Free tool

SMED calculator: changeover time analysis

Enter your changeover steps, their times and whether each is internal or external. Pick a target for every step to compare the time the machine is stopped before and after, with the time saved per changeover and per year on a timeline.

Changeover time with the machine stopped

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How the calculation works

Only internal steps stop the machine, so the changeover time is the sum of the internal steps. Each step’s target sets its after-state: “keep as is” leaves it unchanged, “convert to external” moves it, with the same time, to work done while the machine runs, “reduce” cuts it to the target time you enter, and “eliminate” removes it.

Internal time = Σ time of internal steps
Saved per changeover = internal time (before) − internal time (after)
Saved per year = saved per changeover × changeovers per week × working weeks per year

Example: The tool’s default example is a 9-step die change with 100 minutes of internal and 15 minutes of external work. Bringing the die and fixtures and preheating are converted to external, searching for tools is eliminated, loosening the bolts is reduced from 12 to 4 minutes and adjustment and trial parts from 25 to 10 minutes. The machine stops for 35 minutes instead of 100 (−65%). At 10 changeovers a week over 48 weeks that frees 520 machine hours a year. External work grows from 15 to 50 minutes and has to be done while the machine runs the previous job.

The result is the arithmetic of the targets you enter; trial changeovers show how much of it holds. You can download the steps and results as CSV to share with your team.

Shingo’s method

SMED is described in Shigeo Shingo’s book on his changeover work. Shingo splits changeover improvement into stages: first separate internal and external steps (often revealing preparation done while the machine stands still), then convert internal steps to external (preheating, presetting, standard clamping heights), and finally streamline all remaining internal and external steps (quick clamps, parallel work, eliminating adjustment). The targets in the tool follow these stages.

Sources

Shigeo Shingo, A Revolution in Manufacturing: The SMED System, Productivity Press, Cambridge (MA), 1985 (translated by Andrew P. Dillon).

Measuring changeovers

Taking changeover times from the machine instead of a stopwatch shows the real length of every changeover and whether the target holds. You can record changeover stops with their reasons through downtime tracking and see the effect on availability with the OEE calculator. To check line speed against demand, use the takt time calculator. How the data is collected is on our machine data collection page. All tools are on the tools page.

Frequently asked questions

Common questions

What is SMED?

SMED (Single-Minute Exchange of Die) is the changeover reduction method developed by Shigeo Shingo. The aim is to bring the time a machine stands still between two products below 10 minutes, a single-digit number of minutes. It is used well beyond presses: injection moulding, CNC machining, packaging and filling lines.

What is the difference between internal and external steps?

An internal step can only be done with the machine stopped, such as removing a die or clamping the new one. An external step can be done while the machine is still running the previous job, such as bringing the new die and fixtures, preheating, or cleaning the old die. Only internal steps make up the changeover time, so this SMED calculator measures the saving on internal time.

How do you do a SMED analysis?

Record the current changeover step by step (filming it is common) and note each step’s time. Then follow Shingo’s stages: separate internal and external steps, convert internal steps to external, and streamline every remaining step. In this tool you set each step to keep, convert to external, reduce or eliminate and see what it does to the changeover time.

How is the time saved calculated?

Saved per changeover = internal time before − internal time after. Multiply by changeovers per week for the weekly saving and by working weeks for the yearly saving. In the tool’s example the internal time falls from 100 to 35 minutes; at 10 changeovers a week over 48 weeks that frees 520 machine hours a year.

Why do converted steps matter?

A step converted to external does not disappear; it moves to work done while the machine runs. If it is not finished before the previous job ends, the machine waits again and the saving is lost. That is why the tool also shows how the external work changes; a preparation checklist with a named owner keeps these steps on time.

How does a shorter changeover affect OEE?

Changeover time counts as an availability loss in OEE. A shorter changeover gives more production in the same planned time, or allows more frequent changeovers and smaller batches. Use the OEE calculator to see where the freed time goes.