Numerical and experimental investigations to analyze the micro-hole drilling process in spark-assisted chemical engraving (SACE)

Abstract

With the increased utilization of glass in micro-electromechanical systems (MEMS) applications, need is generated to produce micro-features on glass with excellent surface quality, i.e., better hole circularity and less thermal cracks. Sparkassisted chemical engraving (SACE) has proven to be an emerging and reliable technology for micro-machining of glass that includes local joule heating of the work material for its removal. However, some problems need to be covered in the micro-hole drilling process such as low machining depth, low aspect ratio, high thermal cracks, and an increase in machining time with the increase in depth. Moreover, few finite element modeling (FEM) studies have been reported to analyze the material removal aspects in SACE. This present study developed the FEM-based thermal model to analyze the material removal rate (MRR) and investigated the different machining conditions to improve the micro-hole drilling process in SACE. Improvement in depth and aspect ratio can be achieved by using a different tool's shape which variably enhances the flow of electrolytes and thereby increases the formation rate of gas film. Pointed and cylindrical tools were used for micro-drilling operations. MRR, hole entrance diameter, machining depth, aspect ratio, thermal cracks, and machining time were observed under different machining conditions. FEM study revealed that MRR improves with the increase in both the applied voltage and electrolyte concentration. The MRR was predicted by utilizing the plots of temperature distributions and was found in accordance with the experimental results of MRR. The experimental study concluded that the pointed tool produced micro-holes with a higher machining depth and aspect ratio at an improved machining rate, while the cylindrical tool produced micro-holes with a smaller number of thermal cracks and better circularity.

Prediction of crater shape with different heat flux and parametric simulation in electro-chemical discharge machining

“…17 In the case of parabolic heat flux, the shape of the crater is shown in Figure 5(b), which has an approximate similar nature to the crater formed that of Gaussian heat flux. Similar nature of the crater is also obtained by considering cylindrical tools for the creation of the micro-holes at 25 wt% and 45 V. 28 As discussed, the nature of the crater depends on the temperature distribution within the substrate for various applied heat fluxes and types of tool electrodes used for sparking in the ECDM process.…”

Review on Recent Advances, Research Trends, and Gas Film in Electrochemical Discharge-Based Micromachining

“…The optimum control of the voltage is very crucial since very high voltage values lead to thermal cracks while a minimum value is required to initiate the sparks [59,60]. Higher voltage values result in more thermal cracks at the microhole edge as reported by Rajput et al [54] in Fig. 8.…”

“…The HAZ produced is equivalent to the diameter of the discharge spot. Several authors have demonstrated the applications of the finite element modeling (FEM) for analyzing the ECDM process using single spark phenomena [52][53][54][55]. A summarized report on the development of the FEM-based thermal model in ECDM is shown in Fig.…”

3D finite element modeling and multi-objective optimization for controlling the electrochemical discharge drilling parameters using the tool feed monitoring system

“…Many studies reported that thermal heating is solely responsible for material while many suggested that chemical etching action also plays a crucial role in the removal of material. 12 Wuthrich et al 13 systematically characterized the gravity tool feed control for drilling micro-holes on glass materials. Maillard et al 14 successfully produced holes on glasswork materials and concluded that micro-holes geometrical features depend upon input variables.…”