# A Comprehensive Failure Risk Assessment Method of
## 3 Case Application  
In this paper, a certain type of machining center is taken as the research object. According to the structure and working principle of this type of machining center, it is divided into 12 subsystems, namely tool magazine (M), spindle system (S), electrical system (V), XYZ axis feed system (J), chip removal system (K), hydraulic system (H), pneumatic system (G), CNC system (NC), protection system (Q), cooling system (W), lubrication system (L), and workbench (T). Each component is abstracted as a node, the failure correlation between components is abstracted as an edge, and a digraph of the component correlation of the machining center is drawn, as shown in Figure 4. The components with independent failures are not considered for the time being. The collected field failure data of the machining center were statistical analyzed to obtain the frequency diagram of the failure components of the machining center, as shown in Figure 5. The failure mode analysis is carried out to obtain the failure mode frequency table of the machining center as shown in Table 2, and the failure causes analysis is carried out to obtain the failure cause frequency table of the machining center, as shown in Table 3, as well as the failure cause frequency chart, as shown in the Figure 6.  
It can be seen from Table 2 that the most frequent failure mode of this kind of machining center is parts damage (21.3%), followed by liquid, gas, and oil component damage (14.81%) and liquid, gas, and oil leakage (14.81%), followed by component damage (4.63%), no movement of moving parts (4.63%), and vibration or shaking (4.63%). It can be seen that the quality of components and the quality of assembly adjustment have a significant impact on the overall reliability of the machining center. Figure 4: Digraph of the machining center component association relationship. Figure 5: Frequency diagram of failure parts of machining center. \begin{table}
\begin{tabular}{c c c c c} \hline
**Pattern Code** & **Failure Type** & **Failure Mode** & **Number** & **Frequency** \\ \hline
0101 & 01-Damaged & 01-Parts are damaged & 23 & 0.2130 \\
0103 & 01-Damaged & 03-Damage to liquid, gas, oil parts and components & 16 & 0.1481 \\
0301 & 03-Clogged or leaky type & 01-Liquid, gas, and oil leakage & 16 & 0.1481 \\
0102 & 01-Damaged & 02-Components are damaged & 5 & 0.0463 \\
0501 & 05-Functional & 01-No movement of moving parts & 5 & 0.0463 \\
0605 & 06-State type & 05-Vibration or shaking & 5 & 0.0463 \\
0202 & 02-Loose type & 02-locking parts are loose & 4 & 0.0370 \\
0503 & 05-Functional & 03-Transposition, shift is not in place & 4 & 0.0370 \\
0410 & 04-Dasidjustment type & 10-Spindle misalignment & 3 & 0.0278 \\
0603 & 06-State type & 03-Abnormal noise & 3 & 0.0278 \\
0802 & 03-Clogged or leaky type & 02-Liquid, gas and oil clogging is not smooth & 2 & 0.0185 \\
0205 & 02-loose type & 05-Components and parts fall off & 2 & 0.0185 \\
0607 & 06-State type & 07-Mass function of the components & 2 & 0.0185 \\
0805 & 08-Other types & 05-Dissufficient coolant and lubricating oil & 2 & 0.0185 \\
0502 & 05-Functional & 02-Moving parts are stuck & 1 & 0.0093 \\ : & : & : & : & : \\ : & : & : & : & : \\
0506 & 05-Functional & 06-Moving parts & 1 & 0.0093 \\ \hline \end{tabular}
\end{table} 
Table 2: Failure modes frequency table of the machining center. It can be seen from Table 3 and Figure 6 that component damage, part damage, leakage, etc. are the main causes of failure. Once again, the quality of parts and the quality of assembly adjustment are the key factors that affect the reliability of machining centers. According to the component failure data of the machining center, considering the influence of multiple truncated data, the order of component failure data is corrected, parameter estimation and hypothesis distribution test are performed, and the failure rate model parameters of each component are shown in Table 4. This paper only considers components that are associated with failure, and the rest of the components are not considered for the time being.