What is a spaghetti diagrams (chart)?
A spaghetti chart or spaghetti diagram is the visual description of an actual flow, a snapshot of what a given flow really looks like, not how the procedures expect it to be.
The flow depicted is the path in space (usually through a factory, an office, a building, a campus, on the shopfloor, between machines…) a product, a part, a human or a file follows.
When tracing the flow on a paper, with scaled outlines of machines, desks, offices and so on, the document ends up showing a kind of (cooked) spaghetti plate, as the flow is seldom going in straight lines.
Each line is more or less the distance covered and consequently the time spent in motion or transportation, given the travel speed.
Some more about the basics of spaghetti diagrams >here<
Spaghetti diagram are pretty disappointing at first glance. They look like a toddler’s scribbling on a sheet of paper nearly worn out by the many lines. Onlookers aware that this is an actual flow may get discouraged to understand the chaos at once.
Yet it’s not enough to simply recognize that the flow is a mess and something has to be done about it. What can actually be done?
1. Question the flow
If the “spaghetti” (flow lines) are numbered – I would recommend to do it whenever possible – so that the timely sequence can be seen, search for loops and the flow going back and forth. Then question why these loops and returns occur.
A silly reason would be an employee keeping returning to a computer to check the next item from a list instead of carrying the list with him/her.
The reason behind each line (motion, transportation…) should be challenged in order to identify any unnecessary tasks and suppress them, or to find ways and means to reduce them in space and time if they can’t be suppressed.
2. Question the nodes
It’s common on spaghetti diagrams to see “nodes”, i.e. points where the flow joins to and gets away from, several times during the observation period. Such nodes can be a computer where to get information from or where to input data, an information desk, a kanban board, an elevator, a staircase, a crane, etc.
The first question to ask about nodes is why do they exist? If the answer does not lead to an improvement idea, question their location: is it well situated or does the location force the flow to come back and forth to it? if a relocation cannot significantly simplify the flow, can the “node” be duplicated and its clone wisely positioned in order to simplify the flow, reduce distances, etc.?
3. Reconsider layout
It was common in the past to have specialized shops where only one type of operation was done, e.g. lathing, milling, drilling, etc. This was convenient for accountants happy to have homogeneous shops for easy cost calculation. Lean soon realized the wastes of transportation of parts to be processed between the shops, so flow lines were introduced. In some cases the flow is made unnecessarily complex because the machines are not well located. This is a variant of point 2 (where it’s easy and straightforward to duplicate inexpensive means), in which one must consider rational and optimized machines layout according to the path material or parts have to follow.
4. Consider choreography
According to Wikipedia, Choreography is the art or practice of designing sequences of movements of physical bodies. What I mean is combining the movements of two or more people in order to simplify and speed up the flow. This is usually interesting when motions are extended because someone has to work in front and in the back of some equipment and machine and needs to go around it frequently. By assigning people to front and others to back and synchronizing their activity, the overall duration of a cycle can be reduced. This is a common solution for quick changeovers on some production lines, cells or machines.
5. Consider crunching space
Extended routes i.e. long spaghetti can be caused by available space. Would bringing things together in a tighter space help to simplify flow and eliminate some of the wastes of motions and transportation?
This is one reason why U-shaped manufacturing cells appeared. They can be manned and supervised by less people, losing less time walking from one end to the other. The material flow is also shortened.
Besides, Leanness is correlated with compactness. Think about the relative need for lighting, cooling or heating, the cost of surface in rent or investment… Abundance of space usually attracts clutter and excess inventories, which ultimately can hinder flow.
Do not overlook spaghetti diagrams
As we have seen through these few examples, the mundane sketch can be of great help when analyzing the flow. It might not suffice by itself to solve all flow issues but can give a nice and easy head start.