## 5 Conclusions  
The analysis of the current context regarding the methods and tools of modular design and prosumers shows a clear lack of methods in the phases of primary needs, preliminary design and distribution plans. While the distribution benefits from some of the methods despite not being the main objective, no method covers the conceptual design phase. This lack is also perceived in the definition of the modular design process, where there are currently no design objectives for these phases. This evidences the need to create a model aimed at these phases, as they are also the phases that allow greater intervention and innovation in the final design of the product. The creation of a new design model in this line would also contribute to the generation of new design objectives in the modular design process that have not been covered until now.  
In the real cases analyzed, the most common objectives were the adaptation and evolution of the product, while it was less common to use modular design to reduce costs or customize the product. However, each objective has a certain relationship with each industrial sector analyzed. It has been detected that, in the textile sector, customization is sought-after, and in the home automation and electronic sectors, evolution prevails more; in all sectors, the adaptation to the needs of the user is appreciated. On the other hand, all sectors allow the user to intervene in the phase prior to the acquisition of the product, except toy manufacturers, which only allows this during the useful life cycle. This is because they are ready-made kits that can only be handled once purchased. Some of the cases analyzed also allow the user to intervene in the product during the use phase to respond to ephemeral and variable needs that allow them to better cope with the different situations of use of the product [43; 46].  
Most of the modular design methods focused on prosumers pursue the customization and adaptation of the products prior to their acquisition. This is because many are focused on applying modularity in mass customization, with the goal that the users may personalize the product, adapting it to their needs and wants before purchase. Only two of the methods contemplate the adaptation of the product or service by the prosumer during the use phase, in which the user can apply modifications, make ephemeral adaptations and evolve or improve the maintenance of the product. Current methods are totally oriented towards customization, but, as has been verified in the case analysis, this is not the main objective of prosumers.  
The results show that the new design model must meet three main objectives in order for the prosumer to benefit from modular design. The first is to treat modular design as a design objective (PDS) and not as a tool to solve a problem during the development. The second is to cover the conceptual phases of product design as they are--those in which the user can make a more significant intervention. The third objective is to contemplate the relationship with the prosumer before and during the consumption of the product. On the other hand, to guarantee the effectiveness of the model, it is recommended to present it as an accessible and universal design toolkit. To ensure its consolidation, the model must be applicable in multiple areas and easy to use by non-specialized users.  
Conceptualization, L.A.-S. and I.L.-F.; methodology, L.A.-S. and I.L.-F.; investigation, L.A.-S.; writing--original draft preparation, L.A.-S.; writing--review and editing, I.L.-F.; visualization, L.A.-S.; supervision, I.L.-F. All authors have read and agreed to the published version of the manuscript.  
This work was supported for publication by the \"Conselleria de Innovacion, Universidades, Ciencia y Sociedad Digital\" of the \"Generalitat Valenciana. The authors would like to thank also to the INGECRAF association.  
The authors declare no conflict of interest.