218
S. Gajjar et al.
Table 5 Observed and predicted values of RMSE
Exp. Run order
Observed RMSE (mm)
Predicted RMSE (mm)
Error (%)
1
2.9123
2.8362
2.6831
2
3.2309
2.9849
8.2396
3
3.1072
3.1337
0.8456
4
2.4275
2.3895
1.5902
5
2.3084
2.5382
9.0555
6
2.5044
2.6870
6.7957
7
2.0851
1.9428
7.3244
8
2.0016
2.0915
4.3006
9
2.2614
2.2403
0.94184
10
2.7834
2.8194
1.2769
11
3.0504
2.9681
2.7710
12
3.2247
3.1169
3.4585
13
2.1744
2.3727
8.3576
14
2.2165
2.5214
12.094
15
2.635
2.6702
1.3183
16
1.9029
1.9260
1.1994
17
2.3602
2.0747
13.7583
18
2.337
2.2235
5.1045
3.2 Surface Roughness
Analysis process used for geometric accuracy is also performed for surface roughness. The Analysis of Variance for surface roughness is given in Table 6. It is observed
that number of stages and pitch size are significant and the feed rate is insignificant.
Thus, all three parameters significantly affect the surface roughness except the feed
rate.
Table 6 Analysis of variance for surface roughness
Source
DF
SS
MS
F-Value
P-Value
Remarks
Feed rate
1
0.0055
0.0055
0.17
0.686
No. of stages
2
0.8884
0.4442
13.89
0.001
Significant
Pitch size
2
0.2833
0.1416
4.43
0.036
Significant
Error
12
0.3837
0.03198
Total
17
1.5609
Model summary
S (Std. deviation)
R 2
R 2 (modified)
0.178825
75.42%
65.17%