Definition
The column chart displays the activity volume of each operator during the beat time.
In detail
The Operator Loading Chart (Yamazumi) is a bar chart that shows each operator's workload within the Standard Work cycle and compares it with Takt Time. It helps identify uneven workload, bottleneck stations, and whether staffing is reasonable. In the lean system, it is an important tool for line balancing and Standard Work design. Unlike Value Stream Mapping (macro process) and the Standard Work Combination Sheet (detailed motions), it focuses on operator loading. Its output is typically a loading chart and a line balancing improvement plan.
Example in practice
An electronics factory's assembly line has 5 stations, but the work times at each station vary greatly, causing Work in Process to pile up. They draw an Operator Loading Chart and find that station 3 is loaded far above takt, while station 5 is mostly idle. They then redistribute the work content so that each station's load is close to takt. After Kaizen, line balance improves, the Bottleneck is eliminated, and output increases.