# Review of Responsiveness and Sustainable Concepts in Cellular Manufacturing Systems
## 3 Review of the Responsiveness Approaches
### Reconfigurable Machines  
Flexed machines can be used to improve the responsiveness of production systems. This solution leads to purchasing in advance a degree of flexibility that is expected to be used in the future, often leading to an initial outlay greater than is actually needed. The reconfigurable machines can be a valid alternative to the flexible machines. A reconfigurable machine includes a basic process module of both hardware and software that has the capability to quickly add, remove, or modify the module to react to the changing market demands or technologies. The objective is to reconfigure the machine to provide new functionalities and capacities when needed [25]. [PERSON] et al. [26] in their paper provided an overview of the literature considering the optimization problem of reconfigurable manufacturing systems (RMS). The discussion of the literature is divided in two main parts: the first part discusses the optimization problems for the RMSs addressed in the literature; the second part studied the solutions proposed to solve the optimization problems for the RMSs. This work aims to support researchers to evaluate the main areas and to focus future research paths for optimization in RMSs. [PERSON] et al. [27] studied the design and loading of cellular manufacturing systems that consist of reconfigurable machines. The first problem studied was the design of the cells, and the second problem was the loading of the cells developed by mixed integer linear programming. The input of the mathematical model was the demands of each part type, and the objective was the minimization of holding and movement costs. This objective balances the workloads among the cells in each period and during the production planning period. [PERSON] et al. [28] studied a cellular manufacturing system where the cells consist of reconfigurable machines. There were several auxiliary modules available to change or add operations that the machine can manufacture. The model proposed allocated the auxiliary modules to the reconfigurable machines to improve the workload balance among the cells. The numerical results showed relevant benefits in terms of global time saving, which highlights the fact that reconfigurable machines are an opportunity for the cellular manufacturing systems to face dynamic market changes. [PERSON] et al. [29] proposed an optimal linear programming cost model for the dynamic design of cellular manufacturing systems that include flexible and reconfigurable machines. The numerical results showed a decrease of the system intercellular flows without a high increase of the machine number, but the higher costs due to the flexible machines were not considered. [PERSON] et al. [30] studied the design problem of RMSs that are able to adapt to different product types. The models proposed support a scalable manufacturing system that can change the configuration in the different production planning periods. The approaches proposed considered the possibility of adding and removing modules in the reconfigurable machines to adjust the capacity of the system, minimizing the total costs. [PERSON] et al. [31] developed a mixed integer nonlinear programming model to cell formation, and to optimize the equipment configuration of reconfigurable machines and mixed product plan. The objective was to maximize the profit reacting to the dynamic changes of market demands. [PERSON] [32], in an attempt to overcome the limits of the computational algorithm reducing the problems that can be solved, proposed the use of game theory to reconfigure the reconfigurable machines. The reconfiguration of the reconfigurable machines allowed for the improvement of the performance when new production was introduced or mixed with dynamic demand changes. This approach works in the same way that a single reconfigurable machine can work as a single cell. [PERSON] et al. [33] presented a literature review on the use of reconfigurable machines in the aeronautical industries where cellular manufacturing systems are widely used.