Kanban Pull System
Pull is an important concept (Principle 4 – let customers pull value from the next upstream activity) of the Lean methodology. The Pull system generates culture and operation in which only what is desired is produced. Pull system is especially effective in eradicating the wastes of overproduction and excess inventory.
Taiichi Ohno, then Assembler Manager in Toyota visited the United States and initiated what is called the Toyota Production System. He learned the concept of Pull from his observations in the American supermarket. The fruits in that supermarket were picked by the customer who pulled them from the shelves in the store and the stock was then replenished. Ohno thought that he could apply a similar principle to manufacturing, and that was how Pull systems started being used in manufacturing. When the customers give a signal to their suppliers that they want the products or services, the requirement is Pulled and produced and that is why it is given the name Pull System. Pull is a method of controlling and balancing the flow of resources. It eliminates the waste of handling, storage, rework and excess inventory. It requires that a company produce and ship only what has been consumed. And it provides visual control of all resources.
To the contrary, Push system is like applying force to move the product away from production towards the customer. Therefore, a Push system produces products or services irrespective of demand, thereby forcing products through a process to achieve completion. The traditional Push system makes the product or service even when the customer does not need them. The raw material is delivered ahead of demand to make sure that production does not suffer delays irrespective of the customer demand.
Pull is closely related to another Lean principle called One-piece flow. The focus of One-piece flow is to keep people, products and information flowing through a process. Good flow eliminates waste and maximizes value-added time. Flow is balancing internal resources to meet customer demand, which is exactly what a Pull system tries to achieve. When One-piece flow is non-existing, delays occur, and the process comes to a standstill. Pull eradicates the wastes of overproduction and inventory, two things that interrupt the flow. The two concepts work together; without Pull, One-piece flow is very difficult to achieve. And similarly, without an environment that is supporting One-piece flow, it is hard to implement a Pull system.
The goal of Pull system is to achieve improved throughput in a work environment where work entering the operation is triggered by work exiting the operation. Pull is a method of controlling and balancing the flow of resources and it eliminates the waste of handling, storage, reworks and excess inventory. It requires that a company produce and ship only what has been consumed. And it provides visual control of all resources. It is a simple system to use, but not so simple to design and implement and needs careful planning.
A Pull system requires an organization to commit to producing based on customer demand, rather than forecasting. Once a company decides to implement a Pull system, there are some standard guidelines you can follow to get started.
- Identify the takt time (calculate takt time by dividing the available work time by the number of units to produce)
- Determine the completion rate (comparing completion rate to the required takt time to determine whether your process is working at the right speed)
- Calculate work in process (amount of work in the process required to meet customer demand)
- Create a trigger (system in place to prioritize work as high, medium, or low)
- Develop a Kanban (visual signal) ( Please visit our Kanban training for more information on Kanban system)
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