There is a reason why Heijunka is a block in the foundation of the Toyota House, or the Lean House as some call it. The short answer is stability in an operation. The rest of this article will show Heijunka Examples, then discuss what can go wrong without it. I’ll also share 4 Videos that further explain how to apply Heijunka and share several Heijunka Boards as example.
What is Heijunka?
The Toyota House, or the TPS House, is a great metaphor for the Toyota Production System. The TPS House is based on the idea that “A House Divided Cannot Stand”, Citing the great Abraham Lincoln, who is quoting from the Bible. This means that every part of the house has a role and has a specific purpose.
The foundation of the house is critical. A block in that foundation is Heijunka.
Heijunka is a Japanese term to describe “production leveling”. The distinction between “leveling demand” and “production leveling” is important because we cannot control demand. What we can control is the rate of workload – information, material, raw good, finished goods in fulfillment, or actual production – enters the operation.
Here’s an example:
Suppose you run an operation where you make small widgets (11 A), medium widgets (9 B), and large widgets (7 C). You follow a production schedule that looks like this:
Notice that the forecast requirements are met with 11 A widgets, 9 B Widgets, and 7 C widgets.
This is classic batch production. In this example, the company forecasts that their orders will mostly be A, then B, and then C will probably have the least number of orders, which is why there are much fewer C production hours.
The problem with this approach is the following:
- Suppose there’s a big spike in C widgets on Tuesday. This means the customer has to wait until Friday for the order to be fulfilled.
- Suppose the firm decides that the customer shouldn’t have to wait, then the production schedule is changed and an expedited order is created. This creates an overburden on the employee, overtime pay, and instability in the system.
- Suppose the expected demand for C falls, then we end up with more C widgets than the customer needed – overproduction.
- Suppose we find a defect in production for A widgets on hour 5. This means we’ve produced 4 hours of defective products.
In this example, the forecast requirements are again satisfied.
Notice how the production schedule of A, B, C is dispersed throughout the week. This approach creates a stable and predictable production schedule, less burden on the employee, fewer instances of overproduction, and the ability to fulfill demand during times of uncertain customer demand.
Why Heijunka is a Foundational Block in Lean
We’ve seen from the non-heijunka example above that there are several wastes that come from a non-level production environment. If what I say is true, then much of continuous improvement will be limited if there is no level production. In fact, in that environment most of the mental and physical energy is trying to figure out what is going on. Heijunka is a critical foundation of any application of Lean.
The Challenge of Heijunka
One challenge of Heijunka is in its application. Depending on the industry and business you are in, the application will generally need to adjust. But the principle remains the same – to level production, create stability andÂ predictability.
But to implement Heijunka, we need to first learn a little bit about the Pacemaker Process.
Don’t Forget the Pacemaker
To implement Heijunka, it’s important that you identify the Pacemaker process. Pacemaker is a misnomer in many ways because it doesn’t quite work like the Pacemaker you might find to help someone’s heart beat. The better metaphor for the Pacemaker Process might be that of a conductor of an orchestra.
So, the Conductor of the Orchestra Process is a better metaphor because:
- The conductor dictates which instruments get played and when
- The conductor dictates how loud the instruments need to be – when to get louder and when to get softer
- The conductor manages the coordination between the instruments
- The conductor sets the pace of the overall song
This metaphor works because that’s exactly what we want to the aspire to and identifying the Pacemaker Process is critical to the success of any Heijunka implementation.
Because Heijunka should be strategically placed at the Pacemaker process. Below is a 31 minute video that further explain Heijunka and shows how to implement it.
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Hey guys and welcome to the heijunka section of the stability series.
Now in this section we’ll be covering leveling, a basic heijunkaÂ calculation, as well as the basics of single-minute exchange of dies. ButÂ before we get started, I want to give you a little illustration aboutÂ heijunka.
Now, mura is the Japanese term for unevenness. Now, if you go to a groceryÂ store, you’ll notice that certain lines have more people in line thanÂ others. That is a form of mura. You’ll also notice that depending upon theÂ time of day lines will be longer and shorter. Again, that’s a form ofÂ unevenness.
So in a recent trip to Walmart, I noticed how they were attacking mura.Â They have a digital board that tells the customer which line to go to. SoÂ once the cashier clears the customer, a button is pushed and then theÂ digital board lights up with that particular cash register’s number. TheÂ next customer proceeds to that cash register. This is a way of eveningÂ lines and fighting mura.
