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Kanban: An approach to an evolutionary process

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Kanban: The term is Japanese, meaning ”Sign” or “signboard”

In lean manufacturing Kanban is the specific tool for:

  • Controlling information (functions as a physical tool)
  • Regulating material conveyance (combines control over movement of material with respect to both time and quantity)

Between upstream and downstream production process

Kanban is thus a signaling devicethat gives authorization and instruction for the production or withdrawal of items/goods

streamKanban coupled with takt time, flow processing, pull production, and level scheduling is what enables Just-in-time production

to be achieved in a value stream

Kanban “forms”

Kanban paper cards are the best known and most common examples of these signals within a single facility

Kanban can be:

  • Triangular metal plates
  • electronic signals (when communicating over long distances or inter-facility)
  • Colored balls

Or any other devices that can convey the needed information while preventing introduction of erroneous instructions

Basic information in a kanban

  • Part name
  • Part number
  • External or internal supplying process
  • Lot size
  • Pack quantity
  • Storage address
  • Consuming process address/location

A bar code may be printed for tracking or automatic invoicing

Purpose of Kanban

  • Prevent overproduction (and conveyance) of material between production process
  • Provide specific production instructions between process based upon replenishment principles
  • Serve as a visual control tool for production supervisor to determine schedule adherence status
  • Establish a tool for continuous improvement. Over time reduction in the number of kanban since each kanban represents a container of inventory

TYPES OF KANBAN

There are main 2 types of kanban

1 types of kanban

Distinctive features between the 2

  • Make Kanban

Instruction kanban signals to make something/products to an upstream process for a downstream process

  • Move Kanban

Withdrawal kanban signals that something/products need to be removed from inventory (which then triggers replenishment) and conveyed to a downstream

  1. In-process Kanban

The In-process kanban is used to convey make instructions for small amounts (at least one pitch corresponding to one pack quantity) to an upstream process.

Typical uses include scheduling final production areas based upon withdrawal of inventory from a market or a direct replenishment signal from a customer.

  1. Signal Kanban

The signal kanban is used to convey make instruction for large quantities to upstream batch process.

Signal kanban utilizes lot size in conjunction with market s to feed downstream process while still allowing time for changeover to occur at upstream process

There are 3 variations on the signal kanban: Triangle kanban, pattern production and lot making

  1. Inter-process Kanban

The Inter-process kanban is used to signal the need to withdraw parts from a storage area and convey them to a downstream process withina facility.

A prerequisite for use of the withdrawal kanban is the creation of a material market as well as determination of storage quantities at lineside.

It is normally employed in conjunction with continuous –flow cells that use a large number of s from internal or external sources

  1. Supplier Kanban

The supplier kanban is used to signal the need to withdraw parts from an external supplier for conveyance to a purchased-market or central market at the downstream process

OTHER TYPES OF KANBAN

  • Temporary kanban

There are short term events that require additional kanban to be injected into the system for smooth production.

Reasons could be temporary buildup of inventory to adjust lost time. It is for one-time use only and shows an expiry date

  • Kanban in combination (Dual card kanban)

Production and withdrawal kanban are used in combination to control pull production between processes where some work-in-process must be stored in markets

Dual card kanban allows lot splitting. The transfer batch quantity between work stations, governed by withdrawal kanbans, may be a smallerquantity than the production batch size governed by production kanban

Example of Production and withdrawal kanban

2 EXAMPLE OF KANBAN

Kanban system (external supplier) over view

 3 kANBAN SYSTEM

Prerequisites for successful Kanban implementation

  • Reasonably stable demand
  • Reasonably capable process
  • Preventive maintenance or TPM
  • Reasonably short changeovers times
  • Disciplined workforce -including management

Priority Kanban Board

Operations where there is changeover and/or changing priorities a priority Kanban boardis the usual option

It displays all the products that go through the work centre

The board indicates priority as 1, 2, 3, —-or has bands of green, yellow or red

Kanban hanging in the green zone is a low priority authorization and in the red zone the product to be taken the very next one

Priority Kanban board

4 PRIORITY KANBAN

Number of kanban cards

The general rule on kanban is to start “loose”,with a generous amount of safety stock and to move towards “tight kanban”gradually, but steadily.

The philosophy is to gradually reduce inventory (Muda) either by removing/reducing kanbans or reducing the kanban quantity

The number of kanban depends on demand. When demand changes the number of kanban should change

In line with lean manufacturing the number of cards in circulation should be generally “less than last time” progressively

7-Rules for using kanban

  1. The down stream process (Customer) pulls from the upstream process
  2. The upstream process (Supplier) produces & replenishes the quantity taken away
  3. No defect/ Defective partsshould be allowed to pass on to the next process
  4. Kanban must be alwaysattachedand conveyedwith the part or container
  5. No parts can be produced or conveyed without a kanbaninstruction
  6. The quantity indicated on the kanban must equalthe actual amount in the container (to ensure accuracy of  Information
  7. The number of kanban is reduced carefullyto lower inventories and reveal problems

 

Acknowledgement: Mr. Vinod Grover – Kaizen Institute India

P.S. If your leaders and colleagues are also interested in this subject, do them a favor and share this link. They may thank you for your concern and initiative.

Looking for more info on Kaizen/Lean/Operational Excellence? Click here

 

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Author: Kaizen Institute - India!

Kaizen Institute – India is part of the Global Kaizen Institute operations. Kaizen Institute was established by Sensei Masaaki Imai, the GURU of Kaizen. He wrote the 1st book 28 yrs ago and that is when it all started . We operate in 30+ countries today and have over 400+ coaches helping more then 600 organizations Learn, Apply, Sustain – Kaizen/ Operational Excellence. In India we have two physical offices – Pune & Ahmedabad and 27 coaches in all.

2 thoughts on “Kanban: An approach to an evolutionary process

  1. even a new learner could understand and initiate for adoption on kanban
    kannan

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