6.5 Tools: Documenting the Current State

Like most tools used in lean management, the beauty of value stream mapping lies in its simplicity. It is meant to be a paper and pencil tool—no need for fancy engineering software to map your processes! The result is a visual representation of the process that can easily be shared with and understood by others. The value stream map helps to create a common language for people across the entire organization to discuss the process. Because the flow of the process is evident on the map, so too are the obstacles standing in the way of flow—the waste embedded in the process. The map provides a reference point for discussing improvement opportunities and visualizing their impact. Importantly, the map also shows the relationship between material flows and information flows, which no other tool does.

The Importance of Information Flows

Information flows are critical to a lean operation. In order to minimize inventory, a key form of waste, each activity in the process needs some way of knowing when and what they are to produce. Information flows are the link to telling each activity what to make and when. It all starts with the customer: When the customer demands an item, that is a signal to the last step in the process to produce. Then that signal makes its way, step-by-step, throughout all of the upstream activities in the process. It may sound complicated, but lean practitioners have developed clever and even fun ways to transmit these signals across process steps. For example, one firm uses different colored golf balls passed along a tube connecting process steps to indicate a signal to produce; each different color signifies a specific variety of the product to be made. A few different ways of signaling production are shown in Table 6.1, though it is by no means an exclusive list.

Going to the Gemba

When starting a value stream map, the first consideration involves selecting what product or product family you want to map out. Focusing your map in this way will keep it clean and organized. Too many products or product families on one map will be too confusing—the simplicity of the tool will have been lost! A product family is a group of products that share similar processing steps but may differ on attributes like color or size.

The next important decision is nominating a single person as value stream manager. This is important, because as noted previously, most processes cut across organizational departments. It will not be useful to split up the mapping task among departmental areas and then “paste” maps together at the end. One person with the backing of top management needs to manage the entire mapping process. Top management support should be visible and sufficient power afforded to the value stream manager to get the information they need and implement change across departments.

Finally, this manager will conduct the mapping by “going to the gemba”—meaning going to the place where the work is done. It is not enough to sit in your office and call departments to ask them about the process. The manager needs to tour the process for themselves, talk to the operators of the process, and the area managers, and use a stopwatch to collect the necessary data at each process step. This is the only way to achieve a true and detailed understanding of what goes on from start to finish in this process. The good news is that mapping the process in this manner should not take very long. The goal is not perfection, but rather continuous improvement!

Map Layout

Value stream mapping uses a set of common symbols for shared understanding. Some of these symbols are depicted and described in Figure 6.1. We will use these symbols in drawing a current state map for Krazy Kat, a cat toy manufacturing company. The product family we will map is a plastic spiral cat toy. Figure 6.2 shows the completed current state map for this cat toy production process. Key process activities in this toy-making operation include the inspection of raw materials, injection molding, cutting, and packaging. Obviously, these activities can be further broken down into specific process steps, but that level of detail is not necessary for our value stream map. We simply want to capture the big picture process flow and the average amount of time a toy spends at each activity. Also note that the cat toy company produces and sells other items, like fuzzy felt balls and furry fake mice, but those are different product families with different activities, and therefore each require their own value stream mapping effort.

Material Flows

The map “begins” with the customer in the top right corner. Keep in mind that the customers of some processes may be internal, while others are external to your organization. For our cat toy process, the customers are retailers that are external supply chain entities. The first step of mapping involves understanding the customer requirements for toy springs during some specified time period. For our process, we will use weekly demand for toy springs. From there, the map works backwards, or upstream, through the process, with all the process activities and inventory accumulations shown along the bottom of the map.

In the lower right-hand corner of the map, we find the inventory of toy springs staged at the shipping dock for delivery to customers. The process activity before that is toy packaging. To the left of the packaging process activity is another inventory triangle, representing all the toy springs that have been cut and are waiting to be packaged. You continue to work leftward upstream through the cutting, injection molding, and inspection activities, with inventory triangles observed between each process activity. You eventually make your way to the raw material inventory at the very start of the process in the lower left-hand corner of the map; here we are just noting the inventory of plastic pellets, which is the primary ingredient used in the toy spring production process. There are other purchased items that are used in the process, like, for example, the packaging.

You do not need to map every purchased item, just a single raw material critical to the process is sufficient. Also, plastic pellets come in different colors to add variety to the cat toy springs produced—green springs, but also yellow and red. For mapping purposes, we just aggregate all the colors to a single “plastic pellet” purchase and use that, since the specific color does not affect the sequence of production process activities or how the activities are performed. Remember, the goal is development of a clean and simple map! Finally, in the upper left corner of the map, we show the supplier of plastic pellets. All of these activities now describe the flow of materials through the cat toy–making process.

Information Flows

Next, we add in the information flows. Information flows are modeled at the top of the map page with arrows; straight arrows represent paper flows and staggered arrows are used for electronic flows. These flows are critical for executing on the takt time of the process—how much needs to be produced and when. There is often a Production Control function, shown at the top center of the map. Customer orders come into the Production Control Center, usually in the form of both forecasts and daily demands. Production Control sends their own forecasts and weekly orders to the plastic pellet supplier. Production Control also sends a daily schedule to each of the process activities in this current state map.

Summary Timeline

The final step of the value stream mapping process is to create a summary timeline at the very bottom of the page. The timeline will account for the production lead time at each process activity and inventory triangle, which then culminates in an assessment of the total processing and wait times one toy spring experiences in order to make its way through the process, from raw material delivery to customer purchase. Calculations for the timeline are shown in more detail in the Key Metrics section below.

The End-of-Topic Case walks you through the data used to develop a drawing of the current state map for the cat toy–making operation. It is a good idea that you start with a fresh sheet of paper and try drawing the current state map from scratch. How closely does your map match up to the one in the Figure? Reconcile any errors and then tackle the case questions!

Key Metrics

A key feature differentiating a value stream map from a process flow diagram is the additional metrics reflected on the map. Table 6.2 shows these metrics broken out by Customer Information, Process Box, Inventory Triangle, and Timeline metrics. The formulas and sample calculations from our cat toy-making process are provided in Table 6.3.