So while I was at Walmart I was leafing through a Cosmo magazine and I cameÂ across the mura diet. Conventional knowledge tells us that we should haveÂ five to seven servings of breads and grains, four servings of vegetables,Â two to three servings of meats, and eat fats and oils sparingly.
The mura diet follows the same principle but over erratic periods andÂ quantities. So whereas the food pyramid recommends these foods daily, theÂ mura diet recommends that I eat all meats for two weeks, then switch toÂ grains and breads for eight weeks, and then to vegetables for one month,Â and then I can reward myself by eating pure lard for three weeks.
I decided to give it a shot and after a solid four months of the mura diet,Â I began noticing my body changing. It seems no matter how active I stayed,Â the pounds just kept piling on. This is me just six months after the videoÂ footage you just saw at Walmart.
How about a more leveled approach? Perhaps the old food pyramid made senseÂ after all. A heijunka or leveled approach with balanced meals, meals withÂ all food groups represented, eating frequently throughout the day and inÂ small predictable quantities would help me once again look like a GreekÂ god.
Now, this illustration about the mura diet may seem silly, but this isÂ often how we treat our external customers by batching their orders.Â Now, this is how we can use leveling to help our internal workforce.
Remember the paper airplane exercise? If you’ll recall, worker four had wayÂ too much to do with four folds while worker one had only one fold. TheÂ resulting system produced 57 pieces of WIP [SP]. We can redistribute workÂ and level-load the line to look like this. This is another way we can useÂ heijunka to fight mura in our internal processes.
If you’ll recall from our waste series, mura is the waste of unevenness.Â Now, we use heijunka to combat mura. Now, what do I mean by “unevenness”?Â We know that customers both external and internal can be erratic at times.
So we try to create an environment with even level pull so the customer canÂ pull what’s needed in a calm, even manner. We try to pace the timing inÂ which we replace those items that have just been pulled, and then we try toÂ sequence the items in which we’re replacing in a calm, even manner.
So this is what I mean by level pull. If you recall from our inventoryÂ section, the customer is given the option of taking any color plane fromÂ finished goods. We create a pull friendly environment by giving theÂ customer the option to pull what is needed so he doesn’t feel compelled toÂ hoard. Whatever is taken, the system reacts in a calm, level manner toÂ replace those goods that were pulled.
Now, this is what I mean by level pacing. This system could be veryÂ volatile if we replaced the pace and production to react to short-termÂ changes. Level pacing teaches us that short-term changes in pace at whichÂ the customers pull are generally noise. And a sustained calm and level paceÂ producing the takt time is what is actually needed for long-term stability.
Finally, level sequence means we attempt to balance the sequence in whichÂ we replenish what has to be produced. So obviously customers don’t consumeÂ all of one product, green squares for example, then all red triangles.
So why do we produce this way? Using the level sequence, we mix the orderÂ in which we produce to align better with how the customers consumeÂ products.
Now, traditionally, efficiency was measured in high machine utilization.Â Now, when set-up times were 24 hours or more, it just made financial senseÂ to spread the cost of that set-up across a large batch of items.
Now, set-up times have since dropped, but people still keep that mentality.Â So they use machine utilization and they try to hide set-up across a largeÂ batch of items.
So you can see here, the bar represents the total material, labor, and set-up costs for producing a single item in a batch. Obviously, the set-up costÂ is very high and it would be wasteful to produce only one unit with suchÂ high set-up costs.Â So this is what our cost would look like if we produced five units afterÂ setting up. Notice the per unit cost has gone down. Now imagine if weÂ produced 25 units. You could see how one could easily fall into the trap ofÂ maximizing batches to hide set-up costs.
Now, you can see the relationship between set-up and batch size. Now, whatÂ some people try to do to minimize their set-up is to maximize their batchÂ size. That’s one approach. But the alternative is to minimize the set-upÂ time and then minimize the batch size to correspond to that smaller set-upÂ time.
So here’s our original diagram again. Now, if we apply set-up reduction youÂ can see the impact it has to the total cost model per unit. Once we reachÂ this state, we’re free to produce as many or as few units as we wishÂ because it costs just about the same to produce one unit, five units, or 25Â units. At this state, producing in smaller lots is to our advantage. ThisÂ is what I mean by scaling your batch size to your set-up time.
