Yamazumi charts, also called Yamazumi boards or balance sheets, are a diagram tool used to evaluate cycle times and workloads, while looking for areas in the manufacturing process to optimize. Yamazumi is a Japanese term meaning “to stack up,” and the chart itself is a stacked bar chart. Lean improvement teams utilize these charts to identify wastes and continuously improve processes.
The operations of the whole assembly line can be plotted on a Yamazumi chart, although some choose to focus on one product at a time. Along the x-axis (the bottom of the chart) each operation is listed and the y-axis measures cycle time. Total cycle time of each process is recorded and represented as a bar on the chart. That bar is then segmented into three operation categories: value added, non-value added, and necessary. The steps within a process should be evaluated and put into one of these categories. The stacked bars allow users to quickly notice how much time is being wasted on activities that don’t add value to the product; the first step in improving cycle time is to reduce or eliminate these wasteful operations.
Depending on the size of the facility, Yamazumi charts can range from a simple chart drawn on a whiteboard to more complex and in-depth charts utilizing specific software. Whichever option an organization chooses, the overarching goal is simple: to improve processes. Many choose to also include a bar representing Takt time in their Yamazumi chart, so it is easy to identify which processes are causing delays and operations that may be underutilized.
Yamazumi charts are beneficial to other Lean tools. For example, the represented value added activities can be used as targets for improvement with the 5S methodology. Managers are also able to use the chart to see which operations are wasting time but can take that information on a Gemba walk to get to the root of the problem.