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Just In Time



The principle of Just in time (JIT) is to eliminate sources of manufacturing waste by getting right quantity of raw materials and producing the right quantity of products in the right place at the right time. The main purpose of this project is to provide informations to the people who is interesting in knowing JIT. ( Of course, the main intend users are students in this course.)


Conceptual Theory

1. History of Just in Time

Just-In-Time is a Japanese manufacturing management method developed in 1970s. It was first adopted by Toyota manufacturing plants by Taiichi Ohno. The main concern at that time was to meet consumer demands. Because of the success of JIT management, Taiichi Ohno was named the Father of JIT. (Cheng,2)

After the first introduction of JIT by Toyota, many companies followed up and around mid 1970s’, it gained extended support and widely used by many companies.

One motivated reason for developing JIT and some other better production techniques was that after World War II , Japanese people had a very strong incentive to develop a good manufacturing techniques to help them rebuilding the economy. They also had a strong working ethnic which was concentrated on work rather than leisure, seeked continuous improvement, life commitment to work, group conscious rather than individualism and achieved common goal. These kind of motivation had driven Japanese economy to succeed. (Cheng, 3)

Because of the natural constraints and the economy constraints after World War II, Japanese Manufacturers looked for a way to gain the most efficient use of limited resources. They worked on "optimal cost/quality relationship". (Cheng, 4)

Before the introduction of JIT, there were a lot of manufacturing defects for the existing system at that time. According to Hirano, this included inventory problem, product defects, risen cost, large lot production and delivery delays. The inventory problems included the unused accumulated inventory that was not only unproductive, but also required a lot of effort in storing and managing them. Other implied problems such as parts storage, equipment breakdowns, and uneven production levels.(4-5)

For the product defects, manufacturers knew that only one single product defects can destroy the producer’s creditability. They must create a "defect-free" process.

Instead of large lot production - producing one type of products, they awared that they should produce more diversified goods. There was also a problem of rising cost, the existing system could not reduce cost any further but remember improvement always leads to cost reduction.

Lastly, the existing system did not manage well for fast delivery request, so, there was a need to have a faster and reliable delivery system in order to handle customers’ needs.

Thus, JIT manufacturing management was developed based on this problems.


2. Introduction Phase for Just in Time

According to Hirano, the introductory phases of JIT involves 5 steps. (14)

JIT factory revolution


JIT factory revolution


Step 1: Awareness Revolution

It means giving up old concept of managing and adopting JIT way of thinking. There are 10 principles for improvement:

1. Abolish old tradition concepts. 
2. Assume that new method will work.
3. No excuses is accepted.
4. It is not seeking for perfection, absolutely zero-defect process, few defects is acceptable.
5. Correct mistakes immediately.
6. Do not spend money on improvement.
7. Use you brain to solve problem.
8. Repeat to ask yourself 5 times before any decision.
9. Gather information from several people, more is better!
10. Remember that improvement has no limits. (Hirano, 18)

The idea of giving up old concept was especially for the large lot production, The lot production was felt that "having fewer changeover was better", but it was no longer true. Whereas JIT is a one-piece flow manufacturing. To compare the two, Hirano had this idea:

Lot production: "Unneeded goods...In unneeded quantities...At unneeded times..." (20) JIT: "Needed goods...In needed quantities...At needed times..." (21)

The main point here is to have an awareness of the need of throwing out old system and adopting a new one.

Step 2: 5S’s For Workplace Improvement (Hirano, 28-58)

JIT factory revolution


The 5S’s stand for:

Seiri - Proper Arrangement
Seiton - Orderliness
Seiso - Cleanliness
Seiketsu - Cleanup
Shitsuke - Discipline

This 5S’s should be implemented company-wide and this should be part of a total improvement program.

Seiri - Proper Arrangement means sorting what you have, identifying the needs and throwing out those unnecessary.

One example is using red-tags. This is a little red-bordered paper saying what the production is, how many are accumulated and then stick these red tags onto every box of inventory . It enhances the easiness to know the inventory status and can reduce cost.

Seiton - Orderliness means making thing in order. Examples include keeping shelves in order, keeping storage areas in order, keeping workplace in order, keeping worktables in order and keeping the office in order.