One of the biggest benefits to heijunka is the reduction in lead time. SoÂ this is what the lineup would look like without heijunka, and this is whatÂ it looks like with heijunka. So if I was waiting to receive a blue unit, IÂ would have to wait until the end of the production run. See how long thisÂ takes? Now, if the lineup was level, this is how long I would have to waitÂ for a blue unit, only a fraction of the time.
Now, another benefit is the reduction in liability when producing a defect.Â In my traditional model, let’s assume I got a blue unit and I found out itÂ was defective. I ‘d call the factory and they’d most likely find that allÂ the blue units in that production run were defective.Â Now, they need to produce an entire lot of blue units to replace theseÂ defects. Now, in the heijunka model the same blue unit could be defective,Â but only one was produced in the production run so it costs the company aÂ lot less to replace it.
A benefit related to defect liability is flexibility. In our originalÂ scenario, if one defective blue unit revealed that the entire batch of blueÂ units was defective, then the producer has very limited flexibility toÂ rework those defects.Â Long production runs of other color units would force the producer toÂ either break into the middle of another unit’s production run, or doubleÂ the batch of the blue units on the next run. Either way, this drives upÂ cost or waiting time for me as the customer.Â Now, in the heijunka model, the company has a lot more flexibility inÂ inserting a single blue unit into the production run. Placing a single blueÂ unit into the production run, or running a batch of two blue units, is farÂ less disruptive in this scenario than it would have been in the first.
We know that inventory ties up cash and too much can cripple a company. InÂ our original model this could be the case. Because, at any given moment,Â the production sequence could shift and we could find that the entire batchÂ is defective. We need to keep at least an entire batch’s worth of rawÂ material on hand.
Now, the same assumptions hold true for the heijunka model. But because theÂ batch sizes are so small, one piece in this case, we can hold far less onÂ inventory on hand than if we didn’t have the level production run.
This same scenario applies to finished goods inventory. The customer in ourÂ original state has learned that he needs to hoard product when it isÂ available because lead times are so long. This means, as a producer, weÂ need to hold a lot of finished goods because we have inadvertently trainedÂ our customers to behave this way.
Now, if we demonstrate to our customers over time that we can produce whatÂ is needed, when it is needed, quickly and in small batches, the customerÂ will learn that hoarding is unnecessary. This allows us to decreaseÂ finished goods inventory and free up cash.
Companies that successfully implement lean have a good grasp on static andÂ dynamic scheduling. A dynamic model is purely reactive. In our factoryÂ we’re very confident that customers order five of each color unit duringÂ any given month. We could, in theory, run five of each color in a row everyÂ month and this would satisfy customer demand.
But instead, our dynamic scheduling model functions like a giant black box.Â Orders go in and the black box tells us what to run next. As a result,Â there is little predictability as to how long it will take to beginÂ production on these green units. All we can tell you is that, on average,Â it will take 15 days before the first green unit will begin in production.
Now, this is average. Our system is dynamic, so you can influence it byÂ getting a regional sales manager involved, or by befriending the productionÂ manager. Then you’re lead time is one day. If the production managerÂ decides the high-five you gave him during the last golf outing wasn’tÂ convincing enough, then you’ll wait 60 days or more. This is why dynamic
scheduling is so dangerous.
Now, notice the static loop we have on the bottom. Having the discipline toÂ establish a static loop is what opens the gate for heijunka. As a quickÂ note, when I say static, I don’t mean you won’t have the leeway to makeÂ adjustments. You’ll need to adjust slightly over time to produce theÂ changes in customer demand.
First, five units of yellow, then five units of blue, then five units ofÂ red, then five units of green on a set, static cycle. This is set and noÂ amount of chumming up or threats will change this. Now if someone asks whenÂ they’ll see another green unit run, you can tell them in exactly 16 days aÂ green unit will pop off the end of the line. Again, locking down and having
the foresight to create a static schedule is the first step to makingÂ heijunka work.
Now let’s take it to the next level. We apply set up reduction so you couldÂ reduce batch sizes to lots of one piece. Now, in this static model, you canÂ see if someone just consumed their last green unit, they’ll need to waitÂ exactly four days before another green unit will pop off the end of theÂ line.
