Excerpt
Contents
1 Abstract
2 Introduction
3 Kanban - The Japanese Way of Life
3.1 What are the advantages of Kanban? Worth the sweat?
3.2 I’ve seen all the benefits, but what’s the catch?
3.2.1 Blocking Mechanism
3.2.2 Cycle Issue
3.3 From Simple Cards to High-Tech Devices? .
3.4 Show Me Your Cards And I’ll Tell You How Successful You Are
4 Process-Environment: The true power of a company
4.1 Kaizen
4.2 Seven forms of waste
4.3 Just-in-Time
4.4 5s Circle
4.5 Six rules for Kanban
4.6 Value Stream Mapping
5 Controlling
5.1 Visual Management
5.2 Process Control Chart
6 A Theoretical Approach
6.1 Analysing the initial state
6.2 Step by Step - What Needs To Be Done
6.3 Comment
7 Conclusion
8 Recommendation
References
1 Abstract
It is said that a Kanban-System improves a process by changing the information flow in the process and rearranging rules of responsibilities. The purpose of the study was to find out what a Kanban is, what does it make the superior application to conventional western strategies, and what are the weak points of it. Furthermore, the study aims to have a look at the supporting environment to find out if there are requirements for a Kanban-system to be successful. To control and to measure the success of an introduced Kanban system, various methods and tools were examined, compared with conventional methods and tools, and presented. Finally, the study tried to use all collected information for a theoretical approach how to introduce a Kanban system step by step. To get an unprejudiced sight on this topic the development over the last years, scientific journals, and books from the early 80s until today were inspected.
The principal conclusion of the study was that Kanban can be a very efficient method to improve processes, to reveal problems, and to involve worker more in processes for improved motivation that results in a process improvement. But this needs a good prepared environment with trained staff through all levels. And the more a process is complex due to complex products, the more it is essential that the environment is working properly. Furthermore, the need of controlling tools and proper consequences seemed to be a significant part that decides over success or fail.
List of Figures
1 Pull- and Push-Strategies
2 Example: Kanban Card from Liker’s Book ’The Toyota Way’5
3 Kanban types
4 The Production Kanban as well as the Movement Kanban.2
5 Blocking Mechanism
6 Kaizen vs. radical improvement
7 5s Circle
8 Example for a value stream map
9 Value Stream Mapping symbols1
10 Visual Management Board7
11 Classic Process Control Chart
12 Lean Process Control Chart
13 Value Stream Mapping: Current State
14 Value Stream Mapping: Target State
2 Introduction
In a company’s life-cycle income and expenses are as essential as collecting ’know-how’ or acquisation of qualified staff working for the company. Especially expenses are very complex and multi-layered so it becomes very hard to control it efficiently without an overall strategy.
One of these strategies is called ’Lean’-Principles and was developed in Japan after the second world war when the Japanese industry were suffering and struggling to compete with the western industry nations USA and Europe.1
With Just-In-Time manufacturing system Taiichi Ohno created an important pillow for the ’Lean’Principles. Also known as the Toyota Production System, it seems omnipresent nowadays and it is an example of modern management.
But it is not the only option to organize a company’s structure. Manufacturing Resource Planning (MRP) and the further developed MRP II1 system is a common method that has been chosen by western nations for decades.1
But these different approaches aren’t mutually exclusive. Certainly, they can support each other by applying an hybrid version of both. Taking the best and most reasonable method for specific processes is the challenge and opportunity to improve the company’s productivity and effectiveness. In this study a closer look on Kanbans were taken, a specific tool that helps to carry out ’Lean’- Principles in a manufacturing process. That means to find a common understanding of Kanban, its position in ’Lean’ as one of several methods, and its interdependence with other ’Lean’ methods. Finally, a research about the understanding of controlling Kanban processes was carried out to find differences to classic controlling methods.
3 Kanban - The Japanese Way of Life
Before the term Kanban will be used in this study, it should be clear what it means and what it is used for. A Kanban is basically a simple card or a board that is carrying essential information for a process flow. This Kanban card is used to realize a consumer oriented process flow, called pull strategy. But before going ahead with Kanban in more detail, an explanation of the pull- and push-strategy is important to understand the need of Kanban.
A pull strategy aims to minimize waste in its different forms and to produce only the number of prod- ucts requested by the market. As in figure 1 ’Pull-Strategy’ the single workstations have an exchange of information (implied by the pull arrows between workstations). It’s assumed that in a manufacturing process the subsequent workstation n is the customer of the preceding workstation n-1. In this case, the customer, called workstation n, needs a spare part from the supplier workstation n-1 to start the production. By taking the requested spare part out of the inventory1 from workstation n-1, the work- station n-1 starts itself to replenish its inventory by producing the spare part. To do so, workstation n-1 needs another part from the inventory of workstation n-2 who will then start to replenish its own inventory an so forth. That leads to a process sequence of ’Ordering-Delivering-Producing’.
