BASICS Model Assessment—SMED: Single-Minute Exchange of Die (SMED)
SMED is our third analysis tool (see Figure 13.1). During our past visit to Japan in 2017, we had a small discussion with Ritsuo Shingo. Not only was it fun talking to him about Japan and Toyota, it was eye-opening to see the pride with which he talked about SMED. Ironically, every company we have been to, no matter where in the world, people know of the term SMED. Seventy-five percent of the time, people can almost accurately name what the letters stand for; some get really close, but often they don’t know the true meaning. When he was much younger, and his father, Dr. Shigeo Shingo, was working with Taichi Ohno, he helped his father with this changeover concept. According to Ritsuo, it was he who named this profound discovery “SMED” that his father was working on. They were apparently up late working together on the English translation of the book and couldn’t determine an ideal number for SMED. Ritsuo told us that his father was a big fan of golfing and that in golf a handicap of less than ten is considered to be “really good.” Therefore, they agreed that the changeover should be less than 10 minutes. We then asked why he didn’t call it Single-Digit Exchange of Die, instead of using the word minute. He commented that would have been less confusing but saying the word SDED didn’t flow off the tongue like saying “SMED.” Thus, Smed was born. As we are big on the history of Lean, we found this a fun little tidbit of information, as this is a concept the majority of people have heard of, if they’ve entered into the “Lean World.”
Figure 13.1 The three analysis tools. (Source: BIG Archives.)
SMED Definition
SMED (Single-Minute Exchange of Dies) is a system for reducing the time to complete any type of changeover. The principle of SMED is to convert changeover steps from internal (when the machine is down) to external (performed while the equipment is running), and to simplify and streamline the remaining steps. The name SMED comes from the goal of reducing changeover times to single digits (less than ten minutes). Our definition for changeover is:
From the removal of the last good piece to the completion of the first good piece of the next lot.
This is a strict definition designed to drive the most improvement. This means once you remove the last good piece, if there is paperwork you must do, turn off the machine, or move the job in the MRP system, it all counts as part of the changeover time.
Clock Time
In Lean changeovers, we make a distinction between clock time and labor time. Clock time is the internal time it takes for the changeover while labor time is the total amount of labor involved in the changeover. In the NASCAR pit stop the clock time is 14.7 seconds.
Labor Time
To calculate the total setup labor time, we need to review how many operators are involved before, during, and after the setup. If there are seven people doing the changeover, we would calculate the labor time by multiplying 7 times the 14.7 seconds’ clock time, which equals 109.3 seconds, but we need to add in the time for the steps done to prepare for the pit stop changeover and what work was done after the car was back on the track. If you add people and can distribute the work accordingly, you can reduce the setup time. There is a Formula One® pit stop* that is 1.9 seconds with 22 people.
Internal Time
Another concept we use is internal time versus external time. In the pit stop example, anything done while the car is in the pit is considered internal time. Examples would be changing the tires or refueling. In our machining operations, this translates into anything that can only be done when the machine is stopped.
External Time
Back to our pit stop example … Anything we can do while the race car is going around the track is considered external time. For example, we can get the tires ready and properly located in the pit area ahead of time. For our machine this means gathering all the tools ahead of time, dies are preset so we basically never should leave the machine while setting it up.
Internal Time and Clock Time
So, if you think about it, the 14.7 seconds for the pit stop is only a measure of the internal time and does not include the time driving to or from the pit stop area on pit row. It does not include any external time. Why do we focus on internal time? Because this is the amount of time the machine, person, or asset is not available for use; that is, the car is not racing around the track or the machine is down. This means our SMED, or setup in less than ten minutes, really refers only to the internal time.
Four Components of Setup
The next step needed for setup analysis is to break down each step into its component part or category. Dr. Shingo describes this in his book A Revolution in Manufacturing: the SMED System.1 The four components and codes we utilize for setup reduction are the following:
1. Preparation (P) and organization
2. Mounting (M) and removing
3. Calibration (C), centering dimensioning, aligning, measurement, and testing
4. Trial (T) runs and adjustments.
SMED Process Steps (ICE)
The acronym we utilize for Dr. Shingo’s setup methodology is ICE:
1. Identify all steps as to whether they are performed on internal or external time.
2. Convert as many steps as possible from internal to external.
3. Eliminate, rearrange, simplify, or combine all remaining steps, the Omits process.
Types of Changeover or Setup Improvement
There are six generally accepted types of setup improvement:
1. Single-minute exchange of die (SMED)
2. One-touch exchange of dies (OTED)
3. No-touch exchange of dies (NTED)
4. Zero setup
5. One-shot (cycle) exchange of dies (OSED or OCED)
6. Eliminate the changeover completely
SMED
SMED stands for single-minute exchange of dies. This means the internal setup time takes 9 minutes 59 seconds or one can say less than 10 minutes.
OTED
OTED stands for one-touch exchange of dies. The implication here is we can change over in less than 100 seconds or we can changeover multiple machines with the touch of one button.