Notice we’re running in four day static loops in this scenario as opposedÂ to twenty day static loops in the original static loop without heijunka.Â Either case is much more advantageous to the dynamic black box you sawÂ previously.Â Finally, notice that 20 days if the absolute max lead time for any batch ofÂ any color in this static loop. In the dynamic model there is theoreticallyÂ no max lead time. This means your order may never make it through theÂ production system.
The final and most important advantage to leveling is shortening order-to-cash. In our original model, we have to wait until the end of the entireÂ production run of blue units to get paid for them all at once. But in theÂ second scenario, we can get paid faster and in smaller increments.Â Now, this may not seem like a big deal, but imagine if your company decidedÂ to start paying your salary once a year. Would you be fine with that?
Obviously, we’ve grown accustomed to getting paid weekly or bi-weekly inÂ small increments of our annual salary. Using that same logic, we need toÂ find creative ways to get our company paid faster and in smallerÂ increments.Â So again, traditionally, we like to run large batches. We like lowÂ variation. Again, people like villainize Ford by saying, “You can have anyÂ color, as long as it’s black.” Then we want to minimize the number of set-ups in a traditional run, and we always want to run the largest batchesÂ first in a mixed-model system.
To batch would be something like this. You visit a doctor and he tells youÂ that you need your tonsils out. The doctor tells you setting up theÂ operating room is very expensive, so you need to come back in the thirdÂ week of next month because that’s when he does all of his tonsil cases atÂ once.
Minimizing total set-ups would be something like this. The same scenarioÂ with the doctor but it’s expensive to set-up so he tells you to come backÂ when you need your appendix taken out, you have a broken arm, and he givesÂ you a good look and says, “You might want to think about that liposuctionÂ too.” This way I can take care of everything at once, and set up theÂ operating room once. Is this how you want to be treated as a patient?
Do you realize this is often how we treat clients when we push ordersÂ around and batch them in the name of efficiency?Â So this is the traditional approach to running production. Notice we’reÂ running four types of product: blue, yellow, red, and green. And we’reÂ producing all four types over four weeks. Traditionally, managers thoughtÂ that running the largest orders first was more efficient. So the blue unitsÂ are run first in this model.
Now, take a look at the little truck at the bottom of the board. This truckÂ takes one type of each unit to the client. Notice that the truck has toÂ wait until the end of the fourth week before it can complete an order andÂ take it to the customer. So to compute our heijunka ratio, we take the four types, divide it by four weeks, and this gives us a ratio of 1.0.Â So heijunka, or leveling, is measured in the form of E.P.E.X., which standsÂ for “every part every ‘x'”. So you have every part every month, every partÂ every three weeks, every part every week. It’s best to run every part asÂ frequently as possible.Â So in your mixed-model system, obviously running it every week is betterÂ than running it every month. Who knows? Maybe you can break this down andÂ run every part every day. The more you can reduce set-up time and reduceÂ batches; this number actually gets smaller, which improves your E.P.E.X.Â number.
Now, in a lean environment, we like to run in small batches. LeanÂ environments also thrive under high product variation. We try to maximizeÂ the number of set-ups, not minimize. And we like to level mixed products.Â Smaller batches actually run first, rather than last.Â Remember, running the smallest batches first gets us paid faster. So we’reÂ still running the same four types of units, but we’re running the greenÂ units first because there are only seven in total to produce.Â Now, take a look at the truck at the bottom of the board. It has all fourÂ types loaded by the third week of production. So our heijunka ration isÂ four divided by three, or 1.33. This is a 33% gain over the original run,Â just by sequencing production from smallest to largest.
So now let’s get into a real heijunka calculation. We know the monthlyÂ demand for each product. Each month the customer wants 20 blues, 9 yellows,Â 8 reds, and 7 greens. I divide these by four to get a weekly demand.Â Obviously, I can’t produce in fractions of units, so I round to the nearestÂ whole number. Then I multiply by four again to get a rounded month of whatÂ I need to produce.
Now I have to check my math to make sure I’m not producing too much or tooÂ little of one product. I check my rounded month versus my original monthlyÂ demand. I see that blue and red work out perfectly, but I’m producing oneÂ too few yellow, and one too many green, if I went with the rounded month.Â So I finally make this adjustment during the last week of production. SoÂ during the last week of the month, I’ll make one more yellow and one lessÂ green than I would in a normal week. The math rarely works out perfectly,Â so keep in mind that you have to have an adjustment period just like this.
