Kaizen in Japanese Companies: How Improvement Actually Runs
If you work at a Japanese-owned plant, or supply one, kaizen reaches you in concrete forms: a one-page improvement suggestion form, a QC circle team presenting its results to plant management, a request from the Japanese parent to "yokoten" a fix from another plant, and shop-floor boards full of counts and charts. Each piece looks simple. Together they make up the way a Japanese plant keeps improving, and they are easy to copy in form and miss in substance.
This guide explains where kaizen sits inside the Toyota Production System (TPS), how the four everyday mechanisms work, the tools behind them, and where kaizen tends to stall when a Japanese company brings it into a plant overseas. It ends with a checklist and a list of questions you can ask your Japanese counterparts before a kaizen program starts.
Contents
- What Kaizen Means Inside the Toyota Production System
- How Kaizen Runs Day to Day: Four Mechanisms
- The Toolkit Behind Kaizen
- Where Kaizen Stalls When It Moves Overseas
- A Typical Rollout Sequence
- Who Does What in Kaizen
- Checklist: Before Kaizen Starts at Your Plant
- Questions to Ask Your Japanese Counterparts
- Benefits and Limits of TPS and Kaizen
- FAQ
- Sources
What Kaizen Means Inside the Toyota Production System
Kaizen (改善, "improvement") is the daily practice of noticing problems in your own work and making that work a little better, one small step at a time. Toyota describes its production system as a way of making things that eliminates waste throughout production, so that good-quality vehicles reach customers at low cost and on time. Making the work easier for the people who do it is a stated premise, not an afterthought.
If TPS is the system, kaizen is the engine that keeps it running and improving. TPS is designed so that problems surface as soon as something goes wrong. Each problem that surfaces gets solved through kaizen, and the level of the whole system rises one fix at a time. For the people on the line, that means improving the work is part of the job, not a separate project. The approach has spread well beyond automotive, to electrical, machinery, food, and pharmaceutical plants.
Two pillars serve the goal, and leveling, standardized work, and kaizen form the foundation under them.
Based on Toyota Motor Corporation's official description; arranged by the MONOSCOPE editorial team.
The Two Pillars: Just-in-Time and Jidoka
Just-in-Time (JIT) means making and moving only what is needed, when it is needed, in the amount needed, so material keeps flowing instead of piling up between processes. The key is the pull principle (ato-koutei hikitori): each downstream process withdraws only what it needs from the process before it, and the upstream process makes only what was withdrawn. Compared with pushing parts out to a schedule, this makes overproduction and inventory buildup easier to prevent.
With little inventory, an equipment breakdown or quality problem stops the next process almost at once. That looks like a weakness, but it is deliberate: the problem cannot hide, so it becomes the starting point for kaizen.
Jidoka (自働化) is written with a special character that adds "person" to the ordinary word for automation, often rendered as "automation with a human touch." Machines carry human judgment, detect quality or equipment abnormalities, and stop themselves. Toyota also lets operators stop the line with a switch or cord. As Toyota describes it, defects no longer flow downstream, and nobody needs to stand and watch a machine. An andon (problem display board) alerts supervisors and others the moment an abnormality occurs.
Designing for stopping runs against the common instinct to keep the line moving at all costs. Stopping on the spot and finding the cause keeps the same defect from recurring, and in the TPS view that raises both quality and productivity. The same idea applies to manual work through poka-yoke (mistake-proofing): jigs and part-selection instructions that physically prevent a part from being left off or installed wrong. Like jidoka, it relies on the process rather than on someone's attention: mistakes become hard to make, and any that do happen show up at once.
Kanban and Leveling
Kanban are the cards that make pull work on the shop floor. Each card shows the part number, quantity, and destination, and travels with the parts, telling each process what to make or move, how many, and when. According to Toyota's 75-year history, there are two types: the withdrawal kanban, used when the downstream process picks up parts, and the production kanban, which tells the upstream process what to make. When parts are used, the card is removed and returns upstream as the next production or transport instruction, so only what was used gets replenished, without sending a detailed schedule to every process. Toyota adopted kanban at all its plants in 1963 and extended it to parts deliveries from suppliers in 1965.
Because the number of cards caps the inventory, plants also remove cards on purpose to expose hidden problems. Pull only works if volume and product mix at the final process do not swing widely from day to day, since any swing is amplified upstream and every process ends up staffing and stocking for its peak. Leveling (heijunka) evens out both volume and product mix over a set period; Toyota's history records that it was pursued alongside kanban to avoid excess people and equipment.
Changing how production orders are given changes how inventory and problems show up.
Based on Toyota's official website and 75-year history; arranged by the MONOSCOPE editorial team.
