A Yamazumi chart, also called an operator balance chart, is a stacked bar chart that displays each operator’s work elements by duration against a takt-time reference line to support line balancing.
Each column represents an operator, with labelled segments showing the measured time for individual tasks. Takt time establishes the pace required to meet customer demand. A column above that line identifies an allocation that exceeds the available time per unit. A shorter column indicates capacity to investigate, subject to the equipment access and work sequence needed for any proposed transfer.
For a hypothetical line with a takt time of 60 seconds, one operator might have 68 seconds of work while an adjacent operator has 49 seconds. Moving an eight-second inspection task would bring their workloads to 60 and 57 seconds. That arithmetic establishes a candidate allocation. A production trial must establish whether the receiving operator can perform the inspection without additional walking or interference with other tasks. An allocation at exactly takt leaves no margin for observed variation.
A time and motion study supplies the element-level observations used to construct a Yamazumi chart. Where automatic machine processing overlaps with manual activity, a standardized work combination table clarifies elapsed time and operator involvement so overlapping durations are not double-counted as operator workload.
Within DMAIC, the chart supports analysis of the current allocation and comparison of proposed improvements. Pilot testing verifies the revised balance before it becomes standard work. The control plan then specifies how recurring takt overruns trigger review of the affected station.
