Concept explainers
To develop: Appropriate control chart and determine whether there is any cause for concern in the cutting process.
Introduction: Control charts used to determine whether the process is under control or not. Attributes and variables are the factors under the control charts.
Explanation of Solution
Given information:
The following information is given:
Develop appropriate control chart:
To check whether the process is in control, create the appropriate control charts for the mean
Determine mean of the averages:
It can be calculated by taking the average of all given values for
Hence, the mean of averages
Determine mean of the ranges:
It can be calculated by taking the average of all given values for R.
Hence, the mean of ranges is
Determine the upper control limit and lower control limit of
Determine the upper control limit (UCL) and the lower control limit (LCL) of the
Here, the overall mean
Given the sample size of 4, the Mean factor is
Substitute into the equation (1),
Substitute into the equation (2),
Hence, the upper control limit is
Determine the upper control limit and lower control limit of
Determine the upper control limit (UCLR) and lower control limit (LCLR) of the
Here,
Given the sample size of 4 for
Substitute into the equation (3),
Similarly, substitute in equation (4),
Hence, the upper control limit is
Draw the control chart for the sample means:
The process mean is
Observe that all the sample means are well within the control limits. The first five observations are above the mean of the averages.
Draw the control chart for the sample range:
The average range is
Observe that all the sample ranges are well within the control limits
Hence, the process seems to be in “statistical control”. (However, a process for making precision wires obviously should not have so much of variation in the mean or in the range.)
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Chapter 6 Solutions
Principles Of Operations Management
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