NTED or Zero Minute Setup
NTED stands for no-touch exchange of dies. The process is totally automated with no human intervention. Zero setup is generally accepted to mean setups requiring three minutes or less. It should be equal to setups that take less than one minute.
OSED/OCED
OSED stands for one-shot (cycle) exchange of dies. This means the entire cell is changed over within one cycle time externally, thus zero internal setup time.
Can We Eliminate the Setup?
Every setup reduction team and machine operator should not lose sight of the goal; to eliminate a setup completely. We have successfully accomplished these many times using the group technology matrix tool. Sometimes it takes some rather creative, or “out of the box” thinking.
Why Reduce Setup/Changeover Times?
We find the clock time of almost every setup can be reduced by 50% or more the first time. By reducing setup times, we gain the ability to increase capacity in the operation, and where the demand exists we gain the ability to produce multiple products in less time or what we call mixed model cells or lines. Let’s say we can decrease our setup times in the previous example to two hours to run each model, more often. The first argument we get is we are going to have to change the machine over more frequently. So, yes, we have more setups; but the setup time for all five models is now reduced from five days to ten hours.
Now let’s say we can reduce the setup time to less than ten minutes and want to run each model even more frequently. What does that do for us? We have even more setups but the setups for five models only consume 50 minutes of the whole day versus what used to take five days. Now there is time during the day, to run each of the five models every day. What does this do for our customers?
■ They don’t have to keep any inventory or wait days to receive their parts.
■ We can put a kanban of parts in our customer’s facility and replace it every day or two. Now where are they going to go for parts if your competitors lead times are longer than yours? Can you get a higher price if you manage their inventory for them; a value-added service.
■ You become much easier to do business with.
■ You realize increased machine utilization and capacity for more business and customers.
■ The overall cost of your parts has decreased and your profit increases.
■ No excess inventory to count.
■ No need for production control to keep track of the inventory since it no longer exists or a fraction of it now exists.
■ When the customer says they need to phase in an engineering change you tell them there is no impact or cost to them for the change.
■ You can now offer customers a price break on their product(s).
■ You’ve demonstrated the ability to meet customers’ changing needs.
SETUP Example
Let’s say we have to change a coffee pot over from caffeinated to decaf. At first, all the steps are on internal time because the coffee pot is down!
1. Empty out the pot—five sec
2. Refill the water reservoir—30 sec
3. Place reservoir into coffee pot—five sec
4. Empty the holder for the coffee into the trash—five sec
5. Clean the holder for the coffee—ten sec
6. Get the paper filter—five sec
7. Put in the paper filter—five sec
8. Measure out the decaf coffee—five sec
9. Put decaf in filter—five sec
10. Close the holder—one sec
11. Start the coffee brewing—one sec
12. Wait for coffee to finish brewing—60 sec.
Which Steps Could Be External?
■ For sure, we could have the filter with the decaf coffee ready to go. Savings 15 sec—internal to external.
■ We could have a separate reservoir already filled with water—savings 30 sec.
■ We could even have a second coffee pot and eliminate the changeover completely. Or we could switch to a Keurig and do one cup at a time. Now, other than unloading and loading the machine, the entire changeover is eliminated. We can also fill the Keurig with water on external time.
Omits ERSC
We go through every step of the setup and look to see if it can be omitted, converted from internal to external, rearranged, simplified, or combined. Once again, we can use leanEdit’s* Set Up Reduction tool to give us the ability to classify process steps as either Internal or External. As described in this section, Preparation and Organization, Removing and Mounting, Centering and Aligning and Trial Run categories exist for both Internal and External activities. The user can convert steps from internal to external, convert and improve steps, improve steps, and omit steps during the analysis. Graphical representations of current and future states develop real time and summary data is displayed for export (see Figure 13.2).
Figure 13.2 leanEdit setup summary sheet. Leanedit.com. (Source: leanEdit is the property of leanEdit LLC, 2017.)
External Checklist
The external checklist (see Figure 13.3) lists the steps we have identified as external in the analysis, which need to be carried out prior to the machine stopping or completing the last piece of the previous order or in this case prior to the people leaving the table. Our checklist might look like this:
Figure 13.3 Setup external checklist example. (Source: BIG Archives.)
■ Make sure silverware and dishes are prepared and ready.
■ Double-check for spots on glasses or silverware.
■ Make sure you have dirty bin ready and napkins are pre-folded.
■ (Note: We didn’t cut the overall setup time by the time it took to pre-fold the napkins but we cut the internal time which was spent folding the napkins and where the customer had to wait for their table.)
■ Make sure the carpet sweeper is in proper location.
If we make a video of the new system, then we have a great training tape to go along with the new standard work we have just created. We call this the golden video. If the setup we filmed was indicative of most setups then we just freed up 27 minutes of time per table. If the average guest spends 1.5 hours at the table then roughly for every three guests we have freed up an extra table. So, if we have demand, we have increased our capacity approximately 33%.
Dedicated Setup Teams
We find the use of a dedicated, knowledgeable setup person or teams can more than pay for themselves. However, for this system to work, as in all new Lean systems, there must be a process and procedure behind it with metrics, discipline, and accountability and continuous improvement built into the process.
