Just in time method

Toyota Logo.

The just-in-time method, known by the acronym JIT (in English just-in-time), is a system of organizing of production for factories, of Japanese origin. Also called the Toyota method, it allows to reduce costs, especially in inventory of raw materials, parts for assembly, and final products. The essence of JIT is that supplies arrive at the factory, or products at the customer, "just in time," that is shortly before they are used and only in the quantities needed. This reduces or even eliminates the need to store and move raw materials from the warehouse to the production line (in the case of a factory). JIT can be so accurate that auto parts arrive at the factory the same day they are installed, rolling off the production line on demand.

Summary

The JIT method allows reducing the cost of investment in inventories, and losses in warehouses due to unnecessary actions. For the producer's clients, it is not produced under assumptions, but on real orders. A definition of the objective of Just in Time would be:

“have at hand the elements needed, in the quantities needed, at the time they are needed”.

JIT production is simultaneously a philosophy and an integrated production management system, which slowly evolved through a process of trial and error over a period of more than 15 years. A suitable environment for this evolution was established in Japanese factories from the moment he gave his employees the order to “eliminate waste”. Waste can be defined as:

"anything other than the minimum amount of equipment, materials, parts, space and time, which is absolutely essential to add value to the product" (Suzaki, 1985).

For the development of the JIT there was no master plan or draft. Taiichi Ohno, its creator, describes the development of JIT as follows:

"...when trying to apply it, a number of problems were revealed. As these were clarified, I was told the direction of the next move. I think just looking back, we are able to understand how finally the pieces ended up fitting...".

JIT systems have had an unprecedented boom in recent decades. Thus, after the success of Japanese companies during the years that followed the crisis of the 1970s, researchers and companies from all over the world focused their attention on a form of production that, until then, had been considered linked to traditions both cultural and social aspects of Japan and, therefore, very difficult to implement in non-Japanese industries. However, it was later shown that, although the implementation of the principles and techniques that supported the JIT production systems required a profound change in the philosophy of production, they did not have a specific form of society as an essential requirement.

Fundamentals of the process

Flexible Resources

Flexibility in resources, materialized in the use of versatile workers and multipurpose machines, was one of the first elements to be adjusted. Through the study of movements and times, Ohno observed that the work cycles of the machines and the operators who handled them were very different. Frequently, the employee had to wait a certain time while the machine performed its function.

Thus arose the idea that a single operator could manage several machines. To facilitate implementation, the machines were placed in parallel or in an L-shape. As the number of machines in charge of each employee gradually increased, they ended up being placed in a U-shape, where the beginning and end of the line are together. At first all the machines were of the same type. Subsequently, the variety of machinery handled by each operator was expanding. Therefore, it was necessary to train and prepare workers to carry out different types of tasks, and to create rotation programs for specific positions. It was also necessary to make modifications to the machines. Mechanisms had to be installed that would stop the machines automatically once their work was finished.

Fixations were also devised that facilitated the work, so that it was not necessary to move when necessary. The versatility of the employees stimulated the acquisition of multiple-use machinery, which reduced employee travel, as well as the difficulty of adapting the machines to various uses and the waiting periods for other machines to become available. Important to take into account each of the elements.

Distribution in cell plant

The cells group machines of various types to produce parts of a similar shape or with similar processing requirements. The organization of the machinery in each cell is reminiscent of an assembly line, usually in the shape of a U. Work moves through the cell from one process to another, while employees follow a set path. The way in which the cells are distributed facilitates the simultaneous production of different products, and allows problems arising from variations in production volume to be resolved by incorporating more personnel into the cell. As similar articles are produced in each cell, the adaptation time of the machines is short and the size of the production batches can be reduced.

Pull or starting system

One of the big problems that companies face, particularly automobile companies, is the coordination between production, delivery of materials, parts with the elaboration of partial assemblies and the needs of the assembly line. Traditionally, inventories have been used as a buffer against coordination failures. JIT production's answer to the problem was the pull system.

