What is the Single-Minute Exchange of Die (SMED)?

What is Single-Minute Exchange of Die?

However complex an idea the name may suggest, SMED is a simple concept of minimizing the changeover times in the production of different goods at the same workstations. It’s one of many techniques aimed at reducing waste and delivering products quicker, that Lean practitioners use.

A die is one of the most commonly used manufacturing tools, typically customized to the produced item’s needs. According to SMED, the exchange of tools when moving from manufacturing one part to another should take less than 10 minutes - so a single-digit number of minutes.

The creation of SMED is attributed to Shigeo Shingo’s expansion of the Quick Die Change method, which Taiichi Ohno had implemented at Toyota before him. As a result of both of their efforts, between the 1950s and 1990s Toyota’s tooling changeover times have seen a decrease from hours to single-digit minutes, which was astounding.

How to implement Single-Minute Exchange of Die?

The key to achieving SMED is making the bulk of the tools exchange process external, as in quickly swapping out completely different parts, rather than re-setting one to serve various purposes at various times.

Step 1: Identify and separate internal and external operations

Observing how the changeover process works right now should make it possible for you to differentiate those actions, taking which requires the production to stop - internal operations, from those that can be done outside of the currently running process - external.

Example Being able to externally prepare a mold for a currently working machine facilitates a product changeover without stopping the production. Having to then stop the process to install the new mold counts as an internal change operation.
Operations that typically can be externalized in the first place, to stop cutting down the machines’ run time, are the inspection of done parts for quality and cleaning removable machine elements.

Step 2: Transform internal operations to external

The focus here is to convert as many internal processes as possible to external, starting with those, that have the biggest impact on the process’ halt time and work delay. It often means having to invest in new machinery or extra workstations, that will be able to organize the changing parts outside of their destination tools. Given the amount of time-saving taking and output increase this action can create, this is usually an investment worth making.

Example Let’s say you have a machine that has to manufacture 4 different products with various materials interchangeably, which means you need to have 4 swappable parts, each with its unique settings and controls. When the parts changeover time comes - rather than stopping the machine, fixing in the new part, applying its settings, heating it, running a test production, and then giving it the final go-ahead to operate, you could have an intermediary jig fitting and a test station for each of the 4 parts. Then, each of the parts would be always set and ready, leaving it to only require heating up and testing in the test station, right before the changeover. All that would be left to do during the machine’s downtime (the changeover time) would be to replace the whole jig with its settings applied and tested, not the small part itself. This could mean hours saved every week!

Step 3: Improve the remaining processes

It’s now time to streamline the relations between the changing and stationary equipment elements, including the removal of excessive or avoidable machine adjustments, cutting down any waiting time, unnecessary movements, transport, or control checks.
A commonly seen element of this step is also the standardization of the used tools and machinery so that fewer varied elements are used in general, resulting in less retooling needed.

Example If a removable part of a multi-function machine gets fixed in place with bolts, and then requires careful adjustment down to the millimeter, implement a clamping or quick-locking mechanism to remove and fix it in place instead, and create a set of numerical settings for the multi-function machine, i.e. setting 1 for part A, setting 2 for part B, and so on. Avoid forcing the team to perform the same manual adjustment scenarios with each changeover.

Focus on the right type of changeover improvement

It’s worth noting that SMED can be, to a point, achieved by changes of two kinds - to how people operate, and to how machines work.

When you’re just getting started with improving the changeover times, you may find that simply reshaping the way the team works can bring quick enhancements and at a low cost. A common example of this kind of improvement is just defining whose responsibility it is to manage a specific machine’s retooling. You can also assign more hands to the changeover processes, to speed it up - but there will be times when this, in itself will become a new form of waste.

Hence, you should not stop your SMED application there. A lot of the time-saving improvements can only be achieved by rethinking the way your equipment is dealing with change in operating modes - making parts swapping easier, creating workstations running in parallel to one another, or modularizing machines for better cross-part integration can all help.

SMED for Knowledge Work

Can SMED apply to knowledge work?

Possibly due to the Single-Minute Exchange of Die’s name alone, and possibly due to little overlap between the manufacturing and the strict knowledge work realms, the idea isn’t commonly applied to knowledge-based workflows. However, it definitely could also benefit the white-collar workers and their efficiency.

Of course, there are no magic keys, pressing which helps, let’s say, a scientific researcher switch their mind between analyzing a data set and writing a report on entirely another subject, both of which are one of their modes of operation and will sometimes need doing on the same day. But were the researcher to keep a visual representation of both of these processes’ states in front of them, achieving the required focus switch would, arguably, be easier.

The trouble in human context switching is somewhat similar to machine settings adjustments. It’s not so much that the worker has to recall where their report writing has stopped the previous time they were working on it, it’s that their mind has to readjust to now thinking about a different subject matter, a different form of work, and - very often - a different level of task difficulty. Keeping a record of all notes, to-do items, remarks, and suggestions in one place, separate for each project could help with subject switching a lot, by instantly dropping the researcher back into the “mentality” that they’ve previously associated with looking at this project.

What are the possible gains of running a SMED initiative in a manufacturing setting?

  • Increased speed of production, and hence a decreased inventory size
  • Reduced manufacturing costs
  • Higher flexibility to changing customer demand and the possibility of producing smaller batches
  • Safer working conditions

Just like any improvement initiative, the success of your Single-Minute Exchange of Die implementation lies with careful planning, communication, execution, and observation. Be sure to involve all the team members in the process and listen to their feedback.

Continuous improvement is one of the goals of Lean manufacturing, but don’t lose yourself in automating or mechanizing the changeover process too far. There can be times when the automation and externalization of operations could take your cost and efforts overboard, for very little additional time-saving. Try not to get carried away.