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Table 8.3
Variance analysis of DOE1experiment
Parameter
SS
df
MS
F
0
P-value
(1) Injection time (L)
675.6
1
675.6
233.71
0.000005
Injection time (Q)
13.5
1
13.5
4.68
0.073814
(2) Injection temperature (L)
33.0
1
33.0
11.42
0.014880
Injection temperature (Q)
1.5
1
1.5
0.52
0.497633
(3) Mold temperature (L)
9.6
1
9.6
3.33
0.117968
Mold temperature (Q)
0.1
1
0.1
0.05
0.835974
(4) Packing pressure (L)
386.8
1
386.8
133.80
0.000025
Packing pressure (Q)
10.0
1
10.0
3.47
0.111928
(5) Packing Time (L)
14.3
1
14.3
4.96
0.067622
Packing time (Q)
0.1
1
0.1
0.05
0.832551
Interaction between 1L and 2L
17.6
1
17.6
6.10
0.048428
Interaction between 1L and 3L
10.8
1
10.8
3.75
0.101108
Interaction between 1L and 4L
11.6
1
11.6
4.00
0.092565
Interaction between 1L and 5L
15.7
1
15.7
5.45
0.058317
Interaction between 2L and 3L
11.2
1
11.2
3.86
0.097107
Interaction between 2L and 4L
19.0
1
19.0
6.58
0.042664
Interaction between 2L and 5L
15.5
1
15.5
5.37
0.059674
Interaction between 3L and 4L
15.4
1
15.4
5.32
0.060644
Interaction between 3L and 5L
23.9
1
23.9
8.27
0.028206
Interaction between 4L and 5L
11.0
1
11.0
3.81
0.098703
Error
17.3
6
2.9
Total
1389.5
26
The response surface shown in Fig.
8.6
can be described as a second-order
polynomial, as shown in Eq.
8.1
. Table
8.5
shows equation coefficients.
TRS ¼ a
þ
b T
inj
þ
c T
inj
d P
rec
þ
e P
rec
245f T
inj
50g T
inj
h T
inj
P
rec
þ
11i T
inj
þ
245j P
rec
þ
50l P
rec
11m P
rec
n
ð
8
:
1
Þ
where:
TRS
Surface Residual Stresses [MPa];
T
inj
injection time [s];
P
rec
packing pressure [MPa];
In order to model the response surface of Fig.
8.6
, the following were con-
sidered constant: Injection Temperature 245 C, Mold Temperature 50 C, and
Packing Time equal to 11 s.
Validation of results was carried out through normality analysis and residual
randomness (mean deviation) of the dependent variable, that is, Surface Residual
Stresses. The plotting graph in Fig.
8.7
confirms the hypothesis of normal distri-
bution of the dependent variable, where residue values are on or close to the line
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