- Enter current changeover time in minutes.
- Classify internal vs external activities to identify what can be done while running.
- Click Calculate to see potential time savings from SMED.
The SMED Principle
What Is SMED?
SMED (Single-Minute Exchange of Die) was developed by Shigeo Shingo at Toyota in the 1950s-60s. The name refers to the goal: changeovers in single-digit minutes (under 10). The methodology is systematic — it does not require expensive automation, just rigorous observation and reorganization of changeover activities.
The core insight is that most changeover time is wasted on activities that could happen before the machine stops or after it restarts. By converting these internal activities to external ones, changeover time drops dramatically.
60 min total
Int vs Ext
Int → Ext
15 min total
The 3 Stages of SMED
Real-World Example
A stamping press currently takes 60 minutes per changeover, with 12 changeovers per week. Machine time is worth $2,000/hr.
After SMED (15 min): 12 x 15 min = 180 min/week = 3 hrs/week
Savings: 9 hrs/week x 50 weeks x $2,000/hr = $900,000/year
Plus: shorter changeovers enable smaller batches, reducing WIP inventory and improving lead times via Little's Law.
Why Changeover Time Drives Batch Size
| Changeover Time | Economic Batch Size | WIP Impact |
|---|---|---|
| 60 minutes | Large (days of inventory) | High WIP, long lead times |
| 15 minutes | Medium (shift-level batches) | Moderate WIP |
| Under 5 minutes | Small (EPED possible) | Low WIP, fast response |
The Ripple Effect
Reducing changeover time does not just save machine time. It enables smaller batches, which reduces WIP (Little's Law), shortens lead times, improves quality feedback, and reduces finished goods inventory. Calculate optimal batch sizes with our Batch Size Calculator.
✅ SMED Best Practices
- Video the changeover before improving
- Involve operators — they know the details
- Pre-stage everything before stopping
- Use standardized tooling and quick-connects
❌ Common Mistakes
- Trying to automate before organizing
- Only involving engineers, not operators
- Accepting "we need to adjust" as a given
- Not standardizing between similar products
🎯 Key Takeaway
SMED is one of the highest-ROI lean tools. It costs almost nothing (just observation and reorganization) and typically saves 50-90% of changeover time. The downstream benefits — smaller batches, less WIP, shorter lead times — multiply the value far beyond the direct time savings.
Frequently Asked Questions
What is SMED?
SMED (Single-Minute Exchange of Die) is a lean methodology for reducing changeover times. Developed by Shigeo Shingo, it aims to reduce changeovers to under 10 minutes by converting internal activities to external.
What is internal vs external changeover time?
Internal activities can only happen while the machine is stopped (removing the old die). External activities can happen while the machine is still running (getting tools ready, staging materials). SMED moves as many activities as possible to external.
How much can SMED reduce changeover time?
Typical reductions are 50-90%. A changeover that takes 60 minutes can often be reduced to 15-20 minutes in the first SMED event, and under 10 minutes with sustained improvement.
Why does changeover time matter?
Long changeovers force large batch sizes (to amortize the setup cost). Large batches mean high WIP, long lead times, and inflexibility. Reducing changeovers enables smaller batches and faster flow.
How often should you do changeovers?
As often as your customer mix requires. With short changeovers, you can produce every product every day (EPED). This reduces inventory and improves responsiveness.
What is EPED?
Every Product Every Day. It means your changeover times are short enough to produce every SKU daily. This minimizes finished goods inventory and maximizes responsiveness to demand changes.
Track this automatically every shift
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