# Efficiency Analysis of Manufacturing Line with Industrial Robots and Human Operators
## 7 Industrial Implementation of Robotic Line--Case Study  
The results of simulation experiments were taken into account during an economic analysis of the designed manufacturing line (unfortunately economic data are unavailable) and helped when taking a decision to build the robotic line. * Industrial implementation of robotic line had required the following steps:
* Detailed design of manufacturing line and required equipment;
* Purchase of machines and robots;
* Installation of machines and robots;
* Personnel training;
* Machine and robot programming and testing;
* Material delivery and product distribution contracting. About 2 years after taking the decision, the real robotic line was implemented in Poland and started a production. The manufacturing line with 3 ABB robots for product handling is presented in Figure 8. There are also two human operators for final product inspection and one duty operator for monitoring of the production process. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Simulation** & **24** & **48** & **120** & **480** & **2880** & **5760** & \(\Delta\mathbf{avg}\) \\ \hline \(\Delta\)_OFEh_ & 0.002799 & 0.002735 & 0.002448 & 0.002083 & 0.001096 & 0.002686 & 0.002308 \\ \(\Delta\)_OFEr_ & 0.007869 & 0.006538 & 0.011545 & 0.006445 & 0.007161 & 0.008141 & 0.00795 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The comparison of difference \(\Delta\) between _OFE_ for different scenarios. Figure 7: The trend of average production value [pieces/hour] for (**a**) manually operated line with failures, (**b**) robotic line with failures (20 samples, confidence level 90%). The manufacturing line is now working very well, but there were some technical and organizational problems including:  
* Material delivery delays;
* Equipment failures (mainly milling machines, the drilling machine and washing station);
* Power supply disturbances;
* Lower working speed;
* Insufficient quality. The three industrial robots from ABB are working very well by now, without failures. There were only small problems with robot grippers at the beginning of the production process. The results obtained show some differences between _OFE_ components in the model and in the real line, that are presented in the Table 5. The currently planned _OFE_ factors contain some changes in the production process, including robot programs, time of loading and unloading the milling machines. In reality, _OFE_ factors obtained are fluctuating due to random failures and disturbances and were lower than planned. The main reasons for _OFE_ fluctuation were some technical problems in the first months and the delay of delivery from supplier (Foundry) in the eighth and eleventh months and also the low quality of some casting series. Failures of machines take lower effect, because the main milling machines are working in parallel and in typical cases of failure, only one machine is stopped, and the other machines can work further. The monthly results from the year 2018 are presented in the Table 6.  
Figure 8: Robotized manufacturing line (**a**) main machining cell, (**b**) testing station. \begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Model–Robotic Line** & **Real Line** & **Real Line** \\  & **(without Failures)** & **(Planned–without Failures)** & **(12 Months Average–with Failures)** \\ \hline _Availability_ & 0.9042 & 0.9042 & 0.8824 \\ \hline _Performance_ & 0.8739 & 0.8856 & 0.8856 \\ \hline _Quality_ & 0.9990 & 0.9990 & 0.9962 \\ \hline _OFE_ & 0.7894 & 0.8000 & 0.7785 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _OFE_ components comparison—model assumption and real robotic line. It turned out that the most critical machine is the washing station, because it can block the whole manufacturing line with a bottleneck effect. The quality varies over time and the insufficient quality products were in the range of \(0.17\div 0.59\%\) (average = 0.38%). The average yearly quality index is equal to 0.9962, which is very near to the planned value.