What is the difference between internal and external work?

Internal work can only be done while the machine is stopped, such as taking out the old die. External work can be done while the machine still runs the previous order or already runs the next one, such as fetching the next die, preheating it or getting the tools ready. Only internal work adds to the change-over time.

Where does SMED start?

With watching and timing one real change-over step by step, ideally on video. Then mark each step internal or external, move everything possible to external, and only then shorten the internal steps (quick clamps, locating pins, standard heights, parallel work) and remove adjustments and trial runs. The blank observation sheet is made for the first part.

What is EPEI and why does it get shorter?

Every part every interval: how many periods (days, shifts) it takes to run every variant once. It is the number of change-overs in one round times the change-over time, divided by the time left after running the demand. A shorter change-over leaves the same free time for more change-overs, so every variant can be made more often in smaller batches, with less stock.

Does a shorter change-over always mean smaller batches?

Only if the saved time is used for more change-overs. It can also be used for more output, when the machine is a bottleneck. The tool shows the smaller batch it allows; whether to take it is a decision about stock against capacity.

LIVE TOOL

SMED change-over analysis

Change-over steps as internal or external, with a proposal per step: the new change-over time, the time saved, and the effect on EPEI and batch size.

Input

Example dataReplace with your own steps

Change-over steps

Paste, open a CSV, TSV, TXT or XLSX file (up to 20 MB), or drop it on the field. Files are read in this browser only.

Columns (6 possible, found by the header names)

ColumnsStepDurationInternal / externalCategoryActionNew duration

Found by the header names, or in the order Step, Duration, Internal / external, Category, Action, New duration. Change them if they are wrong.

Step           Duration  Type      Category     Action               New duration
Fetch the die  12        Internal  Preparation  Convert to external  12
Mount the die  12        Internal  Mounting     Shorten              8

Long format
1 row = 1 step

Columns: tab, ; or ,
Decimals: 12,5 or 12.5

Read as: tab-separated · whole numbers · 12 rows · header row skipped

ColumnsDecimal

Data as understood — first 10 of 12 rows
#	Step	Duration	Internal / external	Category	Action	New duration
1	Fetch the next die from the store	12	Internal	Preparation	Convert to external	12
2	Find tools and clamps	8	Internal	Preparation	Convert to external	8
3	Stop the press, release the clamps	6	Internal	Mounting	Shorten	2
4	Remove the old die	10	Internal	Mounting	Keep
5	Clean the die seat	5	Internal	Mounting	Keep
6	Mount the new die	12	Internal	Mounting	Shorten	8
7	Connect water and air	7	Internal	Mounting	Shorten	3
8	Adjust the shut height	9	Internal	Measuring	Shorten	2
9	Trial parts and measuring	15	Internal	Trial	Shorten	6
10	Fine adjustment	10	Internal	Measuring	Eliminate

+2 more rows

One row per step in the order observed. Type: Internal (machine stopped, the default) or External. Category: Preparation, Mounting, Measuring (setting, adjusting) or Trial. Action: Keep, Convert to external, Shorten (give the new duration) or Eliminate.

Durations inDemand per period, all variants (optional)

pcs

Available time per period

min

Cycle time per piece

Variants changed over in turn

With the demand, the available time, the cycle time and the number of variants, the change-over time turns into EPEI (every part every interval) and the batch size of each variant, before and after. Leave all four empty to skip it.

Runs in this browser. Data is not uploaded or stored.

Results

36.0 minChange-over after

98.0 minChange-over before

62.0 minSaved per change-over

63.3%Internal time reduction

Change-over (internal) 98.0 → 36.0 min · 63.3% shorter · EPEI 0.82 → 0.30 periods

Internal: machine stoppedExternal: machine running

Before and after
Quantity	Before	After
Internal time (change-over)	98.0 min	36.0 min
External time	8.0 min	32.0 min
All work	106.0 min	68.0 min

Effect
Quantity	Value
Saved per change-over	62.0 min
Internal time reduction	63.3%
Eliminated work	10.0 min
Run time per period	480.0 min
Free time per period for change-overs	480.0 min
EPEI before → after (periods)	0.82 → 0.30
Batch per variant before → after	490 → 180 pcs
Change-overs that fit per period	4.9 → 13.3

Steps
Step	Category	Type	Duration (min)	Action	New type	New (min)
Fetch the next die from the store	Preparation and checks	Internal	12.0	Convert to external	External	12.0
Find tools and clamps	Preparation and checks	Internal	8.0	Convert to external	External	8.0
Stop the press, release the clamps	Removal and mounting	Internal	6.0	Shorten	Internal	2.0
Remove the old die	Removal and mounting	Internal	10.0	Keep	Internal	10.0
Clean the die seat	Removal and mounting	Internal	5.0	Keep	Internal	5.0
Mount the new die	Removal and mounting	Internal	12.0	Shorten	Internal	8.0
Connect water and air	Removal and mounting	Internal	7.0	Shorten	Internal	3.0
Adjust the shut height	Measuring, setting, adjusting	Internal	9.0	Shorten	Internal	2.0
Trial parts and measuring	Trial runs	Internal	15.0	Shorten	Internal	6.0
Fine adjustment	Measuring, setting, adjusting	Internal	10.0	Eliminate	Eliminated	0.0
Order paperwork	Preparation and checks	Internal	4.0	Convert to external	External	4.0
Return the old die to the store	Preparation and checks	External	8.0	Keep	External	8.0

