Most businesses are cyclical – whether the business is B-to-B or C-to-C. In other words, there will be spikes – or more accurate – there will be feasts and famine in terms of demand. Heijunka is the Japanese term in Lean Manufacturing which mean “Production Leveling” or “Production Smoothing”. Indeed, Heijunka is a foundation in the Toyota House for a reason.
Heijunka facilitates Just-in-Time (JIT). It does this for all departments as well as throughout the entire supply chain – across all suppliers. Heijunka reduces Muda, Muri, and Muda and improves production efficiency by leveling fluctuations in performance in the operation. Customer demand can bring about these fluctuations, or the operation itself with its inherent variation can produce fluctuations.
The Toyota Production System (Lean Manufacturing) uses Heijunka to solve fluctuations brought about by customer demand by assembling a mix of models within each batch, which ensures that there is an inventory of product proportional the variability in demand. For example, The Bullwhip Effect can be avoiced through Heijunka.
For cases where there is disruption in production flow, units and components are sequenced to be available at the right quantities at the right time, and using SMED to make sure changeover periods for really important and vital processes are as short as possible.
Heijunka Video Part 1
Hey guys and welcome to the Heijunka section of the stability series. Now, in this section we will be covering leveling, a basic Heijunka calculation as well as the basics of Single Minute Exchange of Dice. But before we get started, I’l give you a little illustration about Heijunka.
Now, muda is the Japanese term for unevenness. Now if you go to a grocery store, you will notice that certain lines will have more people in line than others. That is a form of muda. You also notice that depending on the time of day, lines will be longer and shorter. Again, that’s a form of unevenness. So in a recent trip to Wal-Mart, I noticed how they were attacking muda. They have a digital board that tells the customer which line to go to. So once the cashier clears a customer, a button is pushed and then the digital board lights up with that particular cash register’s number. The next customer proceeds to that cash register. This is a way of evening lines and fighting muda.
So while I was at Wal-Mart, I was leafing through a Cosmo magazine and I gave across the muda diet. Conventional knowledge tells us that we should have five to seven servings of breads and grains, four servings of vegetables, two to three servings of meats and eat fats and oils sparingly. The muda diet follows the same principle but over erratic periods and quantities. So whereas the food pyramid recommends these foods daily, the muda diet recommends that I eat all meats for two weeks then switch to grains and breads for eight weeks, and then to vegetables for one month and then I could reward myself by eating pure lard for three weeks. I decided to give it a shot and after a solid four months of the muda diet, I began noticing my body changing.
It seems no matter how active I stayed, the pounds just kept piling on. This is me just six months after the video footage you just saw on Wal-Mart. How about a more leveled approach? Perhaps the old food pyramid made sense after all. At Heijunko or leveled approach with balanced meals, meals with all food groups represented, eating frequently throughout the day and in small, predictable quantities would help me once again look like a Greek god. Now, this illustration about the muda diet may seem silly but this is often how we treat our external customers by batching their orders.
Now, this is how we can use leveling to help our internal workforce. Remember the paper aeroplane exercise? If you recall worker four had way too much to do with four folds while worker one only had one fold. The resulting system produced 57 pieces of whip. We can redistribute work and level load the line to look like this. This is another way we can use Heijunka to find muda in our internal processes.
If you recall from the waste series, muda is the waste of evenness. Now we use Heijunka to combat muda. Now what do I mean by unevenness? We know that customers, both internal and external can be erratic at times. So we try to create an environment with even level pull so the customer can pull what’s needed in a calm, even manner. We try to pace the timing in which we replace those items that have just been pulled. And then we try to 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 inventory session, the customer is given an option of taking any colored plane from finished goods. We create a pull friendly environment by giving the customer the option to pull what is needed so he doesn’t feel compelled to hoard. Whatever’s taken, the system reacts in a calm, level manner to replace those goods that were pulled.
