## 1 Introduction  
The Design for Disassembly technique was born by derivation from the better-known Design for Assembly technique (in the early 90s) and is part of the broader Design for Environment (DfE)/Green Design (GD) concept, which is a design concept aimed at optimizing control over products, processes, and services, respecting the problems related to the life cycle of the raw materials that make up its components. The main purpose is to arrive at nondestructive disassembly to safeguard the future reuse of the parts [1, 2, 3]. The reasons why DfD has acquired a more incisive and strategic role in industrial design are to be found firstly in the speed with which technology becomes obsolete, which has forced companies to increase the frequency of the turnover of their products while maintaining a high quality level and a price that is adapted to customer expectations [4]. Secondly, European directives or legislative acts have established common objectives for the countries involved, defining an ecological path for responsible exploitation of resources in order to reduce the waste of products or parts of them at the end of their life (EOL, end of life). However, since manual disassembly involves the use of many tools and a considerable expenditure of energy by the operator, while automated disassembly requires a substantial initial financial investment and does not guarantee the easy attainment of various components, disassembly has been seen in the past as a disadvantageous EOL activity. Moreover, the designers themselves did not pay much attention to making the products easier to disassemble in order to safeguard as many components and materials as possible to be reused. Therefore, there has been an increase in exposure to damage and, consequently, an increase in the time necessary to complete the disassembly operation and, above all, an increase in the wastage of products at their EOL [5]. Optimal disassembly is concerned with recovering materials and components that are reusable in other products or recyclable in a responsible way, removing toxic components or materials, and making the most important parts of the product more accessible to service operations such as preventive maintenance (the maintenance of a component before a real fault occurs in order to reduce the possibility of it happening) or corrective maintenance (replacing/repairing a faulty component that compromises the general functioning of the product). Two main types of disassembly are presented: complete disassembly, when all components are disassembled, and selective disassembly, when the product is disassembled only until a target component is reached, which is the objective of the operation. Furthermore, nondestructive disassembly can occur when the removal of components from the product does not lead to the breakage of the product itself; destructive disassembly, on the other hand, happens at the end of the operation, when the components are no longer usable because they are broken. Therefore, optimal disassembly in compliance with Green Design should be selective since complete disassembly is more expensive; above all, disassembly should be nondestructive. According to the evaluations carried out in the literature regarding the profit of disassembly and recovery interventions (Figure 1) [6; 7], the costs incurred for disassembly/repair become prohibitive as the disassembly depth increases. The gain, on the other hand, initially grows at the same step as disassembly depth and then settles down when disassembly depth becomes too deep. Therefore, the net profit curve presents a maximum point after which a decreasing trend occurs as the depth of the disassembly operation increases. The definition of an optimal strategy for DfD has the intent of increasing the value of profit at its maximum point, trying to move the latter as much as possible towards a greater depth of operation.