• Two designs for the same experiment may yield different results; • The designs normally do not permit determination of the contribution
of each factor; • The interpretation of experiment with a large number of factors may be
quite difficult.
3.7.1 STEP IN DESIGN OF EXPERIMENT
3.7.1.1 Design the Experiment
This step is to develop all the ideas and the objectives of this experiment. The objective is based on selected topics about the effect width of cut on surface roughness during
end milling of D2 tool steel. Through this objectives is helpful to prepare a list of specific problem that are occur during experiment were perform. The problem
considerably to improve being studied and the final solution of the problem can be making it. The objective of this research is to study the effect of cutting parameter on
surface roughness. After the surface roughness is analyze the optimizing cutting parameter was perform by using mathematical model is generates from analysis of
variance ANOVA
3.7.1.2 Define factor and variable constraints
The experiment have three parameter that will be tested consists of cutting speed, feed rate, and radial depth of cut. With three of the parameter, the model can be produced
contains 17 runs of experiment by using full factorial design analysis.
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3.7.1.3 Add interaction term
The effect of surface roughness and surface texture it depends on the parameter that is set and other some factor. Other factor which is the vibration of machine, human error,
apparatus faulty, calibration, and etc also is affected to the result obtained.
3.7.1.4 Determine the number of run
Full factorial experimental design was perform by the box-Behnken approach to investigate the effect of the three process parameters without the repetition of
experiment. The experiment carried out generally, there were three model and was completed with 17 runs for three parameters that is set.
3.7.1.5 Check the design
Considering the factor that causes the effect of surface roughness and the interactions of the studied parameter variables with related to the result obtain. From the result
ANOVA and regression analysis is performed to get the significant effect of the model that is design.
3.7.1.6 Gather and enter the data
