Just in time -JIT Introduction
JIT also is known as Just In Time, may be described as an extension of the original concept of managing the material flow in a factory to reduce the inventory levels. In fact, there is much more involved in a manufacturing organization than reducing inventories to control costs. Manufacturing has to deal with other issues, such as process control, level of automation, flexible manufacturing, machine set up times, direct labor productivity, overhead, supplier management, engineering support, and the quality of product delivered to customers. A modem manufacturing organization has to deal efficiently with these issues in order to operate a smooth, productive, and quality-minded department. This chapter gives an overview of JIT (just in time manufacturing ) system in which all these aspects are taken care of.
JIT or Just in time Manufacturing strategy
With the development of faster means of communication, better quality computers, and rapid transportation systems, manufacturing is no longer restricted at the local level but has become global in character. As a manufacturing company has to become competitive for its survival, it has to supply products of consistently high quality at reliable and reduced delivery time. The market also demands more product variants that mean reduced lot size and high flexibility in operations. Manpower cost has also risen. All these factors tend to increase the product cost. But the industry has to maintain the cost at a reasonable level. Confronting these challenges, companies world-wide are forced to find ways to reduce costs, improve quality, and meet the
Ever-changing needs of its customers. One successful solution has been the adoption of Just-in-time (just in time manufacturing)g in which many functional areas of a company such as manufacturing, engineering, marketing, and purchasing etc. are involved.
Just in time Inventory – Background
The basic idea of JIT (just in time manufacturing) was originally developed in Toyota Company of Japan. In the 1960s, Toyota worked hard on developing a whole range of new approaches to manage to manufacture The development of these approaches was hastened by the ‘Oil shock’ of the 1960s. By 1972, these new approaches had begun to attract wide attention in Japan and in the mid-1970s other Japanese companies began to experiment with, and adopt these approaches. At this stage and for some time later, this was not known as JIT (JUST IN TIME MANUFACTURING); it was called ‘Toyota Manufacturing System’. By the end of the 1970s, the Toyota Manufacturing System had begun to attract attention in the West. One of the many elements of this system was a pull scheduling technique using ‘Kanbans’. The system first became known in the West as the ‘Kanban System‘. However, this was rather misleading, as Kanban was only a small part of the total system. Since the early 1980s, the approach has become widely known. As the approach has been adopted by Western companies, it has been given many shapes including ‘Zero Inventory’, ‘World Class Manufacturing’, and ‘Continuous Flow Manufacturing’.
However, the term that has now become most wide to describe this approach to manufacturing is the ‘Just-in-Time system’. The Just-in-Time system is not one technique or even a set of techniques for manufacturing but is an overall approach or philosophy, which embraces both old and new techniques. Nowadays, JIT (just in time manufacturing) concepts are being applied in a variety of industries across the globe.
Definitions of JIT
It is an approach, which is demand-driven and encourages flow type production. It is also described as a drive to simplify the manufacturing system in order to quickly detect the problems and force immediate solutions. JIT (just in time manufacturing) has been continuously defined and updated by many researchers.
JIT can be summarized as a system to eliminate waste and achieve excellence in an entire organization. The sole purpose of JIT is to eliminate waste. Anything that does not add any value to the product is termed as waste. Waste may also include anything that is not necessary for the manufacturing of a product or is in excess.
Elements of JIT (Just in Time Manufacturing)
Various elements of JIT (JUST IN TIME MANUFACTURING) as stated by many researchers are mentioned below
- Autonomation (i.e. Jidoka)
- Buffer stock removal
- Cellular manufacturing
- Computer integrated manufacturing
- Continuous improvement
- Effective communication
- Flexible workforce
- High quality
- JIT (JUST IN TIME MANUFACTURING) purchasing
- Layout improvement
- Poka yoke
- Preventive maintenance
- Process flexibility
- Product & Process simplification
- Quality circles
- Setup time reduction
- Small lot size
- Smooth flow of materials
- Smooth production
- Standard containers
Brief descriptions of these elements are given below
Automation and autonomation: Autonomation means, “to build in a mechanism to prevent mass-production of defective work in machines or product lines. An autonomous machine is a machine to which an automatic stopping device is attached. Thus the aim is to ensure that 100 percent good units flow to the subsequent process, in a rhythmic, uninterrupted manner.
