SMED Single Minute Exchange of Dies
What Is SMED?
SMED — Single Minute Exchange of Dies — is the technical term behind what's commonly called Lean Changeover or Quick Changeover in the U.S. Despite the name, "single minute" doesn't mean literally one minute; it means single-digit minutes, under 10.
Where It Came From
Shigeo Shingo developed SMED at Toyotain the 1960s, when changing stamping press dies between models took 10-12 hours. That meant a choice: high volume with low variety, or high variety with low volume. Toyota needed both.
Shingo examined the setup process the way any good engineer examines waste — and found it could be cut dramatically, usually at low cost. He also discovered something bigger: the deep look at setup that reduces changeover time also tends to improve the process itself, running better and producing higher quality afterward. (Want the full story? Shingo's own book, [A Revolution in Manufacturing: The SMED System], is the primary source. My followup [Achieving Lean Changeover: Putting SMED to Work] is another good source. As an Amazon Associate, we earn from qualifying purchases.)
Two Core Principles
1. Internal vs. External WorkEvery changeover task is either Internal (can only happen while the machine is stopped — like unbolting a die) or External (can happen while the machine is still running — staging tools, filling out paperwork, moving materials). Moving tasks from Internal to External is often the single biggest lever in a changeover.
Case Study: ExternalizationA surgical implant manufacturer running CNC Swiss lathes stopped production after every new setup to send the first part to a CMM machine for measurement — 10-15 minutes, 3-4 times per shift, every shift. Across a year, that added up to 500 lost hours per machine — roughly 10,000 parts' worth of capacity, at a 3-minute cycle time.
Failures at inspection were rare, and the part cost about $8. So we moved the measurement step to run while production continued — accepting a small risk ($30-40 in scrap on the rare failure) in exchange for the machine never stopping. Result: 10,000 additional parts per machine, per year — no capital investment, no added headcount.
2. StandardizationShingo also found that standardizing die sizes — adding shims so every die shared the same outside dimensions — eliminated the need for custom mounting and adjustment on every changeover.
Case Study: StandardizationA battery manufacturer producing over 1,000 SKUs across national and private-label brands launched a "Small Batch" initiative — 2-day delivery on orders as small as 6 cases. That pushed changeovers to 4-6 per shift across 8 lines, and the plant was running 24/7 with overtime and temp labor just to keep pace.
The root problem: two nearly identical card sizes that plant management knew were a problem, but couldn't get marketing to fix — "too expensive to redo the art." We built the financial case for standardization and a strategy to bring marketing on board. It worked: card sizes were standardized, the plant dropped to 2-shift operation, and the Small Batch strategy grew market share by 8% — a significant jump for a commodity product.
There's More to SMED
These are two of the biggest levers — there's more to a full changeover overhaul. If you want to find out what it could do in your plant, get in touch.
SMED — Single Minute Exchange of Dies — is the technical term behind what's commonly called Lean Changeover or Quick Changeover in the U.S. Despite the name, "single minute" doesn't mean literally one minute; it means single-digit minutes, under 10.
Where It Came From
Shigeo Shingo developed SMED at Toyotain the 1960s, when changing stamping press dies between models took 10-12 hours. That meant a choice: high volume with low variety, or high variety with low volume. Toyota needed both.
Shingo examined the setup process the way any good engineer examines waste — and found it could be cut dramatically, usually at low cost. He also discovered something bigger: the deep look at setup that reduces changeover time also tends to improve the process itself, running better and producing higher quality afterward. (Want the full story? Shingo's own book, [A Revolution in Manufacturing: The SMED System], is the primary source. My followup [Achieving Lean Changeover: Putting SMED to Work] is another good source. As an Amazon Associate, we earn from qualifying purchases.)
Two Core Principles
1. Internal vs. External WorkEvery changeover task is either Internal (can only happen while the machine is stopped — like unbolting a die) or External (can happen while the machine is still running — staging tools, filling out paperwork, moving materials). Moving tasks from Internal to External is often the single biggest lever in a changeover.
Case Study: ExternalizationA surgical implant manufacturer running CNC Swiss lathes stopped production after every new setup to send the first part to a CMM machine for measurement — 10-15 minutes, 3-4 times per shift, every shift. Across a year, that added up to 500 lost hours per machine — roughly 10,000 parts' worth of capacity, at a 3-minute cycle time.
Failures at inspection were rare, and the part cost about $8. So we moved the measurement step to run while production continued — accepting a small risk ($30-40 in scrap on the rare failure) in exchange for the machine never stopping. Result: 10,000 additional parts per machine, per year — no capital investment, no added headcount.
2. StandardizationShingo also found that standardizing die sizes — adding shims so every die shared the same outside dimensions — eliminated the need for custom mounting and adjustment on every changeover.
Case Study: StandardizationA battery manufacturer producing over 1,000 SKUs across national and private-label brands launched a "Small Batch" initiative — 2-day delivery on orders as small as 6 cases. That pushed changeovers to 4-6 per shift across 8 lines, and the plant was running 24/7 with overtime and temp labor just to keep pace.
The root problem: two nearly identical card sizes that plant management knew were a problem, but couldn't get marketing to fix — "too expensive to redo the art." We built the financial case for standardization and a strategy to bring marketing on board. It worked: card sizes were standardized, the plant dropped to 2-shift operation, and the Small Batch strategy grew market share by 8% — a significant jump for a commodity product.
There's More to SMED
These are two of the biggest levers — there's more to a full changeover overhaul. If you want to find out what it could do in your plant, get in touch.
John Henry | The Changeover Wizard 📞 1-787-550-9650 ✉️ johnhenry@changeover.com