One-Touch Exchange of Die (OTED)

A big part of getting changeover time reduced to the point where it is a single-minute exchange of die (SMED), is figuring out how to do it with less motion. One-touch exchange of dies is an offshoot of SMED but is far more aggressive in what it advocates. Where SMED is generally considered to be done in less than 10 minutes (actually a single-digit minute exchange of die), OTED says that with continuous improvement, die change should get to the point where they are nearly instant. The one-touch target simply means that the exchange can be done with a single motion rather than multiple steps.

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Can one-touch exchange of die be accomplished? Absolutely. Should it be accomplished? That depends. Like all continuous improvement efforts, there is a cost to reducing changeover times. At some point, the question becomes whether there is value in continuing to spend limited resources on this type of improvement. As processes get better, it takes more and more effort to continue to improve.^[1]

Most companies are not at the point where going from a 6-minute changeover to a 30 second changeover will drive significant improvement. There are simply too many other, easier obstacles that should be addressed first. OTED is an advanced, challenging tool to take a great company to world-class or best-in-class status.

So, the point is to make sure that there is a need to drive down changeover. Look at the big picture when selecting where to spend your improvement efforts. There may not be a need to go past a certain point on the journey to OTED, because other parts of the system are slower. Reducing setup on a high-volume machine, for example, may not change the way the parts are transported to the point of use. Even if lot sizes got down to 1 with near-instant changeover, is there a way to get parts to the point of use one at a time? An improvement that doesn’t speed up the system is not really an improvement.

NOTE: Localized improvements are sometimes done as part of a bigger plan. An improvement may, on its own, not speed up throughput. But it may be a necessary change for another change to work.

There’s one more complication that comes with OTED. As they attempt to implement flow, Lean manufacturers often begin using smaller, dedicated machines at the point of use. This often negates the need for one-touch exchange of die. A new, dedicated, low tech machine arranged in a product-oriented work cell might remove more waste than a larger, centrally located machine capable of OTED. Plus, the small machines generally have lower upkeep and maintenance costs than big, complicated machines.

The bottom line with OTED, as with all Lean tools, is to not use them just for the sake of using them. Make sure you understand the flow of the system and gain a deep knowledge of the processes before attempting to use a sophisticated tool. Most companies have a lot of room to grow before diving into graduate-level Lean work.

Words of Warning About One Touch Exchange of Die

• Don’t go after OTED unless there is a compelling need. You should understand what will happen to the system when you get down to just a minute or so on changeovers. If you can’t predict how the flow will improve, you got other, more pressing obstacles.
• Make sure that you differentiate between automatic changeovers, and manual changeovers. Some machines are designed with quick tooling changes in mind. They often contain carousels with a variety of tools such as punches or cutting tools. In most cases, automation like this is fairly fast—just a few seconds to complete the changeover of a tool—but the machines are huge and expensive. While they can be good for some applications, they are not necessarily the best option in all cases.

Key Points About OTED

• SMED implies less than 10 minutes for a changeover; OTED generally means minimal motion for a changeover. In practice, at one minute, a changeover is likely to be nearing one-touch.
• One-touch exchange of die is a very advanced means of improving flow that often exceeds the requirements of a system. It is analogous to putting a jet engine on a car. Slow systems won’t make full use of OTED.

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