# Optimization of Wiring Harness Logistics Flow
## 2 Materials and Methods
### Case Study: Increasing Production Capacity by Proposing a New System Architecture
#### 2.3.1 Initial Assembly Line Structure  
The initial configuration of the assembly line structure is based on an assembly line used to produce the full version of the engine harness for K9K engines [26] to provide data that can be used in physical implementation.  
The line presented in Figure 2 is composed of the following:  
* Six fixed workstations are used for wire insertion into the connectors. These workstations are strategically positioned near the initial three assembly boards to facilitate the precise assembly of wires and connectors at a specific stage within the overall assembly process;
* Twenty workstations organized in a rotary assembly line are used for wire layout on the board, making the final subassemblies on the board and adding protections, fixation elements, linked parts, and taping;
* Five workstations are used for clip tests, quality checks, electrical controls, visio tests, and packaging.  
In total, 33 operators serve the line:  
* There are 6 operators working on the fixed workstations;
* There are 20 operators working on the rotary assembly line;
* There are 5 operators working apart the assembly line in the section dedicated to quality checking, testing (clip, electrical and visio) and packaging;
* There are 2 operators in charge of supplying the workstations with components and preassembled elements.  
According to the client's demand, the initial volume estimation was 38,400 pieces per year. The wiring harness-maker organized the production according to their primary work schedule, which means 48 weeks per year, two shifts per week, and five working days per week.  
Figure 2: Initial structure of the assembly line.  
One shift consists of 8 h, with a 30 min break. The working time (SWT) within one shift equals 450 min. This information is mandatory for the \"Takt time\" calculation.  
The \"Takt time\" is a term of German origin (\"Taktzeit\") associated with lean management and used in the industrial production environment to refer to the ideal duration of production of a good when it exactly corresponds to the customer's demand. The production pace must align with \"Takt time\" to produce precisely the number of units requested by the customer. So, after the production process is decided, the repartition of tasks for every workstation must be made considering the \"Takt time\" [27].  
The \"Takt time\" is calculated via the following formula:  
\[Tt=\frac{SWT}{OP}=\frac{450}{80}=5.63\;\text{min}, \tag{8}\]  
As shown in Figure 2, the working area is divided into three sections. Each section has its own challenges when adapting to Takt time; this is why task repartition must also be observed in practice, and re-equilibrated if it is the case. The fixed workstation area is prone to the piling up of stocks on one part of the workstation and not being able to provide the necessary items to the rotary line for the workstations that handle more complex operations. For this reason, the complexity of each workstation in this area must be similar to the skill level of the operators. The operators from the rotary section of the assembly line must be well-trained to handle the complexity of the operations while advancing at the pace of the line. They are also the ones that must reach for the wires and other components that are placed behind them. The section where the tests and packaging are apart from the assembly line but must also be synchronized with the \"Takt time\" of the assembly line to avoid the creation of harness stocks at the workstations.