Seiso - Cleanliness means having a clean workplace, equipment, etc.

Seiketsu - Cleanup mean maintaining equipment and tools.

Shitsuke - Discipline means following the rules and making them a habit.

Step 3: Flow Manufacturing (Hirano, 64-66)

JIT factory revolution


Flow manufacturing means producing one single piece of product at a time but multi-handling which follows the process sequence.

There are several main points concerning flow manufacturing:

1. Arrange machines in sequence.
2. U-shaped production line (Cellular Manufacturing).

JIT factory revolution

3. Produce one-piece at a time.
4. Train workers to be multi-skilled.
5. Follow the cycle time.
6. Let the workers standing and walking around while working.
7. Use small and dedicated machines.

The author continued by comparing lot production with flow manufacturing, here is a short summary of comparison.

Lot Production Flow Manufacturing
1. Floor layout is job-shop type

2. Grouping machines of same type together

3. Large lot product

4. Machines used are large

5. Inventory is easy to accumulate between processes

6. Single-process handling

7. Workers are sitting while working

8. Workers are single-skilled

9. Inspection at the final stage process

1. Floor layout is U-shaped cell

2. Different types of machines are type together put together into one cell

3. One-single piece at a time

4. Machines used are small

5. Less or even no inventory between processes accumulated

6. Multi-process handling

7. Workers are standing while working

8. Workers are multi-skilled

9. Inspection at the end of each process

So, we can see that there was a need to change from large lot production to flow manufacturing.

Step 4: Standard Operations (Hirano, 102)

Standard Operation means to produce quality safely and less expensively through efficient rules and methods of arranging people, products and machines.

The basis of standard operations are:

1. Cycle time It means how long it would take to "carry out part all the way through the cell". (Hirano, 79) Following are the equations for calculating cycle time. (Hirano, 79)

Daily Quantity Required = Monthly Quantity Needed / Working Days per month

Cycle Time = Working Hours per day / Daily Quantity Required

2. Work sequence
3. Standard stock-on-hand
4. Use operation charts

JIT factory revolution

JIT factory revolution

Step 5: Multi-Process Handling

Multi-process handling means one worker is responsible for several processes in a cell. (Hirano, 110)

JIT factory revolution

Some points that should be aware: (Hirano, 110)

· Clearly assign jobs to machines and workers.
· Make a good use of U-shaped cell manufacturing.
· Multi-skilled workers
· Operation should be able to perform multi-machine handling and multi process handling.

Multi-machine handling - a worker should handle several machines at once, this is also called "horizontal handling". (Hirano, 112)

Multi-process handling - a worker should handle several different processes at once, this is also called "vertical handling" and this is the basis for JIT production. (Hirano, 113)

· Uses casters extensively As author written, "Floor bolts are our enemies! Machines must be movable." (Hirano, 119)

The above 5 steps are the basis for introducing JIT. Only after these are completed can JIT be implemented.

3. Elements of Just in Time

According to Cheng, the basic elements of JIT manufacturing are:

· People Involvement (6)
· Plants (6)
· System (6)

People Involvement

Maintaining a good support and agreement from people involved in production. This is not only reduce the time and effort in implementation of JIT, but also minimize the chance of creating implementation problem. (Cheng, 6) The attempt to maximize people’s involvement may carry through the introduction of quality circle and total involvement concept. (Cheng, 7)

Manufacturers can gain support from 4 sources.

1. Stockholders and owners of the company - should maintain a good long-term relationship among them. (Cheng, 6)

2. Labor organization - all labors should be well-informed about the goals of JIT, this is crucial in gaining support from the them. (Cheng, 6)

3. Management support - support from all level of management. The ideas of continuous improvement should spread all over the factory, managers and all shop-floor labor. (Cheng, 7)

4. Government support - government can show their support by extending tax and other financial help. This can enhance the motivation, and also help in financing the implementation of JIT. (Cheng, 7)


Certain requirements are needed to implement JIT, there are:

1. Plant layout - the plant layout is mainly focus on maximizing working flexibility. It requires the use of "multi-function workers". (Cheng, 7)

2. Demand pull production - it means to produce when the order is received. This can manage the quantity and time more appropriately. (Cheng, 8)

