Firstly, I am gonna introduce the mean of kaizen

The word Kaizen means "continuous improvement". It comes from the Japanese words 改 ("kai") which means "change" or "to correct" and 善 ("zen") which means "good".
Kaizen focuses on eliminating waste, improving productivity, and achieving sustained continual improvement in targeted activities and processes of an organization.

Production stage
The cost management in the production phase starts after mass production has begun. Firstly, these costs and standard times are not always met in production lines at least for the first few months, because workers are not used to working in the new system, and also because installations often break down. At Toyota, the learning effects seem to appear almost three months after the launch of new production. If the referential cost is not reached despite learning effects, then kaizen activities in order to reduce the cost or new drawings will be tried. Secondly, when the target profit for each vehicle is not realized efforts have to be devoted on the one hand to increasing sales and on the other to cost reduction. kaizen activities for cost reduction are imperative. At Toyota, the costs to be managed in the Production Divisions consist of materials (including purchased parts, tools and energy) costs and labor cost.

TPS (TOYOTA PRODUCTION SYSTEM) is the essential framework and philosophy organizing Toyotafs manufacturing facilities, and the interaction of these facilities with the suppliers and customers. Its main objective is to eliminate Muda, (waste), a term now familiar even with its American subsidiaries. As quoted by Bruce Bremer, facility engineering manager at Toyota, he said. An important part of the TPS is the Just-in-Time (JIT) inventory system, which all of Toyota manufacturing facilities are required to inculcate into their production lines. The JIT technique was adopted by Toyota in the 1950s and refined to an elevated level of efficiency, one that made it the worldfs leader in employing the JIT system.

JIT is the principle of having parts ready just as when they are desired, thus eliminating the need and more importantly the cost of holding inventory. Besides having less capital held up in inventory with the JIT system, more flexibility is also given to the facility as engineering improvements can also take place much more quickly, with no stockpile of parts needing to be cleared; problems with specific parts can be also be detected much more efficiently since they are used as soon as they are delivered.

Kaizen, is the philosophical outworking of continuous improvement in the TPS. When the art of Kaizen is perfected, it goes beyond delivering improvements; it makes the workplace a warmer environment, reduces menial work, and teaches employees to do rapid experiments via scientific methods and to identify and hence eliminate the Muda within the business. It is applicable for anything from bottlenecks to neck soreness to soaring energy costs and everything in between. A specific example in which Toyota operates Kaizen is in its Obeyamethods of improvements. Obeya, which stands for big room, is where workers usually from different departments or even external stakeholders like suppliers meet face to face in a think-tank like meeting to suggest ways to improve efficiencies or pre-empt production problems. Prior to the production of the Avalon model, Toyota brought all of its key suppliers into a common workroom to identify problems and work out solutions. this process has reduced the number of engineering changes that would otherwise emerge later in the project.