QualiPedia: Kanban

"Pull" system reduces waste.

Published: Thursday, July 2, 2009 - 14:00

The core of lean manufacturing, kanbans use the “pull” system to prevent waste by creating a cyclical relationship between the consumer, supplier, and manufacturer. The user of a material requests or "pulls" material from the supplier, as they need it. They do this using some form of notification.  Product consumption information is sent from the user upstream to the supplier so that consumed materials can be restocked as needed. Ultimately, this eliminates overproduction and waste from the previous unnecessary use of materials and machinery.

Roughly translated as "sign" or "visual card," a kanban can be any device that communicates the need for an item. Kanbans ensure that only what is needed is ordered and in the proper amount.

The first kanbans, signboards, were used to transfer inventory information between production processes. Taiichi Ohno, former vice president of Toyota Motors, designed the concept in the mid 1950s after observing the operating system of an American supermarket. He was taken with the concept of only supplying what was needed, when it was needed, and how greatly this prevented unnecessary production and waste.

Considered one of the most price accessible means for inventory control, kanbans exist in manual and electronic forms (anything from a plastic container to a software program). It reduces unnecessary inventory, eliminate shortages, and cuts costs. Bringing improvements in price and quality, kanbans exists in three types: supplier, in-factory, and production.

• Supplier kanban: Alerts parts suppliers as to what specific production parts are needed and how many.
• In-factory parts-retrieval kanban: is used between factory processes to manage inventory.
• Production kanban: Indicates operating instructions for factory lines.

Successful implementation requires that four rules be followed:

• The production process works against the grain, starting with the consumer order and working it’s way back to manufacturing to eliminate any excess materials.
• Manufacturers must only produce what has been ordered in the exact order and quantity it received in the request.
• Products must remain 100-percent defect-free to continue down the production line.
• Kanbans should be gradually decreased over time to uncover and correct production areas needing improvement.

Sources:

www.strategosinc.com/kanban.htm

www.epa.gov/lean/thinking/kanban.htm

www.kanban.com/ResourceCenter/Kanban101.aspx

www2.toyota.co.jp/en/vision/traditions/mar_apr_04.html

About The Author

Brittany Vogel

Brittany Vogel is a reporter and editor for Quality Digest.