Understanding the effect of variation in a production system

Variation is a root cause to waste in a production system because it creates interruptions in the production system. Variation is dissipating through the production flow and reduces productivity; therefore, to minimize the effect, variations need to be handled with great care. This study examined how task starting time and duration is affected by variation. By simulating a sequence of work tasks using a normal distribution, it has been possible to analyze variations' effect on task starting time, task durations, crew waiting time, and so on. Four situations were simulated, and teen iterations were calculated and analyzed. The analysis revealed that variation itself does not create waste. Waste is only emerging between handoffs; thus, increasing work task duration decreases the effect of variation. Moreover, by comparing a linear sequence and a network of activities, the effect of variation was found to depend on the design of the sequence.