## 1 Introduction  
Science and technology continue to rapidly develop, with businesses moving faster toward smart manufacturing during the so-named 4 th Industrial Revolution. There is a constant demand for specialized products, where customization is becoming prevalent, and where standard available tools are applied in a flexible but effective way within the product design process. Market demand is constantly changing, leaving the industry and designers with the task to develop new and flexible approaches to meet users' needs. For example, wearable products and automotive components are particularly a good exemplar of how small-batch and customized production has been used as a strategy to quickly deliver personalized products to gradually replace mass-produced products [1; 2]. Usually, customization is applied during the manufacturing of a product by adjusting certain product elements rather than restarting the entire production to deliver a new product variation. In this context, customization allows enterprises to adapt to the always-changing customer needs and act accordingly, hence offering a key indicator to measure sustainable economic development.  
Product personalization and design for Mass Customization (MC) have been used by product designers as strategies to adapt to the always changing users' needs. MC calls for flexibility and quick responsiveness in a context with ever-changing factors (i.e., people's needs, market, and processes and technology) to provide customer satisfaction through an increased product variety with a limited effect in cost and lead time, contrary to the old paradigm of mass production (i.e., mass-produced standardized products). MC has had a great appeal to industry and academia during recent years, and some frameworks have been proposed to effectively achieve MC through design. The implementation of MCframeworks during the conceptual design and preliminary development stages has led to the adaptive concept of Design for Mass Customization (DFMC) [3].  
Design as discipline and thinking process has an important role at the fuzzy front end (FFE) of innovation and at new product development [4]. Whether or not MC is implemented as a key element in the innovativeness of a product or service, it is perhaps at the FFE of innovation when it can be considered as part of the product strategy [3]. Therefore, this work approaches the MC framework from the Product Design perspective, and at an early stage of the New Product Development (NPD) process [5].  
In product design, customization has played an important role in the good fit and comfortability of wearable products, hence its use as a way to improve product ergonomics. Some studies have shown that MC capability can be developed using modular systems and innovative product designs and processes [6; 7; 8]. Additionally, MC has allowed large companies to integrate customers into the design process [9]. However, this process relies on the exploration and visualization of the different existing eyewear models to assist customers in the collaborative process. On the other hand, smaller eyewear companies approach customization through the implementation and continuous optimization of flexible tools within the manufacturing process [10].  
This study proposes an MC design framework based on a comparative study of current 3D data acquisition methods and a parametrized design approach that can be used at the early stages of eyewear design to provide a more attainable MC and co-design experience. In this work, a typical eyewear design is used as a case study to explore the development of the aforementioned MC framework. This framework is developed from a product design perspective, trying to implement such workflow at the FFE stage of NPD, where flexibility in the creative process is a key factor for the product designer, as well, as comfortability, good fit, and customization are Unique Selling Points (USPs) and decision-making factors for the customer.