Buffer stock removal: Constant elimination of buffer stocks is emphasized to highlight production problems previously shielded by high inventory levels. These have to be resolved without delay in order to maintain production. The removal of buffers also releases space.
Cellular manufacturing: Many JIT (JUST IN TIME MANUFACTURING) factories are organized in small autonomous modules or cells, each cell being totally responsible for its own production and supply of the adjacent module. The cells are designed so that the material flow between the cells is minimized. For this purpose, it is common to create ‘families’ of parts which are then processed by a dedicated group of machines in a cell. Within the cell, the workforce is trained to work as a group and often many functions normally considered as staff functions such as scheduling and maintenance are brought into the cell or module.
Computer integrated manufacturing: The use of computers to automate manufacturing operations, such as changing the type and quantity of manufactured products through minimal changes in hardware and/or software.
Continuous improvement: JIT (JUST IN TIME MANUFACTURING) is not a one-time effort. It embodies the ethics of continuous improvement, which needs to be supported by all levels of staff in the production team. JIT (JUST IN TIME MANUFACTURING) seeks plant-wide involvement in work improvement projects. Suggestion schemes are therefore strongly encouraged and supported.
Flexible workforce: Flexible workforce is created through multifunctional training and job rotation. Each worker rotates through and performs every job in the workshop to which he is assigned. In the job rotation system, all managers and supervisors are made to rotate through every job, each worker within each shop is rotated through and trained to perform each job in the shop, and scheduling of the workers through job rotation at a frequency of several times each day. A flexible workforce is necessary to match the production rate and product type as closely as possible to the market demand.
Quality: The achievement of high quality levels is a prerequisite of successful JIT (JUST IN TIME MANUFACTURING). Commonly used quality programmes in support of JIT (JUST IN TIME MANUFACTURING) include:
- Zero defects
- Statistical process control
- Statistical quality control
- Process data collection
- Worker centered quality control
- Use of Poka-yoke stops devices
- Autonomous inspection and counting
- Quality circles
JIT (JUST IN TIME MANUFACTURING) purchasing: Materials and components are purchased in compliance with well- defined requirements in terms of quantity, quality, and delivery. JIT (JUST IN TIME MANUFACTURING) emphasizes small lot purchasing, vendor development, long term buyer-seller relationships, vendor involvement in product design, high quality of purchased material, frequent part delivery, cooperative transport system, etc. A full-fledged JIT (JUST IN TIME MANUFACTURING) is virtually impossible without JIT (JUST IN TIME MANUFACTURING) supply.
Kanban: It is a pull system of managing material movement comprising a ‘Kanban Card’ based information system. It helps trigger the movement of material from one operation to the next. Merely by altering the frequency of the circulating Kanban, the production system can be made to adjust to demand fluctuations within limits. The number of cards in the system determines the total inventory. Hence, the objective is to minimize the total number of Kanbans.
Layout changes: The physical layout of production facilities is arranged so that the process flow is as streamlined as possible, i.e. for each component, the proportion of value-added time is maximized. The flow is analyzed in these terms and the layout configured accordingly resulting in the reduction and/or elimination of stores and conveyors. Use of dedicated lines, U-shaped or parallel lines, use of small machines with multiple copies, small plants with multiple copies may be possible. The flexibility of equipment is essential to adjust quickly to changes in market demand, product type etc.
Poka yoke: Autonomous defect control is a pillar of JIT (JUST IN TIME MANUFACTURING). In this system, almost all machines are autonomous, so that mass production of defects is prevented and machine breakdowns are autonomously checked. Poka-yoke is one such mechanism to prevent defective work by putting various checking devices on the implements and instruments. This idea is extended to the production lines of manual work through the Andon light board system. If something abnormal happens in a product line, the worker pushes his stop button, thereby stopping the whole line.
