Kanban

Kanban is a method of production process control. The procedure is based solely on the actual consumption of materials at the marshalling and the place of consumption. Kanban allows a reduction of the local stocks of precursors and close to the production, which are installed there in products of the next integration step.

The aim of the Kanban method is to control the value chain on each Fertigungs-/Produktionsstufe a multistage integration chain at optimal cost. The withdrawals from the respective buffer storage and later sending is asynchronous in the same buffer stock. By distributing the buffer stock in production along the chain integration is achieved with a simple solution simple means of information and with short distances of transport.

Kanban comes from the Japanese. There is,かんばん(看板) as much as " card", " panel " or " document ". Alternative names for kanban are pick-up, call or pull principle.

Historical development

The original Kanban system was developed in 1947 by Taiichi Ohno in the Japanese Toyota Motor Corporation. One reason was the insufficient productivity of the company compared to U.S. competitors. Ohno described the idea as follows: " It should be possible to organize the material flow in production after the supermarket principle, that is, a consumer withdraws from the shelf goods of certain specification and quantity; the gap is filled up again and notice ".

Also presented the increased expectations of customers in the rate of production and delivery capability as well as the ever closer supplier relationships between the companies represents a new situation had to be found for an appropriate solution. High and thus, in particular on a cramped island like Japan, costly inventories of raw materials and semi-finished materials here were the cost drivers. To minimize these costs, a flexible and efficient manufacturing system was sought. This was found in the Kanban method that previous common methods of production control and intra-logistics replaced. The actual production remained unaffected. Subsequently, this concept of short-term planning has been adopted by many Japanese companies, adapted to the respective requirements and finally introduced in the entire Toyota Group. In the 70s of the last century, this management concept of business was adapted and introduced in the U.S. and Germany. Connected to Toyota and thus Japan is also the meaning of the word Kanban, which means " sign" or " cards ". These cards are based element of the PPS system and provide a simple information transfer.

Advantages over the central production control

In traditional, centralized planning systems, production control of all the material needed at a central location is pre-planned to the smallest detail. The individual production points have little opportunity to influence the flow of material in case of fluctuations in throughput. This fact made these systems in a conventional organization with weak IT support inflexible and, in the case of short-term changes in the parts to be produced also slow, since these changes have far-reaching consequences and a high coordination burden. This means that in centrally planned systems, a high stocking is necessary to compensate for the lack of flexibility, which in turn causes high inventory costs.

In contrast, the Kanban system offers a high potential for adaptation to short-term changes in demand, as with the To -tilt walking a required precursor of the contract for post-production is triggered in a timely manner. Here, the information forwarding is always up to date and adjusted to suit the current demand situation from the consumer to the producer or the supplier. This can dramatically reduce unnecessary inventories and shorten cycle times significantly.

Kanban is a way for companies, some of which very complex and nested production control with autonomic control circuits to operate, which significantly reduces the control complexity and increase the transparency of the process contexts. In the run, however, the local chains and the product spectrum are accurately adjust to the Kanban method. If this preparation is met, Kanban is particularly interesting for companies with relatively low variety and relatively constant consumption where storage costs are a major cost factor.

But even with greater number of variants or long supply can be used Kanban useful if, for example, modern information technology is applied. Here, however, a considerably greater planning and coordination effort required.

Kanban is unsuitable for individual products or for special orders or even project production, since the required standardization of the production program is not given.

By reaching high degree of flexibility and delivery reliability JIT with Kanban orders are easier to manage than traditional PPC systems.

The increased responsibility and qualification within the control loops employee motivation can be increased considerably.

Objectives

The aim of kanban systems is the reduction of inventory levels and thus reduce capital commitment and an increase in the flexibility with regard to changes in required quantities. This goal should be achieved without loss of readiness for delivery, without deterioration of scrap rates, without increasing rework, additional transportation, etc.. All of this should take place with strong planning a depreciation expense.

The frequently observed improvements in readiness for delivery, scrap rates, rework, etc. are secondary effects.

