Process parameters have the greatest impact on the hardness of the steel components.

A study was carried out to determine which process parameters have the greatest impact
on the hardness of the steel components. The factors considered are temperature
quenching rate, cooling time, carbon content, and concentration of CO2.
(a) Determine the Taguchi experimental design orthogonal array (show how reduced version
of L8 can be used). The operating conditions for each parameter and level are listed in
Table 1 below.
[3 marks]
(b) Four runs for each experiment were performed and steel hardness measured (Table 2).
Determine the impact of process parameters on steel hardness using SN methodology.
What is the dominant factor?
[20 marks]
(c) Perform mean effect analysis and find the best combination of operational parameters.
[10 marks]
Table 1. Steel production parameters and levels.
Level 1 Level 2 units
Temperature 760 900 °C
Quenching Rate 35 140 °C/s
Cooling Time 1 300 s
Carbon Content 1 6 wt% °C
CO2 Concentration 5 20 %
Table 2. Taguchi L8 orthogonal array and measured hardness in 4 runs.
Exp. A B C D E Run 1 Run 2 Run 3 Run 4
1 1 1 1 1 1 68 61.41 66.33 97.07
2 1 1 1 2 2 69.84 64.76 86.07 51.67
3 1 2 2 1 1 74.36 61.3 94.57 96.81
4 1 2 2 2 2 71.71 58.42 77.23 60.05
5 2 1 2 1 2 91.27 90.89 84.54 63.72
6 2 1 2 2 1 54.39 73.01 50.1 79.62
7 2 2 1 1 2 64.65 91.51 72.68 84.33
8 2 2 1 2 1 60.31 60.69 76.73 74.97