Preventive Maintenance: Effective JIT (JUST IN TIME MANUFACTURING) requires the removal of causes of uncertainty and waste. A major cause of uncertainty is the breakdown. Rigorous preventive maintenance attempts to remove this uncertainty.
Product and Process simplification: This can be achieved by two measures: the rationalization of the product range and the simplification of the methods of manufacture. Simplification is also brought about through component item standardization and component routing standardization.
Small-lots and Set up time reduction: JIT (JUST IN TIME MANUFACTURING) advocates small lot production on the basis that it allows the production of a daily mix of products that more closely match demand. The object of minimizing setup times is to reduce the batch sizes to the minimum possible thus reducing manufacturing cycle time and the manufacturing inventory. This also results in the release of floor space and minimizes material handling. Until the introduction of flexible manufacturing systems, however, small batch production generally not justified because it was too expensive to set up conventional, non-automated equipment for a short production run. Today, however, the driving force behind flexible manufacturing is to make it economically justifiable and technically possible to produce even a single unit. Flexible automation is a prime tool for companies that implement JIT (JUST IN TIME MANUFACTURING). Setups that take hours in a traditional approach take minutes in JIT (JUST IN TIME MANUFACTURING) operations. Use of ‘SMED’- Single Minute Exchange of Dies. System-is are common to set up reduction projects.
Smoothing of production: Smoothing of production is the most important condition to achieve JIT (JUST IN TIME MANUFACTURING). Production smoothing enables the system to adapt smoothly to the variations in customer demand by gradually changing the frequency of lots without altering the lot size in each process. To achieve this, JIT (JUST IN TIME MANUFACTURING) systems often resort to under capacity scheduling. The flexibility of production lines can be increased to allow concurrent assembly of different models on the same line.
Standard containers: JIT (JUST IN TIME MANUFACTURING) emphasizes the use of small-standardized containers. This way it is possible to greatly simplify the material movement and the use of material handling equipment.
Standardization: The emphasis on the standardization of activities arises from balancing between processes, which is expected to improve operational effectiveness and efficiency. By standardizing job activities, resources can be focussed on only a few areas. The resulting impact on productivity can be significantly higher if one standardizes activities and concentrates organizational efforts and resources on those limited activities. Standardization of activities also reduces the time and cost of cross-training employees, but the flexibility has to be maintained in order to serve the different needs.
JIT (JUST IN TIME MANUFACTURING) is a management philosophy affecting every aspect of an organization not only manufacturing but also marketing, human resource management, planning, and all other organizational functions. Successful JIT (JUST IN TIME MANUFACTURING) implementation requires not an only commitment of everyone within an organization but also the cooperation of suppliers, and often of the customers as well. In the literature, the following factors have been suggested for successful JIT (JUST IN TIME MANUFACTURING) implementation.
Top management support: Top management support has been recognized as the most important factor in the implementation of JIT (JUST IN TIME MANUFACTURING) because JIT (JUST IN TIME MANUFACTURING) is an innovative approach, which requires changes throughout the organization as well as the commitment of all people within the organization
Employees’ participation and bottom-up management: Employees’ participation and bottom-up management have been recognized as important factors for successful JIT (JUST IN TIME MANUFACTURING) implementation because they lead to the improvement of performance in quality, productivity, and flexibility. It is achieved through teamwork, education, flexibility in work practices and skills, simple payment schemes, appropriate skill training, an appointment to management positions who understand production.
Education and training: Education and training play a pivotal role in a JIT (JUST IN TIME MANUFACTURING) environment. Both attitude change and skill development are necessary. Management and employees at all levels in the organization must understand and accept the need for JIT (JUST IN TIME MANUFACTURING) change. It is important that all levels of management understand JIT (JUST IN TIME MANUFACTURING) philosophy, how JIT (JUST IN TIME MANUFACTURING) operates, the expected benefits, and needs for JIT (JUST IN TIME MANUFACTURING) implementation. Management also needs to understand the nature of the attitudinal skill and knowledge level changes required of them and their employees. One important requirement for full-scale implementation of JIT (JUST IN TIME MANUFACTURING) is an increase in the level of technical skills and flexibility of workers. Others include better interpersonal and communication skills, stricter adherence to procedures and schedule, increased judgment and responsibility, and greater dedication and commitment.
