Deciding between process or value stream
I teach operational excellence with lean and Six Sigma techniques together, and there seems to be a lot of confusion surrounding process mapping (common in Six Sigma and quality system techniques) and value stream mapping (VSM) (associated with a lean approach). Both tools are completely valid for documenting processes and have their place in your tool box. More importantly, they can be used to identify ways to improve processes. Let’s take a closer look.
Process mapping, as taught under the Six Sigma umbrella today, creates documentation for complex processes, both technical and organizational. Process mapping is heavily used in Six Sigma and other methodologies.
These maps identify all the inputs and factors that can affect processes or the problem at hand. Think elegant—process mapping is very effective for complex interrelated processes that cross over multiple functions, both physical and virtual. There are many variations in the symbology used, but there are some basic conventions to help with documentation. Square or rectangle boxes are used for major task steps, diamonds for decision points and other shapes to standardize the view, all of which are connected by directional lines. If you do a web search using the terms “supplier, input, process, output, customer (SIPOC)” or “process mapping,” you will be able to find many examples and fairly detailed explanations on how they are used.
With SIPOC, the process is typically broken out into a map such as the one shown in Figure 1. By having all the important aspects of the overall process on a single page, it is much easier to understand everything that needs to be considered before any decisions are made—a good thing. Then, if changes are being considered, the map can be redrawn to have an easy way to compare the before and after.
Process maps are a wonderful way to provide a clear understanding of inter-relationships in complex processes, such as software coding, calls to a toll-free operation, product and process design cycles, chemical and pharmaceutical manufacturing and many others.
VSM is also known as information and material flow mapping; and, in its best-known forms, it is credited to Toyota. I have examined and practiced more than 25 methods for VSM, and the permutations are unlimited. VSM is a scalable approach to create a visual representation of a process that includes a great deal of detailed information about what is happening at each step. Due to this, VSMs help identify where changes are needed to improve system performance.
VSMs focus on material and information flow. If a company produces information, such as processing insurance claims, you can imagine the claim as the material in the value stream map, just as if it were a widget. This way, the VSM approach can successfully be used in a service or office process. Information flows always exist and, often, are independent of the action mapped in the material flow. Using a process mapping approach for information flow may make sense, coupled with material flow data boxes. Figure 2 illustrates an insurance claim data box.
In the example, a great deal of information was documented by the VSM team at the onset of the work. The work schedule and staffing for this step in the process are included because they are critical for later work-balancing efforts. However, they will probably not be consistent across the value stream. Next, we have the process step name and the cycle time necessary to perform the work. Cycle time should not be confused with Takt time, which is the pace at which the project must be completed to keep up with demand.
Next, we have the full-time equivalent (FTE) calculation, which indicates actual staffing versus calculated need. An easy way to calculate your FTE requirement is to divide the cycle time by the Takt time. For this example, if Takt time is 36 seconds, the formula would be 190 seconds divided by 36 seconds. This gives us a rounded result of 5.3 FTEs.
Examine more data, and we find rework percentage, uptime percentage, overtime hours worked on average per week and absenteeism percentage. If you study Toyota’s approach to VSM, the data boxes usually have data that line up with the key Toyota metrics of safety, quality, delivery, cost, productivity and morale.
In this data box example, there are two major issues. First, we can see a disconnect between planned staffing and the calculated FTE, evident in the 200 hours per week of overtime being worked. Does this tell the whole story? Hardly, but the data does document the situation and provide an easy way to compare this data box to the others in the VSM. There are just a few process steps that are constraining the overall operation, and process improvement efforts can be focused on these places.
There seems to be an aura of mystery and black magic in making the decision on which tool should be used for a given situation. It doesn’t have to be that way. For typical business problems, VSM can be far more effective than process mapping. However, when the process is complex and the problem can’t be identified unless you drill down, process mapping probably is the better choice. Think creatively; there are cases in which process mapping and VSM should happen concurrently on the same piece of paper. Both have important attributes