So let’s apply our math to the production sequence. We’re still running theÂ smallest batch size first. We chose to run red before green because theÂ difference between the two is negligible.Â Notice the truck fills up with all four types of units within one week. WeÂ divide four types by one week and get a heijunka ratio of 4.0. That’s aÂ 200% gain from the second run and a 400% gain from the original.
So this is a very basic heijunka board. First thing you probably notice isÂ there are four different colors: red, green, yellow, and blue. TheseÂ represent the four different color points we built during the simulation.Â You probably also noticed there are four different columns: week one, weekÂ two, week three, and week four of production. So this board right nowÂ represents a full month’s worth of production.
Now, it works really simple. What I do is pull the withdrawal kanban, andÂ send it into the system. This triggers a red plane to be built. Now, theÂ next thing that we built, again, is another red plane. Send it into thisÂ system, it would come out. Followed by a green plane, and so on, and soÂ forth, for week one.Â So you can see that all these are pretty evenly sequenced right now so weÂ don’t have too much of one being produced at once. In theory, I couldÂ sequence this all over so all the blues are built at once, all the yellows,Â then all the greens, then all the reds.
But obviously, we want to balance and level-load what’s being producedÂ every week. So this is why they call this the “central nervous system” ofÂ our lean environment, because this literally controls the pulling, theÂ pacing, and the sequencing for the entire shop floor.Â Next I want to relate value and batch. Now, this is kind of tough forÂ people to swallow and people get upset at this. But, I contend, that onlyÂ the first piece in any batch is value-add.Â Now, if you don’t believe me, let’s take for a moment if you consider theÂ entire batch value-add. We would make a bigger batch, and that’s actuallyÂ opposite of what we’re trying to do. We’re actually trying to minimizeÂ batch sizes.
So if you believe that you realize there is waste in every batch. TheÂ customer only needs one right now, but they’re buying in the size of aÂ batch because that’s the size in which you produce it.Â Again, I know that’s a tough pill to swallow. Even though you’re changingÂ the form, fit, or function – which is by definition value – only the firstÂ piece in your batch is actually value-add. The rest of the batch is justÂ along for the ride. Keep this in mind, especially when you’re value streamÂ mapping.Â The time associated with producing the entire batch should not be taken as
value-added time. Yes, this means only a fraction of a second may be value-add for a lead time that takes months.Â So here are the major steps. First we need to understand demand. And don’tÂ just skim over this. Often times, if you study the data that the customerÂ is actually giving you, you can find that they’re a lot more predictableÂ than you think they are. Then we need to reduce set-up time using SMED.
Reduce batch size. Now remember, these two always go coupled. Don’t just doÂ set-up reduction. You have to reduce batch size to correspond to set-upÂ reduction, or else it’s pointless. Reduce inventory down the line, andÂ upstream. And then shorten the pay cycle.Â Remember, that’s what this all boils down to. Is owner’s diagram of order-to-cash, we have to compress that. Finally, rinse and repeat. Do this overÂ and over again.
So, Shigeo Shingo is the pioneer behind single-minute exchange of dies, orÂ SMED. Now, I love SMED because once you combine SMED with batch sizeÂ reduction, that’s when lean thinking really starts to take shape.
He started out in 1950 in a Mazda plant, and they were producing three-wheeled vehicles on three very large presses. He approached the plantÂ manager and asked if he could work on set-up reduction.Â This is where he developed the concepts of internal and external work. TheÂ plant manager wasn’t thrilled about this, but he went ahead and let it go.Â And seven years later, in 1957, he continued this work at Mitsubishi HeavyÂ Industries. And then, in 1969, he took it over to Toyota, where we see itÂ today.
Single-minute exchange of dies refers to the ability to change over aÂ machine that is running good product, to running good product of aÂ different type, in nine minutes or less. Single-minute refers to nineÂ minutes being a single digit of time.Â You’re probably already familiar with the pit stop example. During a race,Â a car stops at a pit stop for refueling and a change of tires. The crewÂ works to minimize this time.Â But how about an example that’s more time-critical? The U.S. military knowsÂ that seconds can be the difference between life and death on theÂ battlefield. According to tactical.com, 50-70% of all combat injuries areÂ extremity wounds. 60% of preventable combat deaths are from extremityÂ bleeding.Â Now, tourniquets have been used on the battlefield for centuries toÂ minimize the bleeding by constricting the area that has been injured. TheÂ issue is, during high-stress situations – such as combat – finding aÂ tourniquet often takes more time than is available.Â To mitigate this, the military now has built-in tourniquets in criticalÂ areas on the uniform. So there’s no need to search for a tourniquet. AÂ soldier can now immediately help an injured comrade.Â Obviously, we’re not dealing with a life-and-death situation in a factoryÂ environment. But, in order to reach a single-minute exchange of die level,Â you and your team have to come up with innovative ways to save preciousÂ seconds, just like these built-in tourniquets do.
