Just-in-time production
The anglicism of just-in-time production ( just in time , JIT ; German “just at the right time” ) or demand-synchronized production refers to a logistics-oriented , decentralized organization and control concept in the production economy , in which only the material in the number and is delivered and produced at the point in time that is actually required to fulfill customer orders .
General
This goal is achieved through different production and delivery methods. The principle of the JIT production requires a coordinated production and material flow along a supply chain ( English supply chain ). This can only be achieved through close cooperation between a supplier / subcontractor and a buyer. As a result, the overall process should be leaner ( lean production ), throughput times and capital commitment should be reduced, and the storage risk should be eliminated, making it more cost-effective for everyone involved.
JIT delivery
The JIT delivery is a logistical call-off and delivery process in which the material is only delivered directly to the customer's production facility by the supplier when it is actually needed. In some cases, the part is also made specifically for delivery, especially high-priced parts. This process has established itself in particular in the automotive and aircraft industry, where mainly large and varied parts and assemblies are delivered directly to the assembly line. For this, the required material is ordered according to the needs of the final assembly. The supplier is contractually obliged to deliver the ordered material within a defined lead time. The material is unloaded directly at the place of work or in the immediate vicinity so that it can be installed as directly as possible. If the material is not installed or cannot be installed immediately, small buffers and certain waiting times may arise temporarily, but there is no storage for this material in the traditional sense.
The JIT production is therefore particularly sensitive and susceptible to exogenous influencing factors such as earthquakes, storms, floods or even strikes, traffic accidents, etc. Due to the technical, economic and natural disasters of recent years, many international companies are involved in appropriate risk management for their to build global production facilities and supply chains (see also web links).
JIS delivery
The further development of JIT delivery is just-in-sequence delivery. Here, the required material is ordered and delivered precisely in the sequence of the final assembly of a product. This requires timely and exact planning and adherence to the assembly sequence, which is also known as a pearl necklace . Since there is no longer any stock, delays in delivery , wrong deliveries , quality defects or rejects immediately lead to a bottleneck and interruption of the customer's production. Therefore, the entire production and delivery process as well as the information chain must be precisely planned, reliably implemented and executed without errors.
History of the JIT
The JIT concept was developed by the Japanese Taiichi Ohno as part of the Toyota Production System (TPS) at the Japanese automobile manufacturer Toyota Motor Company, Ltd. developed. At Toyota, JIT is not just a delivery process, but a comprehensive principle that, alongside the Jidoka principle, is the second cornerstone of the Toyota Productions System (TPS). The JIT principle also includes balancing and leveling the production programs, the pull principle, flow production and the cycle time.
Unlike in the US, the Japanese market was not big enough just to carry returns to scale ( englisch economies of scale to be) economically. Kiichiro Toyoda concluded that in Japan economic and competitive automobile production can only be achieved by eliminating waste ( Japanese muda ). He wanted the pure mass production of Henry Ford , needed to produce more than the market and customer, and the stockpiling and storage related overcome because both represented in his opinion wastes.
According to Taiichi Ohno , this innovative direction became vital for Toyota after 1945, when Toyoda Kiichiro demanded that his company join America within three years . Obviously, Toyota did not meet this requirement, but the resulting impetus would not flag for the next 50 years. JIT first became noticeable in 1973 (the time of the oil shock in Japan) due to Toyota's continued success.
In the area of application, JIT is divided into:
- JIT production - includes the JIT-controlled production process,
- JIT delivery,
- JIT Distribution - Ensuring the supply of a large number of consumers who advertise their needs online.
Requirements for use
| feature | description |
| Production program | Continuous demand (very low fluctuation range / exotic species are controlled via pre-planning according to JIT or JIS ) |
| Layout / areas | Should have sufficient storage space / Please note: JIT or JIS have the lowest space requirements compared to storage on the conveyor belt |
| process | Short set-up times , high availability of resources |
| capacity | Flexible capacity reserves |
| quality | Quality assurance accompanying the process / the most important requirement is 100% quality, since defective parts have to be removed again with a great deal of effort and otherwise compliance with the pearl necklace cannot be guaranteed |
| Disposition procedure | Depending on the range of parts a) JIT or JIS: plan-controlled, central b) Kanban : consumption- controlled , decentralized |
| supplier | only involvement of selected suppliers (delivery failure) |
Further considerations
Application area
Just-In-Time is z. B. used in the automotive industry when
- the components have so many variants that not all of them can be accommodated directly on the assembly line .
Example: The Smart has around 150 cable harness variants. All must be kept for production. However, not all variants can be available on the conveyor belt because there is not enough space for them. Therefore, the sequence of the required cable harnesses (see sequencing (production) ) is output via a printer station and the cable harness variants are placed in the vehicle sequence in a sequencing trolley, which is then brought to the assembly line. This internal JIS delivery is also called SILS ( Sequence Inlining System ).
