What is Value Stream Mapping?

The value flow diagram analysis method is the production process from raw materials to customers; the second is the product design process from concept to formal release.

Value Stream Map Analysis

Right!

The value flow diagram analysis method is the production process from raw materials to customers; the second is the product design process from concept to formal release.

For a product, the following two main flow paths are crucial: one is the production process from raw materials to the customer; the other is the product design process from concept to formal release. Value stream is all the activities required to make a product pass through these main processes, including value-added activities, necessary but non-value-added activities, and non-value-added activities (that is, waste). Research shows that companies spend only a very small portion of their time on value-added activities, and spend most of their time on non-value-added activities. Value stream diagram is a tool using pencil and paper, which helps to observe and understand the flow of materials and information as the product passes through the value stream process, as well as the value-added and non-value-added activities in it, so as to find waste and determine the need for improvement Place, set a blueprint and direction for improvement activities. At the same time, it is convenient for employees to understand the status of the company and provide opportunities for participation in improvement. Applying a value flow diagram to analyze a company's production process means looking at the problem from a holistic perspective, rather than focusing on a single process; it means changing the whole, not just optimizing a part. Value flow chart analysis can be to analyze and improve the activities of enterprises (also known as "within four walls"), or "outside the four walls", that is, the entire value from supplier shipment to customer receipt Analysis and improvement of the flow.

Figure 2 Schematic diagram of the value stream diagram In the value stream analysis, there is a set of conventionally used symbols for drawing the value stream diagram. As long as users use it often, they can easily grasp it. Generally, the value stream diagram analysis method first analyzes the current status of the operation process, the so-called "current state diagram". Starting from the customer's side, we must first understand the customer's needs and the takt, because Takt determines the tempo of each production process. Failure to meet the requirements of Takt production cycle may lead to overproduction or stall, underproduction or delay, which are all waste. Delays in shipping can also lead to customer dissatisfaction and further loss of reputation. Then study each process in the operation process, from the downstream to the upstream, to the supplier. Analyze the value-added and non-value-added activities of each process, including preparation, processing, replacement, inventory, material transfer methods, quality status, downtime, shifts, number of people, etc., and record the corresponding time. Next, we need to understand and analyze the method and path of logistics information transmission, including the information transmission from customer to factory, factory to supplier, production material plan to each process, and how the production plan is released. Finally, with the above data, the production cycle (TotalProductCycleTime) of the entire operation process and the corresponding value-added time can be calculated. Generally, people will find that the value-added time before improvement only accounts for a small proportion of Tpct, far less than 5%.

With the "current state diagram", managers can generally easily identify and determine where and why waste is, and provide targets for eliminating waste and continuous improvement. The "Future State Diagram" is guided by lean thinking, and points out the direction for the future operation mode according to the actual situation of the enterprise, and designs new lean processes. The so-called "future state" is also based on the current technology and cognitive level, which is a relatively ideal goal that can be achieved within a certain period of time. With the improvement of people's technical and cognitive levels, the original goals have become unsatisfactory, and people have entered a higher level of improvement cycle. This reciprocation is the essence of "learning with perfection and never ending" in lean thinking.

Common Mistakes of Value Stream Mapping Applications

Wrong tracking object

Everyone is very clear that when doing value stream analysis, the target of choice is product or service. Suppose you are a product flowing in the process, and observe how the shape, function, and packaging will change. In the general manufacturing process, as raw materials, semi-finished products and finished products are relatively clear, and errors are not easy to occur. But in the service industry or administrative office environment, mistakes are sometimes made. Because in the service industry environment, people will leave or transfer jobs at certain stages. The "product" has actually changed or moved, but we will still keep track of the original object.

Talk on paper

Refers to value stream analysis without actually producing products or providing services. Sometimes some products are not produced often, or happen to have not been produced recently, or the production cycle is too long, but they need to analyze the value stream (sometimes from customer pressure, sometimes from management pressure). So someone did not "see" the situation, relying on existing operational data and engineering standards (such as data provided by the production department or IE department) to complete the value stream analysis. What's more, the so-called "benefit" obtained by the project was calculated based on this!

They have forgotten some basic principles of lean production. First of all, if they don't actually inspect the various stocks in the process, they actually get a Process Map instead of a value stream map. Secondly, they did not observe how the various time measurements in the value stream diagram came from, so they could not determine the waste and opportunities for improvement. In addition, the value stream behind closed doors often ignores some details in the actual operation, and the difference from the actual operation will cause the front-line operators to be very confused and lose their due guidance value.