By category (internal time)
Category	Before (min)	After (min)
Preparation and checks	24.0	0.0
Removal and mounting	40.0	28.0
Measuring, setting, adjusting	19.0	2.0
Trial runs	15.0	6.0

Download offline versionSingle HTML file · v1.6 · 565 KB · works without internet

Blank template to print or fill in your own program

PDF114 KB · fillable fields
Excel14 KB

How the SMED analysis is calculated

SMED (single-minute exchange of die) shortens a change-over by separating the work that needs the machine stopped from the work that can be done while it runs, moving as much as possible to the second kind, and then shortening what stays. The method is a common practice, not a standard; the categories and actions here are the usual ones.

Formulas

Change-over time = the sum of the internal steps (machine stopped). External steps are work, but not downtime.
After: an eliminated step is gone; a step converted to external moves to the external time with its duration (or the new one); a shortened step takes its new duration; a kept step stays, with a new duration if one is given.
Saved per change-over = internal before − internal after; reduction = saved / internal before.
Run time = demand × cycle time; free time = available time − run time: the time left for change-overs in one period.
EPEI (every part every interval, in periods) = variants × change-over time / free time.
Batch per variant = demand / variants × EPEI: equal demand for every variant is assumed. Change-overs that fit per period = free time / change-over time.

Worked example (the tool’s example)

Eleven of the twelve steps of the die change are internal: 12 + 8 + 6 + 10 + 5 + 12 + 7 + 9 + 15 + 10 + 4 = 98 min of stop; returning the old die (8 min) is already external.
Fetching the die, finding the tools and the paperwork (24 min) move to external; quick clamps, pins, couplings, shims and fewer trial parts shorten five steps; the fine adjustment is eliminated.
Internal time after: 2 + 10 + 5 + 8 + 3 + 2 + 6 = 36 min, saving 62 min per change-over, a reduction of 63.3 %.
2400 pieces a day at 12 s take 480 min of the 960 available, leaving 480 min. With four variants EPEI = 4 × 98 / 480 = 0.82 days before and 4 × 36 / 480 = 0.30 days after; the batch of each variant drops from 490 to 180 pieces.

Common mistakes

Timing the change-over from memory instead of observing it: steps like searching for tools are forgotten.
Shortening internal steps before moving the external work out of the stop: the cheapest gain comes first from preparation.
Counting external work as saved time: it still needs a person, only not a stopped machine.
Ending the change-over at the first part instead of the first good part at full speed: trial runs and adjustments are part of it.
Reading EPEI with unequal demands as exact: the batch shown is for an average variant.

Input and files

Numbers may use a decimal comma or point. The type, category, action and new duration columns are found by their header names and may be left empty: a step is then internal, not categorised and kept.
Excel export: the steps and a summary sheet whose totals, reduction, EPEI and batch sizes are formulas, so changing a duration, a type or the demand in Excel recalculates them.
Print / PDF prints the results on one A4 landscape sheet; use “Save as PDF” in the print dialog. The blank observation sheet (fillable PDF or Excel) is for timing a change-over on the floor.
Files: CSV, TSV and TXT are read as if pasted (UTF-8, UTF-16, otherwise Windows-1257). XLSX: choose the sheet and the columns or a cell range; formula cells use the value Excel last saved, dates are kept as text. Files up to 20 MB are read in this browser only and never uploaded.
XLSX files are read with SheetJS Community Edition 0.20.3, Apache License 2.0 (license), loaded only when an Excel file is opened or created.

Questions

What is the difference between internal and external work?: Internal work can only be done while the machine is stopped, such as taking out the old die. External work can be done while the machine still runs the previous order or already runs the next one, such as fetching the next die, preheating it or getting the tools ready. Only internal work adds to the change-over time.
Where does SMED start?: With watching and timing one real change-over step by step, ideally on video. Then mark each step internal or external, move everything possible to external, and only then shorten the internal steps (quick clamps, locating pins, standard heights, parallel work) and remove adjustments and trial runs. The blank observation sheet is made for the first part.
What is EPEI and why does it get shorter?: Every part every interval: how many periods (days, shifts) it takes to run every variant once. It is the number of change-overs in one round times the change-over time, divided by the time left after running the demand. A shorter change-over leaves the same free time for more change-overs, so every variant can be made more often in smaller batches, with less stock.
Does a shorter change-over always mean smaller batches?: Only if the saved time is used for more change-overs. It can also be used for more output, when the machine is a bottleneck. The tool shows the smaller batch it allows; whether to take it is a decision about stock against capacity.

OEE calculator: change-overs as part of the availability loss.
Kanban sizing: smaller batches mean smaller containers and fewer cards.
Little’s law and WIP: less work in process shortens the lead time.
Capacity planning: set-up minutes in the load of each machine.