Visual control is any communication device used in the work environment that tells us at a glance how work should be done and whether it is deviating from the standard. It helps employees who want to do a good job see immediately how they are doing. It might show where items belong, how many items belong there, what the standard procedure is for doing something, the status of work in process, and many other types of information critical to the flow of work activities. In the broadest sense, visual control refers to the design of just-in-time information of all types to ensure fast and proper execution of operations and processes. There are many excellent examples in everyday life, such as traffic signals and signage. Because it is a matter of life and death, traffic signals tend to be well-designed visual controls. Good traffic signs don’t require you to study them: their meaning is immediately clear.
Visual control goes beyond capturing deviations from a target or goal on charts and graphs and posting them publicly. Visual controls at Toyota are integrated into the process of the value-added work. The visual aspect means being able to look at the process, a piece of equipment, inventory, or information or at a worker performing a job and immediately see the standard being used to perform the task and if there is a deviation from the standard. Ask this question: can your manager walk through the shop floor, office, or any type of facility where work is being performed and recognize if standard work or procedures are being followed? If you have a clear standard for every tool to be hung in a certain place and it’s made visual, then the manager can see if anything is out of place. This is why a popular 5S activity is to create shadow tool boards. A “shadow” of each tool is painted on the board in the place that tool should be hung; for example, the shape of a hammer shows where the hammer goes, so it is obvious if the hammer is missing. Similarly, having clearly visible indicators of minimum and maximum levels for inventory will help the manager (and everyone else) see if inventory is being managed appropriately. Well-designed charts and graphs that are kept up every day can visually control projects in offices.
Principle 7 of the Toyota Way is to use visual control to improve flow. Devia-tions from the standard should be deviations from working to takt time, one piece at a time. In fact, many of the tools associated with lean production are visual controls used to make visible any deviations from the standard and to facilitate flow. Examples include kanban, the one-piece-flow cell, andon, and standardized work. If there is no kanban card asking to be filled on a bin, then the bin should not be there. The filled bin without a kanban card is a visual signal of overproduction. A well-designed cell will immediately reveal extra pieces of WIP through clearly marked places for the standard WIP. The andon cord signals a deviation from standard operating conditions. Standard task procedures are posted, so it is clear what the best-known method is for achieving flow at each operator’s station. Observed deviations from the standard procedure indicate a problem. In essence, Toyota uses an integrated set of visual controls or a visual control system designed to create a transparent and waste-free environment. Let’s look at a most unlikely place where visual control enhances flow—a “lean” mega-warehouse.