# Analytic Hierarchy Process and Multilayer Network-Based Method for Assembly Line Balancing
## 4 Case Study  
This study was inspired by an industrial case study of wire harness manufacturing, where operators work with several tools that perform different activities at workstations to manufacture cables. The problem assumes that it is possible to improve the manufacturing efficiency if the resources, activities, skills and precedence are better designed. The development of the proposed line-balancing algorithm is motivated by a development project which was defined to improve the efficiency of an industrial wire harness manufacturing process [38]. In this work, a subset of this model is used which consists of 24 activities, five operators, six skills and eight pieces of equipment. The elementary activity times that influence the line balance were determined based on expert knowledge [39] (see Table 2). A more detailed description of the activities, pieces of equipment and skills can be found in Tables 2-6. The following tables give a more detailed description of the activities, equipment (Table 3) and skills (Table 4) which are involved in the proposed case study. Furthermore, the activity-equipment (Table 5) and activity-skill (Table 6) connectivity matrices show the requirements of the given base activity. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Activity ID** & **Description** & **Time** \\ \hline A1 & Connector handling & 4 s \\ A2 & Connector handling & 3 s \\ A3 & Connector handling & 2 s \\ A4 & Connector handling & 3 s \\ A5 & Insert 1 st end + routing & 10 s \\ A6 & Insert 2 nd end & 5 s \\ A7 & Insert 1 st end + routing & 10 s \\ A8 & Insert 2 nd end & 5 s \\ A9 & Insert 1 st end + routing & 10 s \\ A10 & Insert 2 nd end & 5 s \\ A11 & Insert 1 st end + routing & 10 s \\ A12 & Insert 2 nd end & 5 s \\ A13 & Insert 1 st end + routing & 10 s \\ A14 & Insert 2 nd end & 5 s \\ A15 & Insert 1 st end + routing & 10 s \\ A16 & Insert 2 nd end & 5 s \\ A17 & Insert 1 st end + routing & 10 s \\ A18 & Insert 2 nd end & 5 s \\ A19 & Taping & 15 s \\ A20 & Taping & 13 s \\ A21 & Taping & 11 s \\ A22 & Taping & 17 s \\ A23 & Taping & 15 s \\ A24 & Quality check & 10 s \\ \hline \hline \end{tabular}
\end{table} 
Table 2: List of the elementary activities that should be allocated in the line balancing problem. \begin{table}
\begin{tabular}{l l} \hline \hline
**Equipment ID** & **Description** \\ \hline E1 & Connector fixture \\ E2 & Connector fixture \\ E3 & Routing tool \\ E4 & Insertion tool \\ E5 & Taping tool (expert) \\ E6 & Taping tool (normal) \\ E7 & Taping tool (normal) \\ E8 & Repair tool \\ \hline \hline \end{tabular}
\end{table} 
Table 3: List of equipment that should be allocated in the line balancing problem. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline  & **S1** & **S2** & **S3** & **S4** & **S5** & **S6** \\ \hline A1 & 1 & & & & & \\ A2 & 1 & & & & & \\ A3 & 1 & & & & & \\ A4 & 1 & & & & & \\ A5 & & 1 & & & & \\ A6 & & & 1 & & & \\ A8 & & & 1 & & & \\ A9 & & 1 & & & & \\ A10 & & & & 1 & & \\ A11 & & 1 & & & & \\ A12 & & & 1 & & & \\ A13 & & 1 & & & & \\ A14 & & & 1 & & & \\ A15 & & 1 & & & & \\ A16 & & & 1 & & & \\ A17 & & 1 & & & & \\ A18 & & & 1 & & & \\ A19 & & & 1 & & & \\ A20 & & & 1 & & & \\ A21 & & & & 1 & 1 & \\ A22 & & & & 1 & 1 & \\ A23 & & & & 1 & 1 & \\ A24 & & & & & & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Activity–skill matrix that defines which skills are required to perform a given activity. \begin{table}
\begin{tabular}{l l} \hline \hline
**Skill ID** & **Description** \\ \hline S1 & Connector handling skill \\ S2 & Insertion (normal) and routing skills \\ S3 & Insertion (expert) skill \\ S4 & Taping (normal) skill \\ S5 & Taping (expert) skill \\ S6 & Quality (expert) skill \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Description of skills that should be used in the studied production process.