Now this is what I mean by level pacing. This system could be very volatile if we change the pace and production to react to short term changes. Level pacing teaches us that short term changes in pace at which the customers pull are generally noise and a sustained, calm and leveled pace producing the attack time is what is actually needed for a long term stability. Finally, level sequence means we attempt to balance sequence in which we replenish what has to be produced. So obviously, customers won’t consume all of one product. Green squares for example, then all red triangles. So why do we produce this way? Using a level sequence, we mix the order in which we produce to align better with how the customers consume products.
Now traditionally, efficiency was measured in high machine utilization. When setup times were 24 hours or more, it just made financial sense to spread the cost of that setup across a large batch of items. Now setup times are since dropped but people still keep that mentality. So they use machine utilization and they try to hide setup across a large batch of items. So you can see here, the bar represents the total material, labor and setup cost for producing a single item in a batch. Obviously, the setup costs is very high and it would be wasteful to produce only one unit with such high setup costs. So this is what our costs would look like if we produced five units after setting up. Notice the per unit cost has gone down. Now imagine if you produce 25 units, you can see how one could easily fall into the trap of maximizing batches to hide setup costs.
Now you can see the relationship between setup and batch size. Now what some people try to do to minimize the setup costs is to maximize their batch size. That’s one approach but the alternative is to minimize the setup time and then minimize the batch size to correspond to that smaller setup time. So here’s our original diagram again. Now if we apply setup reduction, you can see the impact it has to the total cost model per unit. Once we reach this state, we are free to produce as many or as few units as we wish because it costs just about the same to produce 1 unit, 5 units or 25 units. At this state, producing a smaller lot is to our advantage. This is what I mean by scaling your batch size to your setup time.
One of the biggest benefits to Heijunka is the reduction in lead time. So this is what the lineup would look like without Heijunka and this is what it looks like with Heijunka. So if I was waiting to receive a blue unit, I would have to wait until the end of the production run. See how long this takes. Now if the lineup was leveled, this is how long I would need to wait for a blue unit. Only a fraction of the time. Now another benefit is the reduction in liability when producing a defect. In my traditional model, let’s assume I got a blue unit and I found out it was defective.
I’d call up the factory and they’d most likely find that all the blue units in that production run were defective. Now they need to produce an entire lot of blue units to replace these defects. Now in the Heijunka model, the same blue unit could be defective. But only one was produced in the production run so it costs the company a lot less to replace it. A benefit related to defect liability is flexibility. In our original scenario, if one defective blue unit revealed that the entire batch of blue units was defective then the producer has very limited flexibility to rework those defects. Long production runs of other color units would force the producer to either break into the middle of another unit’s production run or double the batch of the blue units on the next run.
Either way, this drives up costs or waiting time for me as a customer. Now in the Heijunka model, the company has a lot more flexibility in inserting a single blue unit into the production run. Placing a single blue unit into the production run or running a batch of two blue units is far 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. In our original model, this could be the case because at any given moment, the production sequence could shift and we could find the entire batch is defective. We need to keep at least an entire batch’s worth of raw material on hand.
Now the same assumptions hold true for the Heijunka model but because the batch sizes are so small, one piece in this case, we can hold far less inventory on hand than if we didn’t have the level production run. This same scenario applies to finished goods inventory. The customer in our original state has learnt that he needs to hoard product when it is available because lead times are so long. This means as a producer, we need to hold a lot of finished goods because we have inadvertently trained our customers to behave this way.
Now if we demonstrate to our customers over time that we can produce what is needed when it is needed quickly and in small batches the customer will learn that hoarding is unnecessary. This allows us to decrease finished goods inventory and free up cash. Companies that successfully implement lean have a good grasp on static and dynamic scheduling. A dynamic model is purely reactive. In our factory, we are very confident that customers order five of each color unit during any given month. We could in theory run five of each color in a row, every month and this would satisfy customer demand. But instead, our dynamic scheduling model functions like a giant black box.
Orders go in and the black box tells us what to run next. As a result, there is little predictability as to how long it will take to begin production on these green units. All we can tell you is that on average, 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 by getting your regional sales manager involved or by befriending the production manager. Then your lead time is one day. If the production manager decides the high-five you gave him during the last golf outing wasn’t convincing enough then you will wait 60 days or more.
