The Information Model for Poka Yoke:

USB2

In today’s post, I will be looking at poka yoke or error proofing using an information model. My inspirations for this post is Takahiro Fujimoto, who wrote the wonderful book “The Evolution of a Manufacturing System at Toyota” (1999) and a discussion I had with my brother last weekend.

I will start with an interesting question – “where do you see information at your gemba, your production floor?” A common answer to this might be the procedures or the work instructions, or you might answer it as the visual aids readily available on the floor. Yet another answer might be the production boards where the running total along with reject information is recorded. All of this is correct. A general definition of information is something that carries content, which is related to data. I am not going into Claude Shannon’s work with information in this post. Fujimoto’s brilliant view of information is that every artifact on the production floor, and in fact every materialistic thing carries information. Fujimoto defines an information asset as the basic unit of an information system. Information cannot exist without the materials or energy in which it is embodied – its medium.

info asset

This information model indicates that the manufactured product carries information. The information it carries came from the design of the product. The information is transferred and transformed from the fixtures/dies/prints etc onto the physical product. Any loss of information during this process results in a defective product. To take this concept further, even if the loss of information is low, the end-user interaction with the product brings in a different dimension. The end-user gains information when he interacts with the product. If this information matches his expectations, he is satisfied. Even if there is minimal loss of information from design to manufacturing, if the end product information does not match the user’s expectations, the user gets dissatisfied.

Lets look at a simple example of a door.  A door with a handle is a poor design since the information of whether to push or pull is not clearly transferred to the user. The user might expect to pull on the handle instead of pushing on it. The information carried by the door handle is to “open the door using handle”. It does not convey whether to push or pull to open the door.

handle

Perhaps, one can add a note on the door that says, “Push”. A better solution to avoid the confusion is to eliminate the handle altogether so that the only option is to push. The removal of the handle with a note indicating “push” conveys the information that to open the door, one has to push. The information gets conveyed to the user and there is no dissatisfaction.

This example brings up an important point – a defect is created only when an operator or machine interacts with imperfect information. The imperfect information could be in the form of a worn-out die or an imperfect work instruction that aids loss of original information being transferred to the product. When you are trying to the solve a problem on the production floor, you are updating the information available on the medium so that the user’s interaction is modified to achieve the optimum result. This brings us to poka yoke or error-proofing.

If you think about it, you could say that the root cause for any problem is that the current process allows that problem to occur due to imperfect information.  This is what poka yoke tries to address. Toyota utilizes Jidoka and poka yoke to ensure product quality. Jidoka or autonomation is the idea that when a defect is identified, the process is stopped either by the machine in an automated process, or by the operator in an assembly line. The line is stopped so that the quality problem can be addressed. In the case of Jidoka, the problem has already occurred. In contrast, poka yoke eliminates the problem by preventing the problem from occurring in the first place. Poka yoke is the brainchild of probably one of the best Industrial Engineers ever, Shigeo Shingo. The best error-proofing is one where the operator cannot create a specific defect, knowingly or unknowingly. In this type of error-proofing, the information is embedded in the medium such that it conveys the proper method to the operator and if that method is not followed, the action cannot be completed. This information of only one proper way is physically embedded onto the medium.

Information in the form of work instructions may not always be effective because of limited interaction with the user. Information in the form of visual aids can be effective since it interacts with the user and provides useful information. However, the user can ignore this or get used to it. Information in the form of alarms can also be useful. This too may get ignored by the user and may not prevent the error from occurring. However, the user cannot ignore the information in the form of contact poka yoke since he has to interact with it. The proper assembly information is physically embedded in the material. A good example is a USB cable where it can be entered in only one way. The USB icon on top indicates that it is the top. Apple took this approach further by eliminating the need of orientation altogether with its lightning cables. The socket on the Apple product prevents any other cable from being inserted due to its unique shape.

Final Words:

The concept of physical artifacts carrying information is enlightening for me as a Quality Engineer. You can update the process information by updating a fixture to have a contact feature so that a part can be inserted in only one way. This information of proper orientation is embedded onto the fixture. This is much better that updating the work instruction to properly orient the part. The physical interaction ensures that the proper information is transferred to the operator to properly orient the part.