This system requires reversing the usual process-information flow, which characterizes the traditional push or push system. In the latter, a program is drawn up that establishes the work to be carried out for each of the work stations, each of which subsequently "pushes" the work already carried out to the next stage. However, in the pull system, workers go back to the previous station to remove from it the materials and parts they need to process immediately. When the material is removed, the operators of the previous station know that it is time to start production to replace the removed production by the next station. If the production is not withdrawn, the employees of the previous station stop their work. In this way, both excess and defect in production are avoided. Only what is necessary is produced, understanding as such not what is established in a plan, but what consumers demand. To better control the operation of the system, it was considered necessary to establish a formalization mechanism, called the Kanban system (in Japanese, cards).

Producing in small batches is attractive from two perspectives. On the one hand, less space is needed and fewer resources are mobilized, the distance between processes can be reduced, and with it the cost of internal transport between stations. On the other, reduced inventory levels make processes more interdependent, allowing problems to be quickly detected and resolved.

Reduction of manufacturing times and minimization of delivery times

Commercial order taking problems disappear when the manufacturing response is known. No expense is spared on production machinery. Work is done according to work times, nothing more. The completion time (lead time in English) of a product is reduced, which is made up of four components:

• The time of movementwhich is reduced by approaching machines, simplifying displacements, establishing more rational routes or eliminating the need to move materials.
• The waiting timewhich can be improved by better programming production and installing more capacity.
• The time of machine adaptation: it is often the big bottleneck that companies face, and its reduction is one of the vital elements of the JIT system.
• The processing time, which can be reduced by decreasing the size of lots or increasing the efficiency of machinery or operators.

Minimize stock

Reducing the size of the stock also requires a very good relationship with suppliers and subcontractors, and also helps to greatly reduce logistics costs (Ordering, storage and maintenance costs).

Zero tolerance to errors

Nothing should be manufactured without the certainty of being able to do it without defects, since defects have a significant cost and also with defects there are late deliveries, and therefore the sense of the JIT philosophy is lost

5S Methodology

The 5S methodology aims to create more organized, orderly, clean and safe workplaces. Through its knowledge and application, it is intended to create a business culture that facilitates, on the one hand, the management of company resources, and on the other, the organization of the different work environments, with the purpose of generating a change in behavior that has an impact in increased productivity. It directly affects the way in which the workers carry out their work.

They represent basic Japanese principles, whose names begin with the letter S:

1. Seiri (Classes)
2. Seiton (Orden)
3. Six. (Cleaning)
4. Seiketsu (Standard)
5. Shitsuke (Discipline)

Zero technical stops

It is sought that the machines do not have breakdowns, nor downtime in routes, nor downtime in changing tools.

Rapid adaptation of machinery, or SMED system

The SMED system (from English Single-minute exchange of die) reduces the time it takes to change tools on machines, providing competitive advantages for the company. The principles on which the system is based are the following:

1. Separate internal adaptation of the external. The intern is the one to be performed when the machine is stopped. The external one, which can be done in advance, while the machine is still working. By the time the machine has finished processing a batch, it is necessary that the operators have made the external adaptation, and are prepared to carry out the internal one. Only this idea can save 30-50% of the time.
2. Convert internal adaptation to external. This means making sure that all operating conditions (gathering tools, heating moulds, etc.) are met before stopping the machinery.
3. Simplify all aspects of adaptation. External adaptation activities can be improved by properly organizing the workplace, placing the tools near the places where preventive maintenance work on the machinery is used and carried out. Internal adaptation activities can be reduced by simplifying or removing adjustments.
4. Conduct adaptation activities in parallel, or eliminate them completely. Adding an extra person to the adaptation team can significantly reduce the configuration time. In many cases, the time taken by two people to do a job is much lower than half of what would take a single job.

To objectively analyze the adaptation process, it is useful to entrust the improvement work to a team made up of operators and engineers. It is often useful to videotape the processes to try to improve them. You can resort to applying time and motion studies. Once the improvements in the procedures have been devised, it will be necessary to practice until they are perfectly applied.

