Just in Time and KANBAN

Just-in-time Philosophy
JIT manufacturing is defined as the elimination of all waste and continuous improvement of productivity.
Waste means anything other than the minimum amount of equipment, parts, space, material, and workers’ time absolutely necessary to add value to the product. This means there should be no surplus, there should be no safety stocks, and lead times should be minimal.

The concept of JIT:
To have the right parts and quantities at the right time and place.

Many elements are characteristic of a JIT environment: 

• Flow manufacturing
• Process flexibility
• Total quality management
• Total productive maintenance
• Uninterrupted flow
• Continuous process improvement
• Supplier partnerships
• Total employee involvement

Kanban System
With shortened lead times a constant goal in JIT, a system is needed to generate the reorder point signal without having to rely on a formal, structured system that could take time to react.
A simple card system called Kanban, which roughly translated from Japanese means card or ticket.
The system works very simply. The Kanban signal (often a piece of cardboard) identifies the material to which it is attached.
Withdrawal Kanban (WK)
A move signal that calls for refilling the raw material.
Circulated from the customer process (or down station or succeeding station) to the supplying process (or previous station or preceding station).

At customer process:
Operator:
Processes the parts when the PK has been shown.
Removes WK and places it in a collection box once he/she begins to use the first part in that container (or you also can set the rule that once he/she used up the raw materials).
Material Handler (at an established interval):
Collects WK.
Gets the finished parts at preceding station indicated by WK of the down station. When finished part container of the preceding station is empty, post this station’s production kanban.
Delivers the finished parts to down station (customer process) and attach the WK to the container.

Kanban Rules
Six kanban rules:
Downstream process should get right parts at right time from upstream.
Upstream process should produce parts or products in quantity of downstream process.
Defective products should never be passed on to downstream process
Number of kanbans should be minimized.
Kanban can be utilized to adapt to very small variations in production volume. 10%.
The actual number of parts in box must equal to number on kanban.