Single-Minute Exchange of Dies (SMED)

Single-minute exchange of dies (SMED) is a strategic process that reduces the amount of time to complete equipment changeovers. It's made up of five steps:

1. Identify the process needed
2. Remove all external elements from internal elements
3. Convert internal activities into external activities
4. Create and standardize the process
5. Continue training your team

Some organizations expand this to six, seven, or more steps, but the basic principles are the same. It begins with discovery, then trimming down the process, then standardizing and streamlining everything to the fastest level possible.

That’s the process in a nutshell, but there’s much more behind each step that we'll break down later in this post.

History of SMED

The founding ideas behind SMED came about in the 1950s and 1960s when equipment changeovers were very common. Shigeo Shingo, a Japanese industrial engineer, is credited as the father of SMED and did much of the pioneering work. 

In simplest terms, SMED is designed to bring the time needed to complete equipment changeovers into the single-digit numbers. While different companies have different needs, the SMED process remains the same across industries. 

Common SMED Results

Some common outcomes of SMED include:

• Reduced changeover times
• Money saved by eliminating or highly reducing downtime
• Greater employee satisfaction
• Smaller lot sizes, which lead to a faster turnover time
• Improved customer satisfaction
• Less equipment downtime
• Smoother startup processes 
• Lower manufacturing costs 

All of these benefits play into the lean manufacturing mindset: maximizing customer value while minimizing overall waste. Lean manufacturing is probably the best umbrella strategy to use SMED in tandem with, though it’s not the only pairing. Others include total productive maintenance, CMMS software, and any other overarching strategies that focus on that or similar goals. 

That said, SMED works best with lean manufacturing. 

Using SMED for Lean Manufacturing

The SMED process stays the same, no matter what. However, the elements do change depending on the situation. Lean manufacturing has a more specific set of SMED steps. 

It’s important to note that this is an outline of the major steps of SMED, not an ultimate checklist or other “must-do” list. We've also included specific steps that work well with lean manufacturing, but may not work well with other strategies. 

1. Identify the Process Needed

It's important to ask yourself these questions when applying SMED steps to lean manufacturing. What's going on right now? Where are the longest delays and the fastest turnarounds? Do you need new processes, or do you need to adjust what your organization is currently doing? Is everything up to standards and meeting requirements? What do the current processes achieve or block for the company?

During this step, the most important thing to do is to separate the human elements from the mechanical elements. These questions can help you make those determinations.

2. Remove All External Elements From the Internal Elements

In this case, external elements are tasks and procedures that can be accomplished when the machine in question is still operating. Internal elements, on the other hand, are tasks that must happen when the machine is shut down.  

After all the extra elements are removed from the internal elements, you will have a much better picture of what's slowing you down, and what can be eliminated from your changeover processes. 

3. Convert Internal Activities to External Activities

Are there internal processes that can be converted into external activities? This is the question that guides this entire step, and for good reason. Anything that can be converted into external activities frees time and resources up for quick changeovers. 

This is a good time to really dig into your activities and see which ones need to have the machine shut down. Are there activities where it's more convenient to pause?

4. Create and Standardize the Process

Now is the time to standardize your process for each particular piece of machinery in question. This step usually goes through a few iterations before reaching optimal levels. Ensure all team members are on the same page by creating an established communication flow across team members. Project management tools can help all team members align and execute tasks with efficiency.  

5. Continue Training Your Team

Finally, once the process is standardized and set in place, new teams must be continually trained in order to keep the optimal changeover time. Without this training, the machine can't compensate and the process falls apart.

It's a good idea to have the previous team train the next team in order to keep the knowledge within the employees and their experiences. 

Benefits of SMED

Quick Results

The biggest benefit of this process, when applied to lean manufacturing, is how quickly it can change turnover times. As its name indicates, when everything is applied properly, the minutes between equipment changeovers can get down into the single digits.

Elimination of Waste

It's also great at eliminating waste both internally and externally during the manufacturing process. It keeps companies on track when they commit to lean manufacturing and helps employees focus on faster changeover times and more efficient processes. 