This is why dynamic scheduling is so dangerous. Now notice the static loop we have in the bottom. Having the discipline to establish a static loop is what opens the gate for Heijunka. As a quick note, when I say static, I don’t mean you won’t have the leeway to make adjustments. You will need to adjust slightly over time to produce the changes in customer demand. First five units of yellow, then five units of blue, then five units of red, then five units of green on a set static cycle. This is set and no amount of chumming up or threats will change this.
Now if someone asks when they will see another green unit run, you can tell them in exactly 16 days a 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 making Heijunka work. Now let’s take it to the next level. We apply setup reduction so you could reduce batch sizes to lots of one piece. Now in this static model, you can see if someone just consumed their last green unit, they will need to wait exactly four days before another green unit will pop off the end of the line. Notice we are running in four day static loops in this scenario as opposed to 20 day static loops in the original static loop without Heijunka.
Either case is much more advantageous to the dynamic black box you saw previously. Finally, notice that 20 days is the absolute max lead time for any batch of any color in this static loop. In the dynamic model, there is theoretically no max lead time. This means your order may never make it through the production system.
Heijunka Video Part 2
Finally, notice that 20 days is the absolute max lead time for any batch of any color in this static loop. In the dynamic model, there is theoretically no max lead time. This means your order may never make it through the production system.
The final and most important advantage to leveling is shortening order to cash. In our original model, we have to wait till the end of the entire production run of blue units to get paid for them all at once. But in the second scenario, we can get paid faster and in smaller increments. Now this may not seem like a big deal but imagine if your company decided to start paying your salary once a year. Would you be fine with that? Obviously we’ve grown accustomed to getting paid weekly or biweekly in small increments of our annual salary.
Using that same logic, we need to find creative ways to get our company paid faster and in smaller increments. So again, traditionally, we like to run large batches, we like low variation, again people like to villianize four by saying, “you can have any color as long as it’s black.” Then we want to minimize the number of setups in a traditional run, and we always want to run the largest batches first in a mixed model system.
The batch will be something like this. You visit a doctor and he tells you you needed your tonsils out. The doctor tells you setting up the operating room is very expensive. So you need to come back the third week of next month because that’s when he does all of his tonsils cases at once. Minimizing total setups will be something like this. The same scenario with the doctor, you need your tonsils out. But it’s expensive to set up so he tells you to come back when you need your appendix taken out, you have a broken arm and he gives you a good look and says, you might want to think about that liposuction too. This way I can take care of everything at once and set up the operating room once.
Is this how you want to be treated as a patient? Do you realize this is often how we treat our clients when we push orders around and batch them in the name of efficiency? So this is a traditional approach to running production. Notice we are running four types of products. Blue, yellow, red and green, and we are producing all four types over four weeks. Traditionally, managers thought that running the largest orders first was most efficient.
So the blue units are run first in this model. Now take a look at the little truck at the bottom of the board. This truck takes one type of each unit to a client. Notice that the truck has to wait until the fourth week before it can complete an order and take it to the customer. So to compute our Heijunka ratio, we take four types divided by four weeks and this gives us a ratio of 1.0. So Heijunka or leveling is measured in the form of EPEX, which stands for Every Part Every X. So you have every part every month. Every part every three weeks. Every part every week. It’s best to run every part as frequently as possible so in your mixed model system, obviously running it every week is better than running it every month.
Who knows? Maybe you can break this down and run every part every day. The more you can reduce setup time and reduce batches, this number actually gets smaller which improves your EPEX number. Now in the lean environment, we like to run in small batches. Lean environments also thrive under high product variation. We try to maximize the number of setups, not minimize and we like to level mix products. Smaller batches actually run first rather than last. Remember, running the smallest batches first get us paid faster so we’re still running the same four types of units but we run the green units first because they are only seven in total to produce.