Teamwork: The involvement of people at all levels of an organization is paramount in JIT (JUST IN TIME MANUFACTURING) implementation aspects. The creation and maintenance of teams is the mechanism by which this involvement occurs.
Quality: One of the basic requirements for a successful implementation of JIT (JUST IN TIME MANUFACTURING) is the existence of total quality management principles.JIT (JUST IN TIME MANUFACTURING) experts advise against the implementation of JIT (JUST IN TIME MANUFACTURING) unless a company has made a full commitment to quality. JIT (JUST IN TIME MANUFACTURING) requires quality throughout the process, from the supplier through manufacturing all the way to the customer. Commonly used programs in support of JIT (JUST IN TIME MANUFACTURING) include zero defects, statistical process control, process data collection, worker-centered quality control, use of poka-yoke stop devices etc. Employees must perform their tasks correctly the first time. The use of quality circles and Kaizen concepts is helpful in this regard.
A good relationship with vendors: Materials and components are purchased in compliance with well-defined requirements in terms of quantity, quality, and delivery. JIT (JUST IN TIME MANUFACTURING) emphasizes small lot purchasing, vendor development, long term buyer-seller relationships, vendor involvement in product design, high quality of purchased material, frequent part delivery, cooperative transport system, etc.
Benefits of JIT
The most significant benefit of JIT (JUST IN TIME MANUFACTURING) is to improve the responsiveness of the firm to the changes in the market place- thereby affording it overwhelming advantages in competition.
Product cost: Product cost is greatly reduced due to reduction of manufacturing cycle time, reduction of scrap, inventories, space requirements, material handling, and elimination of non-value adding operations.
Quality: Quality is greatly improved due to fast detection and correction of defects, use of automatic stop devices, higher quality of purchased parts, and worker centered quality control and statistical process control. Total preventive maintenance, and lower inventory levels also help quality improvement.
Design: Due to fast response to engineering changes, alternate designs can be quickly brought on the shop floor
Productivity: Productivity improvements are obtained due to the use of flexible workforce, reduced rework, reduced inspection, reduced part delay and reduced throughput time. Workers acquire multiple skills and become highly productive.
Flexibility: System’s flexibility i.e. response to change improves. The change may involve variations in quantity of demand, type of products, routing pattern, alternate materials, workforce availability etc.
Administrative efficiency: There are fewer suppliers, minimal expediting and release of papers, simple communication and receiving. Many times incoming inspection is eliminated altogether.
In most applications, benefits reported have been dramatic. However, a point commonly made by most implementing organizations is that there are so many intangible and non-quantifiable benefits of JIT (JUST IN TIME MANUFACTURING), that it is grossly erroneous to assess JIT (JUST IN TIME MANUFACTURING)’s impact purely from quantified benefits.
Problem In Just in time Implementation
It is easy to understand the concepts of JIT (JUST IN TIME MANUFACTURING) in terms of eliminating waste and improving productivity. But, in reality, the concepts are difficult to implement because of the need for fundamental organizational changes Wafa and Yasin. The factors that hinder the implementation of JIT (JUST IN TIME MANUFACTURING) in the manufacturing environment have been grouped into four categories.
These four categories are:
• Lack of formal training programs for management.
• Extent of management support to JIT (JUST IN TIME MANUFACTURING) implementation.
• Lack of communication between workers and management.
• Lack of formal training programs for workers
• Reduction in labour turnover rate
• Increase in workforce morale
• Extent of cross-training workers
• Extent of workers’ resistance to cross-training
• Extent of the use of unionized workers
• Unionized workers as a hindering
• Reduction in setup times
• Reduction in the levels of workload variability
• Cut down setup time through machine modification or replacement of existing equipment
• Cut down maintenance time through machine modification or replacement of existing equipment
• Lack of cooperation of suppliers in communication and information exchange
• Lack of cooperation of suppliers incorrectly supplied materials
• Lack of cooperation of suppliers in the timing of supplied materials
• Extent of use of sole suppliers