Every changeover — swapping a die, mould, tool, fixture or product on a line — is time the machine doesn't produce. In high-mix factories, changeovers can consume a large share of available time. SMED (single-minute exchange of die), developed in Japanese manufacturing, is a structured way to cut changeover time dramatically, often without major investment.
Why changeover time matters
Long changeovers push factories toward large batches to "save" set-ups, which increases inventory, lead times and the risk of producing what isn't needed. Short changeovers allow smaller batches, faster response to customers and less stock — and they directly increase available production time, improving OEE.
Step 1: Measure the current changeover
Pick one machine and one typical changeover. Record it — ideally on video — from the last good part of the old job to the first good part of the new job at full speed. List every activity with its duration: searching for tools, fetching the die, removing clamps, cleaning, adjusting, trial runs, inspection and approvals.
Step 2: Separate internal and external tasks
Internal tasks can only be done while the machine is stopped (removing the old die). External tasks can be done while the machine is still running (bringing the next die, preparing tools, pre-heating, getting the program and drawing ready). In most first studies, a large share of the changeover turns out to be external work being done while the machine waits.
Step 3: Move external tasks outside the stop
Create a pre-changeover checklist: next die or tool at the machine, fixtures cleaned and checked, tools pre-set, program loaded, material ready, inspection gauges available, drawing and first-piece checklist printed or on the tablet. Simply doing this preparation before stopping the machine often cuts changeover time by a third or more.
Step 4: Convert internal tasks to external
Look for ways to do more before stopping: pre-heating moulds, pre-setting tools in holders off the machine, using standard-height dies so no shimming is needed, preparing a second fixture while the first is in use.
Step 5: Streamline the remaining internal tasks
- Quick-release clamps instead of multiple bolts.
- Locating pins and standard heights to eliminate alignment adjustments.
- Parallel work — two people working on different sides.
- Standard tools — one spanner size for all clamps.
- Eliminating adjustments — settings recorded and repeated, not found by trial.
Step 6: Standardise
Write the new changeover method as a standard procedure with photos — on a tablet at the machine. Train everyone who performs changeovers. Without standardisation, times drift back.
Examples by process
Injection moulding
Pre-heating the next mould, staging water connections, standard mould heights, quick mould clamps, and colour sequencing from light to dark. See MES for moulding.
Press shops
Die carts at the press before stopping, standard shut heights, quick die clamps and pre-set feeds.
CNC machining
Pre-set tools, zero-point clamping fixtures, programs verified offline, and first-piece checklists ready.
Packing lines
Format parts kits prepared in advance, colour-coded change parts, marked settings for guides and sensors, and labels and packing material staged.
Sequencing to reduce changeovers
Beyond faster changeovers, smarter sequencing reduces how many and how difficult they are — grouping jobs by die, material, colour or size. Production scheduling software can apply sequencing rules automatically. See production scheduling.
Measuring and sustaining results
Record every changeover's start and end time and the product pair. Over weeks, average changeover time by machine shows whether improvements hold. Outliers point to missing preparation or new problems. Software that records changeovers as planned downtime makes this data automatic. See downtime tracking.
Common pitfalls
- Studying changeovers without involving the people who do them.
- Buying equipment before fixing preparation and organisation.
- No standard procedure after the improvement.
- Not measuring after the project ends.
Corposol builds OEE and downtime software that tracks every changeover. Talk to us.
A sample pre-changeover checklist
- Next job confirmed and material available at the machine.
- Die, mould, tool or fixture at the machine, cleaned and inspected.
- Tools pre-set and measured; offsets recorded.
- Program loaded or verified; drawing revision confirmed.
- Clamps, spanners and lifting equipment at hand.
- Inspection gauges and first-piece checklist ready.
- Quality inspector informed of expected first-piece time.
Completing this list before stopping the machine is often the single biggest SMED gain.
Involving operators and setters
The people who perform changeovers know where time is lost. Involve them in filming, analysing and redesigning the procedure — and let them propose improvements. Changeover teams that own the new method sustain it far better than those handed a procedure from engineering.
Frequently asked questions
Does SMED mean changeovers must take under ten minutes?
'Single-minute' means a single-digit number of minutes as an aspiration. Any significant reduction is valuable; many plants halve changeover times in the first round.
Do we need expensive equipment for SMED?
Usually not at first. Most gains come from preparation, organisation and standard procedures. Quick-release clamps and pre-setting fixtures come later.
Which machine should we start with?
The bottleneck machine or the one with the most frequent and longest changeovers.
How do we measure changeover time?
From the last good part of the previous job to the first good part of the next job, at normal speed.
Can software help with SMED?
Yes. Recording every changeover's duration by machine, product pair and shift shows where to focus and whether improvements last.
How long does a SMED project take?
A first round on one machine — filming, analysis, moving external tasks and standardising — can often be done in a few weeks. Further reductions through equipment changes follow over months.
Should quality approval be part of the changeover?
Yes. The changeover ends at the first good part, so first-piece inspection is included. Having the inspector and gauges ready is part of good preparation.
