Heijunka and Pitch: Leveling Production
Heijunka smooths what arrives at the pacemaker: the same volume every day and a mixed variant pattern instead of large batches. Pitch breaks the day into small release units, so a backlog becomes visible within minutes rather than at the end of the week.
What heijunka means
Heijunka (Japanese for “leveling”) levels production at the pacemaker process in two directions: volume over time and the mix of variants within the day. The goal is even demand on all upstream processes. If the pacemaker builds 1,100 pcs today and 700 tomorrow, kanban passes this swing on to stamping, suppliers and supermarkets, and every supermarket has to be sized for the peak.
Leveling happens in one place only: at the pacemaker. Everything upstream replenishes by pull; everything downstream flows at takt to shipping.
Volume leveling
The pacemaker builds the average volume every day, not the fluctuating daily release. The finished goods supermarket absorbs the difference. The basis is takt time from average demand.
Mix leveling
Instead of building all standard variants first and then all compact ones, daily demand is spread in the ratio of the variants. Each variant is then available several times a day, finished goods inventory per variant goes down and the load on upstream processes becomes even.
Different work content evens out in the process: if one variant is above takt and another below it, the long variant must not run as a block but has to be spread between short ones.
Calculating pitch
Pitch is the time the pacemaker needs for one pack-out quantity when it works exactly at takt. It is the smallest release unit: one order is released and one full container is taken away per pitch. It is calculated with takt time, not with the cycle time of the process.
Heijunka box and runner
The heijunka box is a card rack with one column per pitch interval and one row per variant. Production control places the day’s kanban cards in the slots according to the leveled pattern. This way the daily schedule is not released all at once but in small increments of work.
- A runner (material handler) takes the card from the next slot in every pitch interval.
- The runner brings it with the material to the pacemaker and takes the finished container from the previous interval to the finished goods supermarket.
- If work from the previous interval is still at the pacemaker on the next round, the backlog is visible immediately: after 20 minutes, not in the weekly report.
- Cards are not pulled ahead and not batched. Anyone who “works ahead” shifts demand and undermines leveling.
Prerequisites
- A pacemaker that can hold takt: effective cycle time must be below takt time, otherwise every pitch builds a backlog.
- Short changeovers: every variant change costs changeover time. A fine mix pattern is only feasible with a few minutes per change.
- Supermarkets upstream of the pacemaker: it withdraws in small quantities, and upstream processes replenish by kanban.
- Stable processes: without a buffer, breakdowns at the pacemaker hit shipping immediately.
- A finished goods supermarket for volume leveling, as long as customer releases fluctuate.
Common mistakes
- Calculating pitch from cycle time instead of takt time: pitch follows the customer, not the machine.
- Leveling in several places: two heijunka boxes in one value stream contradict each other. There is exactly one pacemaker.
- Deciding on mix leveling without checking changeover time: the changes eat up capacity and the pacemaker falls behind.
- Pitch too large: with several hours per slot there is no control effect. Choose a smaller release quantity as the pitch unit.
- Heijunka box without a fixed runner route: without regular pickup, the box becomes a parking place for orders.
- Exotic variants in the pattern: very rare variants with high changeover effort disrupt the pattern. Put them in fixed windows or build them to order.
In the editor
Place the heijunka symbol in front of the pacemaker, enter the pitch as the interval and connect it to the pacemaker with a manual information flow. Through the product mix, the template “Variant production: 3 products, one line” shows mix load, changeover capacity and EPEI per process. This tells you whether the changeover time at the pacemaker allows fine leveling at all.
Practice in the editor
Open the template “Variant production: 3 products, one line”, calculate takt time and pitch for 10 pcs per container and check how many variant changes assembly can handle per day.
Open the template in the editor Start blankFrequently asked questions
What is the difference between heijunka and kanban?
Kanban governs replenishment between two processes: what was withdrawn is produced again. Heijunka determines the sequence and quantity in which the pacemaker receives orders. Heijunka sets the demand; kanban passes it upstream.
How large should the pitch be?
Pitch = takt time × pack-out quantity. In practice good values lie between about 5 and 60 minutes. If the container is very large, choose a smaller release quantity as the pitch unit so that backlogs become visible early.
Do I need a physical heijunka box?
No, the principle is what matters: release orders at fixed intervals, in a leveled pattern, visible at the pacemaker. A screen or a board works too. The physical box has the advantage that any backlog is visible at a glance.
Does heijunka work with many variants?
Yes, if you group variants: runners in a fixed pattern, medium-volume variants in fixed time windows, rare exotics built to order. You then level the work content per pitch, not every single variant.
What does heijunka have to do with EPEI?
EPEI tells you how often each variant can be produced. Mix leveling shortens it, for example from a week to a day or a few hours. That only works if changeover time per change drops accordingly.