## 3 Methods for Analyzing the Disassembly Process  
### First Method  
The first method was introduced by [PERSON], [PERSON], [PERSON], and [PERSON] in a publication entitled \"Research on the selectable disassembly strategy of mechanical parts based on the generalized CAD model\" to find all possible disassembly sequences based on the concept of \"disassembly waves\" [9]. Target component \(\mathrm{C_{x}}\), subject to preventive or corrective maintenance, is considered the point of origin of a wave. Once defined, we proceed with the search for the sequences ending with the choice of the one that best satisfies a specific objective function, such as performing the least number of steps to reach the target component or recording the shortest time spent in the removal operation. Generic component \(\mathrm{C_{i}}\) is defined as 1-dependent when it can be removed with the extraction of only one other component with which it is in contact. It is considered d-dependent when, being in contact with more components, more than one component must be extracted to free it. The wave, starting from \(\mathrm{C_{x}}\), which corresponds to the initial instant \(\tau_{0}\), propagates at time instant \(\tau_{1}\) in all directions, hitting all the components adjacent to the original one. Subsequently, at instant \(\tau_{2}\), another wave propagates, which, this time, hits all the components adjacent to the previous ones. We proceed with an iterative step until all parts of the product are included; it is indicated as the instant of transmission of the last wave \(\tau_{n}\). The graphic choice for this method falls on the removal influence graph (RG), where the different components are represented by nodes and arcs; the oriented arrows define the connection relationships between the different parts. The disassembly wave is identified by a curve that unites all the components that are hit by the wave at the same instant, \(\tau_{i}\). In order to find possible disassembly sequences, components belonging to the last wave, the outermost ones, are the first ones to be removed; then, we proceed inwards to target component \(\mathrm{C_{x}}\), which actually corresponds to the instant \(\tau_{0}\). Application of the First Method  
The conductor, which is essential for the operation of hydraulic pumps, has been chosen as the target component. The front flange (no. 1 in the BOM) and the oil seal  
Figure 6: View of drive and idle gears. Figure 7: Exploded view of the hydraulic external gear pump. (no. 14 in the BOM) are considered a single piece since the removal of one inevitably involves the removal of the other. In fact, to remove the oil seal, you have to lever the side inside the flange; otherwise, there is the risk of damaging it, making it unusable. The two bushings and the shim (no. 10 and no. 7, respectively, in the BOM) are considered a single component (10.7 sx and 10.7 dx) as they are generally preassembled before being assembled with the other parts. The body (no. 6 in the BOM), a central element that is not necessary for the removal of the target component, is left out and considered fixed. In Figure 8, it is possible to observe how the disassembly wave expands in the different instants \(\tau\)\(i\)-th. The possible disassembly sequences obtained are the following:  
\(\rightarrow\) 13, 16, 12, 11, 15, 1-14, 2 dx, 3 dx, 10-7 dx, 9: unscrew the nuts with the washers and screws to then remove the snap ring and the tongue, which would hinder the removal of the front flange; proceed with the removal of the latter in order to extract the OR seals and the assembly of the shim-bushings on the right part of the body.