Lean Six Sigma: Value Stream Mapping
// 2020 Apr 22
By Regu Regupathy, Master Black Belt, Rutgers University
Uncovering the bottlenecks & opportunities for improvements
In a Lean Six Sigma process-improvement project or Kaizen, it’s important to map out the process with your project team before setting about to solve whatever the problems are with that process. Typical steps are to produce a SIPOC (high-level process map) and then a more detailed process map.
These are valuable steps and can help identify wasteful (Non-Value-Added-“NVA”) steps, the stakeholders and “players” in the process, and provide a mutually agreed picture of how the process is done now. But: these tools don’t tell us critical things we need to know if we are to really move our process in the direction of perfection. Value Stream Mapping can help.
What is Value Stream mapping?
A Value Stream Map (VSM) is a visual tool that displays critical data and information relevant to the improvement focus of a process. For example, if the cycle time reduction is the focus of a process improvement, the VSM will display touch time, wait time, whether the process step is value added (“VA”), resources, etc. If the focus is cost, Touch time, material consumption, material waste, inventory and warehousing costs may be what you need to know. What is the focus of your project: cost, cycle time, defects, safety, compliance to regulatory requirements?
Why use Value Stream Maps?
The visualization of critical data and information in the VSM identifies waste and improvement opportunities in the process steps. For example, if your focus is reducing cycle time and wait time is 90% of the total cycle time, that flags what you need to do. Further, if 80% of the wait time is in two of the 18 process steps, you know where your priority opportunities are. VSMs may be used for the current state process, the future state process, the entire process or to a portion of the process as needed by the team.
What are the contents of a Value Stream Map?
There is a wide range of data and information which may be displayed in a VSM. More is not always good. Be judicious in your selectin to ensure value to the improvement focus.
- Customer demand
- Customer specifications
- Touch time
- Wait time
- VA/NVA/BVA* classification
- Resources available (people, equipment)
- Sequence of process steps
- Opportunity to consolidate process steps
- Right the First Time (RFT) designation to represent defect rate
- Type of defects
- Sources of defects
- Inventory or backlog
- Material waste
- Material unit cost
- Labor unit cost
- Information flow method (electronic, regular mail etc.)
- Transportation method
- Sources of variation:
- Measurement methods?
- Other information relevant to your focus
*BVA: Business Value Added: Not value-added according to the Lean definition of “value-added,” but required by regulations, clients, etc.
Steps to create a Value Stream Map
- Identify the process and process boundary
- Identify the focus of the process improvement as defined in the Project Charter
- Identify the process improvement team
- The team draws the current state process map, in flow-chart or swim lane style. Use of white board and sticky notes to draw a process map and perform value analysis by color coding the process steps are a good way to do this.
- Define the data/information that are relevant to the improvement in focus
- Collect the data
- Go to the Gemba (walk the workplace): the most appropriate method to collect data
- Most processes vary with time (peak hours, seasons, etc.)
- If specific information is not available, use a range and most probable value
- Display the data
VSM’s, in most literature, are displayed as shown below. This may be okay where the process steps are 4 to 6.
If the process steps are more than six or so, we recommend use of Tables as shown below. This VSM is a process in a coffee shop. You don’t need to follow the numbers. Just understand the format.
Does Value Stream Map show only “value added activities” as the name suggests? No. It displays all activities in the process flow and highlights areas of inefficiencies and opportunities for improvement. Such as wait times, defect rates, backlog, etc. Just a caution! It is easy to get into the weeds and waste time. Stay at a higher level to capture 80 % of critical areas.
VSM is one of the best tools to lean a process.
See you next time for more insights and tips on Lean Six Sigma Process improvement!