Kanban
KANBAN
Kanban forms an integral part of any Lean Manufacturing System and is classed as a Pull system. Kanban as expected is a Japanese word: KAN meaning CARD and BAN meaning SIGNAL
A pull system is driven by actual customer demand and material is only released into production as it is required, when the parts are required. A Push system such as those driven by MRP would release material and orders as customer orders are processed, MRP (Material Resource Planning / Manufacturing Resource Planning).
It is not a scheduling system but a production control system that will define production using TAKT Times. One of the major Lean Manufacturing Principles is the usage and control of materials.
The ideas of Kanban have been used for many years, a twin bin system was used in the UK before Kanban became popular. The system is simple to install and suits production facilities with a fairly constant demand, such as in the automotive industry.
In companies with a variable demand Kanban would not usually form the principle planning tool, but many of these companies will have core components that are on constant demand and would suit a the system removing potential complicated planning issues.
Basic Production Kanban
Production or materials ordering upstream is only carried out when a downstream operation signals it is needed i.e. a component is used downstream and it is simply replaced. The signal can take a number of forms:
from a simple painted square on the floor, when the square is empty this indicates to the upstream process to produce more.
A card which is passed upstream when a component or container is used.
The principal is the same when the local levels are depleted to a set level the upstream operations receive permission to begin production.
Rules
A signal is only issued when the downstream resource has consumed the component.
If no Kanban is present no production (i.e. components are only made or issued when a Kanban exists).
Only good components are issued to the downstream processes.
No over production
Components should only be produced in the order the Kanbans are recieved.
The number of Kanban cards should be reduced over time and the problems that are encountered by doing this should be tackled as they are exposed.
Calculating the number of cards
The number of Kanbans required can be calculated as follows.
Number = (Demand in period x Order Cycle time x Safety stock) ÷ Batch size (or container quantity)