What is Value Stream Mapping
Value-stream mapping is a lean management tool used to visualize the flow of a good or service through a value stream. By “mapping” the value stream—representing where work is done and value is added—it lets engineers analyze the current state of operations and design more optimized future states, from the point of origin with suppliers through production and on to the customer. It records the key stream of events that occur along the production chain and measures the time spent and volume, as well as the flow of materials and information along the process. It is also known as material-flow mapping or information-flow mapping.
Lean Value Stream Mapping
Value stream mapping is meant for identifying and removing waste, reducing process cycle times, and implementing process improvement. This allows for the existing value stream to operate in a more lean fashion in its future state.
The waste elimination process can be guided by the commonly used 7 wastes of manufacturing ( or 8 wastes of Lean Manufacturing depending on how you count).
8. Unutilized talent
Once the wastes are identified, it is important to decipher what kind of operation they stem from. There are three types:
- Non-value adding operations (NVA)
- Necessary but non-value adding (NNVA)
- Value-adding (VA)
Depending on the value add of the operation, the subsequent wastes can be either entirely eliminated or reduced, or be purposefully overlooked.
Value Stream Mapping Process
All value stream maps have two versions: the current state and the future state. The current state is used to understand the existing flow, whereas the future state is used to plan what the improved state should look like.
Value Stream Mapping Symbols
Value-stream mapping uses recognizable, standardized symbols that make it easy for anyone to interpret the diagram. Therefore, knowing what each of the symbols represents is essential to understanding the language.
Here are some common symbols/icons used in value stream mapping:
Value Stream Mapping Steps
Step 1: Build a Team to Draw out the Value Stream Map
Since value stream mapping is a visual information board for all of the key operations and processes that happen on the shop floor, it is important to gather experts from different departments and levels of the organization to gain specific insights.
Step 2: Determine the Process Families
Identify which products or services go through similar processes along the value chain. Create a matrix if needed. This step will make sure that all of the processes that happen for each and every product on the shop floor are recorded.
Identify the dominant process and start from there. There may be several other processes that can be drawn into a value stream map, but you should always start out with the one that involves a majority of your products or services.
Step 3: Gather Metrics Needed to Create the Current State Map
‘Walk the flow’ of the production process. This is where a gemba walk might come in handy. Talk to people on the shop floor, ask them questions about their day to day operations.
Collect and aggregate metrics such as:
- Cycle Time/Processing Time
- Operational Equipment Effectiveness
- First Pass Yield
- Inventory levels
- Waiting Times/Down Times
- Machine Maintenance Frequency
Any metrics that are relevant to the specific step in a production process should be recorded. These metrics can later be used as KPIs when reducing waste.
Step 4: Draw the Current State Map
Every Value Stream Map will look different, but here are some key characteristics found in most Value Stream Maps:
- Upper-right corner for customer information
- Upper-left corner for supplier information
- Top half of the paper for information flow
- Bottom half for material (or product) flow
- Gutters on top and bottom to calculate value-added and non-value added time
Typically the value stream starts off with value-adding steps drawn across the center. Then the non-value adding steps are added below each value-adding steps with data such as C/T (Cycle Time), C/O (Changeover), Qty (Quantity per__), and Uptime. Depending on the kinds of metrics that are important to a shopfloor, anything in the VSM symbols can be used.
The horizontal value-adding steps is known as the ‘process’ and the non-value adding steps are known as the ‘operations’. The reasoning behind the naming is that non-value adding steps are seen as the preparatory steps that lead to the value-adding steps, hence the ‘operations’ handled by workers or machines. These ‘operations’ all come together and make up the ‘process’.
Here is an example of what that looks like:
Step 5: Create the Future State Map
Once you have reviewed the current state map, create a value stream map for what the ideal future state would look like. To understand what is a reasonable adjustment, you may want to calculate the takt time and, or conduct a bottleneck analysis.
Once you have the future state map in hand, compare which operations and processes need improvement, and create an action plan for how you can achieve this improved state. One thing we are trying to do with a value stream map is to understand the parts of the process that do not flow. Maybe there are large piles of inventory, maybe lots of quality or rework cycles. Maybe you have cells that can be combined to make it a one-piece flow. You want to eliminate waste, but ultimately you want the value stream to flow.