⚖️ Lean Architect · Tyshchenko Lean Academy

Yamazumi Chart

Who’s overloaded, who’s underloaded — and what to do about it

What a Yamazumi chart is

Yamazumi (山積み) means “to stack up” in Japanese. Each operator on the line is a separate column. Each operation is a block inside the column, and the height of the block equals its duration. The columns stand side by side, and one horizontal line — takt time — crosses all of them.

From there, the chart reads in a second. Anything sticking out above the takt line is a station that can’t keep up with customer demand. Anything far below it is an underloaded operator. The tallest column sets the pace of the whole line, no matter how fast the others work.

Key idea: a line runs at the speed of its slowest station. So raising productivity anywhere except the tallest column doesn’t add a single unit of output.
Three colors — three different decisions

Blocks are colored by the type of activity, not by operator. Without that, the chart only shows “who works how much”; with it, it shows exactly where to look for capacity.

V
Creates valueActivity the customer pays for: slicing, laying out, sealing. It isn’t cut — it’s protected from disruptions.
N
No value, but necessaryChecks, labeling, regulatory requirements. The customer doesn’t pay for them, but they can’t be removed. Minimize and simplify them.
W
WasteMoving, waiting, re-handling, unnecessary motion. The first candidate for removal — and the cheapest way to unload the line.
The order of work: remove the red first, and only then redistribute what’s left. Balancing waste just means spreading useless work evenly across people.
Tray packing line · 5 operators

Customer demand is 640 packs per shift, and available time is 8 hours. That gives a takt time of 45 seconds: every 45 seconds the line has to deliver one finished pack.

Click an operation block and move it to another operator. The goal: no column crosses the amber takt line.
Creates value Necessary, no value Waste Takt 45 s
Line operations
How to build a Yamazumi chart for your own area
1
Calculate takt timeAvailable shift time ÷ customer demand per shift. Not average output, but demand — otherwise you balance to your own habits, not to the market.
2
Do a time studyAt least 10 repetitions of each operation; take the median. A one-off measurement gives a random number, and that number then drives how people are assigned.
3
Break it into elementsAn element has to be something you can physically hand over to another operator. “Packing” isn’t an element. “Apply the label” is.
4
Mark the type of each elementValue, necessary without value, or waste. The team does this together — the debate here is more useful than the chart itself.
5
Remove wasteFirst delete what can be deleted. Often the number of operators you need drops on its own after that.
6
Redistribute what’s leftThe goal is all columns slightly below takt, with the same margin. Not “exactly at takt”: with no margin, the first small delay stops the line.
7
Lock it in with a standardThe new assignment goes into the SOP and the skills matrix. Otherwise, two weeks later the line drifts back to the old distribution.
The two most common mistakes
Balancing to the average time instead of takt.
A line balanced to its own average output looks even on the chart and still can’t keep up with demand. Takt is set by the customer, not by the plant.
Building the chart once.
A Yamazumi chart ages along with the product mix. When the product or the volume changes, takt changes — and yesterday’s balance becomes the new bottleneck.