Kaizen (Continuous Improvement)
Improvement is eternal and infinite; build a system where every person, every day, surfaces problems and makes things a little better
Kaizen in the Toyota Production System is not a separate program or initiative but the fundamental operating philosophy that permeates everything. Improvement is eternal and infinite; it should never become fixed at any stage. The system advances by the minute through the accumulated effect of countless small changes: workers suggesting better work sequences, foremen finding ways to reduce setup times, supervisors identifying hidden waste, and managers redesigning production flows. The kanban system itself drives kaizen by making problems visible and by challenging the organization to reduce kanban numbers continuously, which exposes the next layer of issues to solve. Toyota's approach insists that improvement comes from need and from the shop floor, not from desk-top planning. Letting the plant people feel the need is the key to progress. Necessity is the mother of invention, and the system creates necessity systematically.
- Improvement is eternal and infinite; it should never become fixed at any stage
- Necessity is the mother of invention; letting plant people feel the need is the key to progress
- The key is not the speed of improvement but the consistency: the tortoise beats the hare
- Work improvement should come before equipment improvement and contribute at least half of total cost reduction
- Everyone must understand the system; improvements cannot come only from managers but must involve every worker
- Standard work procedures must be written and then continuously revised based on experience on the production floor
- Correct a mistake immediately; to rush and not take time to correct a problem causes work loss later
- Creativity and resourcefulness must be applied continuously; no one can improve manufacturing by just walking through and looking
- Create the Conditions That Make Problems VisibleImplement systems like kanban, andon boards, and standard work that make the normal state explicit and any deviation from it immediately apparent. When problems are hidden by excess inventory, surplus workers, or workarounds, no one feels the need to improve. Reduce buffers systematically to expose problems one layer at a time.Pro tipReducing inventory is like lowering the water level in a river to expose the rocks. Each rock exposed is a problem to solve, and solving it strengthens the system.WarningExposing problems without the organizational commitment to solve them creates frustration rather than improvement. Management must support workers when problems surface.
- Engage Every Worker in ImprovementWorkers on the production floor have the most direct knowledge of waste and opportunity. Train them to write and revise standard work procedures, identify waste in their own movements, and suggest improvements. The supervisor must take the workers' hands and teach them, generating trust while building capability.Pro tipIt should take only three days to train new workers in proper work procedures when instruction in the sequence and key motions is clear. Continuous training is not a burden but a foundation for improvement.
- Pursue Improvements Based on Need, Not TheoryEvery improvement should be driven by a concrete need observed on the production floor. Try ideas, revise them, try again, and correct again. Do not wait for perfect plans or theoretical proofs. The Toyota Production System was built block by block through persistent experimentation, not through desk-top planning.Pro tipOhno decided not to press for quick, drastic changes but to be patient. The gradual spread of improvement built deep understanding and lasting change.WarningImprovements pushed forward before thorough study can end up costing more to implement than they save.
- Systematically Reduce Kanban to Drive the Next WaveContinuously reduce the number of kanban in circulation. Each reduction lowers inventory and exposes the next set of problems. Solving these problems improves the process, which enables the next reduction. This creates a self-reinforcing cycle of improvement that never ends.Pro tipClose supervision of the kanban rules is a never-ending task. The system advances by the minute, and maintaining discipline while continuously improving is the ongoing challenge.
- Measure True Cost Reduction, Not ActivityEvery improvement idea, when boiled down, must be tied to cost reduction. The criterion for all decisions is whether cost reduction can be achieved. List every conceivable improvement idea, examine each in depth, and select the best. Do not confuse the activity of improving with the outcome of reducing cost.Pro tipIf an improvement can be made at zero cost by changing the work sequence, do not spend money on equipment to achieve the same result. The cheapest improvement that works is the best improvement.
Toyota's die change process was reduced incrementally over decades. In the 1940s, changes took two to three hours. As production leveling spread in the 1950s, times dropped to under an hour and eventually to 15 minutes. By the late 1960s, setup was down to 3 minutes. Everyone chipped in with ideas while workers were trained to shorten changeover times.
When asked what Toyota was doing at the pinnacle of its improvement journey, Ohno answered simply: looking at the time line from the moment the customer gives an order to the point when cash is collected, and reducing that time line by removing non-value-added wastes.
The entire Toyota Production System evolved through continuous improvement over decades. Ohno started with small experiments in his machine shop in the late 1940s, arranging machines differently and trying to have one worker operate multiple processes. He encountered resistance, learned from problems, tried again, and corrected again. The spread of kanban from one shop in 1953 to company-wide adoption in 1962 was a ten-year journey of incremental refinement. When Ohno was asked about writing the system down, he resisted because improvement is never-ending and recording it would crystallize the process. Setup times that took two to three hours in the 1940s were reduced to under an hour in the 1950s, to 15 minutes, and then to 3 minutes by the late 1960s, with each increment driven by workers and managers chipping in with ideas and training to shorten changeover times further.