Now take a look at the truck at the bottom of the board. It has all four types loaded by the third week of production. So our heijunka ratio is four divided by 3 or 1.33. This is a 33% gain over the original run just by sequencing production from smallest to largest. So now let’s get into a real heijunka calculation. We know the monthly demand for each product. Each month the customer wants 20 blues, 9 yellows, 8 reds and 7 greens. I divide these by four to get a weekly demand. Obviously, I can’t produce in fraction of units so I round to the nearest whole number. Then I multiply by four again to get a rounded month of what I need to produce. Now I have to check my math to make sure I am not producing too much or too little of one product.
I check my rounded month versus my original monthly demand. I see that blue and red work out perfectly but I am producing one too few yellow and one too many green if I went with the rounded month. So I finally make this adjustment during the last week of production. So during the last week of the month, I’ll make one more yellow and one less green than I would in a normal week. The math rarely works out perfectly so keep in mind that you will have to have an adjustment period just like this. So let’s apply our math to our production sequence.
We are still running the smallest batch size first. We chose to run red before green because the difference between the two is negligible. Notice the truck fills up with all four types of units within one week. We divide four types by one week and get a heijunka ratio of 4.0. That’s a 200% gain from the second run and a 400% gain from the original. So this is a very basic heijunka board. First thing you’ll probably notice there are four different colors. Red, green, yellow and blue. These represent the four different color planes that we built during the simulation.
You probably also notice that there are four different columns. Week one, week two, week three and week four of production. So this board right now, represents a full month’s worth of production. Now it works really simple. What I do is pull the withdrawal kanban and send it into the system. This triggers a red plane to be built. Now the next thing that we built again is another red plane, send it into the system it would come out, followed by a green plane and so on and so forth for week one.
So you can see that all these are pretty evenly sequenced right now so we don’t have too much of one being produced at once. In theory, I could sequence these all over so all the blues are built at once, all the yellows and all the greens and all the reds. But obviously, we want to balance and level load what’s being produced every single week. So this is why they call this the central nervous system of our lean environment because this literally controls the pulling, the pacing and the sequencing for the entire shop floor.
Next, I want to relate value and batch. Now this is kind of tough for people to swallow and people get upset at this but I contend that only the first piece in any batch is value add. Now if you don’t believe me, let’s take for a moment if we consider the entire batch value add. We would make a bigger batch and that’s actually opposite of what we are trying to do. We are actually trying to minimize batch sizes so if you believe that, you realize that there is waste in every batch. The customer only needs one right no but they are buying in the size of a batch because that’s the size in which you produced it.
Again, I know that is a tough pill to swallow. Even though you are changing the form fitter function which is by definition value. Only the first piece in your batch is actually value add. The rest of the batch is just along for the ride. Keep this in mind especially when you are value stream mapping. 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 maybe value add for a lead time that takes months. So here are the major steps.
First, we need to understand demand. And don’t just skim over this. Often times if you study the data that the customers are actually giving you, you can find that they are a lot more predictable than you think they are. Then we need to reduce setup time using SMED. Reduce batch size. Now remember this two always go coupled. Don’t just do setup productions. You have to reduce batch size to correspond the setup reduction or else it’s pointless. Reduce inventory down the line and upstream and then shorten the pace cycle. Remember, that’s what this all boils down to. It’s owner’s those diagram of order to cash. We have to compress that.
Finally, rinse and repeat. Do this over and over again. So Shigeo Shingo is the pioneer behind Single Minute Exchange of Dies or SMED. Now I love SMED because once you combine SMED with batch size 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 pressers. He approached the plant manager and then asked if he could work on setup reduction. This is where he developed the concepts of internal and external work. The plant manager wasn’t thrilled about this but he went ahead and let it go. Seven years later, in 1957, he continued this work at Mitsubishi Heavy Industries and then in 1969, he took it over to Toyota where we see it today.
