4.2 THE SURFACE ROUGHNESS
Table 4.1 shows the results of the surface roughness during machining process of D2 tool steel using the flooded cooling system for the 17 experiments. Through a range of
parameters that have been set, the range surface roughness result obtained of the results obtained is from 0.2129-0.71 µm. the ability of the machining tool show a combination
of milling parameters are competitive for machining D2 tool steel. Generally the value of surface roughness obtained in machining process is usually between 0.8-6.3 µm
Kalpakjian Schmid 2003. This proves that the High Speed Machining technique capable to producing the best surface finish in machining process.
Table 4.1: Surface roughness for machining D2 tool steel
No of experiment
Cutting speed,Vc mmin
Feed rate, fz mmtooth
Width of cut, ae mm
Surface roughness, Ra µm
1 125
0.2 8
0.5550
2 125
0.15 5
0.6945
3 100
0.15 2
0.4991
4 125
0.15 5
0.3733
5 100
0.15 8
0.7100
6 150
0.1 5
0.5350
7 125
0.1 2
0.3038
8 125
0.1 8
0.2763
9 100
0.1 5
0.4556
10 125
0.2 2
0.5025
11 150
0.2 5
0.3600
12 125
0.15 5
0.4817
53
13 150
0.15 8
0.2244
14 150
0.15 2
0.3150
15 125
0.15 5
0.2129
16 125
0.15 5
0.4888
17 100
0.2 5
0.5617
4.3 Analysis Variance of Surface Roughness Using RSM
Table 4.2 shows the analysis of surface roughness with using RSM method. The factors that affect the parameters when the P-value less than 0.05 using 95
confidence interval. ANOVA shows the parameters that influence the output. From the table 4.2 also, the linear model was found significant with P-value 0.0018 and the
F-value is 13.17297. The factors are cutting speed followed by feed rate is found significant and are arranged based on the largest F-value. This factor caused when the
P-value is below 0.05. The parameter that influences the surface roughness was cutting speed, is because this parameter is the most dominant when compared with the feed
rate. The cutting speed model has the most high F-value of 26.11974 compared to the feed rate and the width of cut.
54
Table 4.2: ANOVA for experiment
Source Sum of
squares df
Mean square F-value
P-value prob F
Model 0.107183
3 0.035728
13.17297 0.0018
significant A-cutting
speed 0.070842
1 0.070842
26.11974 0.0009
B-feed rate 0.035756
1 0.035756
13.18358 0.0067
C-width of cut 0.002363
1 0.002363
0.871116 0.3780
Residual 0.021698
8 0.002712
Lack of Fit 0.013328
6 0.002221
0.530862 0.7682
not significant
Pure error 0.008369
2 0.004185
Cor total 0.128881
11 Std. Dev.
0.052079 Mean
0.403501 C.V.
12.90674 PRESS
0.03903 R-Squared
0.831646 Adj R-Squared
0.768513 Pred R-
Squared 0.697159
Adeq Precision 10.85617
55
The model B referred width of the cut parameter is not separated from the ANOVA even if it not significant. The width of the cut parameter is not significant in influencing
the surface roughness during machining is done. Separation of insignificant factor does not affect the calculation and the mathematical model because of the different
average error of 3.8 compared with 3.3 if not saperated unsignificant factor. This is proved by small changes R square values 0.8316 and the adjusted R-square 0.7685
compared R-squared 0.8133 and adjusted R-squared 0.7718 after separation.
4.4 Development of a Mathematical Model of Surface Roughness
Kategori