Workflow diagrams are also known as spaghetti plots. Unlike other plots, they are not the product of a formula or a statistical program. Instead, workflow diagrams are a direct record of the paths taken by flows of people or materials.
These diagrams are based on observation, and they can provide valuable insight into physical efficiency.
Decision makers looking to reduce waste in the areas of transportation, waiting, and motion can all benefit from a well-constructed workflow diagram.
Constructing one of these diagrams is easy, but interpreting it and making sense of how to use it to produce innovation within your Lean (or not so Lean) organization can be another matter entirely.
Spaghetti plots originated in the field of natural science.
They have been used by meteorologists to map atmospheric changes across massive regions. Oceanographers use them to track flows across the oceans of the globe. Ecologists use them to track the patterns of movement of whole populations.
Comparatively, the business application takes place on a much smaller scale.
A workflow diagram for materials may be used for something as large as an entire facility. A diagram at this scale would track the movements of raw materials from the loading dock to the shipping dock.
Alternatively, it may also diagram something as small as a single office or one production cell.
To build a workflow diagram of a space, first start by mapping the workspace as it physically occurs.
Map to scale, and truthfully represent the space.
Once the space is mapped, mark the process steps where they are performed on the map.
Now that the space is mapped and annotated, observe the process in its normal state and record the path that the people or materials take—whichever you are attempting to plot.
Draw the paths using smooth lines that recreate the actual path as much as possible, and include arrows to signify direction.
It may be helpful to use different colored lines to differentiate between different people or processes as needed.
Making Sense of the Results
Now that the workflow diagram is complete, look at the lines.
As the process was carried out time and time again, the lines will accumulate (the tangled strands produce the pasta-oriented name).
If the map was drawn accurately to scale, it should be clear where the flow of work is occurring.
The thickest, darkest concentrations of lines signify high-traffic areas, while thinner lines or smaller bundles represent less-traveled paths.
What decision makers should be looking for are areas where the workflow lines curve unnecessarily or double back on themselves.
Each line should represent an even and (relatively) straight flow that goes directly from one station to the next.
Are there stations that are visited more than once for the process?
Does it make sense to move those stations to increase efficiency?
These questions can be answered by modeling new spaghetti plots and taking measurements instead of moving equipment on the floor. New layouts can be tested and examined in a no-impact testing environment.
Therefore, it is important that your base map is produced to scale.
It is for this reason that before a process is altered, it is a good idea to produce a workflow map of that process. This way, the addition of new steps or workstations can be tested before flow is disrupted by repositioning or other modifications to installation.
Mistakes to Avoid When Creating Workflow Diagrams
When creating your diagrams, sometimes the best way to get things done is with an old-fashioned pencil and paper. While it may seem as though workflow diagrams are straightforward to produce, there are some basic mistakes to avoid.
1. Not Observing the Process in Real Time
This may seem like common sense, but to record the workflow as it happens, it is imperative that the workflow is actually recorded as it happens.
This can mean going down to the shop floor, the factory floor, the finishing room, etc., with a pencil and a sheet of paper and mapping in real time.
Trying to reproduce the workflow from memory or from a secondhand source creates a large margin for error which can easily be avoided.
2. Recording Too Much on One Diagram
Like any other sampling or data-gathering activities, creating a spaghetti plot or workflow diagram of a process should have a narrow focus on the process at hand.
This is especially true if multiple workflows occur simultaneously within the same space.
Therefore, it can be a helpful practice to set observation goals and focus on specific processes for set durations. Trying to monitor every process in a shared workspace can result in information overload. In the case of an overly busy workflow diagram, too many lines and no insights.
Also helpful is the practice of using overlays of each focused process.
This means separate processes can be examined in detail alone, or in conjunction with each process that occurs in that workspace.
Color coding different processes can also be tremendously helpful.
3. Gathering Too Little Data
Just as information overload is detrimental to gaining actionable insight from a workflow diagram, gathering too little information can also lead to poor decision making.
Recording only a few complete cycles of a process doesn’t paint an accurate picture, nor does recording only once during ideal conditions.
The most important aspect of a workflow diagram is that it produces an accurate depiction of what exactly is going on in a process. Noting conditions and recording on several occasions will provide a fuller picture and will help identify outliers if they should crop up.
The Bottom Line
The bottom line is that the creation of a workflow diagram or a spaghetti plot (they are the same thing) provides an important visual tool.
Effective plotting and recording of a process can highlight areas of wasted effort or other waste events. These plots, if recorded accurately to scale, can also serve as no-impact layout testing aids. These aids can come in handy to preview workstation organization or equipment changes.
This article is based on a portion of Chapter 4 of the best-selling Lean Six Sigma QuickStart Guide: The Simplified Beginner’s Guide to Lean Six Sigma, now in its second edition. Published by ClydeBank Media, 2nd Ed. 2016. Benjamin Sweeney is a staff writer and regular contributor to the Business and Process Optimization blogs.
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Benjamin Sweeney is the Senior Business Writer for ClydeBank Media who specializes in the wide and wonderful world of business and process optimization. He has an appetite for waste reduction and an eye for efficiency. He has authored two titles on the subject of Lean manufacturing, both available from ClydeBank Media.