SMED stands for Single Minute Exchange of Die. Invented by industrial engineer Shigeo Shingo in Japan in the 1950s, this Lean process helps companies increase production efficiency by reducing changeover times between one process and the next.
The Basics of SMED in Lean Manufacturing
The simplest way to visualize SMED in action is to think of an F1 pit crew in auto racing. The process is so fine-tuned that it takes just seconds to change the “die”–or, in this case, the tires.
In a manufacturing environment, such speedy results can be achieved by following a standard SMED process.
Firstly, however, the concept of “single minute” doesn’t technically mean the changeover process has to take one minute. Instead, it encourages manufacturing teams to aim for a changeover in the single digits. Separate the elements of the process into steps that must be completed while the equipment is running, and steps that can be completed when it is stopped.
Production teams can further streamline the process by arranging the workplace for precision and efficiency. Teams can lay out the next die or tool ready to switch over immediately, eliminating waiting and wasted motion. Standard operating procedures and uniformity also reduce changeover times.
“Lean Production is considered to be an operational strategy oriented toward achieving the shortest possible cycle time…. This methodology often decreases the lead time between a customer order and shipment, and it is designed to radically improve profitability, customer satisfaction, throughput time, and employee morale.”
PWC
SMED Method
Single Minute Exchange of Die provides a rapid transition from one manufacturing process to the next, creating an incredibly efficient production line.
The formal SMED method follows these seven steps:
- Observe the current process.
- Separate internal and external activities–internal activities are only performed when the machine or equipment is stopped, while external activities are performed after the last run is completed.
- Convert internal activities into external–when possible, set up or prepare tools or parts ahead of time.
- Streamline, simplify, and standardize internal elements.
- Streamline external activities to take roughly the same time or effort as internal activities. This ensures you cut mura, or waste, due to unevenness. Quality Digest explains that “The Toyota Production System (TPS) further defines this waste as muda (nonvalue-adding), mura (unevenness), and muri (overburden). SMED tackles all of these waste areas, but its greatest strength is in helping us eliminate mura.”
- Document the new procedure, either manually or using CMMS maintenance software like MaintainX.
- Continue refining the changeover process, again and again, shaving off time until you can get the entire process under 10 minutes.
SMED Example
How Toyota Reduced Changeovers from 8 Hours to 3 Minutes
Toyota is one of the most famously efficient manufacturers and the epicenter of Lean production. With tool changeover processes that previously took up to 8 hours during the 1950s, Toyota focused on reducing setup times.
In the 1960s, by eliminating unnecessary steps, combining similar parts of the process, and simplifying the changeover, Toyota reduced die changes to 15 minutes. This process continued to be refined, with the time dropping to just 3 minutes in the 1990s.
Implementing SMED Methodology in Your Facility
Should you use SMED in your facility? While a result like Toyota’s may be hard to imagine, your team can likely shave substantial time off its changeover processes.
By implementing SMED, you can achieve greater efficiencies in your operation. The benefits of this Lean manufacturing approach include:
- Improved quality and consistency
- Decreased lead times
- Reduced waste and lower scrap levels
- Reduced work-in-progress stock or components and, therefore, less floor space required for inventory
- Less cash tied up in parts inventory holdings
How to Manage SMED in Your Manufacturing Plant
Observe the Process and Separate Internal and External Activities
Watch the entire process closely. Look at every step involved in the process, no matter how small, and write it down, categorizing each step as either internal or external.
Internal activities are only completed when the equipment, machine, or process is stopped, such as removing safety guards or sharpening a blade.
External activities are completed while the equipment is running. These activities can include checking documentation for the next batch, finding the new die, or putting the old die back on the shelf.
Convert Internal Activities to External
The more you can set up your process ahead of time, the less downtime for the machine. Therefore, try to bring as many activities as possible into the external stage, keeping the machine up and running.
Activities such as pre-heating dies, putting the new tool on a jig ready to shift straight into position in the machine, or getting a trolley or shifting equipment ready to go will all help streamline the process.
Simplify and Improve Internal Elements
Use guides, jigs, and engineering adjustments to improve the internal steps of the process. For example, swap out bolts for wing nuts that can be removed without tools. Or, modify base plate heights for different dies so they are uniform and don’t need additional positioning adjustment.
Consider every part of the process and look for better, more efficient ways to get the same result.
Simplify and Improve External Elements
Once you’ve streamlined the internal elements, shift focus to the external steps of the process. These steps are carried out while waiting for the run or batch to finish.
For example, altering the height of a trolley so you can more easily move the new die onto the machine eliminates the need to lift equipment. Placing visual guides such as floor tape or markers will help workers park the trolley in exactly the right position for a fast changeover.
Consider all the tools, paperwork, lifting and shifting equipment, and manual inputs required for the end-to-end process and assess where you can gain efficiencies.
Additionally, aim to balance the time taken between internal and external activities. A process heavily weighted in one direction creates unnecessary waste, so develop internal and external processes that take approximately the same amount of time.
Document and Refine the Process Using a CMMS
Maybe a paper notepad will technically do the job. However, using a digital CMMS tool like MaintainX will make it easy to share the new process with your team–a crucial part of SMED.
Implementing these new standard operating procedures via a CMMS is critical to making the process easily accessible for your entire team.
And, of course, continuous improvement is at the heart of all Lean approaches. The process should be continuously repeated and refined so that you can achieve even greater efficiency.
Ready to move your new standardized and efficient processes online? Try MaintainX for free.
Caroline Eisner
Caroline Eisner is a writer and editor with experience across the profit and nonprofit sectors, government, education, and financial organizations. She has held leadership positions in K16 institutions and has led large-scale digital projects, interactive websites, and a business writing consultancy.
