Value stream maps are usually drawn using standardized symbols…or that is what most people believe. While there are some symbols that are used pretty much universally, other elements have different symbols in different organizations or by different sources. Other identical symbols are used in a different way by different organizations. And, every day people seem to invent new symbols. In this post I will (try to) give an overview of what is out there, along with my opinion on what I use frequently and what I usually avoid.
Since the material and information flow is represented in symbols, we need different symbols to show the flow. A few of them are used almost universally across industry. However, many symbols have lots of variants and small differences that are either interpreted differently or not used at all in other organizations. I will try to give you an overview of the different symbols, with some (personal) preferences.
This list is also by no means complete. If you do VSM, you will sooner or later come to a point when it will be difficult to represent the VSM using the existing symbols. In this case, many organizations invent “new” symbols. For the sake of clarity, I prefer to stick to common symbols and write a small note next to it. Symbols I use frequently have a white background. Less frequently used variants have a gray background. You can also download a PowerPoint file with an overview of VSM symbols for you to use, although I recommend doing it by hand on paper.
This is the most basic process box. Merely a box and a name within it. While it is sometimes frowned upon by other lean experts, I use it quite frequently when I do not need more detailed information for my processes. Sometimes these boxes are also shaded if they are shared with other value streams. In another version shading could also stand for rework processes, and shared processes have a double cross hatching. Some practitioners also use a triangle for batch processes, an U for one piece flow, or a second box around it for parallel processes. The possibilities are endless, there is no standard.
Optionally, you can add data into the box. The data depends on your needs but may include cycle times, changeover times, number of workers at the machine, number of machines (if this box represents multiple boxes in parallel), number of shifts, defect rates, and whatever you think you need. I have even seen the CO2 footprint of a machine in a value stream.
For data management processes as, for example, the central MRP or logistics system, a slightly different box is sometimes used (although you may as well use the normal process box from above).
Slightly different boxes are used for customers. The image represents a typical saw-tooth roof of many industry buildings. This customer can be both external or internal, but is the end point of the value stream you look at. Usually there is only one customer shown, but you may have more than one.
Suppliers are similar to customers, except that they are the input into your value stream. Again, you should have at least one, but you can have more.
This image represents a worker or a person. In a value stream map it is rarely used, as the info is usually contained in the info box, if needed at all. However, this image is frequently used for layout purposes.
This triangle with an “I” for inventory is the image of a basic uncontrolled inventory (i.e., an inventory that has no fixed upper limit). You can write the inventory observed below, but this depends on why you do a value stream. If you need the number, write it down. If not, just draw the triangle. Some companies draw these in red to indicate that this is not a good way to handle stock.
This is a small variation of the inventory above. This is the type originally shown in Learning to See, but I am usually fine with not adding the two bars on top and below.
The meaning of this symbol is the same as above. This one is used by Toyota for their material and information flow analysis (MIFA). Depending on your interpretation, it represents a pile of material or a normal distribution. Except for the different design, the meaning is identical as above.
A FiFo lane. Some companies make them in green to indicate that a FiFo is generally a good way to store material. You can write either the maximum capacity, the current capacity, or both below the FiFo lane.
An alternative version of the FiFo lane as originally envisioned by Learning to See, although for me it is usually too much effort to draw and write the additional information. However, the arrow in the FiFo is a good reminder that the material flow through the FiFo also contains an information flow too!
Symbol for a supermarket (i.e., the end point of a kanban loop). For a supermarket to be complete, an information flow has to come out of it and bring a kanban back to one of the preceding processes or transports.
This symbol is sometimes used for safety stock, although it is not too common in my experience.
Another version of the safety stock, using a similar triangle as above. Similar icons with an X instead of an S are also sometimes used as a blocked stock that cannot be used.
A cross dock where material is rearranged from inbound or for outbound shipments.
A push arrow, representing a material flow that is not controlled by a pull system (i.e., a cap on WIP). It is often found in combination with the inventory triangles above. I personally hate this symbol. It is a pain to draw it by hand (but maybe this is intentional so you create a pull system in order to avoid the drawing by hand 🙂 ). In any case, I usually use a simple arrow similar to the manual data flow below instead.
Similar to the push arrow but representing a transport to the customer or from the supplier. Also generally called a shipment icon.