As I was researching for this post, I came across James Gleick who wrote the book, “The Information: A History, a Theory, a Flood”. I will finish off with a story I heard from James Gleick regarding information: When Gleick started working at the New York Times, a wise old head editor told him that the reader is not paying for all the news that they put in to be printed. What the reader is paying them was for all the news that they left out.

Always keep on learning…

In case you missed it, my last post was Divine Wisdom and Paradigm Shifts:

Advertisements

Time and TPS:

tardis

I am intrigued by the concept of time. I am a big Doctor Who fan, and I quite enjoy the time paradoxes presented in the Whovian universe. In today’s post, I am exploring the theme of time, and some quotations by Henry Ford, Shigeo Shingo and Taiichi Ohno.

Henry Ford:

Taiichi Ohno, the father of Toyota Production System, has said that if Henry Ford was still alive, he would have eventually created a production system similar to Toyota. Ford has written about the concept of time in his 1926 book, Today and Tomorrow.

“The easiest of all wastes, and the hardest to correct, is the waste of time.”

Ford’s point was that time waste is different from material waste. Material can usually be reworked. However time wasted cannot be salvaged. Ford thought of time as human energy.

Shigeo Shingo:

Shingo was probably one of the best Industrial Engineers in the world. He studied Frederick Taylor and the Gilbreths, and was heavily influenced by them. One of the most cryptic things I read from Shingo was the quotation below;

“Time is the shadow of motion”.

Shingo attributed this to the Gilbreths. Shingo explained this statement better in his 1988 book, “Non-Stock Production”. His point is that time can be explained in terms of motion, as in “it takes a long time to do this” or “it can be done faster”. He urges the lean leaders to understand the “structure” of motion, and understand the most efficient way to do motion. Shingo advises us to understand what it means when a task takes a long time and not complain about the duration. We should instead look at the motions that make the task take longer. As Shingo says;

“It may be necessary to restructure the task to which the motions are tailored”.

The translator may not have intended the pun behind “tailored”/”Taylored”. Toyota uses time and motion studies as the basis for creating standard work.

Taiichi Ohno:

The most common expression attributed to Taiichi Ohno regarding time is;

“All we are doing is looking at the time line, from the moment the customer gives us an order to the point when we collect the cash. And we are reducing the time line by reducing the non-value adding wastes.”

Ohno is often described as a mean and tough sensei. He is also said to have been hard on the supervisors asking to produce more with less people. Ohno has talked a lot about “Respect for Humanity” and the need for ensuring that the operator is engaged in only value added activities. I am going to look at another saying by Ohno.

“Valueless motions are equal to ‘shortening one’s life.’”

Ohno had a way with words and he could explain his ideas beautifully. Not engaging the operator in value added activities, and not allowing him to improve his process is not being respectful. Ohno has also said that motion does not equate to working. Ohno stated it the best.

Final Words:

One of the two pillars of TPS is Just-in-Time. The idea behind this is to produce the right parts in the right amount, and at the right time.  I will finish this off with a story about Just-in-Time from Masaaki Sato’s book, “The Toyota Leaders”. The term Just-in-Time was coined by Kiichiro Toyoda, the founder of Toyota Motor Corporation.

Kiichiro went on a trip to England with some relatives to visit several cotton production facilities and textile factories. He was going to the Platt plant by himself to receive training. He arrived at Saint Pancras station to catch the Manchester-bound train. Unfortunately, by the time he arrived, the train had already left the station. He had an out-of-date train schedule.

“If a train leaves on time, then you miss your train even if you are only a minute late. Now I have to wait for a few hours until the next train comes”, he said to himself.

Kiichiro was taken aback by this incident and he kept on thinking about it to find a way to apply this to plant operations. He then came up with the idea of Just-in-Time. He did not coin the phrase in Japanese, but in English (perhaps as a reminder to himself of the incident in England).

He explained Just-in-Time to his employees as follows;

“I will bet everyone here has missed a train before. If a train leaves on time, you will miss it even if you are just a second late, let alone an entire minute. ‘Just-in-Time’ does not refer only to being on time. It means ‘supplying the right parts at the right time and in the right amount’”.

Always keep on learning…

If you enjoyed this post, you can read more here.

In case you missed it, my last post was The Order for Kaizen.

