Line balancing helps to see where continuous flow might be possible among multiple processes, the idea being that continuous flow can only be achieved when each process operates at the optimal Takt time. It helps improve the process throughput while reducing lead time, inventory and costs. Line balancing is a key concept of Lean manufacturing and the Toyota Production System.
Think of line balancing in terms of the typical home washer and dryer. The washer usually has a cycle time that is much faster than the dryer. If you continue to load and unload the washer at the end of its cycle, an excess inventory of wet clothes piles up ahead of the dryer because the two cycle times are not balanced.
In a perfectly balanced line, all processes would run at the same rate, achieving 100% efficiency. This is rarely the case in reality. Individual processes operating at a faster rate than the required takt time cause inventory to build up. On the other hand, if these processes are running slower than the takt time then there will be unmet demand.
Takt Time, Continuous Flow
Although the most common approach is to balance lines based on Takt time, there are other ways of achieving line balance – by leveling demand, and improving process flexibility and capability.