Successful Setup Characteristics
These Are Just a Few of the Characteristics That Make the Pit Stop Concept Successful
■ Everyone knows their job.
■ Practice, practice, practice.
■ Use multiple operators (pit crew).
■ Focus on doing job steps in parallel.
■ They are dedicated to specific tasks and standard work is created for each person.
■ Lots of practice and training.
■ An external checklist is created and followed
■ 5S—that is, everything in its place prior to, during, and after the changeover.
■ A constant dissatisfaction with the current changeover time until it is zero!
A Couple of Other Points about Parts of a Setup
The final optimized setup process should only be composed of external preparation and organization steps and internal mounting and removing steps. So SMED, or less than ten-minute setups, applies to the mounting and removing steps involved in the setup, which is only internal time. Keep in mind, the overall setup time includes the external steps. Over the years we have discovered that if setup reduction is not driven at the plant manager level, it will not sustain.
What Is a Setup Really?
We often surprise people when we start to explain setup terminology and what constitutes a setup. Anytime we load or unload anything or change from one to another in any process, whether man or machine, it can be considered a setup. In almost every workflow analysis there are steps where the concepts of internal and external work apply. Consider the following—changing: from one person to the next in the grocery store, changing over the Xerox® machine, washer/dryer, one patient to another in an emergency room or surgery suite, classes at college, presidents every four to eight years, or loading and unloading a part in a machine.
Network of Process versus Operations Defined2
We would like to propose that analyzing just the setup/changeover axis will provide the following pieces of the Lean implementation:
■ Enabler for one-piece or one-patient flow or smaller batch sizes.
■ Immediately increases capacity.
■ Improved operator utilization.
■ Reduces labor costs.
■ Increases overall system reliability and predictability.
■ Enabler for chaku‒chaku.
■ Enabler for level loading.
■ Increased man-to-machine ratio.
■ Enabler for mixed model and ability to supply in sets.
■ Provides quick response to demand changes.
■ Less reliance on forecasting.
■ Capital asset utilization rate increases (if demand is there).
■ Reduces material handling.
■ Reduced inventories.
■ Smaller layout footprint.
■ Results in standardization.
■ Improved operator safety.
■ Improved patient/product quality.
■ Integrates mistake-proofing.
Total Process Optimization
Each tool discussed provides another piece of the puzzle required to achieve total process optimization (TPO). Using Lean tools enables one to understand and optimize what the operator does to the product as they move through the process. Just looking and fixing the operator axis piece of the network can yield as much as an additional 20%–40% productivity improvement. When combined with the product piece, which yields a 20%–40% productivity improvement, one can attain a 40%–80% improvement when converting operations from a pure batch environment to flow. The changeover improvement process is sometimes critical to being able to achieve these results.
Analysis Results as True One-Piece Flow Is Attained with Zero Setup
When one obtains true one-piece flow the product and operator pieces become essentially the same analysis. Take the following example: The operator reaches for a part, grabs and moves the part to the assembly and inserts it into the product, and repeats this pattern several times slowly moving the product down the assembly line.
From the product’s point of view, the TIPS analysis looks like this
|
B |
VA |
T |
B |
VA |
T |
B |
VA |
T |
B = Between-process storage while the operator reaching, grabbing, and transporting the part to the unit should take no more than one to two seconds.
VA = When the part is added to the unit (unit is having value added to it).
T = Transport—when the unit is moved to the next spot at the station (or to the next station).
From the operator’s point of view, the workflow analysis (WFA) is
|
P |
RW |
P |
VA |
VA |
RW |
P = Reaching for, grabbing the part, and moving it to the unit should take no more than one to two seconds.
VA = When the operator inserts the part in the unit (operator is adding value to the unit).
RW = Required work—moving the unit to the next spot at the work station (or to the next station).
So when placed on top of each other it looks like this
|
B |
VA |
T |
B |
VA |
T |
B |
VA |
T |
|
P |
VA |
RW |
P |
VA |
RW |
P |
VA |
RW |
Notice the value-added steps align perfectly. Therefore, theoretically one can never get to 100% value added.
Determining Potential Total Savings
Once we know which steps can be omitted or improved, we can take the labor time associated with those steps and convert it to dollars and develop a quick return on investment (ROI) to justify the improvement to management. In some cases, the improvements relate to safety and ergonomics and should just be implemented regardless of ROI. However, labor savings are not fully realized until such time as the personnel are removed from the area and put to work on something else.
Notes
1. Shingo, Shigeo. A Revolution in Manufacturing: the SMED System (Cambridge, MA: Productivity Press),1985.
2. Protzman, Mayzell, and Kerpchar. Leveraging Lean in Healthcare (Cambridge, MA: Productivity Press), 2011.
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* https://www.formula1.com/en/latest/features/2017/1/f1-quest-perfect-pit-stop.html.
* Leanedit.com. The author uses this software and has contributed ideas to its development. leanEdit is the property of leanEdit LLC, © 2017.