Single Minute Exchange of Dies refers to the ability to change over a machine that is running good product to running good product that’d be different type in nine minutes or less. Single minute refers to nine minutes being a single digit of time. You probably are already familiar with the pit stop example. During a race, a car stops at a pit stop for refueling and a change of tires. The crew works to minimize this time. But how about an example that’s more time critical? The U.S. military knows that seconds can mean the difference between life and death on the battle field. According to tactical.com, 50% to 70% of all combat injuries are extremity wounds. 60% of preventable combat deaths are from extremity bleeding. Now tourniquets have been used in the battlefield for centuries to minimize the bleeding by constricting the area that has been injured.
The issue is during high stress situations such as combat. Finding a tourniquet often takes more time than is available. To mitigate this, the military now has built in tourniquets in critical areas on the uniform so there’s no need to search for a tourniquet. A soldier can now immediately help an injured comrade. Obviously, we are not dealing with life and death situation in the factory environment but in order to reach a Single Minute Exchange of Die level, you and your team have to come up with innovative ways to save precious seconds just like these built-in tourniquets do.
Heijunka Video Part 3
…in a factory environment. But in order to reach a Single Minute Exchange of Die level, you and your team have to come up with innovative ways to save precious seconds, just like these built-in tourniquets do.
So this is generally how setup breaks down. You generally spend 5% of your time removing the old tooling, 15% of your time installing the new tooling, 30% of time preparing the new material and jigs, and 50% of your time trialing and processing. Obviously trialing and processing is the largest time bucket.
So here’s a quick demo on how to reduce that large time bucket. So this Etch A Sketch is a simple machine that I use to introduce the concept of trialing and processing. Oftentimes, operators rely on their senses to adjust machinery. Some operators are excellent at doing this, and repeatedly dialing a machine to exact specs with little to no problems. Other operators struggle and this causes wasted time, wasted material, and frustration.
So with this Etch A Sketch, I demonstrate that if you understand the knobs and how they impact the machine’s output, the stream, you can replicate any drawing with far reduced trialing and processing time.
I’ve taken the liberty of marking each knob with a red line. This serves as a reference point for me. I then calibrate the left knob. It turns out that one complete turn clockwise makes a line traveling right that is 3.4 centimeters long.
I turn the right knob 360 degrees and this makes a line that travels up. This line also measures 3.4 centimeters long. I then reset the machine and turn the left knob 180 degrees clockwise. This is to measure linearity. I expect the outcome to be a line traveling right that is 1.7 centimeters long. I measure and this is correct. I do the same for the right knob and get the expected result.
So I reset the machine and do the same thing for both knobs, this time going counter clockwise. I get all the expected mirror image results. Now that I know how the machine behaves and the knobs have been quantified, I can replicate any image with a reduced time in trialing and processing.
So this image presented here is complex. Now, I can take to the traditional approach and mimic what I see using trial and error. But instead, I take detailed measurements and measurements and write down my action plan. Here is my action plan complete with sequence, magnitude and direction. I have to move each knob to replicate this drawing exactly.
At this point, I can literally replicate this drawing with my eyes closed. As you can see, the resulting image I made is identical to the one I was presented with. Quantifying and labeling knobs creates a science out of an art that was known as trialing and processing. It also decreases the training time needed on any machine.
So this is an illustration of a Lean Continuum. Now, it’s been my experience that all companies start out doing obvious things like 5S and T.P.M. and value stream mapping. They also all do SMED. Now, some companies notice that with the 5S, and the T.P.M. and the SMED that they’ve done, they’ve had limited financial gain.
I consider SMED to be the critical defining fork in the road that separates the men from the boys in the world of Lean. Companies that treat SMED as a final destination, and never couple it with batch size reduction and heijunka never grow up. They inevitably veer off the Lean path and wonder why it never worked for them.
SMED is nothing more than a methodology that enables you to produce batch sizes and balance your production load. Again, if you have no intention of coupling SMED with batch size reduction, you should seriously reconsider your Lean journey.
I mentioned that some consider SMED as a methodology to produce lead time. This is absolutely false. The black bars represent setup time between batches. Let’s assume the lead time is 20 days, and each black bar represents 60 minutes of setup. Let’s say you work like crazy on SMED, and you reduce your setup times from 60 minutes down to six minutes. The result is you only reduce your lead time of 20 days by three hours.