So this is generally how set-up breaks down. You generally spend 5% of yourÂ time removing the old tooling, 15% of your time installing the new tooling,Â 30% of time preparing the new material and jigs, and 50% of your timeÂ trialing and processing. Obviously, trialing and processing is the largestÂ time bucket.Â So here’s a quick demo on how to reduce a large time bucket. So this etch-a-sketch is a simple machine that I use to introduce the concept of trialingÂ and processing. Oftentimes, operators rely on their senses to adjustÂ machinery. Some operators are excellent at doing this and repeatedly dial-in a machine to exact specs with little to no problems. Other operatorsÂ struggle and this causes wasted time, wasted material, and frustration.
So with this etch-a-sketch, I demonstrate that if you understand the knobsÂ and how they affect the machine’s output – the screen – you can replicateÂ any drawing with far reduced trialing and processing time.Â I’ve taken the liberty of marking each knob with a red line. This serves asÂ a reference point for me. I then calibrate the left knob. It turns out thatÂ one complete turn clockwise makes a line traveling right that is 3.4Â centimeters long. I turn the right knob 360 degrees, and this makes a lineÂ that travels up. This line also measure 3.4 centimeters long.
I then reset the machine and turned the left knob 180 degrees clockwise.Â This is to measure linearity. I expect the outcome to be a line travelingÂ right that is 1.7 centimeters long. I measure and this is correct. I do theÂ same for the right knob and get the expected result.Â So I reset the machine and do the same thing for both knobs, this timeÂ going counter-clockwise. I get all the expected mirror-image results. NowÂ that I know how the machine behaves, and the knobs have been quantified, IÂ can replicate any image with a reduced time in trialing and processing.
So this image presented here is complex. Now, I could take the traditionalÂ approach and mimic what I see using trial and error. But instead, I takeÂ detailed measurements and write down my action plan.Â Here is my action plan, complete with sequence, magnitude, and direction IÂ have to move each knob to replicate this drawing exactly. At this point, IÂ could literally replicate this drawing with my eyes closed.Â As you can see, the resulting image I made is identical to the one I wasÂ presented with. Quantifying and labeling knobs creates a science out of an
art that was known as “trialing and processing”. It also decreases theÂ training time needed on any machine.Â So this is an illustration of the lean continuum. Now, it’s been myÂ experience that all companies start out doing the obvious things, like 5S,Â and T.P.M., and value stream mapping. They also all do SMED.Â Now, some companies notice that with the 5S, and the T.P.M., and the SMEDÂ that they’ve done, they’ve had limited financial gain. I consider SMED toÂ be the critical fork in the road that separates the men from the boys inÂ the world of lean.
Companies that see SMED as a final destination and never couple it withÂ batch size reduction and heijunka, never grow up. They inevitably veer offÂ the lean path and wonder why it never worked for them.Â SMED is nothing more than a methodology that enables you to reduce batchÂ sizes and balance your production load. Again, if you have no intention ofÂ coupling SMED with batch size reduction, you should seriously consider yourÂ lean journey.
I mentioned that some consider SMED as a methodology to reduce lead time.Â This is absolutely false. The black bars represent set-up time betweenÂ batches. Let’s assume the lead time is 20 days and each black barÂ represents 60 minutes of set-up.Â Let’s say work like crazy on SMED and you reduce your set-up times from 60Â minutes down to 6 minutes. The result is, you only reduce your lead time ofÂ 20 days by 3 hours. Now do you see why SMED alone has almost no impact onÂ lead time?
Now imagine you reduce your batch size and level-load your production withÂ your new six minute set-ups. You reduce your 20 day lead time by 16 days.Â Your new lead time is now only four days.Â So back to Shingo’s definition of internal external work. Internal work isÂ work that has to be done while the machine is off. External work areÂ actions you can take while the machine is still running.
