How do you update and maintain your control charts over time?

2 Why use control charts?

Control charts are useful for several reasons. First, they help you visualize the variation in your process and identify the patterns or trends that indicate problems or opportunities for improvement. Second, they help you distinguish between common cause variation and special cause variation. Common cause variation is the natural and expected variation that occurs within a stable process. Special cause variation is the abnormal and unexpected variation that occurs due to external factors or changes in the process. Third, they help you evaluate the impact of your improvement actions and verify if they have resulted in a stable and capable process.

3 How to create control charts?

Creating control charts requires you to define the process variable and the measurement method, collect and organize the data, calculate the central line and the control limits, plot the data and the control limits, and interpret and analyze the control chart. The process variable is the characteristic or output that you want to monitor and control, while the measurement method is the way you collect and record the data. You need to collect enough data to represent the normal variation of your process and organize it into subgroups or samples. The central line is usually the mean or the median of the data, while the control limits are calculated based on the standard deviation or the range of the data. You can use a spreadsheet or a software tool to create the control chart, plotting the data points and the control limits on the same graph. Lastly, you need to look for any signs of out-of-control conditions and compare the control limits to the specification limits.

4 How to update and maintain control charts?

Control charts are not static, but dynamic tools that require regular updating and maintenance. To keep your control charts relevant and useful, you need to collect and plot new data, recalculate the central line and the control limits, review and revise the control chart, and take action and improve your process. You should measure and record the process variable and add new data points to the control chart to monitor the current state of your process. You may need to adjust the central line and the control limits to reflect the new average and variation of your process. Periodically review and revise your control chart to ensure that it is still appropriate and accurate for your process. Take action and implement improvement solutions when you find any out-of-control or out-of-specification conditions, and verify and validate the effectiveness of your improvement actions by checking the control chart.

5 How to use control charts for Six Sigma?

Control charts are an essential part of the Six Sigma methodology, especially in the measure and control phases of the DMAIC cycle. In the measure phase, you use control charts to establish the baseline performance and the capability of your process. In the control phase, you use control charts to monitor and sustain the improved performance and the capability of your process. Control charts also help you communicate and document your process performance and improvement results to your stakeholders and customers.