Single Minute Exchange Of Die
SMED (Single-Minute Exchange of Die) is a lean manufacturing method that reduces CNC machine changeover time to under 10 minutes. It involves separating internal setup tasks (done while machine is stopped) from external tasks (done while running), converting internal to external, and standardizing remaining internal steps for rapid job transitions.
On the CNC shop floor, SMED means operators stage the next job's tooling, collets, cutters, and fixtures while the current run is still producing. The machine stops only for the minimal internal tasks: unclamping, swapping pallets, loading the new program, and verifying the first part. All other preparation—tool presetting, offset confirmation, material staging, and coolant adjustments—happens externally. This structured approach cuts downtime from hours to minutes, enabling smaller lot sizes and better flow. In millwork, the same logic applies to quick profile changes on edgebanders: pre-warming adhesives, staging edge tapes, and pre-checking cutters before the machine stops. The key is rigorous standard work and checklists to ensure every external step is truly ready.
What is the difference between internal and external setup in SMED?
Internal setup requires the machine to be stopped, while external setup can be performed while the machine is still running. SMED aims to convert as many internal steps to external as possible.
Does 'single-minute' in SMED literally mean one minute?
No. 'Single-minute' means single-digit minutes, typically under 10 minutes, not exactly one minute. The goal is to achieve changeover times in the range of 1 to 9 minutes.
What is the most important rule in successful SMED implementation?
Do not just 'work faster'; redesign the changeover so that as much work as possible happens before the machine stops, then standardize the remaining internal steps. This ensures sustainable, significant reductions.