Where TPS Came From, and How It Relates to Lean
Both pillars go back further than the car business. Jidoka traces to Sakichi Toyoda, founder of the Toyota Group, whose automatic loom stopped itself when a thread broke. Just-in-Time was proposed by Kiichiro Toyoda, founder of Toyota Motor Corporation. Taiichi Ohno and others then turned these ideas into working systems and established TPS, which spread to Toyota Group companies and suppliers through training and study groups.
Outside Japan, ideas drawn from TPS are better known as lean production. According to the Lean Enterprise Institute, John Krafcik coined the term "lean production" in the late 1980s as a research assistant in MIT's International Motor Vehicle Program, and the research reached a wide audience in the 1990 book The Machine That Changed the World. Lean is best seen as TPS generalized for other companies and industries. The core is the same: eliminate waste and keep improving.
How Kaizen Runs Day to Day: Four Mechanisms
Most explanations of kaizen focus on the philosophy. On a Japanese shop floor, it runs through a few concrete mechanisms, and these are what you will be asked to set up, take part in, or report on. Names and formats vary by company, but most Japanese manufacturers use some version of the four below.
Individual ideas, team problem solving, sharing across sites, and making the situation visible.
Names, forms, and rules differ by company. Arranged by the MONOSCOPE editorial team.
Kaizen Teian: The Suggestion System
The individual channel is the improvement suggestion system, usually called kaizen teian (改善提案, "improvement proposal"). Toyota's version, the Creative Idea Suggestion System, started in 1951. According to Toyota Times, Eiji Toyoda modeled it on a suggestion system he saw at a Ford plant. Its first handbook said ideas were welcome no matter how small, and that they could be submitted verbally or written up by someone else on the submitter's behalf. The slogan "Good Thinking, Good Products," chosen in 1953, is still displayed at Toyota plants.
What sets teian apart from a suggestion box is scale and ownership. Because the system asks for ideas of any size, a typical teian is a small change in the submitter's own work area, such as moving a tool closer or adding a guide to a fixture. Each company sets its own rules for who reviews a teian, how it is evaluated, and how it is recognized. If your Japanese parent tracks the number of teian per person, ask what the number is meant to show; in a system built on small ideas, it usually measures participation rather than the value of any one idea.
QC Circles: Team Problem Solving
The team channel is the QC circle (QC サークル). The Union of Japanese Scientists and Engineers (JUSE) set up its QC Circle Headquarters in May 1962, with Professor Kaoru Ishikawa as the driving force, and the first circle registered that same month. JUSE describes a QC circle as a small group of people from the same workplace who carry out quality control activities on their own, using quality control tools and methods, as part of company-wide quality control.
In practice, a circle picks a theme from its own area, analyzes it with data, tries countermeasures, and checks the effect. JUSE has held QC circle conventions where circles present their results since 1963, and many companies run their own internal presentation events. If your team is invited to present, ask in advance whether the event is mainly for recognition or for review, and what format is expected.
Related: 7 QC Tools in Japanese Quality Reports: How to Read Them
Yokoten: Spreading a Fix Sideways
The Lean Enterprise Institute defines yokoten (横展, short for 横展開 yokotenkai, "horizontal deployment") as deploying concepts, ideas, or policies horizontally across the company. Its example: if a defective valve is found on one machine, yokoten means checking similar valves throughout the facility, and at other relevant facilities, for the same defect. Japanese companies apply the same idea to good practices, and to suppliers that make similar parts.
For an overseas plant or supplier, yokoten often arrives as a request: "This happened at our plant in Japan. Please check whether it can happen at yours and report back." It is not an accusation. A short reply that says what you checked, what you found, and what you changed is what the sender needs. The same habit shows up in near-miss reporting and in design reviews such as DRBFM.
Visual Management: Boards on the Floor
Visual management (目で見る管理, me de miru kanri) means anyone walking past can tell how the area is doing. Production counts, defect counts, and waiting time are posted on boards or charts in the work area. When results show up as numbers on the wall, operators can see that their changes worked, which builds buy-in for the next round. The andon does the same job in real time, and 5S, covered below, is what makes abnormalities visible in the first place.
The Toolkit Behind Kaizen
The Seven Wastes
In TPS, waste (muda) is any activity or condition that adds no value. The best-known classification lists seven types. Toyota treats overproduction as the most important one to eliminate, because it tends to create the others: making more than needed adds storage, handling, and management work, and makes the loss larger when a defect is found.
For people on the floor, the seven wastes work as a lens for finding kaizen themes. Watching a job while asking "which waste is this?" turns a vague sense that something is inefficient into a specific problem to fix.
Related: OEE and the 7 Big Losses vs. Six Big Losses in TPM
Seven kinds of non-value-adding work and conditions, used as starting points for improvement.
Overproduction tends to trigger other wastes such as inventory and transportation.
