It is good to see that people see the difference between Lean’s “Value stream mapping (VSM)” and Toyota’s “Material information flow chart” is a difference. There was a quote from my coach, Hajime Oba, speaking in AME that “Toyota does not use VSM.”
So, the conclusion is that “VSM and material information flow charts are different.” That’s it? My coach will simply say, “Write the flow in a different format,” and he will be satisfied? That doesn’t seem to match some of the coaching I received. If things were that simple, we would understand “flow” easily. But describing “flow” on a paper is not that easy. We drew so many different things on paper to represent flow.
My coach's real question is, “Can we describe flow?” Flow is dynamic; something on paper is static. There is a paradox. That doesn’t mean we shouldn’t try. The process of trial and error allows us to learn about flow.
Here are two examples of our trial and error of describing “flow” in different formats with some learning.
1️⃣ Combination table
2️⃣ Graphic paper
1️⃣ Combination table
The combination table is part of the standardized work. Its original intention was to show the combination of human and machine work. The format of this document allows for many creative uses, which helps us to think better. Using this document to describe flow is one application.
The idea of using a combination table is to show the timing of the flow. Inside a flow, there are several critical points that impact. When are those points, and how do they impact the other processes? The idea is to highlight those relationships.
We implemented a pull system, and the factory refilled the inventory when they sold the products. As we started the system, we began to notice a strange gap. They were a delay in reaction from the plant. To understand, we plotted the activities in the flow on the combination table. We drew the time on the horizontal axle. All activities were written on the vertical axle like a standardized work combination table. We made two versions; one of what we thought was how things flowed, and the second was how actual information flowed.
As we drew, we discovered a problem. Every day at 5 PM, sales collect all the data on goods sold. Then, the computer processes the data. Since it takes one hour, production pulls the data at 6 PM to create a production plan. But there was a problem here. On the sales computer, it says that the process was complete, but the data was not yet available for the production to pull. Somehow, there was a time lag. It took another fifteen minutes for the data to be available for the production to pull. This was a lesson to me. We should not discuss flow and lead time based on perceptions, which many do. Because we didn’t consider that fifteen minutes, the data sat for 23 hours and forty-five minutes to be produced. And, we were producing constantly on delay. As we drew such a combination table, we continually asked, “Are we really connected?” And is the timing really right? I found many holes.
Some say the idea of a combination table came from the train diagram, which accurately shows multiple trains' travel and stoppage times. (Because of that, train schedule is called “Dia” in Japan) If this was used for planning railways, which function as the centerpiece of human flow, why can’t we use it to describe material and information flow in business?
2️⃣ Graphic paper
The final assembly line may have multiple sub-flows in the production. How would we draw the flow in such situations?
This idea started from Taiichi Ohno’s “Toyota Production System.”
The chapter on “Toyota-style information system” shows a picture of cars lined up with sequence numbers attached. There are arrows of information that trigger subassembly processes to start their processes. Why don’t we use this? The idea was to draw such a picture for our products. We decided to draw on graph paper. We used one box instead of a product picture as one takt time. This helped us coordinate multiple sub-assembly flows.
As we drew such a picture, we faced many difficulties.
What should we do with processes with variable lead time? The biggest reason why the lead time changes were missing or not following the standardized work. Those processes with such unstable conditions were written on separate paper. This was to show that these sub-assembly processes were not connected. The standardized work includes logistics, order processing, and changeovers. Without good standardized work in these areas, the flow never stabilizes. We didn’t need guesswork on lead time. Standardized work, standardized work, standardized work. Please don’t talk about flow without it.
Some processes have multiple customer lines, so the takt time differs. We kept these on separate paper and only put them back on the main sheet when these processes implemented Heijyun-ka (levelization). The Heijyun-ka helped us stabilize the flow and lead time. Without it, the lead time is just a mess.
The most significant benefit of such an approach was that it became clear where and what types of TPS concepts are being challenged. Senior management will enter the room where we had this picture and ask questions about those processes on a separate piece of paper. We will visit that genba and focus on the Kaizen workshops. Getting processes stable was critical, and the lead time was reduced.
Is this a perfect method? Absolutely not. One problem that this method could not capture is the takt change. After the shift in takt, we need to adjust some segments. Another challenge was that my coach constantly challenged me to put everything on one paper (A3-type thinking). However, I resisted writing different lines or marks because it gave the impression that everything was somehow connected. Simply being on the same paper gave such impressions. This ongoing exchange of how to describe a flow continued.
🔍 So, the trial and error of describing flow continues. But why do we try? That is because we learn more about the flow as we try. One crucial note. When we describe a flow, we start by observing the Genba. As we observe, we find difficulties or hypotheses to improve the flow. Based on such observations, we start describing how to communicate and improve. And we should immediately improve. Otherwise, the paper just “looks good on paper” and has no real meaning.
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