Value Stream Map (VSM)
A value stream map illustrates the flow of materials and information from supplier to customer. Value stream mapping (VSM) is a lean manufacturing technique used to analyze, design, and manage the flow of materials and information required to bring a product to a customer. VSM helps identify waste and streamline the production process.
The first step in value stream mapping is to create a current state map. This map can help identify waste such as delays, restrictions, inefficiencies, and excess inventories. These are then eliminated in the ideal state map, which gives the organization a working plan to achieve lean efficiency.
How to Use a Value Stream Map
Value stream maps are most commonly used in lean manufacturing, but identifying the value stream—the sequence of activities required to design, produce, or provide goods and services to customers—is a beneficial practice for any company in any industry. Value stream maps are used in healthcare, software development, supply chain logistics, even government and service industries. Regardless of industry, the main goal of a value stream map is to visually record information such as:
- Work and wait times along each step in a process
- Labor needs at individual work steps, including the identification of overtime, if necessary
- Error rates at individual work steps
- Downtime at individual work steps
- Inventory excess or shortfall
- Production or process delays
Value Stream Mapping Symbols and Components
A Value Stream Map is made up of a three distinct looking parts: a process map, a corresponding timeline and information flow. The process map is comprised of the steps and the information associated with the steps of your process. The timeline automatically builds from the process map and calculates the data entered. The information flow further explains the interaction and activity between the stations of your value chain.
There's usually also a box in the upper left corner of any value stream map that lists the constants of the value stream map. You add the Demand, the units per day that must be produced for instance, and the Hours, the time available to get the work done, and the Takt, the rhythm required to do the work, is automatically calculated for you.
Value stream mapping uses a set of unique symbols to visualize a process.
Process. A process is represented with a rectangle and the word "Process". To make the value stream map more readable, a process will often represented the collective processes of an entire department.
Inventory. A triangle with an "I" inside represents the exchange of inventory during the process.
Shipment. A shipment of raw materials from suppliers are represented with blank wide arrows. A pushing of materials from one step in the process to another is usually marked with a black arrow with three white squares inside. Shipments made using external suppliers is represented with a truck or another vehicle where applicable such as boat or train.
Supplier and Customer. Suppliers and customers share the same symbol that looks like an abstract, geometric representation of a factory. A supplier usually will mark the beginning of a process and will be found to the left of the value stream, while a customer is often found as the last step, to the far right of the value stream map.
Electronic flow. A line with a zig-zag in the middle refers to electronic information and data exchanges. While a lot of value stream mapping focuses on raw materials and products, electronic exchanges should also be examined because they can be the root of delays and waste.
Kaizen burst. A Kaizen burst, also known as a Kaizen blitz, refers to a short burst of activity that solves a problem with intensity and urgency. Appropriately, it's represented with what looks like a cartoon explosion.
Go see. A go see refers to confirming something visually during the process and it's often represented with a pair of glasses.
Quality. A quality problem anywhere along the chain can be marked with an octagon, like a STOP sign, with the letter Q inside.
How to Create a Value Stream Map
Start by mapping the current state. This map illustrates working on and completing a specific product (or project). View it as a high-level look at the flow of work for that project. Value stream maps do not consider the amount of time people are working on different projects outside of the one focused within the value stream map. With that in mind, there is no single way to create a value stream map but there are generally six steps to follow. What we are after is current information, not historical data.
- Identify the product or process. That is, what is it that you wish to map? If multiple products are involved, you may want to start with those with the highest value, volume, or potential.
- Define the scope of the mapping project. Most value stream maps follow the production process from supplier to customer. Some map the supply chain, which would continue upstream to raw materials.
- Map the process steps. This may take some time and will certainly require "working the floor." Some document the process from customer back to supplier, others go from start to finish. We are not breaking down tasks; these are the major steps in the operations performed on the product.
- Include information flow. How does communication flow during the order, production, and delivery steps?
- Collect process data. This will require some effort to develop a clear understanding of important aspects of each step in the process. Some of the data needed may include:
- Cycle time (how long it takes to make one unit of product)
- Actual work time versus unused/wait time (including number of operators, shifts, etc.)
- Machine uptime and downtime
- Unnecessary movement (of items, material, and workers), scrap rate, etc.
- Create a time line. This information tells us about total process time, inventory demands, and total lead time. This usually shows how lead times may be considerably longer than processing times, indicating how much waste exists in the system.
Evaluation of the Current State and Creating the Ideal State Map
The current state map provides a starting point for applying lean principles to improve the system. This may involve:
- Reducing excess inventory
- Improving cycle time
- Reducing equipment downtime
- Improving quality, reducing errors, and focusing on delivering what the customer wants when he/she wants it
Once the desired improvements are identified, create the ideal state VSM. Identify improvement areas by using the kaizen burst symbol on the map.
Don't expect your "ideal state" map to be ideal on the first attempt. As with the entire process, it will need to go through iteration and improvement as well.