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Just in Time Manufacturing

Just in Time Manufacturing Concept

JIT Philosophy:

With the progression in product-process technologies and the hybrid manufacturing systems, the Japanese have been perfecting a manufacturing system called ‘Just in Time’ or ‘JIT’. This JIT operating system is nothing but a production strategy that strives to improve business return on investment by reducing in-process inventory and associated carrying costs.

The JIT purchasing system has emphasis on timing to supply materials just in time for use on the factory floor. Equally important emphasis is given to close and long term relationship with a few suppliers. The suppliers in JIT manufacturing are geographically closely located.

Concept of just in time manufacturing

Just in Time Manufacturing


  • Producing and delivering finished goods ‘just in time’ to be sold
  • Partly finished goods ‘just in time’ to be assembled into finished goods
  • Parts ‘just in time’ to go into partly finished goods
  • Materials ‘just in time’ to be made into parts.

Loose specifications instead of rigid product specifications are used which leads to best use of supplier specialization and expertise for low cost and better quality.

Frequent deliveries (daily deliveries) of small lots of exact quantities required are supplied directly to the shop floor avoiding large inventories, paper work and double inspection.

The JIT system underlines the mutual confidence between buyer and supplier and long term relationship. This leads to investment by the supplier for the benefit of the buyer in terms of plant and equipment for improvement of quality, reduction of cost and shortening manufacturing lead times.

Just in Time Strategy

Where does the responsibility lie?

‘The responsibility for the quality rests with the manufacturer of the part’ is the principle behind this Japanese practice. The primary responsibility for quality is transferred from quality control department to the production department.

The quality control is considered a line function rather than staff function. The processes are designed to have less specialization on the part of workers. The physical layout is arranged in such a way that workers can operate two or three machines effectively and thereby become multifunctional.

Good Quality First Time Every Time:

Workers are organized in small closely linked groups thereby building team work. The production for each stage is planned in small lot sizes just meeting the needs of the subsequent stage.

The system is such that even if one item produced is substandard, it would affect subsequent processes causing shortages and exposing the process or worker who has produced substandard item. This acts as a great motivator to produce good quality first time, every time. This also heightens the awareness among the workers about the inter dependence of processes.

Taiichi Ohno, Father of the Toyota Production System saw this as an attribute rather than a problem. He used an analogy of lowering the water level in a river to expose the rocks to explain how reducing inventory showed where production flow was disrupted.

Once bottle necks were exposed, they could be rectified or removed. Since one of the main barriers was rework, lowering inventory shoved each shop to improve its own quality. Just-in-time is a means to improving performance of the system, not an end.

Just in Time

The result of the Japanese manufacturing system is quite pervasive in the areas of:

  1. Reduction in inventory

  2. Reduction in scrap

  3. Reduction in work

  4. Reduction in indirect costs

  5. Reduction in spare

  6. Reduction in administrative costs

  7. Increase in motivation of workers

  8. Increase in quality

  9. Better response to customers

  10. Better system flexibility and quicker response.

What is kanban?

Kanban is Japanese for “visual signal” or “card.” Toyota line-workers used a Kanban (i.e., an actual card) to signal steps in their manufacturing process.

The system’s highly visual nature allowed teams to communicate more easily on what work needed to be done and when. It also standardized cues and refined processes, which helped to reduce waste and maximize value.

toyota kanban


Picture Courtesy: Philosophy of complete elimination of waste

Core principles of Kanban:

  1. Visualize the workflow
  2.  Limit WIP (work in progress)
  3.  Manage Flow
  4.  Make Process Policies Explicit
  5.  Improve Collaboratively (using models & the scientific method)

Lean Manufacturing vs. JIT:

Lean manufacturing takes the concept of JIT and reviews it from the viewpoint of customer value. The first step in the lean manufacturing process is to consider what attributes of the product add real value for the customer.

Just-in-time manufacturing is focused on efficiency, while lean manufacturing is focused on using efficiency to add value for the customer. The first principle of lean manufacturing is that every step in the production process must add something of value that the customer actually wants.