**2.4 Design of Experiment (DOE): Taguchi method**

The developed Taguchi method goal is to determine the set of parameters which leads to the best mechanical properties of the PC/ABS injected part.

MINITAB 18 statistical software was used to find out the optimal processing conditions. A confirmation test was performed in order to guarantee the validity of the optimal experimental conditions considered from the design of the parameters.

Following preliminary tests carried out within the SKG Company, the choice of the factors and their levels was made as illustrated in **Table 2**.

The impact of the injection molding parameters on the mechanical characteristics are evaluated through the S/N ratio obtained in the Taguchi experimental plan. The S/N ratio was calculated by the larger is better quality characteristic for determining the effect of each process IM factor. The responses required are the tensile strength and the elasticity module.


#### **Table 2.**

*Geometric and process factors in three levels.*

#### **2.5 Tensile tests**

The tensile tests were carried out, with imposed displacement, on a machine of the LLYOD INSTRUMENT type equipped with a 5 kN load cell.

All tests were achieved at ambient temperature and for a strain rate of 5 mm/ min. The local deformation of the specimens during these tests was measured using an extensometer having an initial length of 25 mm and an elongation of ±1 mm.

The measurement was repeated at least 4 times for the samples and the average of three sample readings was taken for accurate results. The specimens used for the simple tensile test are taken from the ISO 527-2 standard. Its geometry is illustrated in **Figure 2**.

**Figure 2.** *Tensile specimen geometry (in mm).*

#### **2.6 Experimental**

The injection molding (IM) process parameters considered in this study were: material temperature (A), injection pressure (B), holding time (C) and mold temperature (D).

In order to optimize these parameters, the famous optimization approach Taguchi was adopted. One main reason for using Taguchi is the low number of experiments. The

**155**

**Figure 3.**

*Variation of the tensile strength and the elasticity module.*

*Influence of Injection Molding Parameters on the Mechanical Properties of Injected PC/ABS Parts*

As depicted in **Table 3**, an orthogonal array (OA) L**9** was involved to investigate the effect of the process IM parameters. Three levels for each factor were studied.

The elaboration of the injected PC/ABS parts was done within the SKG factory. Each combination was iterated 5 times (9 × 5 = 45). The tensile strength and the elasticity module of the injected PC/ABS parts were regarded as the desired responses.

> **Injection Pressure (bar)**

1 1 1 1 1 2 1 2 2 2 3 1 3 3 3 4 2 1 2 3 5 2 2 3 1 6 2 3 1 2 7 3 1 3 2 8 3 2 1 3 9 3 3 2 1

**Holding Time (sec)**

**Figure 3** shows only the standard deviations of the tensile strength and elasticity module as a function of each experiment number. The mechanical

) experi-

**Mold Temperature (°C)**

number of experiments required could be reduced to nine, instead of 81 (34

The DOF for the three levels was 2 (DOF = number of levels−1).

ments to find out the parameters that influence on the mechanical properties.

*DOI: http://dx.doi.org/10.5772/intechopen.95089*

**Material Temperature (°C)**

**3. Results and discussion**

*Experimental layout using an L9 orthogonal array.*

**Test Number**

**Table 3.**

**3.1 Mechanical test results**
