# Reliability Prediction and FMEA of Loading and Unloading Truss Robot for CNC Punch
## 4 Discussion  
The reliability prediction results show that the failure rate of the loading and unloading truss robot for CNC punch pneumatic system is 3.715 \(\times\) 10\({}^{-4}\) (1/h), accounting for 35.42% of the whole system. The failure rate of mechanical system was 3.628 \(\times\) 10\({}^{-4}\) (1/h), accounting for 34.59% of the whole system. The failure rate of electrical control system is 3.146 \(\times\) 10\({}^{-4}\) (1/h), accounting for 29.99% of the whole system. Therefore, it is predicted that the pneumatic system is the weak link of the loading and unloading truss robot for CNC punch, which needs to be paid more attention. Figure 6: The frequency diagram of fault position of the loading and unloading truss robot for CNC punch considering program factors. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Fault Location** & **Fault Location** & **Fault Record** & **Number of** & **Total System** & **Failures** & **Failure Frequency** \\ \hline \hline \multirow{9}{*}{E} & \multirow{9}{*}{E} & The curtain of light flickers frequently & 1 & & \\  & & Proximity switch failure & 1 & & \\  & & Breaker damage & 1 & & \\  & & Displacement sensor failure & 1 & & \\  & & The emergency stop button is damaged & 1 & & \\  & & PLC controller damaged & 1 & & \\  & & Z-axis motor line is disconnected & 1 & & \\  & & Inverter damage & 3 & & \\  & & Hydraulic lifting platformwing chain line & 1 & & \\  & & disconnected & 1 & & \\  & & Motor line of raw material car is disconnected & 1 & & \\  & & Electrical control & X-axis servo motor drive burned out & 1 & & \\  & & system & The indicator light of the electric cabinet is not on & 1 & 28 & 0.2569 \\  & & & The outer wiring of the light curtain is burnt by & 1 & & \\  & & & short circuit & & \\  & & The fan of the electric cabinet is damaged & 1 & & \\  & & Curtain failure & 1 & & \\  & & Inspection proximity switch is damaged & 1 & & \\  & & X-axis servo drive is damaged & 1 & 1 & \\  & & The fan of the electric cabinet does not work & 1 & & \\  & & The loading drag chain is disconnected & 1 & & \\  & & Z-axis servo motor drive is damaged & 2 & & \\  & & Proximity switch failure & 1 & & \\  & & Full load proximity switch of hydraulic lifting & 1 & & \\  & & platform is damaged & 1 & & \\  & & Access switch of U-axis retaking clamp is damaged & 1 & & \\  & & Unloading tow line is damaged & 1 & & \\  & & The light curtain line is broken by the groove cover & 1 & & \\ \hline \hline \multirow{9}{*}{C} & \multirow{9}{*}{Program} & The sucker failed to pick up the sheet & 1 & & \\  & & Tooling cylinder interference plate & 1 & & \\ \cline{1-1}  & & Sucker with plate & 1 & & \\ \cline{1-1}  & & When loading, the sucker cannot absorb the sheet & 1 & & \\ \cline{1-1}  & & material alarm & & & \\ \cline{1-1}  & & Misalignment of loading material & 1 & & \\ \cline{1-1}  & & U-shait motor will alarm when unloading & 1 & & \\ \cline{1-1}  & & Loading position is unstable & 1 & & \\ \cline{1-1}  & & Loading rebound causes abnormal positioning & 1 & & \\ \cline{1-1}  & & Z-axis motor often alarms & 1 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: _Cont._After analyzing the fault data of the loading and unloading truss robot for CNC punch collected from the fault location, it can be seen from Table 9 and Figure 4 that the pneumatic system failure rate of the loading and unloading truss robot for CNC punch is the highest, accounting for 34.86% of the whole. Mechanical system failure rate followed, accounting for 31.19% of the total; electrical control system failure rate is low, accounting for 25.69% of the total; the failure rate of program problems is the lowest, accounting for 8.26% of the total. Therefore, it is concluded that the pneumatic system is the weak link of the loading and unloading truss robot for CNC punch.