## 1 Introduction
### The DSP Methodology  
Moreover, a new methodology was developed and used in the present case study; this methodology can be schematized in the following block diagram (Figure 2): \begin{table}
\begin{tabular}{c c c} \hline
**Element** & **Previous Designation** & **Updated Designation** \\ \hline \(n.6\) ball bearing & 40 UNI 606 & SKF 6208 \\ \(n.7\) thrust ball bearing reggispinta & not unified & SKF 52308 \\ \(n.19\) gaskets & not unified & not unified \\ \(n.20\) nuts & 8 UNI 205 & M8 UNI 5588 \\ \(n.21\) elastic rosettes & A 8 UNI 1751 & UNI 1751–B8 \\ \(n.22\) captive screws & \(8\times 26\) UNI 114 & UNI 5908–M8 \\ \(n.23\) screws & \(8\times 17\) UNI 256 & TSB M8 \(\times\) 16 UNI 5933 \\ \(n.25\) nuts & 16 UNI 205 & M16 UNI 5588 \\ \(n.26\) captive screws & 16 \(\times\) 97 UNIM 120 & UNI 5914–M16 \\ \(n.27\) nuts & 12 UNI 205 & M12 UNI 5588 \\ \(n.\) 28 screws & 12 \(\times\) 60 UNI 183 & M12 \(\times\) 60 UNI 5740 \\ \(n.30\) gaskets & not unified & not unified \\ \(n.31\) gaskets & not unified & not unified \\ \(n.34\) screws & 10 \(\times\) 34 UNI 183 & M10 \(\times\) 35 UNI 5740 \\ \(n.35\) nuts & 10 UNI 205 & M8 UNI 5588 \\ \(n.36\) lubricators & Type A 2 UNI & not unified \\ \(n.37\) keys & \(18\times 11\times 70\) UNIM 92 & not unified \\ \(n.38\) screws & \(6\times 13\) UNI 137 & M6 \(\times\) 12 UNI 5740 \\ \(n.39\) elastic rosettes & A 6 UNI 1751 & UNI 1751–B6 \\ \(n.43\) gaskets & not unified & not unified \\ \(n.45\) elastic rosettes & A 16 UNI 1751 & UNI 1751–B16 \\ \hline \end{tabular}
\end{table} 
Table 1: Updating of the regulations. It is therefore described that, in order to find out the best disassembly sequence related to a specific case study (i.e., a mechanic assembly--for example, a globoid type), the following steps must be improved:  
1. 3D modeling of the mechanic assembly. In order to simulate the best sequence, it is necessary to build the virtual CAD model of the mechanism object of the study; so, subsequently, it will be arranged a model on which \"physically\" improve the trials of the disassembly sequences;
2. Detection and analysis of the main disassembly sequences in literature. In order to find out the best disassembly sequence, it is important to detect in literature the best and recent sequence available. Many are the scientists in the world that publish disassembly sequence; the present study will analyze some and few of them, applying them to the case study. 3. Classification of the best sequence following times criterion vs. case study. Using times criterion and applying the disassembly sequences found out in literature, it is possible to make a classification of the best sequences, in order to disassemble and maintain a mechanism or a machine. 4. Implementation of the best sequence found to the case study in the virtual environment (CAD). The first implementation of the sequence will take part in the virtual 3D CAD model realized in the step (a). It is possible to see the advancement of the disassembly already in the virtual CAD environment. 5. Possible evolution of the implementation of the best sequence to the case study in an advanced virtual environment (i.e., augmented reality or virtual reality). Finally, what happens in CAD virtual environment could be exported also in an advanced virtual environment, just like AR or VR hospitality. It is also possible to add the following considerations. The analyzed disassembly sequence, and eventually a third one from them derived, can be applied both to a simple and a complex assembly. However, it was demonstrated by several authors ([PERSON] et al., [PERSON] et al., [12; 13] etc.) that each sequence could be the best related to a specific assembly. In other words, potentially, any sequence could be the best one; this depends on the special type of assembly. The best one found in this paper could not be the best one if applied to another products. It does not depend on assembly complexity but only from the specific geometry.