**3. Taguchi design of experiment (DOE)**

Taguchi DOE is a well-known factual strategy that gives a legitimate and productive technique for process optimization. The Taguchi technique enables us to improve the consistency of production. Taguchi design recognizes that not all factors that cause variability can be controlled. These uncontrollable factors are called noise factor. Taguchi design tries to identify the controllable factor that minimizes the effect of noise factors. During experimentation, you manipulate the control factor to evaluate variability that occurs and then determines the optimal control factor setting, which minimizes the process variability. A process designed with this goal produces more consistent output and performance regardless of the environment in which it is used. It is world widely used for product design and process optimization. As a result, time is reduced considerably. Taguchi DOE methodology uses an orthogonal array that gives different combinations of parameters and their levels for each experiment [6].

### **3.1 The layout of the experiment**

The following sequence is followed while forming the experiment.


### **4. Selecting base material and their mechanical properties**

AISI 316 stainless steel sheets of dimension 100 75 4 mm are welded autogenously with the butt joint without edge preparation [7]. The chemical


**Table 7.** *Chemical composition of the base material (wt %).*


**Table 8.**

*Mechanical properties of AISI 316 stainless steel.*


**Table 9.**

*Process parameters working range.*

composition and mechanical properties of 316 stainless steel sheet are given in **Tables 7** and **8**. The process parameter working range is given in **Table 9**.

#### **4.1 An orthogonal array is selected**

The input process parameters selected are four, and each parameter is divided into five levels [6]. Different Standard orthogonal array used for optimization is shown in **Table 10**.

These above standard orthogonal arrays provide full information for all possible combination of input parameter. In this experimental work, four factors with their five levels are used for which the corresponding orthogonal array is L25 as shown in **Table 11**. Minitab 18 statistical software is used to a developed orthogonal array, response table, main effect plot for mean and S/N ratio. AVOVA is developed by Minitab 18 software to determine the % contribution of each input parameter [8].

**4.4 Experiment conducted for all input parameter**

**4.5 Response table for bead width**

**Table 10.**

**173**

*Standard orthogonal array.*

**4.6 Main effect plot for bead width**

Specimen 316 austenitic stainless steel is welded as per the combination of parameters given in orthogonal array L25, five trails are performed for each combination of parameters for BW then average value is taken as shown in **Table 14**. S/N ratio is obtained by using Minitab 18 statistical software as shown in **Table 15**.

**Orthogonal array Number of rows Maximum no. of factor Maximum no. of columns at these**

*Application of Taguchi Method in Optimization of Pulsed TIG Welding Process Parameter*

*DOI: http://dx.doi.org/10.5772/intechopen.93974*

L4 4 3 3 ——— L8 8 7 7 ——— L9 9 4 — 4 — — L12 12 11 11 ——— L16 16 15 15 ——— L'16 16 5 — — 5 — L18 18 8 1 7 — — L25 25 6 ——— 6 L27 27 13 1 13 — — L32 32 31 31 ——— L'32 32 10 1 — 9 — L36 36 23 11 12 — — L'36 36 16 3 13 — — L50 50 12 1 — — 11 L54 54 26 1 25 — — L64 64 63 63 ——— L'64 64 21 — — 21 — L81 81 40 — 40 — —

**levels 2 345**

The response table is obtained for the S/N ratio and mean for bead width as shown in **Tables 16** and **17**. The response table is obtained by Minitab 18 statistical software which represents the significance of each individual input parameter. Delta value is obtained for peak current, base current, pulse frequency and pulse on time which is the difference between the highest value to the lowest value. The rank

The main effect plot will help to determine the optimum value of the input parameter. Main effect plot is obtained for S/N ratio and mean for bead width by using Minitab 18 statistical software [8]. The main effect plot will represent significant the level of each input parameter as shown in **Figures 1** and **2**. Optimum value to obtained optimum bead width with their significant level is given in **Table 18**.

of the input parameter is decided as per the highest value of delta [8].

#### **4.2 Conduction of experiment**

By putting the values of four parameters in L25 Orthogonal array as shown in **Table 12** [8].

#### **4.3 Signal to noise ratio**

The S/N ratio help in measuring the sensitivity of quality characteristic to external noise factor which is not under control. The highest value of S/N ratio represent more impact of the process parameter on the output performance. On the basis of characteristic three S/N ratios are available namely lower the better, higher the better and nominal the better as shown in **Table 13**. In this paper, higher the better is used for maximizing depth of penetration as shown in Eq. (1) [6].

$$\text{S/N Ratio} = -10 \log\_{1}{\text{1/n}} \left[ \sum\_{i=0} \text{1/yi2} \right] \tag{1}$$


*Application of Taguchi Method in Optimization of Pulsed TIG Welding Process Parameter DOI: http://dx.doi.org/10.5772/intechopen.93974*

**Table 10.** *Standard orthogonal array.*

composition and mechanical properties of 316 stainless steel sheet are given in **Tables 7** and **8**. The process parameter working range is given in **Table 9**.

**Yield strength 0.2% proof (MPa)**

*Quality Control - Intelligent Manufacturing, Robust Design and Charts*

564 MPA 515 205 40 95 217

**Process parameter Code Level 1 Level 2 Level 3 Level 4 Level 5** Peak current P 140 150 160 170 180 Base current B 60 70 80 90 100 Pulse frequency F 50 75 100 125 150 Pulse on time T 35 40 45 50 55

**Elongation (% in 50 mm) min**

**Hardness**

**Brinell HB max**

**Rockwell HR B max**

The input process parameters selected are four, and each parameter is divided into five levels [6]. Different Standard orthogonal array used for optimization is

These above standard orthogonal arrays provide full information for all possible combination of input parameter. In this experimental work, four factors with their five levels are used for which the corresponding orthogonal array is L25 as shown in **Table 11**. Minitab 18 statistical software is used to a developed orthogonal array, response table, main effect plot for mean and S/N ratio. AVOVA is developed by Minitab 18 software to determine the % contribution of each input parameter [8].

By putting the values of four parameters in L25 Orthogonal array as shown in

The S/N ratio help in measuring the sensitivity of quality characteristic to external noise factor which is not under control. The highest value of S/N ratio represent more impact of the process parameter on the output performance. On the basis of characteristic three S/N ratios are available namely lower the better, higher the better and nominal the better as shown in **Table 13**. In this paper, higher the better

> i¼0 1*=*yi2 h i

(1)

is used for maximizing depth of penetration as shown in Eq. (1) [6].

<sup>S</sup>*=*N Ratio ¼ �10 log 1*=*<sup>n</sup> <sup>X</sup>

**4.1 An orthogonal array is selected**

*Process parameters working range.*

**4.2 Conduction of experiment**

**4.3 Signal to noise ratio**

shown in **Table 10**.

**Tensile strength**

**Table 8.**

**Table 9.**

**Tensile strength (MPa) min**

*Mechanical properties of AISI 316 stainless steel.*

**Table 12** [8].

**172**
