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In lean manufacturing, Andon refers to any visual display that shows status information on the plant floor. Its origin is in the Japanese word for “paper lantern”. The first Andons in manufacturing were simple lights that enabled operators to signal line status based on color: green for normal operation; yellow when assistance was needed; and red when the line was down. Today, more sophisticated visual displays are often used for Andons, but their purpose – efficient, real-time communication of plant floor status – remains the same.
One of the earliest descriptions of Andons can be found in the book Toyota Production System: Beyond Large-Scale Production, written by Taiichi Ohno, creator of the Toyota Production System. Mr. Ohno describes line stop boards that show “the location and nature of trouble situations at a glance”. He outlines a three-color system of lights controlled by the operator, where green indicates normal operation; yellow indicates a call for an adjustment; and red alerts that the line is stopped.
Over time, the nature and role of Andon systems has evolved. Visual cues are sometimes reinforced with audible cues, and basic stack lights are sometimes replaced with more sophisticated message boards. Nonetheless, the basic principles remain the same:
- Show line status at a glance (e.g. running, stopped, changeover).
- Enable operators to call for help as needed (e.g. from maintenance or supervisors).
One of the key principles underlying Andon systems is empowerment. By giving operators the authority to stop the line and call for assistance – for instance, to address a quality issue – Andons promote employee involvement in the production process.
Another key principle underlying Andon systems is efficient communication. Andons are a simple, consistent, and instantaneous method of conveying information. Simplicity comes from focusing on a few key pieces of information. Consistency comes from applying visual cues in a standardized way (e.g. green is normal, amber is slightly deviating, and red requires immediate attention). Instantaneous comes from using lights or message boards on the plant floor that can be seen over long distances.
Andon systems also encourage companies to better define the role of plant floor employees to address questions such as:
- What does “normal operation” mean?
- When should an operator call for assistance?
- When should an operator stop the line?
At their core, Andons both empower and inform the plant floor. They enable operators to add more value to the production process, and to be an integral part of process improvements. Although the underlying technologies continue to evolve, the value and benefits of timely communication and shared information remain the same.
Andons are powerful and effective communication tools that:
- Bring immediate attention to problems as they occur in the manufacturing process.
- Provide a simple and consistent mechanism for communicating information on the plant floor.
- Encourage immediate reaction to quality, down time, and safety problems.
- Improve accountability of operators by increasing their responsibility for “good” production and empowering them to take action when problems occur.
- Improve the ability of supervisors to quickly identify and resolve manufacturing issues.
Visual Factory emphasizes the role of visual communication, and more broadly the role of information sharing, in empowering and motivating employees, and aligning their efforts with the goals of the company. Andons are an important part of establishing a Visual Factory.
In a lean manufacturing environment, the time and resources devoted to communicating information are considered waste, as they are not part of the value stream, or what the customer is willing to pay for. Since communication is nonetheless essential, it must be achieved in the most efficient way possible.
Information that is broadcast visually travels much faster than information conveyed verbally or in written form. It is also more “error-proof”, since everyone is seeing it first hand, rather than down a chain, where it can be misinterpreted. Thus, Andons provide a key element to efficient communication.
The process of stopping a production line in order to fix problems as they occur is referred to as Jidoka. Jidoka is a fundamental component of the Toyota Production System. In fact, it is one of the two main pillars of TPS (the other is Just-In-Time production).
The goal of Jidoka is to minimize defects by correcting problems at their source and thereby continually building quality into the production process. When a problem occurs, root cause analysis is used to understand the true nature of the problem, and countermeasures are implemented to help ensure that the problem does not recur.
Andons are an essential element of Jidoka, as they provide operators with a practical and effective mechanism for instantly calling attention to problems.
The alignment and broadcasting of strategic objectives from the top to the bottom of a company is known as Hoshin Kanri. With Hoshin Kanri:
- Top management sets strategic goals.
- Middle management develops tactics to achieve those goals.
- Plant floor supervisors and operators implement the tactics – making them operational.
For example, top management may determine that, in order to stay competitive, the company must reduce production costs by 10%. Middle management then develops tactics to achieve this strategic goal. One of these tactics may be to implement a program for monitoring and improving OEE. Since OEE is a somewhat abstract concept, supervisors suggest using an Andon for the plant floor that displays Target, Actual and Efficiency information so that operators can pace their work according to Takt Time.
In this example, Andons provide a link to the plant floor that visually reinforces strategy and tactics developed at higher levels of the company. Andons can alert plant floor employees to a variety of deviations from operational goals, and when patterns of problems emerge, Kaizen techniques can be applied to make the necessary process improvements.