- The components as larger, multi-variant assemblies (cockpit, front end, door panels, wheels, etc.) are pre-assembled and delivered by an external supplier in accordance with the order in the required sequence. The supplier is informed of the individual variant via EDI approx. 180 minutes before the installation, this is then pre-assembled by the supplier, several assemblies are combined into a truck lot size and then delivered to the manufacturer.
The just-in-time concept means that several suppliers are located in industrial parks or logistics distribution centers in the immediate vicinity of the manufacturer . The suppliers are thereby directly involved in the assembly process. The final assembly time of a car is reduced from the original 20 to approx. 8 (Smart 4) hours thanks to the JIT concept. The supplier must keep the stock of raw materials for the corresponding assemblies so that the manufacturer can reduce his storage capacity. Since the customer's production can come to a standstill if the parts arrive too late, companies with JIT production often purchase the same parts from several suppliers. High contractual penalties are also not uncommon with such manufacturing concepts.
In the case of just-in-time delivery that is not close to the location , the number of trucks increases because the loading volume of large assemblies is significantly greater than that of the individual parts. With shorter delivery frequencies, more smaller trucks are required, which also increases the number of trucks. For local just-in-time deliveries, e.g. For example, from logistics or industrial parks in front of the factory gates of automobile manufacturers, there is almost no truck volume if the just-in-time items are transported directly to the assembly hall by the supplier or logistics service provider.
Kanban
A subsystem of the just-in-time concept is the Kanban system: with the help of a card-based instrument for controlling the flow of materials and information at the workshop level in the production control, the aim is to keep stocks low. Short lead times and guaranteed deadlines are further overarching goals. For this purpose, production is divided into self- regulating control loops , which are supplied according to the supermarket principle. With the help of a Kanban (Japanese for: sign / card), the respective consumer triggers an order with the supplier with a predefined quantity and a specific arrival date. The supplier or producer then brings the required quantity to the customer on the required date in the required installation quality. This is a so-called pulling or pulling principle. Nowadays, physical cards are increasingly being replaced by "electronic" cards (see E-Kanban ), with data transactions being carried out via EDI or WebEDI . Building on the Kanban concept, JIT production can come to full bloom. According to Hernandez, Kanban means "visible records".
Holistic approach
To implement just-in-time production, a holistic approach to customer order processing in a logistical chain (see also supply chain management ) is required.
In order for the production efficiency to be measured, in addition to costs and productivity, the throughput and replenishment times must be considered. With JIT, the production flows and not the individual functions must be optimized. This makes it possible to minimize the total order lead time, i.e. to produce in line with demand and thus to minimize inventory levels (costs).
literature
- Toyota Motor Corporation: The Toyota Production System - Leaner manufacturing for a greener planet. TMC, Public Affairs Division, Tokyo 1998.
- I. Majima: JIT, cost reduction through just-in-time production . Langen Müller / Herbig, Munich 1994, ISBN 3-7844-7310-5 .
- Horst Wildemann : The just-in-time concept . TCW, Munich 2001, ISBN 978-3-934155-63-3 .
- A. Eisenkopf: Just-in-time-oriented manufacturing and logistics strategies . Hamburg 1994, ISBN 3-87154-209-1 .
- Stephan Mühlhäuser: The Toyota production system - a role model for the German automotive industry ?: Just-in-time viewed from a human resource perspective . GRIN Verlag, Munich 2009, ISBN 978-3-640-33226-7 .
- W. Herlyn: PPS in automobile construction - production program planning and control of vehicles and assemblies . Hanser Verlag, Munich 2012, ISBN 978-3-446-41370-2 .
Web links
Individual evidence
- ↑ Gerd F. Kamiske / Jörg-Peter Brauer, quality management from A to Z . Hanser, Munich / Vienna 2011, ISBN 978-3-446-42581-1 , p. 107.
- ↑ Wilmjakob Herlyn, PPS im Automobilbau , 2012, pp. 196–220
- ↑ Gerd F. Kamiske / Jörg-Peter Brauer, quality management from A to Z . Hanser, Munich / Vienna 2011, ISBN 978-3-446-42581-1 , p. 107.
- ^ The Toyota Production System - Leaner manufacturing for a greener planet. Toyota Motor Corporation, p. 11 ff.
- ^ Taiichi Ohno, in: Wallace J. Hopp / Mark L. Spearman, Factory Physics: foundations of manufacturing management , 2nd edition, Irwin / McGraw-Hill, 1988
- ^ Taiichi Ohno: Toyota Production System: Beyond Large-Scale Production . Productivity Press, Cambridge MA 1988, ISBN 0-915299-14-3 . (translation of Toyota seisan hoshiki, Tokyo: Diamond, 1978)
- ^ Wallace J. Hopp, Mark L. Spearman: Factory Physics: foundations of manufacturing management . 2nd Edition. Irwin / McGraw-Hill, Boston 2001, ISBN 0-256-24795-1 .
- ^ Arnaldo Hernandez: Just-in-Time manufacturing. A practical approach. Prentice Hall, Inc., New Jersey 1989, p. 53 .