Lean tools

Spaghetti diagram

In French: Diagramme spaghetti

The spaghetti diagram traces on a floor plan the actual movements of a person, a document or a part. The tangle obtained makes visible a distance nobody was counting.

Record before drawing

You start from a scale plan of the premises, and follow a real journey, tracing the path as you go, without correcting it. The record covers a significant duration — a whole shift, a file end to end — because half an hour brings out only the most frequent back-and-forths.

The accumulated line gives the method its name: after an hour, the sheet looks like a plate of pasta. It is that image, and not a table of figures, that carries conviction in a meeting — including that of the people concerned, who discover their own route.

The trace is completed with two pieces of information the drawing does not carry: the distance travelled, obtained from the scale, and the reason for each movement. Without the reasons, one observes a mess without knowing what to do about it.

What the trace reveals

Repeated back-and-forths to the same point designate a badly placed resource: a printer, an inspection station, a consumables cabinet, a piece of software accessible from a single screen. Moving it is often the least expensive and most immediately measurable action of a project.

Crossings between different routes signal a layout where the flows get in each other’s way. In a workshop, it is a source of waits and risks; in an office, a source of interruptions, every pass in front of a colleague being an occasion to solicit them.

Large loops, finally, indicate a sequence that follows the organisation chart rather than the work. They are rarely corrected by a move: it is the order of operations that must be revised, and the diagram then serves to show the cost of the current order.

What is drawn from it

The quantified distance is the most solid argument. Multiplied by the number of repetitions in a day, then by the number of days, it turns a discomfort into a quantity comparable with others — and makes a layout investment defensible.

The second trace, made after the change, is what proves the effect. It is also the most often forgotten: the project stops at the finding, and nobody can say six months later whether the move produced what was expected of it.

The tool applies as is to administrative processes, by following a file rather than a person. The routes there are as much physical — pigeonholes, signature folders, offices — as logical, and a file that crosses four floors before signature is drawn exactly like a part in a workshop.

The common mistakes

Drawing from memory, as a group, in a meeting room. The trace obtained represents the idea the team has of its movements, which systematically leaves out the short, repeated trips, precisely those that weigh.

Recording for too little time. Half an hour shows only a portion of the day and misses the movements linked to disruptions, which are nonetheless frequent.

Stopping at the picture. An impressive trace with no quantified distance or recorded reasons produces a consensus on the finding and no decision.

On the shop floor — Hospital pharmacy

Tracing a technician over half a day gave a little over four kilometres. A third came from back-and-forths to a single computer workstation, placed at the entrance of the department during a reorganisation two years earlier. The second workstation installed at the other end cost less than a week of the time lost.

The other tools illustrated by this trade: healthcare and life sciences.

Frequently asked questions

How long should the record last?

At least one complete shift for a person, and the whole journey for a file or a part. Duration counts less than representativeness: a record made on a low-activity day shows an organisation that does not exist the rest of the time, and that is an easy reproach to make when the conclusions are unwelcome.

Should the person being followed be told?

Always, and it should be explained that the object of the record is the layout, not their way of working. Without that precaution, the trace is distorted by the behaviour of someone who knows they are being observed, and the exercise leaves a memory that will complicate every subsequent project in the department.

Does the spaghetti diagram apply to offices?

Yes, and the gains are often easier to obtain there than in production because the layout constraints are smaller. Either a person or a physical file is followed, and the movements linked to printing, signatures and transmissions very quickly emerge as the dominant reason.

What is the difference from a process flow analysis?

Process flow analysis lists the operations in order, with their nature and duration; the spaghetti diagram projects them onto a plan and gives the distance. The two complement each other: the list says what is done and why, the trace says what the layout costs. Carried out together on the same journey, they cover the subject.