While this method was developed in Japan the western countries where focusing on the push strategy. As in figure 1 ’Push-Strategy’ the single workstations communicate only with the production control system called MRP II. That means the entire process is controlled by the Electronic Data Processing (EDP) system and no communication between customer workstation n and supplier workstation n-1 exist. That leads to a process sequence of ’Ordering-Producing-Delivering’.
But to realize or to organize a pull-strategy a mean of communication is required. A mean that signals the supplier workstation n-1 that the customer workstation n took a spare part out of the shelf. That’s the point where it gets back to Kanban. Kanban is that mean that has two essential functions: At first, a card is a visual signal that implies that something happened. Thus, the first function is a signal function. The second function is the ability to carry information. The information carried by Kanbans are basically always the same (Figure 2): The Kanban type (’Parts-Ordering Kanban’, also
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Figure 1: Pull- and Push-Strategies
called ’Production Kanban’), the area code (Storage Area: A 1-1), the number of the item (Item No. 53018-60011), the number of the Kanban (21 of 50), and the number of the capacity of the box (Box Capacity: 30). Further information can be put on the card if necessary, depending on the exact process
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Figure 2: Example: Kanban Card from Liker’s Book ’The Toyota Way’5
situation. Besides the production Kanban there are two more Kanban types that are frequently in use. The Transportation or Movement Kanban that doesn’t trigger a production but a transport of an item. The Movement Kanban can be categorized in a Supplier Kanban which signals external suppliers to deliver parts and an Internal Kanban for company intern transport issues. The last Kanban type is a Triangle or Signal Kanban1 which is used to balance different process paces of workstations (figure 3). Unlike other Kanbans a Triangle Kanban is not allocated to a specific container or a specific item. It
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Figure 3: Kanban types
is allocated to a buffer and signals the time when the buffer needs to be replenished. At this point it is good to have a look on a pull process supported by Kanbans using a pictured description from the inventor of Kanbans, the Toyota company (figure 4). The picture shows a production process that can be considered as a supplier represented by the green colour, while the customer process is represented in red.
Transport Process
When the customer starts to use a full container to consume the parts at ¿ by taking the parts out of the container to put them on the assembly line the Kanban (pictured as the red A) has to be removed and handed over to a responsible person to signal the removal. This person will then go with the Kanban and an empty container ¡ to the inventory of the supplier and exchange the empty container with a new full container ¬. The new full container has got a Kanban label attached (pictured as the green A) which will be taken off and handed over to a responsible person in the production process to signal the removal. The red Kanban gets now attached to the new container √ and brought over to step ¿ where the process starts over again.
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Figure 4: The Production Kanban as well as the Movement Kanban.2
Production Process
When the green Kanban gets handed over during step ¿ the workstation begins to produce new parts to replenish the empty container ¡. After, the full container gets the green Kanban reattached and moved over again to the inventory of the production process ¬.
3.1 What are the advantages of Kanban? Worth the sweat?
In the very first place Kanban requires to understand the entire process in detail where Kanban is supposed to be implemented. It is not possible to implement Kanban properly by just guessing or proposing the process steps and process flow. But this is also the first indirect advantage of Kanban - grasping what actually happens on the shop floor. But furthermore, waste in the process becomes visible. Questions like ’Why do we send all the spare parts over there even when we need it here?’ will come up and help to improve the process without even implementing Knaban cards yet. It has been seen that talking about the benefits of Kanban includes not only Kanban itself. Furthermore, all ’Lean’ methods that are necessary to be carried out around the Kanban will bring a benefit to the process (’Lean’ methods will be discussed in Chapter 4 in more detail). After preparing the process properly Kanban can finally be implemented.
Now, the push process will be turned around into a pull process as described in Chapter 3. The ideal flow of a process would mean that there is no Kanban in the process. At first this may sound strange, but it will come clear by having a closer look what actually Kanban does. As explained in Chapter 3, Kanbans are attached to an item or box stored in a buffer area. And buffer means waste or also known as work-in-process. All items in this area cost money without benefiting the company at all. This is also one of the 7 wastes in ’Lean’ called Inventory. That means, in an ideal process flow, oriented to the customer, perfectly balanced, no inventory would be necessary. The items would just go from one process station to another and finally to the customer just in time. So, no Kanban card is needed in such a ideal process. But because this is more idealistic than realistic, Kanban cards come in action. The rule of thumb is: ’The less Kanban cards needed, the better the process performance is going to be’. That means just by telling the number of Kanbans in use gives an idea about the effectiveness of the process (A closer look on the calculation of the number of Kanbans will be discussed in Chapter 3.4). Finally, Kanban can be used to test the efficiency of a process by removing cards from the process. If the process keeps working without any trouble too many Kanbans were in use and waste could be reduced. In this way a Kanban controlled process shows its limits about what buffer it actually needs.
