The term Kanban is a Japanese word of common vocabulary that signiﬁe ” label, Fiche…” ».
This is the origin of a simple plug that is fixed on the bins or parts containers within an assembly line or a storage area. With each collection of parts (bins or containers) by the downstream Position , the label goes back to the upstream Position .
Developed by T. OHNO after the second war, his first application took place during the years 1950 on the production lines of the Toyota Motor Company1.
It is during this time and through his trip to the United States that Mr. Ohno finds that “ people always tend to overproduce ” and looks for the means to produce:
1. The product requested
2. At the time it is requested
3. In the quantity requested
Improvements in production processes sought to maintain flexibility allowing the company to produce small batches of different products in order to meet the different market demands2. In 1949, Ohno supervised the machining shop himself and was concerned about the hunting of the stock which meant for him the stagnation of the production. Several employees are looking to overproduce in order to reach their quota3. Therefore, Ohno has sought to solve this problem by deploying a stock management.
In fact, he rediscovered the just-in-time that would have been initiated by Kiichiro Toyoda in the mid-1930 years. This concept implied that it was sufficient to buy (or produce) exactly the quantity of parts needed and that suppliers should bring them just when they are required and not accumulate. The realization of this idea helped to reduce the needs of the working capital. Only produce the necessary quantity, buy only the necessary parts, and sell to dealers at the time when Toyota their vehicle book was Kiichiro’s policy. At the time, this idea was not applied in a systematic way. In fact, at the dawn of the Second World War, the company had six months of inventory of parts or components. Moreover, during the Second war, the Army paid the fifth of the truck order as soon as it was launched, which avoided much of the liquidity problems4.
Ohno wants to create a tense flow between the production stages. To do this, it is based on a management model that is experiencing a major boom in the aftermath of World War II, the supermarket. The client (the downstream workstation) will search for goods (parts) on the shelves (upstream workstation), and it is sufficient for this empty space to replace (produce) the goods sold (parts taken). A visit to the United States in 1956 will allow it to refine its knowledge of this sector of activity and to apply its conclusions to the production line5.
It starts its experiments between workstations of the same workshop. At the beginning of the years 1950, he sought to ensure that the needs of the Assembly workshop triggered the production of the Machine shop. Initially, employees were in charge of multiple production machines. They had to harmonise the flow of production between these units6. Synchronization attempts prevented the appearance of a stock of work pieces. He notes that during this synchronisation exercise, the production of parts that would be needed later or to produce too much is triggered too early.
For Ohno, this problem is just a problem of sharing information. To solve it, it introduces in 1954 the Kanban to prevent excess production. Initially, the system was made up of a fixed number of bins containing a certain amount of a given item. Each locker has a Kanban. All the pieces were kept in a locker and did not accumulate on the factory floor. It is thus possible to manage by the eyes the flow of parts and the state of the stocks. In addition, Ohno orders each operator to stop production rather than accumulating inventory of current products.
It should be clarified that the Kanban was deployed very slowly within the production operations. In 1954, it is applied to the machine shop and then to the Assembly workshop in the second manufacturing division. It should be understood that initially for operators and supervisory officers this approach was contrary to the usual practices based on the size of batch7 and Ohno then forces the application of Kanban to the framing agents. In 1959, it was extended to the workshops of sheet metal and stamping, painting and assembly of the new plant of Motomachi. In 1962, the method was extended to the smelting and forging activities. So all of Toyota’s workshops were synchronized with this approach. In all these situations of expansion, these were sites under the responsibility of Ohno. In 1963, the company’s senior management decided to generalize the Kanban to all sites to use as a tool to transform the production system8. In 1965, we began to deploy the Kanban to suppliers.
The Kanban label, by its function, must contain the following minimum information:
- The reference to or elements to be provided
- The quantity to be supplied
- The customer Position Reference
- The reference of the Position ” supplier “
The Kanban loop
The Kanban label plays a role in Command that goes to the reverse of the physical flow. The upstream Position should only produce what is requested by its downstream post Position , which should only produce what is requested by its own downstream Position , and so on… The most downstream Position to produce only to meet customer demand.