Conditions for the application of Kanban

Kanban requires companies may require a variety of changes to introduce this material control system effectively. Takeda identifies seven essential requirements that must be met before the use of Kanban.

Furthermore, high quality of the precursors in conjunction with a strong quality assurance key prerequisites for a functioning kanban system as it may cause a compensation of bad parts are interruptions in the production process by the low level of inventories. Therefore, a quality management system must be implemented, which consists of automatic quality control, self-control by the staff and of process controls.

Suitability for the Kanban manufacturing

Kanban is not suitable as a management tool for production in any case. In addition to these requirements for the use of Kanban in particular must be aligned on the Kanban product structure. Here are the main criteria that must be met:

• Particularly useful products with high value content and high quantitative prediction accuracy, low demand fluctuations (AB / XY products ) and low proportion of special requests. A large number of variants, a single unit or frequent product changes for the Kanban system, however, are problematic and are therefore less suitable.
• In the manufacturing sector only production facilities are suitable, which are characterized by relatively constant and low set-up times, qualified personnel and adequate and relatively flexible disponierbare capacity.
• If Kanban to control the external purchasing department is to be used, both the suitability of suppliers to high delivery reliability and consistently high quality are crucial.

If the conditions and the criteria are not met, problems that may have the failure of introduction of the Kanban system of impact arise. Therefore, it is of the utmost importance to critically examine these points in advance and make changes if required in the processes.

Areas of application

The system can be used with parts from the warehouse very good at single-stage production depth ( final production) for the supply of production equipment. A reduction in inventory is then alone, is not possible.

Kanban can generally be used in most production areas, regardless whether the parts removed from the storage or just made ​​. In larger plants, the Get the parts ( and thus the need for automatic notification) by an independent in-house transportation must be done. In particular, for relatively standardized products with low number of variants with a relatively stable demand Kanban is suitable.

Ultimately, Kanban is particularly suitable for series production.

Kanban is not suitable for individual production. The purchasing of raw materials and parts can be about not handle. Similarly, bulky parts, it is not suitable ( for example, packaging), which are delivered in each truck or container size.

Operation of a Kanban system

A kanban system is basically controlled by the production of the final stage: there falls below the stock level of a particular material a defined minimum value ( reorder point ), this is reported to the upstream production unit or the competent stock. This is met if necessary production and the provision of material for the site.

In the traditional Kanban system, this communication chain uses the kanban cards that come with the filled transport containers to the sink. Once the contents of the container is used, sets the sink, the Kanban card in a kanban collection box. The cards are regularly distributed to relevant sources. The source is then responsible for the timely provision of material needed in the Valley.

Upon receipt of the kanban card, the source begins with the production or supply of the specified on the card type and quantity of material and stores them in kanban containers. Once the kanban container is filled with the required amount, he is transported into the buffer storage of the source with the Kanban card. From there, the sink itself then supplies this way, a self -controlling loop without central planning authority.

Often this system is also compared with a supermarket, in which the customer ( lower) self- serve and the staff ( sources) for adequate inventory on the shelves (buffer stock) makes. Achieved the consuming point again the reorder point, the cycle begins anew.

Differ generally been divided into the two- card system which works with production and transportation kanban, and the Einkartensystem which the transport container served as auxiliaries.

During the two- card system mainly finds application in -house production, the Einkartensystematik is often used because of the ease of handling for the control in collaboration with external suppliers.

Thus, a sufficient number of kanban cards present in the system, determines a Kanban Coordinator prior to the required number of cards and adjusts them if necessary changed circumstances. Basically for the number of kanban cards in the system, the rule that must circulate enough material to cover the required quantities occurring in the replacement period.

Kanban rules

To ensure a low-friction operation of the Kanban system, the implementation of legally binding rules is essential. These are:

To comply with these rules are the employees who are highly involved in the functions of the Kanban system to train, and the strict observance of these basic requirements have to be accepted by the staff.

