Question

For this question, place yourself in the position of an instructor training a group of enthusiastic quality engineers who are eager to understand Statistical Process Control (SPC). As you are preparing your lesson, keep in mind that you are preparing to face a highly educated and critical audience.

a. Define the term Statistical Process Control.

b. Outline the steps for setting up a control chart to monitor a process in every detail. You may write these steps in bullets as if you were creating a Power Point presentation.

Answer 1

Define of Statistical Process Control:

“Statistical Process Control is a standardized methodology for measuring and controlling quality during the manufacturing process.”

a.      The quality data is collected in the form of process or product measurement or reading from various machines and from the instruments.

b.      The data is then used to evaluate, monitor and control a process.

c.       This information will continuously monitor the processes and ensures the process operates at full potential.

The X bar and R bar are the most widely used control charts. The X bar represents the average or mean value of x. It displays the variation in the average or the mean. The R bar shows variation in the subgroup. The range is the difference between the highest and lowest value.

The steps required for setting up a control chart and to monitor a process in every detail are as follows:

• Determine the sample size: The sample should be 8 or less. How frequently sample should be collected must be defined.
• Start collecting the samples: The general rule is to collect 100 samples in a group of 4 with 25 data points.
• Determine the average value: Calculate the average value for the group of 25 samples collected.
• Determine the Range: Calculate the range between the groups of 25 samples of 4 measurements.
• Calculate the R values: The average of sample range known as the R-value is calculated. This is the center line of the Range chart.
• Calculate the upper and lower limit of the chart.
• Plot the data

The information and data should be calculated at regular intervals including the date and time to analyze the stability of the process. The causes should be identified and the necessary corrective action taken to control the process. The adjustments should be made to stabilize the process.