The order of the Kanban loop is as follows :
- the downstream operator: It starts a container. It then releases the kanban attached to the container and disposes it in the Kanban table of its Position (the table that constitutes the orders for its supplier Position ). If on his control board, he has his client’s Kanban, he continues to produce using his security stock. Otherwise, he’s waiting.
- The handler: He picks up the Kanban and goes to the upstream Position .
- The upstream position: It removes the Kanban present on a solid container, puts it on the Kanban board of this Position (table which is also the orders for its supplier Position ) and substitutes the Kanban Position .
- The Warehouseman: He brings the full container with the Kanban to the downstream Position .
- The upstream position: It filled a container. If there is a Kanban in its control panel of the downstream Position , it removes it, fixes it to an empty container and resumes production. If there is no Kanban, it means that the in-progress is sufficient and it waits.
The production flow and production stock levels are automatically regulated, with the upstream Position producing only if the downstream Position has consumed products.
A relatively similar system was found in Europe in pharmacies to allow automatic replenishment of stocks. On every medicine box, we put a small label. Each time a box was sold, the label was placed in a container. In the evening, it was enough to place an order of each label to replenish the stock. The ordered labels were then placed in a container awaiting receipt. When the order arrived, the label was placed on the box again.
This very simple system allowed to know what to order (the labels of the first container) and what was waiting for delivery (the labels contained in the second container) without any writing or registration.
Concept of security Stock
The security stock is an essential notion in the Kanban. When the downstream Position issues a Kanban, the security stock is left to the Position post. This stock must allow the operator to :
- Produce Although the customer demand accelerates while the card is supplied.
- Produce Although the return of the card is longer than expected.
Advantage of the system
There are many advantages to setting up a Kanban. We find:
- The communication of information is faster.
- Production is harmonised and the bottlenecks are more easily identifiable and resolved.
- The delivery times are more respected.
- Production planning is simplified.
- A lower stock level (in-progress, raw materials, finished products) thus generating better cash flow, reduced storage areas…
The limits of the Kanban
- The Kanban does not allow to have a long-term vision because it does not make a forecast on the customer demand and the evolution of market trends.
- The Kanban, in its strict implementation, is poorly adapted to productions that are too highly subject to the variability of demand that requires anticipation and expectation of customer expectations.
- In the case of parts a very low consumption class C (called Slow Moving), the Kanban fits poorly. We will prefer the Chakko Hiki that works in a pushed stream.
The Chakko Hiki
This is a production planning mode of MRP type. The customer request is distributed in a delivery schedule. From this schedule and the breakdown of the nomenclature, we will plan the production of the parts. This system with an inverse philosophy of the Kanban and the drawn stream adapts however correctly to very low consumption parts.
Setting up the Kanban
The Kanban is the key tool for setting up the just in time. It is especially interesting for philosophy and its culture. Indeed, the Kanban will force the company to follow the customer demand so to focus on its needs and expectations.
1. Initial Condition
The condition of success in setting up the just-in-time in a physical process or in an information process is to have ensured upstream a smooth load.
If you do not smooth, the JIT will speed up your process and therefore speed up the increase the effect of the variation!
2. Scope of implementation
If the process still suffers too many variations, it is necessary to have first short interfaced flows between them to process the variations and avoid propagations in short loops.
Depending on the maturity of the process with respect to variations, the short or longer loops will have to be adjusted to end up with a continuous loop.
3. Choice of 3 types of Kanban loops
The Kanban allows you to meet the constraints of your sector of your product specification.
Conditions for success in setting up a Kanban
Far from regulating disturbances, the Kanban system tends to ampliﬁer their effects, unlike the stocks that dampen them. It must be ensured before its implementation that:
- The workshops are well established.
- The series change times are reduced.
- The hazards are deletion (faults, non-conforming parts…).
- The variability in the customer demand is limited.
Rules for using Kanban
The sustainability of the Kanban will depend on the respect of some essential rules:
- The upstream Position only manufactures the quantity of product indicated on the Kanban.
- Without a Kanban, we must not produce or do any product Handling .
- Reduce the amount of kanban cards or reduce the size of the batch on the Kanban force to question and improve.
- Avoid increasing the number of Kanban as soon as you encounter a problem of failure of stock.
- A specific Kanban is associated with products, wherever they go and wherever they are.
- The downstream workstation Position operator goes to the upstream Position to pick up only the number of parts indicated on the Kanban.