Elements and tools of Kanban control

Kanban cards

Kanban cards are classic kanban system, the primary control element and the basic information carrier, which contains all relevant production, storage, purchase and transport from the source to the sink data. These include:

• Item numbers / identification numbers
• Information about the nature and capacity of the transport containers
• Names of sources and sinks
• Work instructions / data quality
• Number of kanban card

Commonly around six types of kanban cards differ:

• Production kanban
• Transport Kanban
• Shopping Kanban
• Running Card Kanban
• Stock -Kanban
• Special -Kanban

The determination of the number of kanban cards within a kanban loop ( distance between source and sink ) is based on the following formula:

This means:

About the number of cards in Kanbankreis ( between source and sink ) and the estimated average inventory can be determined in units:

Average inventory in units

This value can therefore be used, since in the Kanban quantity demanded and the quantity produced subject to large fluctuations; thus uniformly consumed and reproduced.

Production kanban

This kanban trigger an order for the production of the said material on the map and be attached to the material, which is located in the buffer storage of the valley. Once the sink material removes from the buffer stock, the production kanban is sent to the source, after which the production order is triggered.

In the event that the material produced is ordered in the same loop, the production kanban can simultaneously serve as a transport order from the source to the sink. Importantly, according to the kanban rules listed shall be no production without production Kanban, otherwise the production is not more consumption-based.

Transport Kanban

Once a sink has a container completely consumed, it relates by forwarding a transport kanban replenishment from the buffer stock. There, the transport container enclosed production kanban is replaced by the transport Kanban the valley, and the material needed is supplied according to the information on the map of the valley. Thus, the transport Kanban is used as internal transport order. At the same time the kanban container enclosed production kanban is sent to the source and triggers a post- out.

Kanban container

Alternative to the illustrated card system can also be controlled via the container necessary for the transport of materials kanban control cycles. For this purpose, all required information is attached to the shipping containers themselves, and the control of the production on observation of the spent container. So that means that the input of an empty container at the source of production order is created ( bin Kanban ). Regardless of whether it is controlled by or Zweikartenkanban Behälterkanban, it is necessary to ensure the size and shape of the parts, and the handling, safety and distinctness of the container in the design of the transport container. To prevent possible confusion here, must be noted on each kanban container which is to be transported with the container material, for example, one article number. To avoid unnecessary and costly transport, the size of the container, the production lot of the material should be adjusted.

Kanban boards

Kanban boards have several functions in the control loops. On the one hand, they serve the sequencing triggered by various kanban cards production orders, and on the other hand, they serve to capacity planning and the organizing of kanbans in various levels of urgency. By Kanban boards also the loss of kanban cards is prevented by using a single storage system for the cards involved in the production process. Although this tool is not an essential component of a Kanban system, but the use of such boards is recommended for the above mentioned reasons.

Incoming Kanban cards are discarded to their corresponding item number in the blanks of the table starting from the left. One of these fields is marked with "Start". Once a newly arrived card on the "Start " field is stored, all these article number to run relevant production orders. Additionally it can be used for special orders the " Haste " box. It is important for a functioning kanban board that the number of allocated tickets is not too high. Otherwise, the advantage of clarity, omitted, and possible disruptions or bottlenecks in the system are not recognized.

Kanban boards with barcode

In addition to the signaling of the states "full " and " nachzuliefern " is possible with three-level information and the state " Ordered " or " Will be delivered shortly " present. It is illustrated with a simple sliding mechanism of the state of the kanban container all parties involved in the material cycle. For example, the color green is "full " or " containing sufficient material ". If by moving the panel, the bar code visible, for example on yellow background, which means the request for subsequent delivery. By scanning the bar code of the delivery order is generated and processed electronically, in the same part of the panel is moved further on, such as red, so the scan is documented and all is signaled that the goods are coming soon. An example of such a sliding panel is SLIDELOG. Especially suitable this approach is at the end points of computerized systems where a fully electronic recording would be awkward or time-consuming.

