Electrical Discharge Machining. Optimization of chromium powder mixed EDM parameters during machining of H13 tool steel

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CHAPTER 3
OPTIMIZATION TECHNIQUE USED
This chapter provides the brief introduction about the various techniques used for optimization of input parameters in the present study. Response Surface Methodology (RSM) was used to design the experiment in this research work. Response Surface Methodology was implemented by using Minitab 16 software for constructing the experimental design. The optimization of input parameters was done by using Desirability approach. Minitab 16 was used to optimize PMEDM input parameters. A brief description of these methods is highlighted below:
3.1 Response Surface Methodology
Response surface methodology is a collection of mathematical and statistical techniques for empirical model building. By careful design of experiments, the objective is to optimize the response (output variable) which is influenced by several independent variables (input variables). An experiment is a series of tests, called runs, in which changes are made in the input variables in order to identify the reasons for changes in the output response. Suppose there are two input variables having different levels influence a response variable y, the relationship between input and output variable can be shown as
y = f(x1, x2) + e (3.1)
Where e is the error observed in response y. If we donate the expected response as per following:
E(y) = f(x1, x2) = µ (3.2)
then the surface represented by equation (3.2) is called response surface
µ = f(x1, x2) (3.3)
In most of the RSM problems the form of relationship between the response and the independent variable is unknown. Thus the first step in RSM is to find out the suitable approximation for the true functional relationship between y and set of independent variables.
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Almost all problems use these models for mathematical equation formation. The method of least square is used to estimate the parameters in approximating polynomials.
In Response Surface Methodology, normally surface plots and contour