SMED — Single Minute Exchange of Die

SMED is a lean technique for reducing the time required to change over manufacturing equipment from producing one product to another. The goal is changeover time under 10 minutes ("single minute" refers to single-digit minutes). It separates internal activities (machine must stop) from external activities (can be done while running).

Why companies use it

·Shorter changeovers enable smaller batch sizes without increasing cost, improving responsiveness to customer demand
·Reduced changeover time increases machine availability, directly improving OEE
·Enables mixed-model production lines that can respond to demand variation without large inventory buffers
·Used in injection moulding, metal stamping, packaging, and semiconductor process equipment changeovers

What hiring managers look for

·SMED expertise is highly valued in environments where short runs and product variety are increasing
·The ability to film, time, and categorise changeover steps into internal/external is a practical analytical skill
·Understanding the four SMED phases (observe, separate, convert, streamline) shows depth beyond surface-level knowledge
·Results from a SMED project — time reduced from X to Y hours — are highly credible interview evidence

Typical interview questions

What is the difference between internal and external setup in SMED?

Walk me through the four steps of a SMED analysis.

A machine changeover takes 6 hours. How would you approach reducing it to under 2 hours?

What recording and measurement techniques do you use when analysing a changeover?

Describe a SMED improvement you have led. What was the changeover before and after?

Common mistakes

·Starting SMED by immediately trying to speed up internal activities, before first converting them to external
·Not recording the changeover on video — time studies taken by observation alone miss the nuances that slow operations down
·Focusing on the longest individual steps without checking whether converting internal steps to external would have more impact
·Neglecting the tooling and staging area design — most changeover time is in locating, carrying, and returning items
·Measuring SMED success only at completion of the project, not tracking whether gains are sustained

Real engineering example

A pharmaceutical packaging line had a 3.5-hour changeover between product batches. Video analysis showed that 70 minutes was spent on documentation that could be prepared while the line was still running (external), and 90 minutes on sequential cleaning steps that could run in parallel with two operators. By preparing documentation in advance and adding a second cleaning operator, changeover dropped to 68 minutes — an 67% reduction. Run rate for the shift increased by 22%.

Topics covered

SMEDchangeoversetup reductionleanOEEmanufacturingsingle minute

Related interview guides

Manufacturing Engineer →Continuous Improvement Engineer →