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Direct Definition: Single-Minute Exchange of Die (SMED) is a lean manufacturing methodology developed by Shigeo Shingo that reduces machine changeover and setup times to less than ten minutes (single-digit minutes), enabling high-mix, small-batch production.
Single-Minute Exchange of Die (SMED) is a cornerstone of lean manufacturing. By minimising setup downtime on CNC machines, stamping presses, and fabrication cells, manufacturers can switch between customer jobs rapidly without sacrificing machine utilisation.
Internal vs External Setup Operations
The core breakthrough of SMED relies on dividing setup tasks into two distinct categories:
- External Setup: Activities that can be performed while the machine is still actively running the previous job (e.g. retrieving tooling, pre-heating dies, staging raw stock, downloading CNC programs).
- Internal Setup: Activities that can only be performed when the machine is stopped (e.g. removing old fixtures, clamping new tooling, dialing in zero points).
Converting and Streamlining Setups
The goal of SMED is to convert as many internal setup steps into external tasks as possible. Schedulers support SMED by grouping similar tooling setups together in the daily sequence, reducing the total changeover duration required between consecutive jobs.
Frequently Asked Questions
- What does SMED stand for?
- SMED stands for Single-Minute Exchange of Die, referring to the goal of reducing machine changeovers to single-digit minutes (under 10 minutes).
- What is the difference between internal and external setup?
- Internal setup requires the machine to be powered down and stopped. External setup can be prepared in advance while the machine is actively running.
- How does fast changeover help small manufacturers?
- It allows shops to run smaller, high-mix batches economically, slashing lead times and reducing excess work-in-progress inventory.