The Order for Kaizen:

kaizen order

In today’s post, I will be talking about Kaizen and specifically the order for kaizen. Kaizen has come to mean “continuous improvement” today. Kaizen originally translates from Japanese as “change for better”. I will be presenting three different views on approaching kaizen. These are;

  • Taiichi Ohno’s view,
  • Shigeo Shingo’s view, and
  • Hiroyuki Hirano’s view

Taiichi Ohno’s View (Semi-Strategic in nature):

Taiichi Ohno is the father of Toyota Production System (TPS). He has stated that there is a proper order for kaizen. These are;

  • Sagyo kaizen (Operations improvement),
  • Setsubi kaizen (Equipment improvement), and
  • Kotei kaizen (Process improvement)

I believe that Ohno wanted to focus on developing the abilities of people first since this is the lowest level where kaizen is possible. As Hirano says, “The starting point of manufacturing is always people.” Any production system should be people oriented. The first step of all kaizen is to raise the awareness of the people. This allows them to view the waste as a lean leader would. This is achieved only through operations kaizen. The operators involved are finding ways to make their work easier with what they have. This has minimal cost impact of all the kaizen. Ohno has also said;

“People with no capacity for improving operations are a problem because they like to buy new machines all the time.”

Ohno has also said;

“First improve operations. If you start out by bringing in the latest machines people with no capacity for improvement simply end up being slaves to the machines.”

The next in line is Equipment kaizen. Ohno challenges us to find new and creative ways of using the current equipment. Ohno advises us;

“You must have the ability to tinker with and improve the machines you already have.”

Ohno recommends buying new equipment when you have made the maximum use of current equipment and when it is no longer possible to increase effectiveness without new equipment. Purchasing new equipment should result in an improvement of quality. Ohno cautions against purchasing costly specialized equipment and advises going for flexible and low cost equipment. Equipment kaizen alone without operation kaizen results in extreme waste. Now the organization can make waste much better, and lot more of it. Machines cannot see waste, and machines cannot improve anything on their own. Machine kaizen alone foster status quo and invites complacency.

The last in line is Process Kaizen. His view was;

“Making things extremely well by turning the process upside down is Process Improvement.”

With process kaizen, you are looking at rearranging equipment or operations, changing layout, or improving the flow by linking processes.

Shigeo Shingo’s View (Tactical in nature):

Shigeo Shingo has provided us four targets for improvement. They are, in the order of priority;

  • Easier,
  • Better,
  • Faster, and
  • Cheaper

I was watching a Paul Akers (FastCap) video on YouTube and I made a connection to what Shingo said. “Easier” is an improvement from the point of the operator. This also means that it is safer for the operator to do. Any improvement activity should be first focused on Safety. “Better” is an improvement activity resulting in an improvement in quality of the operation/product. “Faster” is an improvement activity that increases efficiency. The final level is “cheaper”, and this should be the last target of all improvement activities. The goal of kaizen is not necessarily to first make the process cheaper.

Hiroyuki Hirano’s view (Strategic in Nature):

Hirano has pointed out the following as the normal progression of kaizen;

  • Point kaizen,
  • Line kaizen,
  • Plane kaizen, and
  • Cubic kaizen

“Point kaizen” is very similar to the operations improvement. This is the basic small improvement activity at the operations level. The next level is “line kaizen”. This is where a lot of the point kaizens merge together to result in flow manufacturing, as in an assembly line. Hirano calls this a vertical development. This is akin to selecting a model line and transforming it to make the process flow better. Once we have line kaizen, the next progression is through “plane kaizen”. This is the idea of “yokoten” or horizontal deployment. This is where the ideas and learning from the model line is used to create more model lines across the plant.  Thus this results in horizontal development. The final level is “cubic kaizen” where the development is made across multiple departments and even the supply chain of the enterprise.

My thoughts:

As with any other buzzword, kaizen has come to mean many things. My goal has been to provide a little more structure to the wonderful idea of kaizen. I would encourage the reader to also read my previous post on this topic here (A brief look at kaizen in the light of the Toyota Way). I will finish this off with a great story on Equipment kaizen from Hitoshi Yamada, a student of Ohno from the book Forging a Kaizen Culture (Japanese version 2009):

Yamada was at a large component manufacturer, Stanley Electric’s Tsuruoka plant. They were looking at a machine that assembled extremely small light bulbs. The cost of the machine was $150,000. The machine had two turn tables, and several robot arms. Due to the high cost of the machine, the factory manager felt that he should rely on mass production to make the maximum use of the machine.

