SMED Analysis (Changeover Reduction)
Slash setup and changeover time. SMED, Single-Minute Exchange of Die, separates internal from external setup, converts internal steps to external, and streamlines the rest, so changeovers shrink from hours toward minutes and small-batch flow becomes affordable.
Run SMED Analysis →What is SMED?
SMED, Single-Minute Exchange of Die, is a Lean method developed by Shigeo Shingo for dramatically reducing the time it takes to change over equipment from one product to the next. The name refers to the goal of performing setups in single-digit minutes, under ten, though the method delivers large reductions even where that exact target is not reached.
The central distinction is between internal setup, steps that can only be done while the machine is stopped, and external setup, steps that can be done while the machine is still running the previous job. Most changeover time is lost because tasks that could be external, gathering tools, staging materials, pre-heating, are performed internally while the machine sits idle.
SMED reduces changeover in stages: first separate internal from external setup, then convert as much internal setup to external as possible, and finally streamline all remaining steps through parallel work, quick fasteners and standardization. Short changeovers make small batches economical, which is what enables level flow and low inventory.
In plain terms: Every minute a machine is stopped to switch products is lost production. SMED's big trick is realizing that much of that stopped time is spent on things you could have done while it was still running, like fetching tools. Move those outside the stoppage, streamline the rest, and long changeovers shrink to minutes.
The SMED Stages
Separate Internal & External
Classify every setup step: internal (machine must be stopped) or external (can be done while running). Simply doing external steps beforehand often cuts changeover sharply.
Convert Internal to External
Redesign steps so more can be done while the machine still runs: pre-stage tooling, pre-heat, pre-assemble, use standardized fixtures.
Streamline Everything
Speed remaining internal steps with quick-release fasteners, parallel operations by multiple people, and eliminated adjustments.
Key Formulas
Why SMED Matters Beyond Setup
The first stage alone, moving already-external tasks out of the stopped period, often yields a large reduction with little cost, because so much idle time is spent on preparation that never required the machine to be down.
The deeper payoff is strategic. Long changeovers force large batches to amortize the setup cost, which creates inventory and slows flow. Short changeovers make small batches economical, enabling the level, low-inventory flow that Lean depends on. SMED is therefore an enabler of pull systems, not just a local efficiency.
Assumptions & Validation
Observed Changeover
The analysis is based on watching an actual changeover, step by step.
If violated: Record a real changeover (video helps) before classifying steps.
Honest Classification
Each step is correctly labeled internal or external.
If violated: Re-examine steps assumed to be internal; many can be external.
Standardized Method
The improved changeover is standardized so gains persist.
If violated: Document and train the new setup procedure.
⚠️ Check assumptions first
The biggest and cheapest SMED gains come from recognizing that steps currently done during the stoppage do not actually require the machine to be stopped. Teams often assume the whole changeover is internal and jump straight to buying faster equipment. First separate internal from external and convert what you can, then standardize the new method, otherwise the improvement is not repeatable and setup times drift back up.
When NOT to Use SMED Analysis
No Changeovers
For continuous processes with no product changeovers, SMED has nothing to reduce.
Flow or Quality Problems
For issues of flow, waiting or defects rather than setup time, value stream mapping or mistake-proofing fit better.
Rare Setups
Where changeovers are very infrequent and not constraining, the effort may be better spent on the actual bottleneck.
Industry Applications
Batch-Size Reduction
Cut changeover time so smaller batches become economical, reducing inventory and improving flow.
Bottleneck Capacity
Recover capacity at a constrained machine by shrinking the time lost to setups.
Flexibility & Responsiveness
Enable faster product switching to respond to variable demand without large stockpiles.
Kaizen Focus
Provide a well-bounded, high-impact target for a focused changeover-reduction Kaizen event.
Frequently Asked Questions
What does SMED stand for and what is the goal?
SMED stands for Single-Minute Exchange of Die. The goal is to reduce equipment changeover time to single-digit minutes, under ten. Even where that exact target is not achieved, applying the method typically produces very large reductions in setup time. Short changeovers make small production batches economical, which is essential for level flow and low inventory.
What is the difference between internal and external setup?
Internal setup consists of steps that can only be performed while the machine is stopped, such as physically exchanging a die. External setup consists of steps that can be done while the machine is still running the previous job, such as gathering tools, staging materials or pre-heating. The core of SMED is recognizing that many tasks treated as internal can actually be external, and moving them out of the stoppage.
What are the stages of SMED?
SMED proceeds in three stages. First, separate internal setup from external setup and ensure external tasks are done before or after the stoppage. Second, convert as much internal setup to external as possible by redesigning steps, for example pre-staging and pre-assembling. Third, streamline all remaining steps using quick-release fasteners, parallel operations and eliminated adjustments. Each stage compounds the reduction.
Why does reducing changeover time matter so much?
Long changeovers force large batch sizes, because the setup cost has to be spread over many units to be economical, and large batches create excess inventory and slow flow. Reducing changeover time makes small batches affordable, which enables level production, faster response to demand, and the low-inventory pull systems that Lean depends on. SMED is therefore a strategic enabler, not just a local efficiency gain.
How do I start a SMED analysis?
Begin by recording an actual changeover step by step, ideally on video, and noting the time each step takes. Then classify every step as internal or external. Often the first insight is that a substantial share of the stopped time is spent on tasks that never required the machine to be down. Moving those external tasks out of the stoppage delivers immediate gains before any equipment is modified.
Does SMED require expensive equipment?
No. The largest early gains usually come from reorganizing the changeover, separating internal from external steps and converting internal to external, which costs little. Streamlining may later introduce quick-release fasteners, standardized fixtures or parallel work, but these are generally modest investments. Jumping straight to buying faster machinery, without first reorganizing the setup, misses the cheapest and often largest improvements.
Turn Hour-Long Changeovers Into Minutes
Separate, convert and streamline setup steps to cut changeover time. Free during Beta.
Run SMED Analysis →