So in washing dishes, an example of internal work is loading and unloadingÂ dishes. You can’t do this while the machine is running. But, while theÂ machine is running, you can pre-soak the next set of dishes to be washed.Â This is an example of external work.Â Here are the major steps to SMED as defined by Shingo. First of all, all ofÂ your tasks for both internal and external will be mixed throughout yourÂ productions procedure. You should then clearly separate those that areÂ internal and external tasks. Then convert as much internal work intoÂ external work, then reduce all remaining activities. You finally want toÂ standardize.
When evaluating a set-up, I always watch the person and take detailedÂ notes. Those tasks that are obviously not adding value with respect to set-up, I segregate and eliminate immediately. This way, I start with a cleanÂ state when using Shingo’s five steps.
So again, the first step is to recognize that internal and externalÂ activities are mixed. Don’t just skim over this step, because it isÂ important for your operators to realize that there is a lot of opportunity,Â even if this is your second or third wave of SMED. Classroom exercises,Â examples from other companies, and free, high-quality SMED videos foundÂ online help in getting the ball rolling.
Next is to clearly separate those items that are internal and external.Â It’s important to challenge every single step. As a facilitator, you needÂ to ask, “Does the machine really need to be off for this step?” You may beÂ surprised as to how many steps can actually go into the external bucket ofÂ activities.
You then want to convert internal work into external work. You can oftenÂ purchase cheap alternatives to allow you to perform work externally. ForÂ example, this die-cast company. Prior to SMED, they had to wait two hoursÂ for the dies to heat up when performing a set-up. Then an operatorÂ suggested that the dies be heated externally.
This raised some eyebrows, but a quick trip to Sears and few hundredÂ dollars later, the dies were being heated externally in this cheap, homeÂ oven. And the company was indeed saving two hours per set-up on this multi-million dollar machine.Â So there’s still opportunity to make improvements. I’m big on quantifyingÂ knobs on your machines. Operators often have a great feel for what knobsÂ do, but they rarely truly know how the machine behaves. That’s why it’sÂ important to study your machine and understand what the knobs do, just likeÂ this etch-a-sketch.
Also, you encourage your operators to make adjustments while the machine isÂ off. Needlessly running while making adjustments is like letting the waterÂ run while you brush your teeth. Although the primary metric is timeÂ savings, material savings is also very helpful.Â This is perhaps the hardest part of any lean effort. Everybody always wantsÂ to revert to their old way. Make sure you carefully capture the standardÂ sequence for set-up and monitor operators as they work through the newÂ routine.
Growing up in Florida, I loved being on the water, and fishing is one of myÂ favorite pastimes. Believe it or not, fishing is a lot more science thanÂ art. On one fishing trip, we were catching far more tarpon than any otherÂ boat out there.Â One boat later approached us and asked how we were so quickly able to zero-in on the depth, tackle, and the bait to use. I showed them my standardizedÂ sheets that allowed us to reduce the time of trial and error to allow us toÂ pinpoint fish in less time. I explained that starting out with a largeÂ standard array of options, then eliminating those choices that are notÂ working in a standard manner, helps us catch fish faster. He was notÂ impressed.
So in this demonstration, we’re reducing the set-up time of the gas pump.Â When performing SMED, I always have a copy of the tasks that are beingÂ performed. I record the actions. I have a spaghetti and a meatball chart,Â and of course, a timer. I also use a pedometer to capture the number ofÂ steps I take. This gives me two solid metrics to improve. You can pick up aÂ cheap pedometer for about $10.
Now, walking may seem trivial to you, but I’ve measured operators literallyÂ walking two miles during a set-up. Remember, set-up time is the elapsedÂ time between good part to good part. In the example you see here, it’s theÂ time that elapses between the last green square and the first red triangle.Â In our example, it’s the time that elapsed between the last drop of gasÂ that goes into the car in front of me, and the first drop of gas that goesÂ into my car. So the clock starts the moment he stops pumping gas. As aÂ quick side note, 30 seconds elapse before he pulls away and my car is inÂ position. I start by paying for my gas. We have a lot of love bugs inÂ Florida, so I always start by washing my windshields, both front and back.Â Now, I personally always start by washing my windshields because I findÂ that I always forget when I pump gas first, and I don’t feel like gettingÂ back out of the car to do this. You can see that the sponge doesn’t holdÂ much water, so I have to keep walking back and forth to the bucket. I comeÂ back and open my gas cap and begin filling my tank. Now, by definition, theÂ moment I start pumping gas, the set-up time is over.