Yamada told the manager to study the machine and find areas of wasted movement. And even better- to build a smaller and better machine.

This improvement activity took several weeks of trial and error. The final machine was $5,000 and 1/27th the size of the old machine. Since the machine was much smaller in size, it was also more efficient.

Always keep on learning…

In case you missed it, my last post was Ohno and the Gemba Walk.

Chewbacca, Poka-Yoke and Respect for People:

Sir Chewbacca

One of key concepts in Toyota Production System with respect to Quality (other than Jidoka/Autonomation) is Poka-Yoke (ポカヨケ), or Error Proofing. “Yokeru” in Japanese means “to avoid”. “Poka” means “error” or “blunder”. The story behind Poka-Yoke has an underlying theme of respect for people.

Baka to Poka:

The concept of Poka-Yoke was made famous by Shigeo Shingo, perhaps one of the best Industrial Engineers. He coined it as “Baka-Yoke”. “Baka” in Japanese means “idiot” or “fool”. Thus, Baka-Yoke means “fool proof”.

Around 1963, Arakawa Auto Body adopted a fool proofing device as part of a Baka-Yoke program. This device prevented seat parts from being spot welded backwards. The story goes that one of the part–time workers started crying when the supervisor explained about the fool-proofing device because the workers were sometimes mixing up left and right handed parts.

“Have I really been such a fool”, she asked. She ended up staying home that day. The supervisor had to go to her home to convince her to come back by explaining that she is not a fool. The device was being used because anybody can make inadvertent mistakes.

Shingo was told this story, and after some thought he changed the name to “Poka-Yoke”. Thus choosing a term that communicates more respect for the worker.

Poka-Yoke and Respect for People (RFP):

The story above shows that Shingo was being respectful and the new name of Poka-Yoke is certainly more meaningful since it does not put any blame on the employee. I have heard this story being used to explain Respect for People. But more than the story, I feel that the concept of Poka-Yoke is a part of Respect for People. You may have heard that things go wrong sometimes, especially when the operator is doing a highly repetitive activity. The big red book of Poka-Yoke by Nikkan Kogyo Shimbun states the following;

The idea behind Poka-Yoke is to respect the intelligence of the workers. By taking over repetitive tasks or actions that depend on vigilance or memory, Poka-Yoke can free a worker’s time and mind to pursue more creative and value-adding activities.

Extrinsic and Intrinsic Respect for People:

The more I read about TPS and Respect for People, I am coming to view Respect for People as Extrinsic and Intrinsic RFPs.

extrinsic and intrinsic

The Extrinsic RFP is superficial in nature. This is the basic respect you give to your fellow human beings. This is you being nice to people, the basic manners!

The Intrinsic RFP is the meat and potatoes or the true essence of Respect for People. As a leader in your organization you ensure that the work performed by an employee is value added. As the leader of your organization, it should be your job to develop your employees and ensure that they remain valuable assets. Toyota says that they believe in making people before making cars. Respect for people means that the organization is providing an environment where the employees are doing only value added activities.

How does one increase the worth of an employee? You can increase their worth by developing the employee to understand the value in his work. You can increase the worth by training him to look for gaps between the ideal state and current state. By understanding this gap, you can further develop him to take countermeasures and corrective actions to move closer to the ideal state. Ideally, the employee would now be able to train the employees underneath him. The employee is now at a stage to be making decisions and implementing the improvements on his own. In other words, he is empowered.

You might wonder whether Respect for People is value added. The traditional notion of value added activity is that the activity is something that the customer is willing to pay for. My view is that by creating the equation making things is making people, Toyota has transformed people development as a value added activity.

Chewbacca’s Connection to Baka:

I came across an article that suggested that maybe George Lucas created the name Chewbacca from the Japanese phrase “Chū baka” which means “Medium Stupid/Fool” or “Average Idiot”. There is of course no conclusive evidence for this. George has admitted that he was influenced by Japanese culture and movies while making Star Wars. I thought this was a nice story with relation to Poka-Yoke and Respect for People. Let Chewbacca remind you the need for Poka-Yoke as opposed to Baka-Yoke, and Respect for People.

Always keep on learning…

Image Credit – Sir Chewbacca (mcfeezy )

In case you missed it, my last post was “Would Ohno Change the term ‘Lean’”.