- A Kanban can only take into account the 100% defect-free products.
Prioritize management with Kanban
In order for the operator to be autonomous in the management of its priorities, the principles of the Visual Management. For each product, an index showing the total of each type of Kanban and the stock levels is highlighted.
- Red Zone: This is the safety stock to avoid production hazards by keeping a minimum stock of parts containers. it becomes urgent to produce because from the next consumption of the customer Position , you will be out of stock.
- Orange Zone: It corresponds to the ” normal ” Production wait time without the risk of a break in the course.
- Green Zone: This is the normal manufacturing cycle.
The Kanban : Just a label ?
The Kanban is a label that includes the information necessary for the upstream Position to be able to deliver the downstream Position . However, to improve the use of the Kanban, some arrangements are possible. Below are examples.
The site Kanban
This involves replacing the Kanban labels with ground-based locations, located geographically between the supplier Position and its customer (or customers). A location is a container or a crate of products. The number of locations of each type is determined by the operation of the system. If one or more locations is or are empty, the provider must produce. If all the locations are full, the supplier must not produce.
This system has many advantages:
- It is very visual, whether one is supplier or customer, it sufﬁt to take a look at the level of the sites to know where it is.
- There is no manipulation of labels: it is not likely to forget to return them to its supplier. We don’t risk losing them either.
In the example, the vendor Position produces 3 product references a, B, and C for its two internal clients.
The locations are physically materialized between the supplier Position and the customer’s Position. It sufﬁt to look at the stocks to observe that there are:
- Only one product container has been available and 5 empty locations.
- All B product locations are full.
- Only one product location C is empty.
The production priority therefore lies at the level of product A.
Note that the Kanban spéciﬁque per location is not as flexible and ﬂexible as the Kanban per label: If consumption varies, it is easier to change the number of labels in circulation than to modiﬁer the number of slots.
The system says double box
This consists of putting on all items 2 boxes per product Reference: A box represents what is in use, the second represents the security stock. The process is as follows :
- The operator uses the elements of the ” in progress ” box.
- Once it is finished, the operator places it aside on a specific location.
- Then he takes the “Security” box.
- A Logistician, on his tour, takes the empty boxes to fill them and put them back in their place.
The interest of this system is to be simple and visual. It is widely used for consumables (hardware, bolt, pen, Eraser…) because it facilitates the work of replenishment and avoids losing cards.
Other type of setting up
Many companies show great imagination and originality in the creation of Kanban spéciﬁque lines. A company, for example, has replaced the Kanban labels with colorful ping-pong balls that are returned very quickly from the customer Position to the supplier Position by compressed air hoses. The color of the ball represents the reference as well as the number of parts to be manufactured. The management of priorities is extremely simple: first ball arrives, first ball treated.
Some tips on how to design the Kanban card
A Kanban card can be relatively “Cold” and simply contain the name of the Part, the quantity… To improve their management, you can set up a visual management:
- Replace the customer and vendor Position Reference with a color code.
- The Partreference s can be replaced by an actual Part Voireune schema.
- Quantities May work differently. For example, in a double-box Kanban, you can use boxes with a size of the required quantity.
1-T. Ohno (1988)-The Toyota production System: Beyond Large-Scale production.
2-It should be noted that in order to help employees correctly choose the parts to be mounted according to the different batches to be produced, ahari-gami sheet tells them the technical specifications of the car.
3-A. Taylor (1990)-Why Toyota keeps getting better and better and better
4-E. Daito (2000)-Automation and the organization of production in the Japanese automobile industry: Nissan and Toyota int the 1950s
5-S. Regani, S. Dutta (2004)-Taiichi OHNO and the Toyota Production System
6- Toyota (1988) – A History of the First 50 years, Toyota Motors Company
7- Specify that there are two types of Kanban : A first for parts that must be incorporated into an operation and a second for parts that must be produced in order to satisfy downstream operations (S. Regani. and S. Dutta, Op. Cit.).
8-M. Udagawa (1995)-The Development of Production Management at the Toyota Motor Corporation
A. Courtois, M. Pillai, C. Martin Bonnefous (2011)-Production Management
D. Baeli, G. Loures (2012)-Kanban for Dummies