3. Kanban - a Japanese term for card or tag. Special inventory and process information are written on the card. This helps tying and linking the process more efficiently. (Cheng, 8)

4. Self-inspection - it is carried out by the workers at catch mistakes immediately.

5. Continuous improvement - this concept should be adopted by every members in the organization in order to carry out JIT. This is the most important concept of JIT. This can allow an organization to improve its productivity, service, operation and even customer satisfaction in an on-going basis. (Cheng, 8)


This refers to the technology and process that combines the different processes and activities together. Two major types are MRP(Material Requirement Planning) and MRP II (Manufacturing Resource Planning). (Cheng, 8)

MRP is a computer-based, bottom-up manufacturing approach. This involves two plans, production plan and master production schedule. Production plan involves the management and planning of resources through the available capacity. Master production schedule involves what products to be produced in what time. (Cheng, 8)

MRP II is mainly involved the management or planning of financial resources in order to carry out the operation. (Cheng, 8)

The above three factors formed the element of JIT.

4. Goal of Just in Time

According to Cheng in Just-In-Time Manufacturing – An Introduction, he explains the ideas of Suzaki for the objectives of JIT. (9-10) There are three main objectives:

1. Increasing the organization’s ability to compete with others and remain competitive over the long run. The competitiveness of the firms is increased by the use of JIT manufacturing process as they can develop a more optimal process for their firms.
2. Increasing efficiency within the production process. Efficiency is obtained through the increase of productivity and decrease of cost.
3. Reducing wasted materials, time and effort. It can help to reduce the costs.

Other short-term and long-term objectives(Cheng, 11) are:

1. Identify and response to consumers needs. Customers’ needs and wants seem to be the major focus for business now, this objective will help the firm on what is demanded from customers, and what is required of production.

2. Optimal quality/cost relationship. The organization should focus on zero-defect production process. Although it seems to be unrealistic, in the long run, it will eliminate a huge amount of resources and effort in inspecting, reworking and the production of defected goods.

3. Reduce unwanted wastes. Wastes that do not add value to the products itself should be eliminated.

4. Develop a reliable relationship between the suppliers. A good and long-term relationship between organization and its suppliers helps to manage a more efficient process in inventory management, material management and delivery system. It will also assure that the supply is stable and available when needed.

5. Plant design for maximizing efficiency. The design of plant is essential in terms of manufacturing efficiency and utility of resources.

6. Adopt the work ethnic of Japanese workers for continuous improvement. Commit a long-term continuous improvement throughout the organization. It will help the organization to remain competitive in the long run.

Some other similar ideas are presented by Melnyk and Denzler(387-388):

1. Reduction of Inventory. JIT reduces inventory at all level of the organization.

2. Reduction of Lead Time. Lead time such as setup time and move time and waiting time is reduced.

3. Quality Control. JIT improves the quality control by increasing its efficiency of managing shop floor production and increasing its commitment to its suppliers.

4. Improvement for Performance. In JIT manufacturing, the organization can obtain a greater impact/control over its suppliers. With fewer suppliers, organizations have larger control because the amount purchased is usually large. And, organizations can obtain a tighter requirement on products from their suppliers.

5. Total Preventive Maintenance. JIT provides preventive maintenance to lessen the risk of machine breakdowns.
6. Continuous Improvement. JIT is a never-ending method in operation management.

7. Strategic Gain. JIT helps organization to remain competitive in the market place.

8. Reduction of Wastes. JIT helps significantly in reducing wastes.

There are seven wastes discussed in the book.

· Overproduction wastes – waste from producing too much.
· Waste from waiting time – unproductive waiting time for job processing.
· Waste from transportation – unnecessary movement of jobs.
· Waste from process – unnecessary operation of products.
· Waste from inventory – excess accumulation of products.
· Motion Waste – unnecessary human activity. · Product defects waste – waste resulted from scrap, rework, etc.

JIT can help organization remains competitive by offering consumers higher quality of products than their competitors, it is very important in the survival in the market place.

These major objectives are suitable for all organizations. But each organization is unique in some way, adjustments of JIT objectives for each form should be made in order to complement the overall production process.