Standardized Work
Standardized work sets out the waste-free sequence of a job, built around the operator's movements. It usually has three elements:
- Takt time: the time allowed to make one unit
- Work sequence: the order of the tasks
- Standard work-in-process: the minimum in-process stock needed in the process
For example, if daily operating time and required output give a takt time of one minute, each process is built to fit within that minute. A process that runs over takt becomes the bottleneck; one with a lot of time left over creates waiting. Building the standard is itself a way of finding waste.
Standardized work is not there to lock the job down. It is the baseline for kaizen: without a standard, you cannot see a deviation as an abnormality, and you cannot lock in an improvement as the new standard. Hence the saying "no kaizen without standards." For how Japanese plants teach the standard, see TWI Job Instruction and OJT.
Related: Standardized Work Instructions: Sagyo Hyojunsho Template
5S
5S takes its name from five Japanese words:
- Seiri (sort): throw out what you do not need
- Seiton (set in order): place what you need where you can get it at once
- Seiso (shine): clean, and inspect while cleaning
- Seiketsu (standardize): keep the first three in place
- Shitsuke (sustain): build the habit of following the rules
5S is more than tidying up. Once every item has a set place and the floor and machines are clean, abnormalities and shortages are obvious at a glance, which is the precondition for visual management. It is also an entry point new employees can join right away: outlining tool positions on a shadow board or tagging unneeded items for disposal produces visible results quickly. For the maintenance side of the same idea, see jishu hozen (autonomous maintenance).
5 Whys
Treating only the visible symptom lets a problem come back. The "5 whys" (naze-naze bunseki, "why-why analysis") asks why the problem happened, again and again, until it reaches the true cause (shin'in). The kaizen library from OJT Solutions, supervised by former Toyota employees, stresses the difference between a stopgap that handles the symptom (taisho) and a countermeasure that removes the true cause (taisaku). Two more points: look for the cause in the process, not the person, and keep asking as many times as needed; five is not a fixed number.
Where Kaizen Stalls When It Moves Overseas
The failures below are common wherever TPS is introduced, and most come from adopting the tools without the thinking behind them. The table summarizes typical patterns; the points after it are what to clarify locally.
Most failures come from adopting the tools without the thinking behind them.
General patterns arranged by the MONOSCOPE editorial team, not cases from any specific company.
- Tools without a foundation. Putting kanban in before leveling and standardized work exist causes shortages and confusion, and the plant concludes that "TPS doesn't fit us."
- Inventory reduction as the goal. Cutting stock without solving the problems it was hiding raises shortages and the workload on the floor. Lower inventory is a means to expose problems, not the target.
- Top-down campaigns. If kaizen depends on a few staff or on orders from above, it ends when the campaign ends. Whether supervisors accept suggestions, let people try them, and recognize the results decides whether kaizen takes root.
- Blame instead of analysis. When a 5 whys session turns into finding who made the mistake, the countermeasure stops at "be careful" or "retrain," and the problem returns. Recurrence prevention starts with the job, the equipment, and the rules.
For an overseas plant, a few points are worth settling in writing before launch: how teian are judged and recognized locally, whether operators get time during paid hours for QC circle work, what language forms and boards use, and who answers yokoten requests from Japan.
A Typical Rollout Sequence
Companies that introduce TPS and kaizen usually start with the foundation, not with kanban. 5S comes first, to make abnormalities visible. Then one model line is chosen, the work and material flow are observed, and the seven wastes are listed. Standardized work is set, and repeated kaizen smooths the flow. Running visual management at the same stage helps, because visible numbers build buy-in.
Once the model line has shown results and a working method, leveling and kanban are added, and the approach is spread to other lines, plants, and suppliers. Toyota itself refined TPS through trial and error at its Honsha plant before extending it step by step to all plants, group companies, and suppliers.
Build the foundation, prove it on a model line, then extend the system.
The sequence varies by company and industry.
Who Does What in Kaizen
TPS and kaizen are not a single department's job; they apply to everyone in manufacturing. Some roles are more deeply involved than others:
- Operators: follow standardized work, notice abnormalities and stop, and propose improvements
- Production engineers (seisan gijutsu): design low-waste material flow and equipment that stops on abnormalities. See Seisan Gijutsu: Japanese Production Engineering Explained
- Production control: build leveled schedules and set kanban quantities
- Quality assurance: lead 5 whys analysis and recurrence prevention
The skills that matter most are observing the floor with your own eyes, reasoning from data and facts, and getting colleagues involved. A practical starting point is to look at your own area through the seven wastes and carry out one small improvement, then add quality control methods and the basics of production planning and inventory control.
Checklist: Before Kaizen Starts at Your Plant
Use this list when a Japanese parent company or customer launches a kaizen program at your site.
