Kanban system
A Kanban system is a means to achieve just in time (JIT) production. It works on the basis that each process on a production line pulls just the number and type of components the process requires, at just the right time.
The mechanism used is a Kanban card. This is usually a physical card but other devices can be used Two types of such cards are usually used.
Withdrawal KANBAN
Production KANBAN
Each process (area, cell) on the production line has two KANBANS "post-boxes", one for withdrawal and one for production ordering KANBANS.
At regular intervals a worker takes withdrawal KANBANS that have accumulated in his process post-box, and any empty pallets, to the location where finished parts (components, assemblies) from the preceding process are stored. Each full pallet has attached to it one or more production ordering KANBANS which he removes and puts in the appropriate post-box belonging to the process that produced the parts. The worker now attaches a withdrawal Kanban to the pallet and takes it back to his own process area. When this new pallet begins to be used, its withdrawal Kanban is put back into the withdrawal post-box. At each process on the line, production ordering KANBANS are periodically removed from their post-box and used to define what parts and quantities to produce, next.
Single card KANBAN system:In a single card KANBAN system, parts are produced and bought according to a daily schedule, and deliveries to the user are controlled by a "conveyancing" (withdrawal) KANBAN. In effect, the single card system is a push system for production coupled with a pull system for delivery to the point of use. Single card KANBAN system controls deliveries very tightly, so that the using work center never has more than a container or two of parts and and the stock point serving the work center is eliminated. Single-card systems work well in companies in which it is relatively easy to associate the required quantity and timing of component parts with the schedule of end products. These are usually companies with a relatively small range of end products, or products which are not subject to rapid, unexpected changes in demand levels.
Advantages of KANBAN:
Low costs associated with the transfer of information
Provides quick response to changes
Delegates responsibility to line workers
It is a simple technique not involving computers so its cost is low.
Lead times are reduced.
Disadvantages of KANBAN:
It is less effective in shared-resource situations. Suppose the upstream station made several parts. Then a request to make more of the part needed by the downstream station will have to wait if other parts have to be made. A buffer is needed to ensure the downstream station doesn't run out meanwhile. And, because each part needs a separate signaling card, the system becomes more complex than if the resources were dedicated.
Surges in mix or demand cause problems because KANBAN assumes stable repetitive production plans. It is less suited to industries where mix and volumes fluctuate.
KANBAN in itself doesn't eliminate variability, so unpredictable and lengthy down times could disrupt the system; poor quality in terms of scrap and rework also affect its good functioning.
KANBAN systems are not suited for manufacturing environments with short production runs, highly variable product demand, poor quality products, and a multitude of product types.
A breakdown in the KANBAN system can result in the entire line shutting down
The mechanism used is a Kanban card. This is usually a physical card but other devices can be used Two types of such cards are usually used.
Withdrawal KANBAN
Production KANBAN
Each process (area, cell) on the production line has two KANBANS "post-boxes", one for withdrawal and one for production ordering KANBANS.
At regular intervals a worker takes withdrawal KANBANS that have accumulated in his process post-box, and any empty pallets, to the location where finished parts (components, assemblies) from the preceding process are stored. Each full pallet has attached to it one or more production ordering KANBANS which he removes and puts in the appropriate post-box belonging to the process that produced the parts. The worker now attaches a withdrawal Kanban to the pallet and takes it back to his own process area. When this new pallet begins to be used, its withdrawal Kanban is put back into the withdrawal post-box. At each process on the line, production ordering KANBANS are periodically removed from their post-box and used to define what parts and quantities to produce, next.
Single card KANBAN system:In a single card KANBAN system, parts are produced and bought according to a daily schedule, and deliveries to the user are controlled by a "conveyancing" (withdrawal) KANBAN. In effect, the single card system is a push system for production coupled with a pull system for delivery to the point of use. Single card KANBAN system controls deliveries very tightly, so that the using work center never has more than a container or two of parts and and the stock point serving the work center is eliminated. Single-card systems work well in companies in which it is relatively easy to associate the required quantity and timing of component parts with the schedule of end products. These are usually companies with a relatively small range of end products, or products which are not subject to rapid, unexpected changes in demand levels.
Advantages of KANBAN:
Low costs associated with the transfer of information
Provides quick response to changes
Delegates responsibility to line workers
It is a simple technique not involving computers so its cost is low.
Lead times are reduced.
Disadvantages of KANBAN:
It is less effective in shared-resource situations. Suppose the upstream station made several parts. Then a request to make more of the part needed by the downstream station will have to wait if other parts have to be made. A buffer is needed to ensure the downstream station doesn't run out meanwhile. And, because each part needs a separate signaling card, the system becomes more complex than if the resources were dedicated.
Surges in mix or demand cause problems because KANBAN assumes stable repetitive production plans. It is less suited to industries where mix and volumes fluctuate.
KANBAN in itself doesn't eliminate variability, so unpredictable and lengthy down times could disrupt the system; poor quality in terms of scrap and rework also affect its good functioning.
KANBAN systems are not suited for manufacturing environments with short production runs, highly variable product demand, poor quality products, and a multitude of product types.
A breakdown in the KANBAN system can result in the entire line shutting down