Now do you see why SMED alone has almost no impact on lead time? Now imagine you reduce your batch size and level low your production with your new six minutes setup. You reduce your 20-day lead time by 16 days. So your new lead time is now only four days.
So back to Shingo’s definition of internal and external work. Internal work is work that has to be done while a machine is off. External work are actions you can take while a machine is still running. So in washing dishes, an example of internal work is loading and unloading dishes. You can’t do this while the washing machine is running. But while the machine is running, you can presoak the next set of dishes to be washed. This is an example of external work.
Here are the major steps in the SMED as defined by Shingo. First of all, all your tasks for both internal and external will be mixed throughout your production procedure. You should then clearly separate those that are internal and external tasks. Then convert as much internal work into external work. Then reduce all remaining activities. You finally want to standardize.
When evaluating a setup, I always watch the person and take detailed notes. Those tasks that are obviously not adding value with respect to setup, I segregate and eliminate immediately. This way, I start with a clean slate when using Shingo’s five steps.
So again, the first step is to recognize that internal and external activities are mixed. Don’t just skim over the step. Because it’s important for your operators to recognize that there’s a lot of opportunity even if this is your second or third wave of SMED. Classroom exercises, examples from other companies, and free high quality SMED views found online help in getting the ball rolling.
Next is to clearly separate those items that are internal and external. It’s important to challenge every single step. As a facilitator, you need to ask, “Does the machine really need to be off for this step?” You may be surprised as to how many steps can actually go into the external bucket of activities.
You then want to convert internal work into external work. You can often purchase cheap alternatives to allow you to perform work externally. For example, this die cast company. Prior to SMED, they had to wait two hours for the dies to heat up when they’re forming a setup. An operator suggested that the dies be heated externally. This raised some eyebrows. But a quick trip to Sears and a few hundred dollars later, the dies are being heated externally in this cheap home oven. And the company was indeed saving two hours per setup on this multi-million dollar machine.
So there’s still opportunity to make improvements. I’m big on quantifying knobs on your machines. Operators need to have a great feel for what knobs do. But they rarely truly know how the machine behaves. That’s why it’s important to study your machine and understand what the knobs do, just like this Etch A Sketch.
Also, you should encourage your operators to make adjustments while the machine is off. Needlessly running while making adjustments is like letting the water run while you brush your teeth.
Although the primary metric is time savings, the material savings is also very helpful. This is perhaps the hardest part of any Lean effort. Everybody wants to revert to their old way. Make sure you carefully capture the standard sequence for setup, and monitor operators as they work through the new routine.
Growing up in Florida, I loved being on the water, and fishing is one of my favorite pastimes. Believe it or not, fishing is a lot more science than art. On one fishing trip, we were catching far more tarpon than any other boat out there. One boat later approached us to ask how we were able to quickly zero in on the depth tackle and the bait to use. I showed them my standardized sheets that allowed us to reduce the time of trial and error to allow us to pinpoint fish in less time.
I explained that starting off with a large standard array of options, then eliminating those choices that are not working in a standard manner helps us catch fish faster. He was not impressed.
Heijunka Video Part 4
Helps us catch fish faster.
He was not impressed.
In this demonstration, we’re reducing the set-up time at the gas pump. When performing SMED, I always have a copy of the tasks that are being performed. I record the actions. I have a spaghetti and a meatball chart and, of course, a timer. I also use a pedometer to capture the number of steps I take. This gives me two solid metrics to improve. You can pick up a cheap pedometer for about $10. Now, walking may seem trivial to you, but I’ve measured operators literally walking two miles during a set-up. Remember, set-up time is the elapsed time between good part to good part. In the example you see here, it’s the time that elapsed in between the last green square and the first red triangle. In our example, it’s the time that elapsed between the last drop of gas that goes into the car in front of me and the first drop of gas that goes into my car. So the clock starts the moment he’s done pumping gas. As a quick side-note, 30 seconds elapses before he pulls and my car is in position.
