Chapter 8

Visual Systems

Visual systems, or visual tools, are devices that make apparent what should be, and is, going on in a process. Depending on how they are employed, visual tools can make the following apparent:

1. When something in the process is going wrong, where it is going wrong, and what is going wrong. For example, a visual device might signal when a step in the process has broken down or is running slow. Thus the need for attention is visually apparent.
2. When the process is being executed according to plan.
3. What employees need to do next, lessening the burden on supervisors to direct employees’ every move. This facilitates a more worker-directed process with less management intervention.
4. Where a piece of equipment or a unit of work-in-process should be placed. This can eliminate wasted time looking for material whose whereabouts is uncertain.
5. When errors have been made. They can also prevent errors and defects from occurring. Many devices that serve this purpose are called “mistake-proofing devices,” and chapter 9 is devoted to these mechanisms.

One hallmark of an effective visual device is that its intended meaning is apparent even to someone who is not familiar with the process. One example is the picture of an airport tarmac with a Jetway with wheels parked in the center of a segment of concrete painted with diagonal lines (see Figure 22). Given that only one of many segments of concrete is painted, a reasonable conclusion is that the paint strips indicate where the Jetway wheels should be located when it is not in service. In this case, observing the scene in Figure 22 would lead you to believe that everything was in order and there is nothing to worry about. Conversely, Figure 23 shows an airport tarmac that is clearly out of order. The picture indicates where the (illegible) words “Belt Loader” appear. One would guess that the square surrounding these words is where the belt loader should be parked. Hence, one would conclude that the belt loader is mislocated because it is parked elsewhere. Is this a significant problem? In some cases, the rationale for the belt loader’s location might be to provide for a more efficient process, as would result from a Lean implementation. Specifically, the specified belt loader location might reduce wasted motion when a plane arrives and bags need to be unloaded. Alternately, equipment locations might be specified for safety reasons: Keeping equipment a safe distance from the plane prevents damage to the plane and the equipment. For example, a piece of equipment kept in the path of an aircraft could damage a wing or fuselage if it were too tall. Regardless of what rationale might be behind the specified belt loader location, Figure 23 shows that the process is not being practiced as defined and any intended safety or efficiency benefits are not being realized. To return to the question of the significance of the mislocation of the belt loader, it represents a loss of efficiency at a minimum. At its worst, it could present a safety hazard and the possibility for equipment damage. While many may agree that the latter effect is significant, some may say that the former effect is minor—certainly less significant than potential equipment damage. However, if a company wants to improve its processes using Lean, not properly and consistently locating the belt loader is a sign that the company will not be able to implement productivity improvements found through Lean. Recall the in-depth discussion of this topic in chapter 5.

Tape, paint, or other floor markings can be used in other contexts. Markings on a factory floor can indicate various work protocols. For example, tape of various colors on the floor often indicates where various items should be placed, such as trash receptacles, recycling receptacles, and other pieces of equipment. Colored lines on the floor can also help ensure compliance with safety, health, and hazardous-material procedures. A blue line on the floor, for example, might indicate an area where safety glasses or other protective equipment is required. The blue line would allow a manager or worker to react more quickly to an unsafe situation, as recognition of the blue line is immediate, whereas looking up written documentation would take time, accurately remembering the boundaries of the safety-glass area might be difficult, and different recollections might cause debate. More importantly, the blue tape quickly communicates to people entering the area the required safety equipment and they know that everyone can easily observe them violating safety protocol if they were to enter the area unsafely. Thus a manager’s time is less likely to be taken up with monitoring safety practices.

Still another use of floor markings can be observed in the Toyota Production System along automotive assembly lines, where signal lines painted on the floor subdivide the segment of the assembly line where each worker performs their job. Each line might represent when 10% of the allotted cycle time had passed. Thus these lines allow workers to gauge the amount of time remaining to work on the current vehicle and to determine if they are likely to complete work on that car in time. If not, then managers can be signaled using an andon cord (discussed later in this chapter—andon is a Japanese word that means “lantern” or “lamp”).

Shadow boards are devices to visually show where equipment goes and when it is missing. Silhouettes on shadow boards specify positions for each tool or piece of equipment so that when the silhouette is visible it indicates that the tool is missing. Figure 24 shows an example of a shadow board used by a cabinetmaker. Specifically, Figure 24 shows the outlines for two bevel gauges and a mortise gauge in one image and another image where the shadow of one bevel gauge makes it apparent that it is missing. Shadow boards can also facilitate greater efficiency by having tools arranged in the order they are needed for specific procedures, such as medical operations, jet aircraft overhaul, and machine changeovers.

Andon devices, like markings on floors and shadow boards, visually alert management and workers when a problem exists with a process. (Andon is a term used in the Toyota Production System.) Andon devices can take many forms in manufacturing, including a stack of green, yellow, and red lights in the bottom, middle, and top positions, respectively, as shown in Figure 25, which are used to indicate a machine’s status. Each colored lens has a light within it and one light is illuminated at any one time. The lights sit atop a pole sufficiently high that they can be seen from a reasonable distance, and the particular color that is glowing indicates the status of a workstation:

1. Green means the machine or station is running.
2. Yellow means that a station is not running due to another machine. Yellow can indicate either that a machine is starved for material from a prior workstation or it is backed up to the next machine.
3. Red means the machine has broken down.

