Kanban

In this article we want to talk about another classic from Lean Management Kanban or the so called Pull System.

The word Kanban itself has its roots in the Chinese Japanese language and means card, label or sticker. In industrial manufacturing planning systems or general in logistics control Kanban describes a replenishment system for consumed parts according to the amount used steered by cards that give the signal following the Pull Principle.

The material in the Kanban System is exclusively oriented to the consumption of your production process. The cards are a key element of this kind of control system and provide proper information transfer. Kanban control loops from the work station of flexible production control and serves to smooth material flow through your inbound or even outbound logistics. In addition Kanban serves you to implement a sustainable reduction of material stocks, increases the ability to deliver and saves you pure cash.

In an ideal world Kanban would control your entire value chain from the supplier to the end customer. In this way you would have installed an complete smooth supply chain with almost no chance of interruption and massive stocks. And now comes the but – to steer production with Kanban – a continuous monitoring is required for a smooth material supply. To make it short: it requires discipline from all involved parties along the supply chain.

Lets have a look to the development of Kanban.

The first Kanban System was developed by none other than Taiici Ohno (of course) at Toyota Motor in the 1940s. One of the main reasons for the implementation of Kanban was the low productivity and efficiency of Toyota compared to western competitors. With the Kanban System, Toyota achieved a significant change towards flexible and efficient production control that had a massive impact on productions output while at the same time reducing the costs for inventory in raw material, work in progress (WIP) and finished goods.

To give the complete picture it wasn’t implementing the Kanban system itself to drive the success of Toyota, there are other key factors that together where making the difference. Just to name Just in time as an example of key elements of the Toyota Production System. It is and always will be a combination of different methods and philosophy that brings you forward.

In the 1970s the Kanban Concept was adapted in the industry in the USA and Germany. As they haven’t known better, they pretty much copied the complete Toyota Production System (TPS) in order to get the principles running.

Pull or Kanban System

Either way you call it, the material flow is controlled by boxes or cards. Kanban Cards serving in a simple way all information needed to identify what parts are needed in what quantity at what place. The amount typically is defined by the replenishment time at the work station. With the so called two box principle you make sure that the operator never runs short on components. Nowadays there are also digital version of it called eKanban, but the principle behind is the same. The trigger of supply is the Kanban Card starting of the pull chain of material.

To use Kanban efficient, it is not suitable for all parts. Kanban is perfect for small parts with a small amount of variants and a consistent demand. For this reason, you’ll see Kanban Systems in the industry mostly used for C-Parts management. The rest of the components are steered with the support of MRP. Only in rare cases you find that even the supply of big components are controlled with the Kanban methodology.

One nice side effect with Kanban, you can set up the way you can steer your bottleneck. That means, when you have done a proper value stream analysis you know the capacity for your bottleneck and will only order what this process step can handle.

One Piece Flow

The term One-Piece-Flow basically describes the radical reduction of lead times through flow-optimized production. In an ideal state processed parts or components are moved from one process step to the next without any interim storage. The quantity moved consists only of one part or one batch. You will only be able to achieve this when your work systems are closely connected. The transition of a work system to an one-piece-flow oriented system can only succeed if there is a high availability of existing capacities and flexibility.

Getting your production to flow combines increased productivity and increased employee motivation.

As with most of the lean terms the one-piece-flow principle made its way from the Toyota Production System where it is referred as operator centric work flow. Instead of day in and day out performing the same task at a fixed work station the operator moves with the workpiece through the complete process steps, station after station, for which he/she has to be qualified for all process steps. It is quite similar to a Chaku Chaku line, while Chaku Chaku describes a concrete line layout, one-piece-flow is a principle or mindset so to say. The basic idea behind it is to reduce defects through lacks of concentration and increase motivation of operators through variety.

Lean Manufacturing terms might seem complex, but as most of the time, the principle behind is straight forward and quite simple. As they seem to be no brainers they easily get forget about it which will automatically lead to waste. The best example for waste is the so called TIMWOOD(S), where two main drivers are high amount of Work in Progress (WIP) and high inventories.

Now let us have a look how the One-Piece-Flow principle can help.

The principle of One-Piece-Flow is a new form of flow production. In contrast to conventional forms of flow production the worker in the one-piece.flow production does not remain in his place. Generally speaking the operator has no place of his own - he is always moving with the good. This is exactly where the reference to Chaku-Chaku comes from. With the sequence principle, on the other hand, the operator only interacts with the workpiece on one process step.

After on part is finished the operator starts again at the beginning of the line. This procedure comes with certain demands on the assembly line. U-Shape Layout is the most favorite one, as start and end should be as close as possible to each other in order to keep ways short and transition seamless. The U-Shape Layout is also great as raw material and other components are supplied from the outside, what makes the job of the Mizusumashi easier, and the value adding activities are on the inside.

But speaking about the advantages of One-Piece-Flow, the try to make it short:

• Arrangement of workstations simplifies the arrangement of operators

• If deviations occur, the operator knows exactly where it is coming from

• With the CIP the continuous optimization is really driven on a constant basis

• Applied correctly, lead times are drastically reduced

• Inventory is drastically reduced

• Used space on the shop floor can be reduced by 60% compared to conventional production

• Motivation of operators raises as they are responsible from start to end and do not have this monotone daily routine of just one work station

In addition, the use of U-Shaped assembly lines, and if they are build up on standard profiles or standard shelvings, it gives you a huge amount of flexibility. Where workstations or the complete line can be easily extended, reduced or adjusted to new needs.