**2. Experimental details**

This study experimented on a MIKROTOOLS DT110 (hybrid micro-EDM), as shown in **Figure 1**, which includes micro-drilling, micro-milling, micro-grinding, micro-turning, and micro-EDM. The experiment used the Taguchi design, a robust design modeling method. Taguchi's philosophy of robust design focuses on making products and processes less sensitive to sources of variation, such as environmental conditions or manufacturing fluctuations. An L8 orthogonal array was constructed for this experiment. Orthogonal arrays are pre-arranged tables that allow researchers to explore multiple factors and their interactions with relatively few experimental runs, thereby saving time and resources. The equilateral triangle tool of tungsten carbide having a side of 400 μm and a corner radius of 8 μm, as shown in **Figure 2(a)**, is used. The designed experiment was further optimized using ANOVA, a statistical method used to analyze the variance in data by partitioning the total variability into

**Figure 1.** *Hybrid micromachining Centre-MIKROTOOLS DT110.*

#### **Figure 2.**

*(a) Tool of an equilateral triangle of side 400 μm, included angle 60°, and initial corner radius of 8 μm (b) triangular hole generated through micro-EDM.*

different sources, such as the variability between groups and within groups. In optimization, ANOVA helps identify significant factors and interactions that influence the response variable, enabling practitioners to make informed decisions to improve processes and achieve optimal outcomes [15, 16]. The corner radius and included side angle of the triangular hole are calculated using image analysis with the help of the Zeiss AXIO Scope A1 optical microscope equipped with the inbuilt AXIO Vision software (**Table 1**).

*Effect of Process Parameter Variations on Triangular Microcavity Fabrication Using Micro-EDM DOI: http://dx.doi.org/10.5772/intechopen.113233*


#### **Table 1.**

*L8 Taguchi design of experiment with responses corner radius and included angle.*


#### **Table 2.**

*Analysis of variance for corner radius of triangular microcavity.*

### **3. Results and discussions**

#### **3.1 Corner radius**

In the field of micro-EDM, the corner radius of a triangle microcavity is of utmost importance. For numerous reasons, it is crucial to precisely manage this dimension, defined as the curvature or rounding at the microcavity's corners. A lower radius produces sharper corners, which has an impact on the geometric correctness of the workpiece. It has an impact on machining accuracy, first and foremost. **Table 2** defines that in the case of corner radius, voltage contributed 4.9%, capacitance 94%, and feed 0.03%.

**Figure 3** presents a main effect plot that graphically illustrates the impact of varying key process parameters, namely input voltage (V), capacitance (μF), and feed rate (μm/sec), on the corner radius of triangular microcavities manufactured using Micro-EDM. The plot provides a clear depiction of how changes in these parameters influence the corner radius of the microcavities. The plot represents two different input voltage levels, specifically 90 and 120 V. Each voltage level is associated with a data point on the graph. It is evident that as the input voltage increases from 90 to 120 V, there is a noticeable upward trend in the corner radius of the microcavities. It suggests that higher input voltage settings result in larger corner radii. As capacitance increases from 10 to 100 μF, the corner radius of the microcavities also increases.

**Figure 3.** *Main effect plot for corner radius.*

**Figure 4.** *Residual plot for corner radius.*

An upward slope on the graph represents this relationship. It indicates that higher capacitance settings lead to larger corner radii.

The effect of feed rate on the corner radius appears to be relatively minimal compared to the other parameters. There is only a slight change in the corner radius as the feed rate varies between 5 and 15 μm/sec. It is represented by a nearly horizontal line on the graph, suggesting that changes in feed rate have less pronounced effects on the corner radius when compared to input voltage and capacitance variations. **Figure 4** provides a comprehensive view of the residuals from the model used to predict the corner radius of triangular microcavities. It includes visualizations and analyses to assess whether the residuals meet key assumptions, such as normality and independence, which are crucial for the reliability of the model's predictions.

*Effect of Process Parameter Variations on Triangular Microcavity Fabrication Using Micro-EDM DOI: http://dx.doi.org/10.5772/intechopen.113233*

These diagnostic tools are essential for validating the model and ensuring its suitability for practical applications in micro-EDM microcavity fabrication. **Figure 5** shows an interaction plot for corner radius, which clearly shows the interrelation of voltage, feed, and capacitance with the combination of one to another in a single figure.

#### **3.2 Included angle**

The included angle of a triangular microcavity is a critical parameter of interest. This angle, formed by the two sidewalls of the triangular cavity, holds immense importance in micro EDM for several reasons. Firstly, it directly affects the shape and dimensions of the machined feature, which is pivotal in achieving precise geometries in micro components. Secondly, the included angle impacts the EDM process stability and efficiency, influencing factors such as discharge energy distribution and material removal rates. Also, studying the included angle is essential for optimizing electrode design and machining parameters, ensuring that the microcavities meet various industries' specific requirements, including microelectronics, medical device manufacturing, and microfluidics. **Table 3** defines that in the case of the included angle of the triangular microcavity, voltage contributed 24.3%, capacitance 61%, and feed 0.5%.

#### **Figure 5.**

*Interaction plot for corner radius.*


#### **Table 3.**

*Analysis of variance for the included angle of triangular microcavity.*

**Figure 6** illustrates the impact of varying input voltage (V), capacitance (μF), and feed rate (μm/sec) on the included angle of triangular microcavities fabricated using micro-EDM. Higher input voltage and capacitance levels result in larger corner radii, as evidenced by the upward trends in the graph. In contrast, changes in feed rate between 5 and 20 μm/sec have a comparatively minimal effect on the included angle, as indicated by the nearly horizontal line on the plot. **Figure 7** describes the residual plot for the included angle of microcavity. **Figure 8** shows an interaction plot for the

**Figure 6.** *Main effect plot for included angle.*

**Figure 7.** *Residual plot for included angle.*

*Effect of Process Parameter Variations on Triangular Microcavity Fabrication Using Micro-EDM DOI: http://dx.doi.org/10.5772/intechopen.113233*

**Figure 8.** *Interaction plot for included angle.*

included angle of microcavity, which clearly shows the interrelation of voltage, feed, and capacitance with the combination of one to another in a single figure.

### **3.3 Optimization using ANOVA**

Optimization using Analysis of Variance (ANOVA) in Minitab involves using statistical techniques to determine the optimal settings or conditions for a process or system by analyzing different factors or variables that affect the response variable the model to perform optimization using ANOVA, as shown in **Figure 9**. The optimum solution for both corner radius and included angle of triangular microcavity achieved through ANOVA is 90 V, 10 nF, and 5 μm/sec, as in **Figure 10**.
