The Value Stream Map (VSM) is one of the most common “Lean tools” mentioned by books and consultants, including here at CMC. But learning how to draw, or read, a VSM takes time and effort.In this post we'll show you how it's done...
Why Use Value Stream Mapping?
A VSM makes the flow of information and materials visible. Its purpose is to show where some of the waste lies in the systems… and to plan for changes that will result in improvements to the whole system (not to only one specific process). In short, it helps get close to the just-in-time (JIT).
It is too easy to get bogged down in the specific conventions of value stream mapping symbols (which are not always intuitive and, for some of them, take a long time to draw). We developed a step-by-step approach to drawing a basic VSM that focuses on the most important information.
1. Draw a simple flow chart firstThe most important aspect of a VSM is the visualization of the steps in a process.
If you are new to value stream mapping, do not try to draw your first full map while getting familiar with a process.
Pick 1 product and follow physically the materials from arrival in your facility to departure to customers (which might be another facility within your group).
Here are a few examples of steps to show on the flow chart:
- Getting a sale order from a customer
- Entering that order in the IT system
- Sending POs to suppliers for the materials
- Shipment from suppliers
- Receipt in incoming warehouse
- Incoming QC
- Heat treatment
You get the point… Go into the details and be systematic:
Note: Try to pick a product that is representative of significant share of your products (i.e. several products share the same steps), if applicable.
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2. Do not restrict the scope of your study
You want to visualize the steps of a process… ideally through the whole supply chain. You might want your VSM to focus on what happens within your walls, but it is always good to show, on a more macro scale, what happens in the end-to-end supply chain.
For those who have read Lean Thinking, you will remember the example of Tesco, the British supermarket chain, studying all the steps necessary to make an aluminum can of soda… from the Australian mine to the smelting factory in Scandinavia and until the supermarket aisles in the UK. Getting a bird’s eye view of what happens in the entire supply chain is a good first step before delving deep into a VSM.
You will probably not be able to be as granular as I suggested in section 1. That’s no problem. It might look like this:
- Collected at mine (Australia)
- First processing (Australia)
- Shipment (Australia to Sweden)
- Melting and processing (Sweden)
Two interesting pieces of data to collect at that stage is the time each processing step takes, and the time the materials spend sitting in inventory before each processing step:
3. Collecting more data and starting the VSM
Show a box for each process step
Most likely you will need to go back to observe each process step and evaluate the following metrics:
- Cycle time (how many seconds it takes to process 1 piece)
- Changeover time (how many seconds it takes between the end of processing one 1 product type to the first good processing of another product type)
- Uptime (what percentage of the time is the process up and running?)
Note: You will probably need to get on the ground to collect some of the information required here. For example you will need to count what is in inventory (waiting for processing), unless your company has an accurate MRP system.
4. Most common value stream mapping symbols
One of the downside of VSM conventions is the number of symbols to learn. A best practice is to put a VSM on the wall and share it with everybody, but the special symbols make it hard for people to understand what is communicated. Be prepared to give explanations.
Here is a great overview of the most common symbols:
5. Learning all the details of a good VSM
In this article I can’t explain the concepts of a supermarket, pull vs. push, central production planning vs. Kanban vs. linked and flowing processes, etc. I also can’t go into the differences between a VSM of production processes and one of office work (and how to make them coexist in the same map). Instead I will point to two good books on the subject.
- For manufacturing environments (restricted to production activities): Learning To See
- For admin/office environments: The Complete Lean Enterprise: Value Stream Mapping for Office and Services
These two workbooks go deep in a few value stream mapping examples.
6. If you want your VSM to shine
So far, I would expect you to have mapped the process steps in pencil on a large piece of paper, while observing processes and “following” a product.
Do you need to show that VSM in a nice report, in soft copy? There are now quite a few professional solutions. Here are three popular ones.
- Lucidchart has a VSM toolbox and is an easy-to-use and inexpensive solution
- Visio (by Microsoft), the most commonly used in big companies
- Quality Companion (by Minitab), a serious competitor to Visio for manufacturing-related diagrams
7. Take some liberties
I have never met a “VSM nazi” who rejects any symbol that is not part of the standard suite. If you have space on your map and if you think it is desirable, add extra information. One example is human movement (in case some operators have to walk from one process to the next). Most mentors would be thrilled to see their mentee appropriate a tool to the point where they become creative and add to it!
Was this useful? Have you got other tips to share? We hope you can leave a comment about your experiences with value stream mapping below for our community.