Value stream maps are very useful in analyzing processes because they help identify ways to improve flow and eliminate waste and non-value-added (NVA) activities. Value stream mapping can also help you achieve other objectives:
- Establish a baseline for improvement
- Determine where bottlenecks occur in the process
- Measurement of key metrics, such as cycle time, downtime, yield, changeover time, etc.
A value stream map is a drawing that illustrates the process flow, information flow, and flow of material from the time a customer places an order until they receive the product or service.
You might start by determining customer demand. For example, how many products or service offerings are required on a daily, weekly, or monthly basis? Once you know the demand, you can establish the “takt time,” or the amount of time required to produce a unit of demand. “Takt” is a German word for a precise unit of time. Takt time, then, refers to the rate of time needed to match the pace of customer demand. If a service needs to be provided every two minutes, a certain pace must be maintained to achieve continuous flow. For example, if an office operates 480 minutes every day and the customer demand is 200 transactions per day, the takt time is 2.4 minutes or every 144 seconds for each transaction. Takt time is calculated by dividing the net available time by the average demand.
The value stream map breaks down a process to identify what factors, or non-value-added activities, are hindering the pace of demand.
A value stream map can also be used to understand process lead time, which is the amount of time it takes for a single product to move through the entire process, from beginning to the end.
Value stream maps consider the flow of three different areas:
- Flow of information from the customer to the producer; from the producer to suppliers; and among the various producer departments
- Flow of material from supplier to producer and then to each process step required to make the product or deliver the service
- Flow of operation from one process step or task to another
At each process step, information is collected; this information can include cycle time, scrap levels, defect or error rates, yield, changeover times, machine uptime, etc. Each of these represent an opportunity for improvement and should be viewed as potential kaizen events.
Typically, there are two versions of a value stream map. One is the current-state value stream map (CSVSM) that captures the value stream as it exists today. The CSVSM shown above illustrates opportunities to improve flow, reduce work-in-process (WIP) inventory, and improve efficiency. The alternative version is a future-state value stream map (FSVSM) that shows the desired future-state value stream objective.
The value stream map is a great tool to help you understand what is going on in the process and it can help you identify bottlenecks, cycle times, lead times, and waste that is occurring in the process. Your effectiveness in making improvements is going to rest on your ability to identify and eliminate the source of the process waste.
When developing a value stream map, be sure to avoid these common errors:
- Trying to map the process without observing what is going on at the gemba. Make sure you and your team thoroughly walk the process from start to finish and observe what is happening. Don’t assume anything!
- Make sure everyone on your team is in agreement on the starting and ending points of the process and the process steps themselves. The starting point, or starting boundary, is the action that triggers the process to begin. The starting point could be a phone call, an email, a customer service request or order, a patient walking in the door, etc. The ending point, or ending boundary, is the last step in satisfying the customer. The ending point is the point in time when the customer has received the requested product or service.
- Don’t get sidetracked by following the people who are working within the process instead of your true focus – the flow of the process.
- Consistently record any data or information that needs to be collected, especially if multiple team members are collecting the data. If necessary, establish an operational definition on how to make calculations, and then make sure to follow it.
- Make sure you focus on one product or service at a time. I’m often asked by companies which product or service they should value stream map first. My suggestion is to start with the product or service that absorbs the majority of your time. Your goal should be to get this product or service to flow flawlessly!
- Don’t worry about all the “what-ifs.” They occur a small percentage of the time and should be handled on a case-by-case basis. The products and services you provide daily should flow without any interruption. If they don’t they become prime candidates for kaizen or PDCA events.