Process Fundamentals
Flexible resources
Flexibility in resources, materialized in the employment 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 operated them were very different. Often, the employee had to wait a certain amount of time while the machine performed its function.
Thus the idea arose that a single operator could operate 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 expanded. It was necessary, therefore, to train and prepare workers to perform different types of tasks, and to create specific job rotation programs for this purpose. It was also necessary to make modifications to the machines. Mechanisms had to be installed that would stop the machines automatically once their work had been completed.
Fixations were also designed to facilitate the work, so that it was not necessary to move when necessary. The versatility of the employees stimulated the acquisition of multi-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. It is 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 U-shaped. Work moves through the cell from one process to another, as employees follow an established path. The way in which the cells are distributed facilitates the simultaneous production of different products, and allows problems derived from variations in production volume to be resolved by incorporating more personnel into the cell. Since similar items are produced in each cell, the adaptation time of the machines is small and the size of production batches can decrease.
Pull or starting system
One of the big problems that companies face, particularly automotive companies, is the coordination between production, delivery of materials, parts with the preparation 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 prepared that establishes the work to be carried out for each of the workstations, each of which subsequently “pushes” the work already done to the next stage. However, in the pull system, workers go back to the previous station to remove the materials and parts they need to process them immediately. When material is removed, operators at the previous station know that it is time to start production to replace the production removed by the next station. If production is not withdrawn, the employees at 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 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 transportation between stations. On the other hand, reducing inventory levels makes processes become more interdependent, allowing problems to be quickly detected and resolved.
Reduction of manufacturing times and minimized delivery times
Commercial order-taking problems disappear when the manufacturing response is known. No skimping on production machinery. We work 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:
Minimize stock
Reducing the size of 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 error tolerance
Nothing should be manufactured without the security 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 meaning 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, the aim is to create a business culture that facilitates, on the one hand, the management of the company's resources, and on the other, the organization of the different work environments, with the purpose of generating a change in behavior that results in an increase in productivity. It directly affects the way workers do their work.
They represent basic Japanese principles, whose names begin with the letter S:.
Zero technical stops
The aim is to ensure that the machines do not have breakdowns, no downtime during routes, or downtime when changing tools.
Quick adaptation of machinery, or SMED system
The SMED system (from English Single-minute exchange of die) allows you to reduce tool change time on machines, providing competitive advantages for the company. The principles on which the system is based are the following:
To objectively analyze the adaptation process, it is useful to entrust the improvement work to a team in which operators and engineers collaborate. It is often useful to video record processes to try to improve them. You can resort to applying time and motion studies. Once improvements in procedures have been devised, it will be necessary to practice until they can be applied perfectly.
TPM Methodology
Total Productive Maintenance (TPM, from English Total Productive Maintenance) 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, quality, etc., which were traditionally treated separately, must be integrated. This situation generates in operators an environment of responsibility in relation to the safety and operation of their workplace, involving workers in maintenance tasks, inducing them to prevent breakdowns and, ultimately, involving them in the more general objective of continuous improvement.
This maintenance approach can be implemented quickly and quickly results in a significant reduction in machine unavailability, while reducing error levels, increasing productivity and reducing costs. Maintaining a statistical system and statistical process control to verify the evolution and regularity in the evolution of the machines is also part of TPM.
Uniform production
To eliminate waste, JIT production systems try to maintain a uniform production flow. Changes in final demand cause strong variations in the production rate of the final assembly line, which are multiplied to the component production cells. Small variations in demand can be absorbed without problems 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 objectives. 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 about producing the same amount of each product every day, but rather about mixing small quantities of different products in daily production. This makes it possible to produce something of each item every day, thereby better responding 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, very high levels of quality must be achieved. 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 requires identifying quality problems at the source (also called rocks), resolving them, and never passing up a defective product. 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 quality problems are discovered. 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 each day are noted down, and a part of the work 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.[4] It is necessary that suppliers meet demanding quality requirements, and that they are located in close proximity to 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 providers do not also implement the system. If done correctly, they can take advantage of stable and secure demand, advance notice of variations in production volume, assistance with engineering and management issues, and, in general, the benefits that come from the close customer-supplier relationships that characterize just-in-time production.
Some of the recent trends in provider policies are:.
Continuous improvement
JIT production is a practical system, arising from the attempt to eliminate waste and simplify production through the application of trial and error. The last element 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, 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 that are attached to cards. intermediate or final products of a production line. The cards act as a witness to the production process.
External references.
VIDEO Introduction JIT / Toyota Production System in 3 steps.
Article about JIT, what is Lean and Toyota.