What Heijunka is
Heijunka is the technique of leveling production volume and mix over time, instead of producing large batches of a single item at once. It's one of the foundation-level principles in the "house" of the Toyota Production System, designed to prevent overload spikes (muri) and variability (mura) that create waste.
Volume leveling vs. mix leveling
Volume leveling
Spreading total production evenly across days and shifts, avoiding internal demand spikes and lulls.
Mix leveling
Alternating production between different models or products in small batches, instead of running one full model before switching to the next.
Running one item at a time looks efficient — until you count the inventory sitting idle waiting its turn.
The Heijunka box
A Heijunka box is a physical board with slots organized by time and by product, where Kanban cards are inserted in the planned leveled sequence. It makes it visible in seconds whether production is keeping pace with the planned takt time or falling behind.
Leveling requires smaller batches and faster changeovers, which is why Heijunka projects usually go hand-in-hand with SMED (quick changeover).
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About the author
Lean Manufacturing & Behavioral Management Specialist
Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.