The word Heijunka (平準化) means 'levelling' or 'smoothing' in Japanese. In lean management, Heijunka is a fundamental technique for levelling production and avoiding peaks and troughs in workload. Instead of producing 1,000 parts on Monday and 0 parts on Tuesday, you produce 200 parts every day. It sounds simple, but it is revolutionary. Heijunka reduces stock, improves quality, stabilises the teams and increases productivity. For an industrial SME with variable demand, Heijunka is the key to turning chaos into order.
The problem without Heijunka: peaks and troughs in workload
Imagine an electronics SME that receives its customer orders irregularly. Monday: 1,000 parts to produce. Tuesday: 0 parts. Wednesday: 500 parts. Thursday: 0 parts. Friday: 2,000 parts.
- Monday (1,000 parts) : total overload. The teams work in firefighting mode, the machines run flat out, defects increase (5% defects = 50 parts to redo).
- Tuesday (0 parts) : total underload. The teams have nothing to do, the machines are idle, finished goods stock accumulates.
- Wednesday (500 parts) : average load, but the machines, teams and flows have to be readjusted. Time lost.
- Thursday (0 parts) : underload again.
- Friday (2,000 parts) : extreme overload — overtime, temporary staff, errors.
The consequences: huge stock (1,000 parts accumulated every week), poor quality (5-10% defects), high costs (overtime, temporary staff, rework, storage), frustrated teams (stress, high turnover), long lead times. It is chaos — and it is the situation of many industrial SMEs.
Heijunka: production levelling as the solution
Heijunka solves this problem by levelling production, with a simple formula:
Levelled production = Total demand / Number of days
Example: total demand of 3,500 parts per week, 5 production days → 3,500 / 5 = 700 parts per day. Instead of producing 1,000 on Monday, 0 on Tuesday, 500 on Wednesday, 0 on Thursday and 2,000 on Friday, you produce 700 parts every day.
The consequences:
- Reduced stock : you produce exactly what you sell, every day. No accumulation.
- Improved quality : steady workload = less stress = markedly fewer defects.
- Reduced costs : no overtime, no temporary staff, no rework.
- Stable teams : regular, predictable, less stressful work.
- Short lead times : with little stock, customers are served quickly.
Heijunka vs Kanban: what is the difference?
Many SMEs confuse Heijunka with Kanban. They are two different, complementary lean tools.
| Aspect | Heijunka | Kanban |
|---|---|---|
| Objective | Level production | Control the material flow |
| Level | Production planning | Stock and order management |
| Horizon | Week, month | Day, week |
| Tool | Levelling formula, schedule | Kanban cards, containers |
| Decision | How much to produce each day? | When to order? How much? |
| Example | Produce 700 parts per day instead of peaks and troughs | When material stock falls to 100 parts, order 500 parts |
Heijunka answers the question: 'How do I level my production to avoid peaks and troughs?' Kanban answers the question: 'How do I manage my stock and my orders efficiently?' Ideally, you use both: Heijunka to level production at 700 parts per day, Kanban to trigger raw material orders. Together, they create a smooth, efficient production system with little stock and high quality.
Steps for implementing Heijunka
Step 1: Analyse customer demand
Start by analysing your actual demand over the last 4-12 weeks. How many parts did you sell each week? What is the variation?
| Week | Demand | Variation |
|---|---|---|
| S1 | 3 000 | +20% |
| S2 | 2 500 | −17% |
| S3 | 3 500 | +40% |
| S4 | 2 000 | −43% |
| Average | 2 750 | ±30% |
Step 2: Calculate the levelled production
With your average demand: Levelled production = 2,750 / 5 = 550 parts per day. Instead of producing 3,000 one week and 2,000 the next, you produce 550 parts every day.
Step 3: Adapt your production capacity
Check that your production capacity supports this levelled production. Example: 2 machines × 300 parts per day = 600 parts per day of capacity; levelled production required = 550 parts per day → capacity is sufficient (600 > 550). If not: increase machine speed, add a machine, increase working hours, or negotiate demand with the customers.
