Control Chart: Use of SPC and SQC in manufacturing

Control Chart
1 | P a g e
Use of SPC and SQC in
manufacturing

Control Chart
Contents
PART-A...........................................................................................................................................3
Solution I)....................................................................................................................................3
Solution ii)...................................................................................................................................6
Solution iii)..................................................................................................................................7
Solution iv)..................................................................................................................................7
PART-B...........................................................................................................................................9
Solution I)....................................................................................................................................9
Conclusion.....................................................................................................................................10
References......................................................................................................................................11
2 | P a g e

Control Chart
PART-A
Solution I)
My assessment is on measuring the length of the bearing housing box which dimension is
100*80*60 mm. The first five batches, when each batch consists of 10 boxes. The measurements
are as followed.
Table 1- Measurement of boxes length
D1S1 D1S2 D1S3 D1S4 D1S5 D2S1 D2S2 D2S3 D2S4 D2S5
100.6104 99.4156 98.0457 97.9015 100.1984 101.5872 100.3808 98.9976 98.852 101.1712
100.837 100.0027 100.2705 99.498 99.5186 101.816 100.9736 101.244 100.464 100.4848
97.2423 99.086 93.0811 99.6834 98.4165 98.1864 100.048 93.9848 100.6512 99.372
97.6131 97.8809 97.5925 99.1272 99.1272 98.5608 98.8312 98.54 100.0896 100.0896
99.9924 100.0233 98.9727 100.4971 100.6722 100.9632 100.9944 99.9336 101.4728 101.6496
100.3117 99.3538 100.3014 99.4362 99.6525 101.2856 100.3184 101.2752 100.4016 100.62
100.0336 101.0327 99.3435 99.3744 100.2087 101.0048 102.0136 100.308 100.3392 101.1816
99.2714 100.3426 99.1066 99.3023 101.1872 100.2352 101.3168 100.0688 100.2664 102.1696
98.9315 100.631 98.7049 99.4774 99.3126 99.892 101.608 99.6632 100.4432 100.2768
100.4456 100.4765 101.0018 100.425 99.8173 101.4208 101.452 101.9824 101.4 100.7864
Each column in the above table is represented as D1S1, D2S2 .... etc. this represents day one and
students one, similarly day 2 and students 2 etc. From the given table of measurements, it looks
like variation is very high, but to know that this variation is within specification limits, we must
draw Shewhart control chart. A control chart which is discovered by Walter Shewhart in 1920.
This discovery is very useful in finding the variation of the process due to basically two reasons,
one is common cause and second one is chance cause. The common cause is considered as
within acceptable limits, while chances cause is considered as reason to analyse the process and
control according to customer specification. This also helps to know that weather our process is
capable or not for customer requirement. The Shewhart control chart calculation is given as
follows (Hart, 2007).
Table 2-Calculation for Shewhart Control Chart
Range X_BAR Centre Line X_BAR R_BAR Centre Line R_BAR
Sample
No. X-Bar R_BAR UCL X_BARBAR LCL UCL R_BARBAR LCL
1 99.71604 3.6857 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
2 100.51092 2.318 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
3 97.97517 7.5701 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
3 | P a g e

Control Chart
4 98.74521 2.4971 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
5 100.51713 2.6769 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
6 100.29564 1.9318 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
7 100.48401 2.6701 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
8 100.32669 3.063 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
9 99.89406 2.9031 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
10 100.92078 2.1651 100.9081767 99.938565 98.96895328 5.59415593 3.14809 0.70202407
As per the data given above, the Shewhart control chart can be prepared is follows
0 2 4 6 8 10 12
0
1
2
3
4
5
6
7
8
R_Bar Chart
R_BAR UCL Center Line LCL
Graph 1-R_baar control chart
0 2 4 6 8 10 12
96
97
98
99
100
101
102
X_Bar Control Chart
Center Line X-Bar UCL LCL
Graph 2-X-Bar Control Chart
4 | P a g e