SMED; Shigeo Shingo's Single Minute Exchange of Die

Shigeo Shingo’s Single Minute Exchange of Die or SMED is the technique within lean manufacturing to reduce the setup or changeover times for your process, as the name suggests the aim is to literally reduce this time to single minutes.

This techniques has been developed within the Toyota Production System(TPS) by an engineer known as Shigeo Shingo, he started this process looking at changeovers of tools on 500Tonne Presses producing body panels. The tool change over could take several hours or even days, now they take a few minutes.

SMED is one of the tools that will help you to implement Just in Time production (JIT), without being able to reduce your set up times it will be impossible to run smaller batches to enable you to gain the many benefits of JIT.

I have experience of this in action having worked with these presses, a company that I previously worked at had managed to get a production line of 4 500 tonne presses to change completely over from last part of one component to the first good part of the next in just ten minutes. If you have ever seen these machines and the tools that weigh several tones in their own right you would wonder how this could be achieved.

I guess the most famous application of Shigeo Shingo's SMED or single minute exchange of die that most people have seen is that of changing a tire, how long does it take you to change your tires and how long does it take the formula one team in the pit lane to change all four of theirs?

SMED is all about removing those wasteful steps in the changeover process that will enable you to turn your production process set ups from being the road side tire change to the formula one race (business) winning change overs.

Within Lean Manufacturing and Just in Time (JIT) we are aiming to reduce the waste within the system, waste being one of three main areas as defined in Lean / Toyota Production System (TPS). The Waste of Muda (Non-Value adding), Mura (Unevenness) and Muri (Overburden).

SMED tackles all of these waste areas but it’s greatest strength is in helping us to achieve the elimination of Mura (Unevenness). To gain a smooth predictable flow and help us to meet customer demands we need to be able to process smaller and smaller batches, the biggest obstacle to having smaller batches is the change over time of our equipment.

Developed by Shigeo Shingo at Toyota, SMED is probably one of the most important lean manufacturing tools, if not the most important for enabling just in time production.

If Change over times are many hours then we try to maximize our output from these machines by minimizing the number of non-productive changeovers that we do, running as large a batch as possible to make the process “economical” to use.

The only way that we can make smaller batches possible is to reduce the length of time each change over takes, we need to minimize the setup as much as possible to the point where it is of little consequence to our process, this is where SMED comes into play.

The aim of SMED is to reduce the setup time to enable smaller batches to be run enabling Just In Time Manufacturing (JIT)and Kanban. The benefits of this are many fold;

We reduce the amount of cash tied up in stock.

We reduce the amount of handling and handling equipment required.

We reduce floor space required for stock.

We reduce lead times through our company.

We increase our flexibility to produce a variety of products.

We increase our Capacity.

We improve our quality.

We reduce scrap levels.

We reduce the level of operator skills required.

But most importantly we reduce costs and improve profits!

For a broader discussion regarding the benefits of lean manufacturing have a look at the linked hub.

We normally break SMED implementation down into seven steps, many of which are iterative, we repeat them over and over until we get to our target.

The aim of SMED is to reduce our setup down to single digit minute, less than 10 minutes, the quicker the better.

Implementing SMED is a team activity, involve those people from the process who actually conduct the change overs, cover all shifts worked so that you gain everyone’s perspective. Involve other people from other areas for alternate ideas.

The first stage of smed is to look at each step of the setup process and separate internal from external activities. Internal Activities are those activities that can only be done when the process is stopped such as unbolting the tool in the machine, whereas external activities are those that can be done whilst the process is still running such as fetching the next tool.

Do not rely on what should be done for the setup, go and actually watch it, if possible video it so that the whole team can watch it over and over analyzing each and every step of the process.

Record every step of the process and define if it is possible to conduct it as an external or an internal activity.

The second stage of Smed is to look at the identified activities that have been classified as external, those that can be done whilst the machine is still running and standardize them. We want to ensure that everyone conducting the setup does it in the same efficient manner, this is very similar to the first few stages of 5S or 5C. We need to make sure that everything we need is available, in the right place to be used and that the process is documented to ensure that we do it right.