TPM Methodology

Total Productive Maintenance (TPM) is an adaptation of Western Productive Maintenance, to which the Japanese have added the word “Total” to specify that all production personnel must be involved in maintenance actions and, likewise, that aspects related to equipment maintenance, equipment preparation must be integrated, quality, etc., which were traditionally treated separately. This situation generates in the operators an environment of responsibility in relation to the safety and operation of their workplace, involving the workers in maintenance tasks, inducing them to prevent breakdowns and, ultimately, involving them in the more general objective of improvement. keep going.

This approach to maintenance can be implemented quickly and quickly leads to a significant reduction in machine downtime, while lowering error levels, increasing productivity and lowering costs. Carrying out a statistical system and statistical control of processes to verify the evolution and regularity in the evolution of the machines is also part of the TPM.

Uniform production

To eliminate waste, JIT production systems try to maintain a smooth production flow. Changes in final demand cause strong variations in the production rate of the final assembly line, which are transferred multiplied to the component production cells. Small variations in demand can be easily absorbed by the Kanban system. However, more abrupt changes end up causing the accumulation of stocks or the need to establish overtime in order to meet production targets. One way to reduce uncertainty is to improve demand forecasts. Another alternative is to try to balance, as far as possible, production over the planning horizon. It is not a question of producing the same quantity of each product every day, but of mixing small quantities of different products in daily production. In this way, it is possible to produce something of each article every day, which better responds to variations in demand. It is also possible to stabilize the production of components, reduce inventory levels and support the pull production system.

Quality at the source and zero defects

For the JIT system to work properly, it is necessary to achieve very high levels of quality. The very characteristics of the system promote the elevation of quality levels. Thus, production in small batches allows operators to better detect defects and identify their causes. The goal is to achieve “zero defects”, which means identifying quality problems at the source (also called rocks), solving them, and never letting a defective product pass. To this end, responsibility for quality is shifted from inspectors to operators, giving them the power to exercise jidoka, which means they have the authority to stop the entire assembly line if problems are discovered. quality. To promote the use of this power, all workers have access to a switch that activates emergency lights or stops the production process. The problems that arise every day are recorded, and a part of the working day is reserved for preventive maintenance. Spending time planning, training, problem solving, and improving the work environment is key to successful JIT production.

Supplier networks

Having a network of trustworthy suppliers is vital for the JIT system. It is necessary that suppliers meet demanding quality requirements, and that they be located in the vicinity of the company, to facilitate frequent deliveries of small batches of parts or components. One of the most widespread beliefs regarding JIT systems is that they do not eliminate the need to maintain stocks, but only shift it to suppliers. This is only true if the providers do not also apply the system. If they do it correctly, they can take advantage of stable and secure demand, advance notice of variations in production volume, engineering and administrative assistance, and in general, the benefits that derive of the close customer-supplier relationships that characterize just-in-time production.

Some of the recent trends in provider policies include:

1. Get close to the customer.
2. Pack small, side load trucks, and make joint shipments.
3. Set small warehouses near the customer, or share the warehouses with other suppliers.
4. Use standardized containers and make deliveries according to a precise delivery program.
5. Become a certified provider, and accept to charge for time intervals instead of for deliveries.

Continuous improvement

JIT production is a practical system, born from the attempt to eliminate waste and simplify production by applying the trial and error method. The last of the elements that characterizes it, continuous improvement, is the most defining of all, because JIT is a system that seeks to permanently optimize inventory levels, adaptation times, quality levels, etc. Therefore, it can be said that lean production is a system that is in a situation of permanent evolution, that is, of continuous improvement.

Kanban

Kanban (from Japanese: kanban, usually written in kanji 看板 and also in katakana カンバン, where kan, 看 カン, means "visual," and ban , 板 バン, means "card" or "board") is a term used in the manufacturing world to identify cards attached to intermediate products or end of a production line. The cards act as a witness to the production process.