Heijunka: levelling production
平準化 · Instead of large lots (“towers”), the range of variants is spread evenly over time – a takt that repeats every week. The video example is built in 1:1 and is fully editable: change a demand figure, and the daily grid, waiting time and value-added share adjust immediately.
At a glance
Classic production in large lots vs. levelled Heijunka production.
Framework & variants
Working time and monthly demand per product variant – everything is editable.
Working time
Product variants & monthly demand
Classic approach – large lots
Sorted by demand in descending order (“A-class first”), each variant as one continuous block.
Heijunka calculation – from month to week
Monthly demand ÷ weeks, round down, distribute the remainder by largest remainder; the last week balances out.
Heijunka pattern – one takt per week
Variants are spread evenly within the week; small quantities move to the middle instead of the end.
How we distribute – in one sentence
Instead of first making all pieces of one colour and then the next, every colour gets its turn regularly: spread evenly over the week – the more pieces, the more often. We place rare colours in the middle of the week so that they do not slip to the end. This one week is repeated; the last week balances out rounding remainders.
Work it out in detail (optional) +
Comparison – what really changes
Same processing time, just arranged better.
Why does this work?
The total time for all units stays the same. What changes is the period over which they are spread. In the classic approach, a large part of the demand waits until the end of the month for tool changes that have not yet taken place. Heijunka spreads the changeovers out from the start.
Caution: the assumption
The model assumes changeover time = 0. In reality every changeover costs time – and we have multiplied the number of changeovers. Without SMED, capacity collapses: Heijunka and SMED are twin methods.
Understanding Heijunka (guided)
The method step by step – technical terms are underlined, hover over them with the mouse.
Video companion · Questions & answers
All terms and calculations from the video – in plain language. Click a question to open the answer. Technical terms are underlined (hover over them).
Key terms explained +
Heijunka (平準化, “levelling”) spreads volume and variant mix evenly over time instead of producing in large lots. Here are the most important terms in plain words:
How saving works +
This HTML file is your document. Everything you enter ends up in exactly this file when you save – just like a Word document. If you pass the file on, all plans in it go with it.
Save (green button or Ctrl+S) stores the current state – without any prompt. As long as no working file of your own has been created, the state is kept in the browser and is there again the next time you open it.
Save as (under “Plans”) creates a file on your hard drive. This is the only place where you are asked where to save. After that, every further Save writes silently into exactly that file.
The first time: open the file, click “Plans” and then Save as. From then on the green button is enough.
Saved automatically: as soon as a plan has been saved once, the tool backs up every further change by itself after a few seconds.
If something goes wrong: the tool continuously keeps an interim state in the browser. If the browser crashes or you close the window by accident, your work is there again the next time you open it.
Note on browsers: writing directly to the file currently works in Chrome and Edge. In Firefox and Safari everything stays saved in the browser – the file itself remains unchanged.