Supply Chain · Make
Level Scheduling (Heijunka)
Level volume and mix over the horizon so upstream processes see a stable, repetitive pattern instead of waves.
- Time1 h
- FormatTeam
- StageMake
Level Scheduling (Heijunka): what it is and why it works
Level scheduling, or heijunka, smooths both the volume and the mix of production over a planning horizon so that upstream processes and suppliers see a stable, repeating pattern rather than peaks and gaps. Instead of producing each product in long campaigns, often driven by month-end targets, the plant calculates average daily demand by product and builds a short sequence that is repeated several times each day. For example, if daily demand is 60 of product A, 30 of B and 15 of C, a repeating unit of four A, two B and one C, run fifteen times a day, levels both volume and mix. A small finished goods buffer absorbs the difference between the level plan and actual daily orders.
Leveling works because variability amplifies upstream: a campaign of product A followed by a week of B creates waves of demand for components, labor and suppliers, forcing each to hold capacity or stock for peaks. A stable pattern allows smaller buffers, steady staffing and simpler pull systems. It depends on short changeovers, since frequent product switching is only economic when setups are fast, which is why SMED is usually a prerequisite. The finished goods buffer and monthly review let the plant decide explicitly between leveling, chasing demand, or a mix. Level scheduling supports WIP control upstream and translates S&OP volume decisions into daily execution.
What you need
- Daily demand by product or family for at least the last quarter
- Changeover times between products on the pacing process
- Available production time per day and the resulting capacity
- Current finished goods inventory and service targets
What you get
- Average daily volume and mix per product
- A repeating production sequence, such as a pattern run several times per shift or day
- A sized finished goods buffer to absorb real demand variation
- A monthly review rule: level, chase, or a documented mix of both
When to use it
When month-end pushes drown the plant and the first week of the month idles it.
How to do it, step by step
- Plot daily demand mix over the last quarter.
- Compute the average daily mix and use it as the level pattern.
- Sequence production in repeating small cycles instead of campaign waves.
- Hold a small finished-goods buffer to absorb real variation.
- Review monthly: level the plan, chase the demand, or mix both explicitly.
Worked example: Leveling assembly at a centrifugal pump plant
Illustrative scenario — figures are realistic but not from a real company.
A pump manufacturer assembled three pump models on one line: a standard model at about 1,200 units a month, a mid-size model at 600 and a high-pressure model at 300. The line ran each model in weekly campaigns, and machining and suppliers struggled with alternating overloads and idle weeks, with heavy overtime in the last week of each month.
- The team plotted daily orders for the last quarter and found that customer demand was far steadier than the production plan suggested.
- Over 20 working days, average daily demand came to 60 standard, 30 mid-size and 15 high-pressure pumps. They defined a repeating unit of four standard, two mid-size and one high-pressure pump, run fifteen times a day.
- Because changeovers on assembly took several minutes each, the team first applied SMED to fixture changes, bringing them down to under two minutes.
- They set a finished goods buffer of about two days' demand per model to cover daily order fluctuations while keeping the pattern stable.
Result. Machining now received a steady daily mix of castings and shafts, and end-of-month overtime dropped sharply. Component inventory fell because suppliers delivered smaller, regular quantities. The monthly review adjusted the pattern when demand shifted, and the team learned that leveling only became practical after changeovers were short.
Common pitfalls and how to avoid them
- Leveling the mix before changeovers are short enough to support it.Apply SMED to the pacing process first so frequent product switches do not destroy capacity.
- Changing the pattern every day to follow orders, which recreates the waves.Hold the pattern steady and let the finished goods buffer absorb daily variation, reviewing the pattern monthly.
- Sizing the finished goods buffer by guess.Base it on observed daily demand variation and the review interval, and adjust as data accumulates.
- Leveling assembly while upstream processes keep their own batch schedules.Connect upstream processes with pull signals so they also see the leveled pattern.
Frequently asked questions
What is heijunka in lean manufacturing?
Heijunka is the Japanese term for leveling production by volume and product mix. Rather than making products in large batches as orders arrive, the plant produces a steady, repeating mix based on average demand. This reduces peaks and troughs for upstream processes and suppliers, stabilizes staffing and inventory, and supports pull systems. It is one of the foundations of the Toyota Production System.
What is a heijunka box?
A heijunka box is a visual scheduling tool, usually a board with slots for time intervals and rows for products. Kanban cards placed in the slots show what to produce in each interval according to the leveled pattern. Material handlers pick up cards at fixed intervals, which paces production and makes deviations from the plan visible.
What is the difference between a level and a chase production strategy?
A level strategy keeps production steady and uses inventory to absorb changes in demand. A chase strategy adjusts production to follow demand, using overtime, temporary staff or idle time. Leveling reduces variability in the operation at the cost of some inventory; chasing reduces inventory at the cost of capacity flexibility. Many plants use a mix and review it in S&OP.
Origin
Heijunka — Toyota Production System; Monden, 1983.
Used in these playbooks
Lead time halving week 1 week
One week to find where time hides: map the flow, walk it, compress queues and lots — measure before and after.
- Value Stream Mapping
- Bottleneck Walk
- Lead Time Compression
- WIP Control
- Level Scheduling (Heijunka)
Related methods
- WIP ControlCap work-in-progress with a fixed number of job cards; new work only enters when finished work leaves.
- SMED ChangeoverConvert internal setup work to external, streamline the rest, and cut changeover from hours to minutes.
- S&OP Meeting DesignSet up the monthly Sales & Operations Planning rhythm: demand review, supply review, and one reconciliation…
More in “Make”
Turn materials into products at the constraint’s rhythm.