Heijunka: Production Leveling for Smooth Flow

Heijunka is the Toyota Production System tool for leveling production volume and mix over time. Instead of producing in large batches by product family, heijunka schedules small quantities of each product in a repeating sequence — creating smooth, predictable flow and eliminating the demand spikes that cause chaos upstream.

The core idea: Smooth demand outward, not just internally. If customers buy a little of everything every day, you should make a little of everything every day — rather than batching all of Product A on Monday and all of Product B on Tuesday.

Batch vs. Leveled Production — Visual Comparison

📅 Weekly Production Schedule

Batch Production — 3 products, 1 per day

{"".join(f'

{day}
{prod}

' for day,prod,bg in [("Mon","Product A (200 units)","#1D4ED8"),("Tue","Product A (200 units)","#1D4ED8"),("Wed","Product B (200 units)","#166534"),("Thu","Product C (200 units)","#92400E"),("Fri","Product C (200 units)","#92400E")])}

⚠ Upstream suppliers see huge demand spikes. Changeover is rare but costly. Defects in a batch aren't found until batch end.

Heijunka — leveled daily mix

{"".join(f'

A — 80

B — 80

C — 80

' for day in ["Mon","Tue","Wed","Thu","Fri"])}

✓ Smooth, predictable flow. Defects found quickly. Smaller batches mean less WIP. Requires short changeovers (SMED).

Prerequisites for Heijunka

Short changeover times (SMED)

Heijunka requires frequent product switches. If each changeover takes 90 minutes, leveling is impossible. SMED must reduce changeovers to under 10 minutes first.

Reliable process capability

Process variation must be low enough that you can predict hourly output reliably. This requires 5S, standard work, and stable equipment.

Accurate standard hours

Each product's standard time must be known at the subprocess level. TaktClock's standard hour database provides this — ensuring the leveling calculation is accurate for each product type.

❓ Knowledge Check

A facility implements heijunka and starts making a mix of products every day instead of batching by product. Which downstream effect is MOST likely?

✓ Correct! Heijunka reduces WIP because smaller batches move through the system faster. Defects are found sooner because batch size is smaller — a defect introduced at the start of an 80-unit daily batch is caught within hours rather than days. Lead times typically decrease with heijunka, not increase.

See It Live

These Principles, Running on Your Floor

30 minutes. Live TaktClock demo configured for your areas and processes.