For the analysis of value stream, I suggest to do it at least once a month to observe the actual situation in different situations and compare them.

Hearsay

This point is similar to the second point, that is, staying in the office without completing the on-site observation to complete the value stream analysis. I have coached many corporate cadres. They are generally in the middle management position of the enterprise and find that they are often reluctant to practice in depth. Today, computers are widely used, and a lot of data is stored in computers. When drawing a value stream map, some people are reluctant to go to the front line of the workshop to observe, but rather stay in the office and call the data (such as inventory) in the computer. Another situation is that you like to listen to live data provided by others (such as calling subordinates to find data, and then report back), but the data itself is unconfirmed and has great differences. From a technical point of view, some data can indeed be obtained from files or data stored on a computer, and the general flowchart can be pieced together. For example, how many processes are there in a process, how many operators are there, how much is the warehouse inventory, what is the layout of the workshop, and how far is the distance traveled.

But technically correct does not mean that the actual situation is the same, the actual situation may be very different. If the person doing the value stream analysis does not go deep into the workshop site, it means that many places where waste is observed.

4. Repeat calculation time

When preparing to fill in the information box with the observations, be sure to consider what is the process step, what should be put into the data box, and what should not be. For example, the changeover time that occurs, everyone knows that you want to put it in the data frame, because this is all said in the book. But still some people don't understand why it is not listed separately, there is a separate record in Lead time. Another example is walking time. Assuming that 15 minutes of walking time is spent between the two processes, should I draw a separate data frame on the value stream chart? Are the two times mentioned earlier considered process processing time? Would you like to put it in the data frame?

The key here is to separate the causes of inventory accumulation from the actual product or service process and not to be confused. The too long changeover time and walking distance, as mentioned above, often cause inventory accumulation at a certain place / post in the process, which is the cause of various forms of inventory for the enterprise. In fact, it is where we implement lean production to eliminate. . This is not really a product or service process. When we count inventory, we actually include these factors in the lead time of production.

When analyzing the value stream, it is necessary to analyze which are the causes of the inventory backlog and which are the actual process steps for processing products or services.

5. Ignore shared resources

In many cases, there are shared resources in the process. Shared resources refer to resources that support / service more than one product family. They may be people, they may be the entire assembly line, or they may be a machine. For example, an injection molding company mainly produces mobile phones and MP3s, and a machine in the spray shop specializes in spraying all smaller parts. The products of these small parts include mobile phones and MP3 small accessories. Another example is the receiving and dispatching area of a warehouse. All kinds of goods and raw materials are processed here to receive or send goods. In the above two examples, the spraying machine and the receiving area are shared resources, including the employees here. If you forget this, it is easy to draw wrong conclusions.

Take a simple comparison of the receiving and sending areas above. Assume that this area provides services to two heavy workshops. Each workshop will produce an average of 80 products per day, receive a total of 160 products a day, and receive an average of 20 products per hour. 10 pieces per workshop. If a transceiver can complete 10 tasks in an hour, obviously two transceivers are needed to work in this post. If the workload of only one product family is incorrectly calculated in the value stream analysis, it will make people think that only one person is needed in this position. Perhaps this example is too simple, but when you face hundreds of products and many product families, errors may occur, and some product families may be missed or ignored. So be sure to pay attention to whether you are sharing resources.

Please remember to identify the shared resources correctly, otherwise it will lead to some important calculation errors, such as cycle time and cycle time.

6. Product family (series) is confusing.

When reviewing the value stream diagrams submitted by enterprises, the author sometimes finds that there are many small value streams in and out on the main value stream diagram, which looks very complicated and increases the difficulty of analysis. This kind of problem occurs mainly because the product family analysis is not done well before starting analysis. Some product families are very obvious. For example, home appliance companies produce different models of televisions, microwave ovens, refrigerators, etc., and you know them at a glance; others are not very obvious. For example, electronic component manufacturers, there are hundreds of products, even more than a thousand. The product types are similar, and the product processing procedures are complicated, ranging from a dozen or more to dozens of them, among which there are many branches and confluences. It is generally believed that if the research object has more than 80% of the same processing steps, it can be judged as the same product family. In the analysis process, if the shared resources in the process are not well identified, and the flow of the appropriate product or person is not well tracked, the value stream diagram is often very complicated and cannot reflect the true situation of the product family. Going further and further down the wrong path.