The more that can be achieved whilst the process is actually running the less time the process or machine actually has to be stopped for. So if we can look at the activities that we have identified as being Internal and somehow convert them to being external then we can further reduce the setup time.

Some examples of this can be pre-heating dies or moulds before putting them into the machine so that you don’t have to wait for the machine to heat them (Formula One tires are heated to driving temperature before fitting so the driver does not have to wait for his car to get to temperature!).

Other examples can include having additional sets of clean common tooling that would otherwise have to be cleaned, setting cutters and other equipment off line, having “intermediate” fixtures to set and just slide in when the machine stops.

Shigeo Shingo once said “only the last turn of the bolt actually tightens it, the rest is just movement (waste)”, look at everything that is done as part of your internal activities and look at if they can be eliminated or made more efficient.

Bolts can be replaced with shorter ones, spring loaded clamps that are pushed into place, or wing nut headed versions that require only hands not tools and so on.

Location points can be made “more positive” so that things do not have to be measured or gauged into place.

Tools can be modified to give a standard fit to the machine.

Your teams imagination here is the limit, consider ever action, what is the purpose of it, do we need it, can it be done quicker, can it be done a different way.

Review what you have done in earlier stages and further improve on what you have done to improve change over times, look at your layout, sequence of activities, materials and tools required and placement. Again video and list out every step of what you do, what steps of the process are wasteful, just movement for instance. Review every step in the way you would for 5S considering each of the seven wastes.

At this point it is worth revisiting the entire process, beginning again at the first stage and repeating the entire process to see what additional improvements you can make.

This stage of the process is not always required or justifiable, in most cases you will already have achieved your single digit target for your changeover.

However in some rare instances you will need to consider actually mechanizing the process to achieve the saving that you require.

The ideal situation would be to totally eliminate the need for any type of changeover, how would it be if there was no need to ever make another setup?

This is achievable in some cases with a little thought and by going back into the design process. Often we can design out the need for multiple versions of a component and make do with only the one thus eliminating the need to make setup changes at all.

Another option is to look at the design of the process and tooling, for example instead of having several injection molding tools producing several components could they all be incorporated into one tool like an Airfix model aircraft kit.

The following are useful links for business support and lean manufacturing resources that may be able to provide you with more information or even physical help with Implementing SMED or any other Lean Manufacturing tools.

Manufacturing Improvements The Institute for Manufacturing at Cambridge University has a group dedicated to helping manufacturers to improve their processes. They can give you more information, often run seminars, and can even provide you with consultants to help you implement single minute exchange of die or other lean improvements.

Quality Institute Chartered Quality Institute situated in London has many publications which can help you with getting more information and can also point you in the direction of more tangible help and support.

American Quality Society American Society of Quality can provide help and support just as the UK version can.

Manufacturers Association American National Association of Manufacturers can provide you with support and guidance on many lean tools.

Business Innovation and Skills Improvement UK Department for Business Innovation and Skills can help you with finding trainers and consultants to implement SMED, they may also be able to provide you with funding.

Lean Manufacturing Improvements UK Manufacturing Advisory Service can provide you with training and even run projects for you to implement various lean tools including single minute exchange of die, their services are often free or heavily subsidized.

Business Improvements UK Business Link are another government body who can provide you with support, they may be able to access other areas and funds as well as the Manufacturing advisory service.

US Business Improvement US Business Link can help you with support and guidance in much the same way the UK business link can.

Toyota Lean Manufacturing and TPS Toyota as the birthplace of these techniques is always worth a look, you can see if they have made any additional advances.

Motor Manufacturers and Traders Society of Motor Manufacturers and Traders have many publications on subjects such as SMED and other lean tools as these ideas have been initially developed and spread through the automotive industry.

Automotive Industry Action Group Automotive Industry Action Group can provide you with help in the same manner as the SMMT above.

These Links will help you to find more information regarding Lean Manufacturing, Just in Time and Shigeo Shingo's SMED, Single Minute exchange of die to help reduce your setup times.