Improvement of Production Lines Efficiency Using a Mathematical Model Based on Line Balancing Techniques

The efficiency of assembly lines is one of the most important indicators for industrial companies. A high-efficiency value means high productivity with the least resources. Among the problems that most impact on productivity is the unbalanced workload between the workstations of an assembly line. Many line balancing techniques are used to remedy this problem and are mainly based on the Yamazumi chart, but these methodologies do not give a precise vision of the values to be achieved, nor of the indicators to be reached as a result of the balancing actions, so these methodologies aim to improve efficiency through tests and attempts until the ideal line balancing state is reached. This paper proposes a line balancing methodology based first on data collection and elimination of non-value added operations, Yamazumi chart and then on a mathematical model that allows to determine precisely the conditions and values to be respected to reach directly the perfect state of line balancing. And this also applies to the capacity study of a new production line. This mathematical model has been translated into a Visual Basic application that allows one to easily calculate the values of Takt Time (TT), the necessary number of workstations, ideal cycle time, the interval of cycle times and also an estimation of the new efficiency value, by entering the values of the available production time, the quantity required during this time and also the total process time. Through this application, it was possible to balance the workstations of a production line in the case study of an automotive wiring industry in Morocco, which allowed to improve the line efficiency from 63% to 94.5% with a reduction of the manpower from 6 to 4 operators.