This is a sequenced pull ball. It is part of the original set of symbols in “Learning to See”. It is used as a sort of kanban for a supplying system that can produce the parts needed in a short period of time. This fast “just in time” production does not need a supermarket. The symbol originates in colored golf balls used as kanban signals. Can be useful, but is little known and I have not yet seen it in a real value stream.
A parts withdrawal symbol. This represents a pull system and is usually found after a supermarket.
An icon for transport by truck. It is usually combined with the white push arrow from above, although I rarely use it.
A milk run representing a cyclical transport of material.
A fork lift (sort of). More similar icons for airplanes and other things can easily be invented.
A symbol for a Kanban card. This is usually drawn on top of the information flow going back from a supermarket to a preceding process or transport. Technically speaking, a white card indicates only a production kanban, although I do not make this distinction.
Alternative MIFA symbol for a production kanban.
Symbol for a withdrawal kanban that does not start reproduction but merely takes the material out of a preceding inventory. I find this redundant, as the end point of a normal white kanban tells me where the material came from. Hence I skip the shading. Some companies also use different colors for production and withdrawal kanbans.
Alternative MIFA symbol for a withdrawal kanban.
Symbol for kanban arriving in batches. I usually do not use this symbol and prefer to use a single kanban and make a small note in or on top of it.
A triangle kanban, which is a special type of kanban system with only one kanban. Loosely similar to reordering points of Economic Ordering Quantity. I have rarely seen this used, and I don’t use it myself on VSM, although I find triangle kanbans in general quite useful.
Box for collecting kanban (Learning to See calls this a kanban post). It is usually near a supermarket and indicates that kanbans are collected and picked up only periodically. I have used it sometimes, but only when the information flow needed this detail.
Load leveling, or more generally, leveling. It is part of the information flow in a kanban loop.
Heijunka board, or leveling board. This is not part of the set in Learning to See, but rather in MIFA. Yet it fulfills a very similar function, although I rarely see it.
This arrow indicates a manual information flow. Can be combined with text on the type of information.
This arrow indicates a digital information flow. However, I usually simply use the manual information flow for everything, unless it is critical that the flow is digital.
These”go and see” goggles indicate an observation as part of the information flow. For example, if a supervisor checks the inventory and then decides what to produce next. Usually too many goggles are not a good sign, as they indicate an unstructured firefighting type of manufacturing.
Rarely used symbol for a document.
Symbol used to indicate problems and trouble spots identified on the value stream.
Symbol used to indicate a solution, idea, or improvement suggestion.
Timeline below the value stream, used to calculate the percentage of the time in value add. Usually the “troughs” are waiting times, and the “hills” are processing times. In most value stream, I find this not necessary, but sometimes it is useful. The length of the symbol depends on the number of processes above, with one “dent” in the line per process.
On the Symbols…
As you have seen, there are tons of different symbols. Often, there are different symbols for the same thing, depending on which organization you are in. Many of them are also a pain to draw (e.g., the push arrows or all of these truck symbols). At other times, you will find that these symbols are insufficient to express the details of your value stream and you are lacking some symbols that you need to describe your system.
While the above symbols look like a worldwide standard, they are not. I often find lots of gaps, redundancies (push arrow and unstructured inventory), and uncertainties on how to draw them exactly. Often my colleagues and I have different opinions, eventually coming to the conclusion that “both are possible.” In any case, pretty much any value stream drawn needs to be understood only by the team that is working with the improvement. For everybody else, especially higher up, they are just eye candy.
Hence, feel free to adjust, skip, or modify the above symbols to fit your need. It’s not like primary school where Miss Krabappel grades you on your spelling. I usually stick to a basic set of symbols (the ones above that are not grayed out). I mostly skip or ignore the others, because I often don’t need them, don’t like them, and find that they can confuse others on the team.
I also often find the existing symbols lacking. Every now and then I come across a situation that I cannot represent to my satisfaction using the existing symbols. I urge you to resist inventing new symbols; we already have more than enough. If anything, write a small text on the document explaining what you want to do. Nevertheless, the set of symbols sometimes feels incomplete or inadequate. Am I the only one, or did you sometimes have this feeling too? Let me know.
These above are also only the tip of the iceberg. There are many other sets of symbols out there – for example, for flow diagrams and layouts, many of which are surely used somewhere in value stream maps.
In any case, the value stream map can be a great help with some problems but a burden if they are done without proper purpose. Do what is necessary, but don’t over-complicate the things to organize your industry!