Читать книгу Statistical Quality Control - Bhisham C. Gupta - Страница 31

We turn now to process control. In process control or statistical process control, steps are taken to remove any defects or errors before they occur by applying statistical methods or techniques of five kinds: define, measure, analyze, improve, and control. We discuss these techniques in Chapter 2. Deming describes statistical quality as follows: “A state of statistical control is not a natural state for the manufacturing process. It is instead an achievement, arrived at by eliminating one by one, by determined effort, the special causes of excessive variation.” Another way of describing statistical quality is as an act of taking action on the process based on the result obtained from monitoring the process under consideration. Once the process‐monitoring tools (discussed in detail in Chapters 5–8) have detected any cause for excessive variation (excessive variation implies poor quality), the workers responsible for the process take action to eliminate the cause(s) and bring the process back into control. If a process uses statistical control, there is less variation; consequently, quality is better and is continuously improved. If the process is under control, then it is more likely to meet the specifications of the customer or management, which helps to eliminate or significantly reduce any costs related to inspection.

Quality improvement is judged by the customer. Very often, when a customer is not satisfied with quality improvement, they do not bother to file a complaint or demand compensation if the product is not functioning as it is expected to. On the other hand, if there is significant quality improvement, the customer is bound to buy the product repeatedly. These customers we may define as loyal customers. So, quality improvement is best judged by loyal customers, and loyal customers are the biggest source of profit. If there is no significant improvement in quality, then not only do we lose dissatisfied customers but we also lose some of the loyal customers. The loss due to dissatisfied customers or losing loyal customers usually is not measurable – but such a loss is usually enormous, and sometimes it is not recoverable and can cause the collapse of the organization. Thus, quality control and quality improvement are the best sources of good health for any company or organization.