But let’s continue with this exercise to see the total elapsed time. ThisÂ takes a minute or so, but after I’m done, I replace the pump and close theÂ gas cap on my car. A total of five minutes and thirty-six seconds elapsesÂ from the moment the previous guy stops pumping gas, to the second that I’mÂ ready to pull away. My pedometer shows me that I took a total of 88 steps.Â So let’s follow Shingo’s five steps to reducing set-up time.
So this is step one. Obviously, internal and external tasks are mixed. IÂ recognize this and I’m ready to improve.Â So, step two. Can I pay for gas while the pump is running? Sure I can.Â While the guy in front of me is pumping gas, I can go pay in advance, soÂ this is an external task. We have to go through a number of steps to washÂ the windshield.
Again, does the gas pump have to be off in order for me to wash theÂ windshield? Yes, because I can’t hold the gas handle and wash the windowsÂ at the same time. So all the tasks associated with washing the windshieldsÂ have to happen while the gas pump is off. So by definition, these areÂ internal tasks.
So how about opening the gas cap? I can do this while the previous guy isÂ pumping gas when I go to pay for my fuel. So this is task is alsoÂ externalized.
Next, pumping gas is by definition an internal task because the machine isÂ running. Now, how about closing the cap when I’m done? Well, I can’t doÂ that while the previous guy is pumping gas, nor can I do it while I’mÂ pumping gas.
But, I can pull away and do it while the guy after me is pumping gas. So IÂ can externalize this task and do it after I free up the gas pump. IÂ definitely don’t want to get back in the car while the gas is pumping, soÂ this remains an internal task.
The next step is for me to convert as much internal work to external workÂ as possible. So I notice there is a little tab on the handle of my gasÂ pump. This frees me up to wash the windshields while I’m pumping gas.
Remember from our history lesson that the Toyota family created a loom thatÂ would automatically stop when a thread broke. This freed up workers toÂ perform other tasks while the machine was running.
This handle works the same way. It stops once it detects that the gas tankÂ is full. So I can safely externalize all the tasks associated with washingÂ my windshields.
Step four is to minimize the internal and external tasks. Now, I don’t seeÂ many internal tasks I can minimize, but there are some opportunities in theÂ external tasks. Particularly around washing the windshields. I take a lookÂ at my spaghetti and meatball diagram and notice that the majority of theÂ numbers are tied to me walking back and forth to the bucket to wet the
sponge on my wiper.
What if I invested $2 and bought a spray bottle, and filled it up withÂ soapy water? I wouldn’t have to walk back and forth to the bucket anymore,Â saving me many steps. It would also get my windshields cleaner, because IÂ wouldn’t be dipping the sponge back into that filthy water. So armed withÂ my new sequence, I give my new, improved state a go.
Having a set, standard sequence is the last step. I carefully study myÂ sequence and begin. First, I go pay and open my gas cap while the previousÂ guy is pumping gas. Like in the original scenario, 30 seconds elapsesÂ before I pull in and I’m ready to go.
Because my gas is paid for and the gas cap is open, I can begin fuelingÂ right away. I use the tab on the handle. Now I can go wash the windshieldsÂ while the machine is running. I already have my spray bottle out, and IÂ walk over to the wash bucket to get the wiper. I wash the windows with theÂ exact same level of care as I did in the first scenario.Â Eventually, the gas handle clicks, indicating that refueling is complete. IÂ return the wiper to the wash bucket and I put the gas pump away. I refrainÂ from closing the gas cap until I pull away because this is an externalÂ task. I pull away, and then close the gas cap.Â We completed all of our tasks in a minute and fifty-nine seconds in thisÂ run. This is a 64% reduction from the original five minutes and thirty-sixÂ seconds. My pedometer says I took 22 steps this time compared to 88 stepsÂ originally. This is a 75% reduction in steps. I think the $2 spent on aÂ spray bottle will pay for itself in no time.
Now, this little exercise doesn’t do a full SMED-kaizen event justice, butÂ hopefully it opens your eyes to opportunity that you may not have seenÂ before.Â So here’s a quick review of what we’ve learned. We reviewed mura and weÂ learned that heijunka can be used to combat mura. We learned aboutÂ production leveling and product leveling. We learned about single minuteÂ exchange of dies and how this links to batch size reduction and leveling.