Streamlined Processes

Finally, the last major area where SMED can impact your organization is by providing the tools to help you understand how your plant is performing. When the five steps of SMED are followed, processes become simpler and streamlined almost immediately. And this is a huge benefit, particularly in complicated manufacturing situations.

Limitations of SMED

On the other hand, many of the limitations of SMED center around the fact that it's designed for manufacturing systems. It focuses on large assets with recurring or one-time work orders. 

There's also a distinct lag time that can never fully be eliminated, particularly when humans are deeply involved in the process. 

Perhaps the biggest limitation of the system is that it's heavily dependent on all the steps of the process. There's no room for half measures or skipping one step over another. In order to bring SMED to its completion, all the steps must be carried out to the very best of the company's ability. And this depends on the employees and leadership in question.

For example, consider a situation where not every external factor has been considered by management. This hinders the entire process from the beginning all the way to the end. It's not the fault of the process; rather, one should examine external factors that were not considered in the beginning.

Other common situations include untrained employees, outdated or overrated company policies, overextended leadership, and failure to streamline processes appropriately. 

How do companies make sure that all the steps are being followed appropriately and that the process is implemented correctly? One of the easiest ways to make sure that this happens is a checklist. 

Basic SMED Checklist

In order to create a basic, generalized checklist, we've organized a series of questions under each step of the process. This keeps each step in its correct order and maintains the integrity of the process across its entirety.

1. Identify the Process Needed

• What is the current process?
• Is the duration of the changeover long enough to make SMED practices viable?
• Will the changeovers happen frequently enough to make new processes more efficient than the old ones?
• Are your employees engaged, motivated, and invested in the change?
• Will there be sufficient return on investment? 

2. Remove All External Elements From the Internal Elements

• Can the element in question be performed while the machine is running?
• Do the people running the project understand the difference between external and internal elements?
• Have all the tools, documentation, and processes been examined before moving to the next step? 

3. Covert Internal Activities to External Activities

• Can this effort or process happen when the machine is running? 
• If it can, why hasn't it been done while the machine is running in the past?
• If there's a way to make an internal element external, what would it take to accomplish? 
• Will it be worth it to switch the internal efforts in question to external efforts?

4. Create and Standardize the Process

• What steps will be repeated each time? 
• Which steps will only be repeated occasionally?
• What is the fastest way to get the work done?
• What is the most efficient way to reach completion?
• Where is the medium between the above answers? 

5. Continue Training Your Team

• What steps can be cut out of the process altogether?
• Are people adequately trained?
• Does the team understand the process and the practices behind implementing SMED on their machines?
• Can motions be eliminated? Can waiting be eliminated? 
• What can be standardized? What does not need to be customized?
• How can we get this done in less time?

SMED Examples in Lean Manufacturing

Probably one of the simplest examples that's used to demonstrate SMED practices is the classic example of a racetrack driver, their car, and their team. The faster they can make the needed repairs, the faster the driver can get back on the track and go. There's a lot of motivation there to streamline the process down to single-digit minutes. And that's what SMED is all about. 

When companies want to see what results look like, the implementation of SMED in an automobile factory setting is a great place to start. These factories ideally make thousands of parts in the exact same way in the exact order every single time. The time needed is calculated down to fractions of a second, and when something goes off schedule, it can dramatically affect the completion time needed by every part of the product.

Another great example is in the plastic injection molding industry. Many of these factories are fairly new, given the nature of the industry. They haven't had a lot of time to build up processes, regulations, and other common situations that drag a factory down. Many manufacturers are leveraging this new field of opportunity into higher and higher rates of speed and efficiency. And a lot of this is due to SMED practices.

However, these examples may not apply to you and your manufacturing needs. This brings us to the final question.  

Should You Use SMED for Your Needs?

At the end of the day, the answer is that it depends. If your factories, manufacturing plants, or other large-scale operations use processes that cycle or repeat a number of tasks, the answer may be yes. These cases can generally benefit from faster, more efficient processes. 

However, if these are not challenges that you're facing, it may be better to simply optimize the practices that you already have in place instead of adopting SMED.