Control chart, known as a Shewhart chart or process-behavior chart

 A control chart, also known as a Shewhart chart or process-behavior chart, is a graphical tool used in a factory and various other industries to monitor and control the quality of a manufacturing process. Control charts help identify variations in a process over time and determine whether these variations are within acceptable limits. They are a key component of statistical process control (SPC).

Control charts consist of a horizontal line (the centerline) that represents the process's mean or target value and two horizontal lines (the upper control limit and lower control limit) that indicate the acceptable range of variation. The data points from the manufacturing process are plotted on the chart over time.

There are different types of control charts, but one of the most commonly used is the X-bar and R (average and range) chart. Here's how it works:

1.  X-bar Chart : This chart monitors the process mean or average. The process data points are collected and averaged, and the X-bar chart displays the central tendency of the process.

2.  R Chart (Range Chart) : This chart monitors the process variability or dispersion. The range of the data points is calculated, and the R chart displays how much the data varies from the average.

Control charts serve several important purposes in a factory setting:

1.  Quality Control : They help identify when a process is going out of control or when it's producing an excessive number of defects or non-conforming products.

2.  Process Improvement : By monitoring variations in the process, control charts provide insights into which factors may be causing these variations. This information can be used for process improvement and problem-solving.

3.  Early Detection of Problems : Control charts allow for the early detection of process problems before they lead to significant defects or waste, enabling proactive intervention.

4.  Data-Driven Decision-Making : They promote data-driven decision-making by providing a visual representation of the process's performance over time.

5.  Documentation and Reporting : Control charts create a historical record of process performance, which can be used for audits, compliance reporting, and continuous improvement initiatives.

Control charts are a fundamental tool in quality management and process improvement within a factory. They are often used in conjunction with other quality control techniques and methodologies to ensure that manufacturing processes consistently produce high-quality products and meet specified standards.