- 5S is in place in the target area, and abnormalities are visible at a glance
- Standardized work exists for the model line (takt time, work sequence, standard WIP)
- A suggestion form exists in the local language, with a named reviewer and a response time
- Recognition rules for suggestions are written and agreed locally
- QC circle time, membership, and presentation schedule are decided
- Boards show output, defects, and open problems, and someone updates them daily
- One person owns replies to yokoten requests from Japan
- Root-cause reviews focus on process, equipment, and rules, not on individuals
- Inventory targets are tied to the problems they are meant to expose
- Suppliers affected by kanban or leveling have been consulted
Questions to Ask Your Japanese Counterparts
- Which kaizen mechanisms do you expect here: teian, QC circles, yokoten, boards, or all four?
- How are suggestions evaluated and recognized at your plants in Japan, and can we adapt that locally?
- Is the suggestion count a target per person, or a participation indicator?
- Do QC circles at your plants present to management, and how often?
- When you send a yokoten request, what reply format and deadline do you expect?
- Which lines in Japan can we visit or study as a model?
- Which KPIs will you review from our boards, and how often?
Benefits and Limits of TPS and Kaizen
Done well, TPS improves quality, cost, and lead time (the time from order to delivery) at the same time. Lower inventory cuts storage and management cost, and visible problems raise quality. When everyone on the floor finds and fixes problems, improvement no longer depends on a few specialists, and less searching, waiting, and rework can mean less physical strain and overtime. In Japan, TPS is also drawing renewed interest as a way to raise productivity amid labor shortages.
The system has limits, though. Minimal inventory means production can stop quickly when a disaster or epidemic cuts off parts, and balancing lean inventory with supply chain resilience, for example by holding some stock of critical parts, has become a key issue. JIT also depends on suppliers and logistics; if one company cuts its inventory by pushing it onto suppliers, the chain as a whole gains nothing. Finally, an automotive assembly line model does not transfer directly to products with large demand swings, one-off build-to-order work, or continuous process industries. Each plant has to adapt the ideas to its own production type, and the details of teian, QC circles, and yokoten differ from company to company.
Related: Japanese Automotive Supply Chain: Tiers, Keiretsu, Pricing
FAQ
What is kaizen in a Japanese company?
Kaizen is continuous, small-step improvement carried out by the people who do the work. In Japanese plants it runs through suggestion systems (teian), QC circles, yokoten, and visual management boards, on a base of standardized work and 5S.
What is the difference between kaizen and lean?
Lean is a generalized version of the Toyota Production System, named in the late 1980s at MIT. Kaizen is one part of it: the ongoing improvement activity that keeps the system working. Both center on eliminating waste.
What does yokoten mean?
Yokoten means spreading a fix or good practice horizontally. When a problem is found in one place, similar equipment, lines, plants, and sometimes suppliers are checked for the same problem.
What is a QC circle?
A QC circle is a small group of people from the same workplace who solve quality and workplace problems on their own, using quality control tools. JUSE in Japan began organizing QC circles in 1962.
Why does a Japanese parent ask for a number of kaizen suggestions?
Because the suggestion system values many small ideas from everyone, not a few big ones. The count shows how widely people take part. Ask how the target is set and how ideas are evaluated before you adopt it.
Sources
- TPS definition, two pillars, jidoka, andon, kaizen: Toyota Motor Corporation, "Toyota Production System"
- Kanban types, adoption in 1963 and 1965, leveling: Toyota Motor Corporation, "75 Years of Toyota" (sections on TPS)
- Creative Idea Suggestion System (1951) and the 1953 slogan: Toyota Times, "Imaginative and Creative," part 1
- QC circles and the QC Circle Headquarters (1962): JUSE, "Father of the QC Circle: Prof. Kaoru Ishikawa" (PDF)
- Yokoten: Lean Enterprise Institute, Lexicon, "Yokoten"
- Origin of "lean production": Lean Enterprise Institute, Lexicon, "Lean Production"
- Seven wastes and 5 whys: OJT Solutions, Kaizen Library (Japanese)
Original article in JapaneseThis guide is adapted from a MONOSCOPE article written for readers in Japan: トヨタ生産方式・カイゼンとは？仕組みと基本原理を図解でわかりやすく解説
About the editor
MONOSCOPE EditorFOUNDER & EDITORSpent about ten years at a plant equipment maker and a plant engineering company, proposing, designing, and commissioning equipment, then moved into web marketing. Now a web consultant for B2B manufacturers, helping them explain their products and technology. Licensed in Japan as an Energy Manager and a Third-Class Chief Electrical Engineer.
Has run an engineering blog since 2017 (500+ articles) and a Japanese YouTube channel with about 20,000 subscribers. Each English guide is written from the Japanese shop-floor point of view and checked against the cited standards.
