Muda of Processing Itself

One of the seven types of Muda, as defined by Taiichi Ohno.

But these days, when I look up the seven types of waste, we often see “Over-processing” or “Extra-processing.” In fact, when AI is used, they say that “Over-processing” is correct and that “Muda of process itself” is similar, but not one of the seven types of waste. 😱

The original Japanese states that this is “Processing itself.” Because of this, if I search in Japanese, the results will be “Processing itself 【加工そのもの】” or “Processing【加工】.” I have not seen “Over-processing【過剰加工】” in Japanese as part of the seven.

In the English version of Taiichi Ohno's Toyota Production System, the main text translates as “Waste of processing itself.” However, the glossary section translates as, “too much machining (over-processing).” The original Japanese text is the same, but the English translation differs. It's unclear why there is a difference and why the glossary option is more popular.

However, the question is: is it the waste of processing itself, and the waste of over-processing the same thing?

I don’t believe so.

I visualized the concepts with a bar chart. “Over-processing” is shown by the dotted box area, which looks like fluctuations or variations. “Processing itself” covers everything. Overall, “Processing itself” is a much larger and more complex topic.

There is a similar concept, which supports the “processing itself,” which is “Net Work.”

One of the explanations I have read about this waste is by Hiroyuki Hirano.

The Muda of processing involves questioning the essence of the work or part.

Hirano, H. (2001). “Mindset revolution and 5S3Tei.” Nikkan Kogyo Shimbun, Ltd.

Another way to consider it is, what is the science behind the processing?

Here are some examples;

🔹 Name

There are many processes with names I have never heard before. It might be a new process, but often it is not. When we observe the process, it usually involves inspection and repair. The reason behind such re-naming is to manipulate the KPI, such as first-time yield. Instead of directly passing the products into official inspection, they go through a pre-step, making the numbers at the official inspection appear better. Whenever you hear a process with an unusual name, check what science is behind it.

🔹 Bad habit

There was a factory that claimed they needed to store the product for 24 hours after the process. When we asked about the reason for this, there was no answer. The inventory did not follow the FIFO method and did not guarantee a 24-hour lead time. It was just a justification of safety stock.

🔹 Basic science

At a metal mill, my coach asked, “Why is the temperature of the smelter set 300 degrees higher than the melting point?” This question opened the door to many aspects of waste in the process. Temperature affects speed, machine capacity, quality, energy, and more. The production and engineering teams constantly increased the temperature without proper testing or root cause analysis. (Later, we found that the methods, not the temperature, caused quality problems.) The CEO, who has a doctorate in physics, called the question the most important for the business and was envious of the experiments and Kaizen efforts we did afterward. But he argued that science is the same everywhere, so why are the standards different among smelters? When thinking about this, I asked my coach if we need to memorize the melting points of elements. He said no. But before visiting the plant, he remembered from middle or high school physics that each element has a specific melting point. So, he just googled it. Basic physics helped him question the logic behind the process. There is a concept in Japan called the 5 Gen principle, which includes five elements: Genba, Genbutu, Genjitsu, Genri, and Gensoku. Genri is the law of science. Gensoku is the rules. We always need to respect them.

Sometimes I wonder why “Over-processing” or “Extra-processing” has become more popular than Ohno’s original “Processing itself.” One possibility is that it’s easier to create an acronym with “O” and “E.” 🤣 Whatever the reason, the terms “Over-processing” or “Extra-processing” represent the Mura (Fluctuation) of the Muda of the processing itself.