The validity of both the archetype and the tool has been tested, in collaboration with an eyewear manufacturer, designing and manufacturing two new models of frames

An inspection system to master dimensional and technological variability of fashion-related products: A case study in the eyewear industry

Innovation of fashion-related products implies the continuous search for new and appealing shapes and materials in a short period of time due to the seasonality of the market. The design and manufacturing of such products have to deal with a dimensional variability as a consequence of the new shapes. An additional difficulty concerns properly forecasting the technological behaviour of the new materials in relation to the manufacturing process phases. The control of dimensional variations requires time and resource intensive activities. Human's manual and visual inspection solutions are more common than automatic ones for performing such control, where skilled operators are typically the only ones capable of immediately facing non-standard situations. The full control of such variations is even more subtle and mandatory in the field of spectacles, which are fashion-related products and also medical devices. This paper describes an inspection system developed to monitor the dimensional variations of a spectacles frame during the manufacturing process. We discuss the methodological approach followed to develop the system, and the experimental campaign carried out to test its effectiveness. The system intends to be an alternative to current inspection practices used in the field, and also to provide a methodological approach to enable engineers to systematically study the correlations existing among the frame main functional and dimensional parameters, the material behaviour and the technological variables of the manufacturing process. Hence, the system can be considered a method to systematically acquire and formalise new knowledge. The inspection system consists of a workbench equipped with four high-quality commercial webcams that are used to acquire orthogonal-view images of the front of the frame. A software module controls the system and allows the automatic processing of the images acquired, in order to extract the dimensional data of the frame which are relevant for the analysis. A case study is discussed to demonstrate the system performances

Detection of Voids in Carbon/Epoxy Laminates and Their Influence on Mechanical Properties

Defects, such as voids and delaminations, may significantly reduce the mechanical performance of components made of composite laminates. Distributed voids and porosity are generated during composite processing and are influenced by prepreg characteristics as well as by curing cycle parameters. On the basis of rheological and thermal analyses, as well as observations of laminates produced by different processing conditions, curing pressure appears the most influent factor affecting the void content. This work compares different methods for void analysis and quantitative evaluation (ultrasonic scan, micro-computed tomography, acid digestion, SEM image analysis) evidencing their applicative limitations. Carbon/epoxy laminates were produced in autoclave or oven by vacuum bag technique, using different processing conditions, so that void contents ranging from 0% to 7% volume were obtained. Effects of porosity over laminates mechanical performances are analysed. The results of tensile and compressive tests are discussed, considering the effect that different curing cycles have over void content as well as over fibre/resin fraction. Interlaminar strength, as measured by short beam shear tests, which is a matrix-dominated property, exhibits a reduction of failure strength up to 25% in laminates with the highest void content, compared to laminates with no porosity

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