Kanban

Kanban originates from the Toyota Production System

‍

Based concepts

1. All efforts to attain low-cost production are “reduction of cost through elimination of waste.” This involves making up a system that will thoroughly eliminate waste by assuming that anything other than the minimum amount of equipment, materials, parts, and workers (working time) which are absolutely essential to production is merely a surplus that only raises the cost
2. Recognition of Japanese diligence: the high degree of ability and favoured labour environment requires full use of the workers’ capabilities. Treat workers as human beings and with consideration. Build a system that will allow the workers to display their full capabilities.

From the materialisation of this system, Toyota has attached special importance to “just-in-time production” and “Jidoka”

‍

Distinguishing features of the automotive industry

To have an efficient production system in the automotive industry, it is required that the following three distinguishing problems be solved:

1. The automotive industry is a typical mass production assembly where each vehicle is assembled from several thousand parts that have undergone numerous processes. Therefore, trouble in any of the processes will have a large overall effect.
2. There are very many different models with numerous variations and with large fluctuations in demand for each variation
3. The vehicles are completely remodelled every few years, and there are also often changes at a part level.
   

‍

Just-in-time Production

To avoid problems such as inventory imbalance and surplus equipment and workers, Toyota recognised the necessity of schemes that could be adjusted to conform to changes due to troubles and demand fluctuations.

The just-in-time production is a method whereby the production lead time is greatly shortened by maintaining conformity to changes by having

All processes product the necessary part at the necessary time and have on hand only the minimum stock necessary to hold the process together

The goal is to make full use of workers’ capabilities.

‍

One-piece production and conveyance

• All processes approach the condition where each process can produce only one piece, can convey it one at a time, and have only one piece in stock both between the equipment and the process
• No process for any reason is allowed to produce an extra amount and have a surplus stock between the process
• Each process must approach the condition where it produces and conveys only one piece corresponding to the single unit that is coming off the final assembly line.

Outcomes:

1. Reducing lot size
2. Thoroughly shortening setup time
3. Improving production methods
4. Elimination of in-process inventory
5. Improving conveyance
6. Reduce repetition and mixed loading

‍

Leveling production

The conditions required for levelling:

1. Small lot production
2. Quantity withdrawn by the subsequent process varies
3. The process maintains peak capacity or holds execessive inventory at all times.

What to know:

• To make just-in-time production possible, the prerequisite will be to level the production at the final assembly line (the most important line that gives out the production instructions to all processes).
• The production per day is averaged by taking the number of vehicles in the monthly production schedule classified by specifications and dividing by the number of workdays.
• In regard to the production sequence during each day, the cycle time of each different-specification vehicle is calculated, and in order for all specification vehicles to appear at their own cycle time, different-specification vehicles are required to follow each other.
• Produce only as much as is sold. On the one hand, adjusts to its production level according to the change in the market, but on the other hand, producing as smoothly as possible within a certain range.
• Even after the monthly production schedule has been decided, Toyota will still make changes among the different specification vehicles based on daily orders and even the total number. If necessary to meet changes in market conditions, Toyota will make revisions in the monthly schedules to reduce the shock of market fluctuation as much as possible.

‍

Elimination of waste from over-production

The value of the existence of inventory is disavowed.

The conventional system: the existence of inventory is appreciated as a means to absorb troubles and fluctuations in demand and to smooth fluctuations in the load of the process