Step 4: Put the levelling system in place
You produce 550 parts every day, whatever the actual demand, absorbing the variability with a small buffer stock:
- Monday : demand 600 → production 550, stock −50... then evened out: the stock fluctuates over the week
- Tuesday : demand 400 → production 550, stock +150
- Wednesday : demand 700 → production 550, 150 drawn from stock
- Thursday : demand 300 → production 550, stock +250
- Friday : demand 800 → production 550, 250 drawn from stock
With Heijunka, your stock varies between 0 and 250 parts. Without Heijunka, it varies between 0 and 1,000 parts. A 75% reduction in stock.
Step 5: Measure and adjust
Illustrative example of a monitoring table:
| KPI | Before Heijunka | After Heijunka (3 months) | Improvement |
|---|---|---|---|
| Average stock | 800 parts | 200 parts | −75% |
| Defect rate | 5% | 2% | −60% |
| Delivery lead time | 10 days | 5 days | −50% |
| Productivity | 500 parts per day | 550 parts per day | +10% |
If the results do not materialise, you adjust: the levelled production (too high or too low?), the capacity (enough resources?), the levelling system (properly understood by the teams?).
Measurable benefits of Heijunka
- Reduced stock : generally to a significant degree — less capital tied up, less storage space, less obsolescence risk.
- Improved quality : defects clearly down — less rework, less scrap.
- Shorter lead times : delivery lead times clearly down.
- Increased productivity : significant gains — no time lost readjusting machines and teams.
- Stable teams : engagement up, turnover down, safety improved.
Illustrative example: Heijunka in an electronics SME
An electronics SME manufactures circuit boards for the automotive industry.
Situation before Heijunka: highly variable demand (2,000 to 5,000 boards per week), chaotic production (peaks on Monday/Friday, troughs on Wednesday/Thursday), huge stock (2,000 boards on average), 6% defects, 12-day lead times.
Implementation: demand analysis (average = 3,500 boards per week) → levelled production 3,500 / 5 = 700 boards per day → capacity check (3 machines, 800 boards per day: OK) → fixed production schedule → weekly KPI monitoring.
Results after 6 months: markedly lower stock, sharply reduced defects, shorter lead times, higher productivity and improved customer satisfaction.
Financial impact: capital released by lower stock, recurring savings on rework and additional revenue linked to productivity — a substantial ROI in the very first year.
To deepen your understanding of lean management and the supply chain:
- Discover our full guide to Lean Management — philosophy, principles, tools
- Explore our approach to the Supply Chain — flow optimisation, cost reduction
- And our approach toContinuous Improvement
- In the industrial glossary : Kanban, Takt Time, VSM
Frequently asked questions
What should you do if customer demand is highly variable and unpredictable?
This is the most common question. If demand varies by ±50%, Heijunka matters even more. You level your production at average demand and manage the variability with a buffer stock. Example: average demand = 700 parts per day, variation = ±50%, buffer stock = 350 parts. This lets you absorb the peaks without overloading your teams. The buffer stock is smaller than before Heijunka (350 vs 1,000), but it exists.
How do you handle demand peaks with Heijunka?
You have several options: (1) Temporarily raise production above the levelled figure (but this creates stress and defects). (2) Use a buffer stock to absorb the peak. (3) Negotiate with the customer to level their demand ('Instead of 2,000 parts on Monday and 0 parts on Tuesday, could you order 1,000 on Monday and 1,000 on Tuesday?'). (4) Decline certain orders (if they are not profitable). Ideally, you combine options 2 and 3.
What is the link between Heijunka and Takt Time?
Takt Time is the production rhythm required to meet customer demand. Formula: Takt Time = Available time / Demand. Example: 480 minutes per day / 700 parts = 0.69 minutes per part = 41 seconds per part. Heijunka tells you how much to produce each day (700 parts). Takt Time tells you at what rhythm to produce (1 part every 41 seconds). Together, they create a smooth and efficient production system.
In which sectors is Heijunka applicable?
Heijunka is applicable in all industrial sectors: mechanical engineering, electronics, food processing, chemicals, textiles, automotive and more. Anywhere there is variable demand and repetitive production. Heijunka is less applicable in project-based sectors (construction, civil engineering) where each project is unique.