These lights placed on a sequence of machines or workstations that constitute sequential steps in a process allow the point of trouble to be easily identified when one exists. A maintenance or production person, whoever is responsible for responding to equipment breakdowns, would look for red lights and proceed to that machine to repair it. Machines that display yellow lights are not operative, but the problem is not at any of those locations. However, the yellow lights do give some indication of the severity of the problem or how long it has been going on: A greater number of yellow lights indicate that the machine breakdown has been occurring for a longer period of time.

Other types of andon systems can also be employed, such as andon boards and andon cords. Andon boards display the status of production. Figure 26 shows typical information that might be communicated on an andon board. At the top of that andon board the number of units produced thus far in the shift is shown, as is the target for that point in the shift. The difference between those two figures is the number of units ahead or behind schedule. In this case, production is 42 units behind where it should be, and that number is displayed in red as the status. The andon board in Figure 26 lists the numeric codes for work areas through which parts proceed: 10, 20, 30, and so forth. When those work area numbers are displayed in red, yellow, and green, it has the same meaning as the andon light stack. Additionally, the andon board gives a visual bar chart–style display of buffer inventory between the work areas, where red, yellow, and green bars indicate low inventory, inventory that is not quite up to desired levels, and satisfactory inventory levels, respectively.

Andon cords are used on manufacturing lines to let workers alert managers of problems. A typical andon cord setup would have a piece of rope or wire running alongside an assembly line that an operator could pull if a problem occurred, such as when parts do not fit or when a shortage of parts exists. Pulling the cord, which would be attached to an electrical switch, would cause a light or lights to be illuminated and, in some cases, music to play. The music is sometimes unique for a particular workstation so that a manager knows the location of the problem without needing to look for lights and can promptly go to that location and help to resolve the problem.

The use of visual systems is not limited to manufacturing processes. They can also be used in administrative and service processes. One example from food service is one that many readers may have observed. Some fast-food restaurants use electronic screens to display the queue of orders that have been placed but not yet delivered to customers waiting in the drive-thru lane. In some restaurants, each order will have a clock running associated with that order displaying the elapsed time since the order was placed. This allows workers to gauge progress and determine how likely it is a particular order would be delivered within the allowed time. (Restaurants such as this often have a specified lead time within which to fulfill a customer’s order, which demonstrates that Lean is particular appropriate for these operations.) An order might even start flashing in yellow or red when it is imminently or actually past due, respectively. Another example in health-care services occurred when a Lean consultant improved the productivity of a dentist’s office by indicating to the dentist via an andon board which examination rooms held patients who were ready for him, as shown in Figure 27 (P. Blossom, personal communications, March 21, 2011).Lights appeared on a computer screen to show the rooms in which patients resided whose service had progressed to the point where he was needed. Before the andon system, the dentist did not know when he was needed and so he was idle at the same time that a patient was waiting for him. The resulting productivity gain greatly increased the profitability of the practice.

Visual systems seem more difficult to implement in administrative processes where information, rather than a physical good, is being processed. Where physical goods are processed, the work-in-process is easily observed and can itself serve as a signal. Particularly where service and administrative work-in-process is held in digital form, it cannot be observed within a computer unless some physical manifestation of it is rendered. In these situations, visual systems might be real-time displays on computer screens showing the number of units at various stages in the process and, perhaps, some color-coded signal (e.g., red, yellow, green) that indicates favorable or unfavorable circumstances. Data mining and other business-intelligence methods might also provide for visual signals when an unacceptable delay or backlog was imminent. Many, if not most, companies gather quite a bit of data about their businesses from day-to-day transactions, but few companies use this information to its full advantage. For example, one landscaping company had a transactional software system that recorded all of the work that it did for its various accounts, including the prices charged, the number of hours spent on the account, and the cost of materials used. The software system, however, did not provide a report to answer an important question that the company’s owner had: Which clients are we making money on and which are costing us money? The company developed a customized piece of software to dip into the database of the transactional software and generate a report on the profitability of various accounts on a spreadsheet, including color-coded cells indicating the most and least profitable accounts. This report was useful in adjusting prices for the upcoming year. While data processing in this manner is not usually considered in the context of Lean, it is indeed taking a business situation and creating a visual representation of it that is actionable.

In summary, visual systems reduce the seven deadly wastes in these ways:

1. Motion wasted in looking for things is reduced. Shadow boards and lines on floors indicate where items can be located and where they should be returned.
2. Progress lines painted on assembly line floors indicate production problems. This could signal impending defects or a shutdown that would cause workers’ time to be wasted.
3. Visual indications of equipment placement can eliminate damage (which can be interpreted as being in the defect category of wastes).
4. Supervisory direction, which can be interpreted as wasted motion or effort, is reduced. If an automatic means of communicating what needs to be done can be devised, then it can be argued that the supervisor’s time giving direction is wasted.
5. There is less downtime and underutilized people and equipment. If visual systems make process problems more apparent and the problems are resolved quickly, then less machine and people time is spent idle.

We later describe a mechanism for controlling material flow called a kanban system. It will be apparent that kanban systems provide a visual signal that directs workers to either do work or move material. We will also discuss mistake-proofing devices that, by definition, provide a visual signal that a mistake has been or is about to be made. Thus making the status of a process and its steps visually apparent is a fundamental tactic used in Lean.

Exercises

1. Look for visual systems in the processes you encounter on a day-to-day basis. Are the systems effective?
2. Document the value stream map for a process and identify waste in the process, or use the value stream map for a process that you have documented as part of prior exercises in this book. Determine how visual devices might be used to reduce waste.