3.2 I’ve seen all the benefits, but what’s the catch?
Even if Kanban sounds like a very simple method there are some obstacles that needs to be taken. Two main issues will be discussed: The Blocking Mechanisms4 and Cycle Issue.
3.2.1 Blocking Mechanism
Two different types of blockings with due to a variety of issues were identified:
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Figure 5: Blocking Mechanism
1.0 Single Card - Instantaneous
If two workstation are close together they can share one buffer area for both, the preceding worksta- tion’s output buffer as well as the subsequent workstation’s input buffer. This is called the Single Card4 system that can cause an instantaneous blocking effect due to buffer area restrictions.
1.1 Blocking due to part-type
A restriction of container with various part types in the storage area can lead to block the output of a workstation due to part-type. That means if workstation A processes a variation of part-types x, y, z and the restricted space of part-type z container is already full due to any reason that leads workstation B to be slower than A, workstation A is blocked and can’t produce more z parts until workstation B starts to consume type z parts again.
1.2 Blocking due to queue-size
A restriction of total number of container in an area regardless the type of parts in it can lead to block the output of a workstation due to queue-size. If X is the maximum number of container in the area and X is also the number of actual container in the area, workstation A is blocked as long as workstation B doesn’t consume a container of this area so the number of container will become less than X.
1.3 Dual blocking mechanism
In a situation where both blocking types, blocking due to part-type and blocking due to queue-size, appear at the same time is called a dual blocking mechanism.
2.0 Two Card - Non Instantaneous
If two workstations are too far away from each other to share the same buffer area seperate buffers has to be installed, one for the preceding workstation’s output and one for the subsequent workstation’s input. This is called a Two Card4 system that can cause a non instantaneous blocking effect due to buffer area restrictions.
2.1 Blocking due to part-type
A restriction of container with various part types in the output storage area can lead to block the process of a workstation due to part-type. That means if workstation A processes a variation of parttypes x, y, z and the restricted space of part-type z container is already full workstation A is blocked and can’t produce more z parts. But workstation A can still produce part type x and y.
2.2 Blocking due to queue-size
A restriction of total number of container in an output storage area regardless the type of parts in it can lead to block the output of a workstation due to queue-size. If X is the maximum number of container in the output storage area and X is also the number of actual container in the area, workstation A is blocked as long as a container has been moved off this output area so the number of container will become less than X.
2.3 Dual blocking mechanism
In a situation where both blocking types, blocking due to part-type and blocking due to queue-size, appear at the same time is called a dual blocking mechanism.
Blocking mechanism Operative on Material Handling The same blocking types as mentioned before can occur as they are: Blocking due to part-type, blocking due to queue-size, and blocking due to mechanism. But this time, it will occur due to Material Handling between workstation A’s output storage area and workstation B’s input storage area.
2.4 Blocking due to part-type
A restriction of container with various part types in the input storage area of workstation B can lead to block handling operation between output and input storage area due to part-type. That means if workstation B’s input storage area can store X parts of type z, the material handling is blocked of the actual number of type z parts in the input storage area are already X. But material handling is still permitted for other part types.
2.5 Blocking due to queue-size
A restriction of total number of container in an input storage area regardless the type of parts in it can lead to block the material handling between the output and input storage area due to queue-size. If X is the maximum number of container in the input storage area and X is also the number of actual container in the area, material handling between both areas is blocked as long as a container has been moved off the input area so the number of container will become less than X.
2.6 Dual blocking mechanism
In a situation where both blocking types, blocking due to part-type and blocking due to queue-size, appear at the same time is called a dual blocking mechanism.
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1 MRP II is the abbreviation for Manufacturing Resource Planning II, which is the further developed version of the MRP system, and is responsible for creating and distributing the work schedule to the single workstation by processing all necessary information as consumer forecast, inventory information, work force information, etc.
1 The inventory in this example is also called a supermarket due to the similarity with the process in a supermarket where the shelves get replenished when the customer takes out a product. E.g.: If the milk is empty in the shelf the grocery’s staff will replenish the shelf with new milk.