SMED is one of the lean tools and short for Single Minute Exchange of Dies. It is a collection of techniques that dramatically reduce the time for a change over.
History of Single Minute Exchange of Dies (SMED)
Single Minute Exchange of Dies (SMED) was developed at Toyota when it started competing with the American automotive manufacturers after Second World War. One of the main differences was that the American companies had many more press tools and machines than Toyota, and therefore did not waste as much time on change over every time a different product had to be produced in the line.
By 1970 Toyota had managed to reduce the changeover time for a 1000 ton press from over 4 hours to less than 3 minutes. This was mainly achieved through the work of Shigeo Shingo who was working at Toyota as a quality consultant under Taiichi Ohno.
What is Changeover Time
Many companies use same machine to produce several products. When a different product has to be produced on the machine, there is some downtime where it is being prepared for the next product. There are a few different ways to define the downtime which all a fine to use, as long as the same definition is used consistent and understood. If the same definition isn’t used consistently, then the improvements cannot be measured or understood.
- The time a machine is idle
- The time between last good part of batch A and first good part of batch B
- The time between normal running speed of batch A to normal running speed for batch B
Everyday Example of SMED
If looking at the process of changing a tire on a car, then for a normal person it can easily take more than 10 minutes. Compare that to how much time they use to change it on a Formula 1 car which is just seconds.
The way they do it is by using some of the similar techniques that is used in Single Minute Exchange of Dies (SMED). For example do as much of the process as possible before the car comes in, perform multiple steps in parallel and create an optimised and standardised process.
Benefits of SMED
From the name it may look that the greatest benefit is the reduced downtime of the machines, but there are several other benefits from implementing Single Minute Exchange of Dies (SMED).
- Increased capacity as less time is spend on changeovers.
- You can run smaller batch sizes due to the changeover times are reduced.
- Better flow in your production due to machines being down for far less time, this will support Just in Time (JIT)
- Increased flexibility as an urgent order can easier be fitted in.
- Lead times can often be reduced a lot from implementing SMED.
Implementing Single Minute Exchange of Dies (SMED)
When implementing Single Minute Exchange of Dies (SMED), it usually covers 8 areas that the journey goes through.
Before continuing with the steps, below are the definitions of internal and external activities.
- Internal Activities: Items than can only be done when the machine is not running
- External Activities: Items than can be done while the machine is running
Step 01 – Create List
- Create a list of dies, tools, fixtures, gauges and storage locations used for each changeover.
Step 02 – Review Process
- Review the process and list each step taken (with recorded times) from last good part of batch A to first good part of batch B.
- Each activity should now be categorised into following four categories.
- P: Preparation Activities
- R: Replacement Activities
- L: Location Activities
- A: Adjusting Activities
- Classify if they are internal or external activities.
Step 03 – Convert Internal to External
- Analyse of ways to convert internal to external activity
Step 04 – Standardise
- Standardise sizes and dimensions of machine parts and tools.
- Standardise functionality of tooling, fixtures and dies.
- Make setup operation uniform including clamping, cantering, dimensioning etc.
Step 05 – Clamps and Fasteners
- Use one touch functional fasteners
- Use interlocking methods
Step 06 – Jigs
- Use intermediate jigs to reduce external and internal setup times, with faster clamping and positioning.
Step 07 – Parallel Activities
- When two people perform tasks in parallel it reduce waiting time.
- Do an analysis on each person’s role and responsibility during the changeover to get them synchronised as much as possible.
Step 08 – Eliminate Adjustments
- Adjustment is when the limit switch is repeatedly adjusted at a new position. Eliminate this by using gauges to determine the exact position of the limit switch
Single Minute Exchange of Dies (SMED) is one of the lean tools, if you found it interesting then our 5S Training might be of interest to you. It is usually the first step to take when starting out with lean, as it creates the foundation for further improvements to be implemented.
Alternatively you can continue to our Quality Training page to see some of the other types of training we provide.Go to Quality Training