ECET- 462
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Application of Computers in Process Control
Purdue University, Calumet
[LABORATORY 12]
PROCESS CAPABILITY DETERMINATION OF AN INDUSTRIAL
MANUFACTURING SYSTEM USING STATIT EXPRESS QC
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Process Capability Determination of an Industrial Manufacturing
System using Statit Express QC
LAB 12
Objective:
1) To determine the Process Capability of a Process from a given set of data.
2) To use a Vernier Scale as an data input device to the Statit QC software and to determine
the process capability
Software required: Satit Express QC.
Procedure:
1.
2.
3.
4.
Go to StartAll ProgramStatit SoftwareStatit Express QC.
Go to File Data Entry setup Proceed With Setup
In Name box write Dia, then hit Create VariableDoneContinue
Write the following data from the Table under the column ‘Dia’. All data should be in the
same column and the sequence should be from left to right:
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Dia in
Dia in
Dia in
Dia in
Dia in
INCH
INCH
INCH
INCH
INCH
0.06350
0.06365
0.06325
0.06325
0.06290
0.06390
0.06305
0.06355
0.06400
0.06290
0.06315
0.06315
0.06350
0.06255
0.06370
0.06290
0.06280
0.06445
0.06260
0.06255
0.06310
0.06300
0.06265
0.06295
0.06290
0.06355
0.0636
0.06325
0.06285
0.06275
(A factory is producing electrical wires. Six samples are chosen from a big bunch. And the
measurement for the Dia for those samples are listed here)
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5. The column should look like:
6. From the toolbar hit the process capability chart icon (
).
7. Make the following changes. The Subgroup Size is 5 as there are 5 readings in a sample:
Here, specification limit: USP = 0.064 and LSP = 0.0625 is chosen arbitrarily.
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8. After you hit Apply OK, you will get the Process Capability chart
9. This chart gives you a clear idea about the whole process. You can easily find that 3.33%
products are beyond specification. So, almost 96.67% products are usable under specified
specification limit. And the process capability index for the process is 0.563.
10. Now, you will be given with several samples of wires. You have to measure the Dia
using the Vernier Scale, while using the Vernier Scale as a data acquisition device. The
instructor will show you how to connect the Vernier Scale to the computer.
11. Take 3 samples (of wires) and there should be 3 readings on each sample. Choose USP
and LSP for your data. Find the Process Capability Index for the chosen specifications.
Discussion:
1. Take a print out of the Process Capability Chart.
2. Explain the capability index of your process.
3. Perform the X-bar/Range chart operation. Take a print out the X-bar/Range Chart.