I start by paying for my gas. We have a lot of love bugs in Florida, so I always start by washing my windshields both front and back. Now, I personally always start by washing my windshields, because I find that I always forget when I pump gas first and I don’t feel like getting back out of the car to do this. You can see that the sponge doesn’t hold much water, so I have to keep walking back and forth to the bucket. I come back and open my gas cap and begin filling my tank. Now, by definition, the moment I start pumping gas the set-up time is over. But let’s continue with this exercise to see the total elapsed time. This takes a minute or so, but after I’m done I replace the pump and close the gas cap on my car. A total of 5 minutes and 36 seconds elapses from the moment the previous guy stops pumping gas to the second I’m ready to pull away. My pedometer shows me that I took a total of 88 steps. So let’s follow Shingo’s 5 steps to reducing set-up time.
This is step one. Obviously, internal and external tasks are mixed. I recognize this, and I’m ready to improve.
So step two. Can I pay for gas while the pump is running? Sure, I can. While the guy in front of me is pumping gas, I can go pay in advance, so this is an external task. We have to go through a number of steps to wash the windshield. Again, does the gas pump have to be off for me to wash the windshield? Yes, because I can’t hold the gas handle and wash the windows at the same time. So all the tasks associated with washing the windshields have to happen while the gas pump is off. So by definition, these are internal tasks. How about opening the gas cap? I can do this while the previous guy is pumping gas when I go to pay for my fuel. So this task is also externalized.
Next, pumping gas is by definition an internal task, because the machine is running. Now, how about closing the cap when I’m done? Well, I can’t do that while the previous guy is pumping gas, nor can I do it while I’m pumping gas. But I can pull away and do it while the guy after me is pumping gas. So, I can externalize this task and do it after I free up the gas pump. I definitely don’t want to get back in the car while the gas is pumping, so this remains an internal task.
The next step is for me to convert as much internal work into external work as possible. I notice there’s a little tab on the handle of my gas 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 that would automatically stop when a thread broke. This freed up workers to perform other tasks while the machine was running. This handle works the same way. It stops once it detects that the gas tank is full, so I can safely externalize all the tasks associated with washing my windshields.
Step four is to minimize the internal and external tasks. Now, I don’t see many internal tasks I can minimize, but there are some opportunities in the external tasks, particularly around washing the windshields. I take a look at my spaghetti and meatball diagram and notice that the majority of the numbers are tied to me walking back and forth to the bucket to wet the sponge and my wiper. What if I invested $2 and bought a spray bottle and filled it up with soapy water? I wouldn’t have to walk back and forth to the bucket anymore, saving me many steps. It would also get my windshields cleaner, because I wouldn’t be dipping the sponge back into that filthy water. So, armed with my new sequence I give my new and improved state a go.
Having a set standard of sequence is the last step. I carefully study my sequence and begin. First, I go pay and open my gas cap while the previous guy is pumping gas. Like in the original scenario, 30 seconds elapses 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 fueling right away. I use the tab on the handle. Now I can go wash the windshields while the machine is running. I already have my spray bottle out, and I walk over to the wash bucket to get the wiper. I wash the windows with the exact same level of care as I did in the first scenario. Eventually, the gas handle clicks, indicating that refueling is complete. I return the wiper to the wash bucket, and I put the gas pump away. I refrain from closing the gas cap until I pull away, because this is an external task. I pull away, and then close the gas cap.
We completed all of our tasks in a minute and 59 seconds this run. This is a 64% reduction from the original 5 minutes and 36 seconds. My pedometer says I took 22 steps this time, compared to 88 steps originally. This is a 75% reduction in steps. I think the $2 spent on the spray bottle will pay for itself in no time. Now, this little exercise doesn’t do a full SMED Kaizen event justice, but hopefully it opens your eyes to an opportunity that you may not have seen before.
Here is a quick review of what we learned: We reviewed muda and we learned that heijunka can be used to combat muda. We learned about production leveling and product leveling. We learned about Single-Minute Exchange of Dies and how this links to batch size reduction and leveling.