Title : Design of experiments to specify the optimal process parameters in nano-powder-mixed EDM of IN800 with coated electrodes
Abstract:
The low thermal diffusivity and high thermal strength of INCONEL materials are useful in the construction of equipments of electrical power plant, chemical vessels, gas turbines and nuclear reactors. For machining of such hard materials, there is a need for heavy-duty machining equipment and tooling to minimize chatter. Optimal electrical discharge machining (EDM) parameters are to be specified for producing quality products. Karunakaran and Chandrsekharan have performed experiments employing the die sinking CNC EDM machine (Xpert1 model of Electronica India Limited). Aluminum powder is mixed with the low viscosity kerosene and stirred for 9 hours in the magnetic stirrer, which minimizes the particle size to 5 Nm. Aluminum nano powder concentration is 3g/l. The nano powder mixed EDM (n-PMEDM) minimizes arcing problems. This presentation focuses on machining of INCONEL 800 in PMEDM with electrolyte copper electrode as well as silver coated electrolyte copper electrode. Three independent process variables considered in the design of experiments are gap current, pulse-on-time and pulse-off-time, whereas the material removal rate (MRR), the surface roughness (SR) and tool wear rate (TWR) are the dependent performance indicators. Modified Taguchi approach is followed to perform few experiments and generate output responses for the full factorial design of experiments with expected range. Different sets of optimal process parameters are obtained for the output responses. The process designer needs a set of optimal process parameters. A simple and reliable multi-objective optimization technique is followed to identify a set of optimal process parameters. Empirical relations for MRR, SR and TWR are developed in terms of the EDM parameters and validated with test results. Test results are found to be within the expected range. Statistical factor is worked out on the output responses due to machining of INCONEL 800 in PMEDM with electrolyte copper electrode and silver coated electrolyte copper electrode.
Audience take-away:
- Majority of industrial engineering problems are complex in nature and very difficult to formulate theoretically. Hence, there is a need for experimental investigation. As the number of parameters and assigned levels to each parameter are increasing, it is practically impossible to perform that many tests. In such situations, Taguchi method explained in the presentation will help them to perform few experiments and obtain the information for full factorial design of experiments.
- Modified Taguchi method explained in the presentation will help the audience to estimate the range of output responses for the specified process parameters. This type of analysis will be helpful to know well in advance the scatter in the output responses due to repetition of tests.
- The simple and reliable multi-optimization technique will definitely help the process engineers to identify a set of optimal process parameters for achieving the desired output responses.
- Development of empirical relations for the output responses help the process engineer to understand the behavior in case of slight variations in the assigned levels of the process parameters. Statistical factor will help the designer in understanding the influence of change in the process
