Quality Improvement Methods
46. Spaghetti Diagram
a. Definition: A graphic which presents the actual movement that takes place as a particular process is executed or as work is done in a particular area. It can help identify wasteful or unnecessary movement and opportunities for improvement. This finding may mean changes to equipment location, reassigning work responsibilities or changing the facility layout (see also Section 13). Sometimes, the effectiveness of a process is constrained by a poor arrangement of the space and such a diagram is a simple way to understand it. The Spaghetti Diagram is done by drawing on an area's floor plan with a continuous line showing the movement of a particular person or group as they are observed. By drawing the line with a pencil or pen and not lifting it up from the page while observing a worker, a pattern of movement often is visible from the drawing. The observation and drawing should be done over a long enough time period to get sufficient movement, which could vary from a few minutes to longer periods, such as several hours.
b. Literature: Spaghetti diagrams are explained and examples given in books on the Lean Method or Toyota Production System. The diagram creation and use are relatively self evident.
Example: By observing a worker, such as a nurse or physician, and tracing her movement continuously on a floor plan of the area where she is working, a continuous line will show what movement is occurring over a limited time. Perhaps an hour or two will be sufficient to diagram the movement pattern. The result can help identify movement that could be reduced by rearranging the workplace. Sometimes, the drawing can be done over an architectural layout, although generally a rough sketch of the floor plan, along with key equipment, is sufficient.
Two examples are:
1) Determine the location in need of study and arrange to observe work being done there on a normal basis. This is an example of Gemba (see Section 18) by observing work in place, as it is normally done.
2) Obtain a drawing or floor plan which provides a simple layout of the workplace. Or make a simple sketch of the workplace layout, including workplace equipment which might be relevant to the movements involved.
3) While observing a worker, trace his movement on the drawing without lifting the pen or pencil. Do this for a sufficient time period such that patterns, if they exist, emerge.
4) Review the resulting drawing for opportunities for improvement. The drawing can also provide information for future workspace designs.