Signal -Kanban for buffer stocks

Another Kanbanform works without moving maps as a tool: Control is performed by visual monitoring of the buffer stocks, which are stored at fixed locations in the vicinity of the source. These storage areas are characterized by fixed, usually triangular maps, which identify maximum and minimum stocks. Once a material has reached the minimum stock level, the post-production begins. It is recommended that a classification of such a storage area in different colored segments to increase the clarity of the source.

E -Kanban

Modern production systems are often dependent on strong use of information technology due to their complexity and variety. Therefore, it was important for companies to integrate the introduced Kanban system in their PPC system. For this integration are from different manufacturers, such as SAP, Cell fusion and other solutions offered which enable kanbangesteuerte supply chain over the Internet. This kanban is also possible for companies whose sites are widely distributed, or that are dependent on other companies as subcontractors. However, this caused a number of interfaces that must be served by such a PPS system. Among other things, the areas of production control, purchasing, quality assurance, transport and assembly are affected and must be elements of the EDP. In order to create an easy-to -use by the employees and thus error-free system, the use of Kanban cards, which are provided with barcodes recommends. Through this, the status of an article by can be "present" changed to " post production " and thus automatically trigger a production order with the supplier. At goods receipt, the material is re- booked by re- scanning as a "present". Of particular importance is that both consumption and input of materials are recorded by the staff consistently. Otherwise stoppages in production can arise due to the long delivery times may turn.

Another advantage of a computerized Kanban system is that all the control loops, sources and sinks, as well as buffer stock at any time can be represented graphically, making bottlenecks or problems can be countered quickly. Often the supply chain is represented graphically by dynamic networks, whereby an identification of weak points in this can be done easily. An example of the successful use of e -Kanban over a large spatial distance represents the Daimler factory in Sindelfingen, which successfully controls the order of seat leather to producer in South Africa.

For example from the production

The practical implementation of an electronic Kanban system will be illustrated on a real example of a luxury goods manufacturer, who introduced such a system in 2003. The objective was to reduce the lead times for production, and the capital commitment involved. The advantage is the high proportion of AB- XY parts proved with approximately 66 % in the products of the manufacturer, which well appropriated by their relatively constant consumption for Kanban production and accounted for a large proportion of total sales. For the remaining parts, which were likely due to their low consumption predictability and less good for Kanban, large stocks have been introduced to compensate for fluctuations in demand. Similarly, the existing hitherto high inventories should substantially reduced and simultaneously the delivery reliability be increased. Prior to the processes involved a detailed examination were subjected to their suitability and staff receive extensive training in order to achieve understanding and acceptance of the new system. As the software already present in the company system was extended to the Kanban functionality, which minimized software-based problems. To create an error-free order management, a barcode system was introduced, which triggers production orders by simply scanning the kanban cards and also completes. External suppliers who could meet the requirements for Kanban are now integrated directly into the Kanban control cycles, and the remaining suppliers turn to reorder process in order to continue to use their conventional PPC - systems.

Overall, this led to a reduction in inventory levels by 48% and by reducing the setup times and batch sizes to increase the flexibility to change requirements. Similarly, the readiness for delivery could be increased to 98 %, which was previously not feasible due to storage in warehouses. Thus, the production more efficient and customer satisfaction has improved, what the company is rated as very positive.

Disadvantages and problems

Although the system sounds simple, the implementation is complex. At the point of consumption must be space for at least two containers each part. The container size and the number of containers depends on the spatial dimensions of the individual products, the consumption of material per day, the target safety stock, the desired range of the stock, and thus the frequency of filling and the space at the point of consumption. The prefabrication and the internal transport must be carried out before the stock is exhausted to the point of consumption.

There are also also production processes, in which instead produced by consumption " stockpiled "; For example, plastic parts or stampings. The setup of the machines ( change of form or tool change) takes a long time and the start-up losses (Committee ) are high. Here, the needs of a particular period is satisfied either by average fuel consumption, due to a sales plan or a control loop with trigger stock, minimum stock, maximum stock and possibly optimal lot size.