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<p>Deep-small holes (DSHs), with diameters ranging from 1 to 3 mm and depth-to-diameter ratios greater than 5, are widely used in applications such as aero-engines, molds, and medical devices. Electrochemical drilling (ECD) is an advanced technique for machining DSHs, offering advantages such as no tool wear, no cutting force, and high surface quality. However, electrolyte flow resistance increases as machining depth grows, reducing flow velocity and hindering the removal of electrolytic by-products. Additionally, electrolyte tends to accumulate near the DSH’s edges, diminishing machining accuracy and quality. To address these issues, this study proposes a vacuum-assisted electrochemical drilling (VA-ECD) method for DSH machining. In this approach, vacuum pressure is applied at the hole entrance to accelerate electrolyte flow, facilitating electrolytic by-products removal and improving machining quality. Titanium alloy TC4 was chosen as the workpiece material, and a stainless-steel sacrificial layer (SUS-SL) with a lower dissolution voltage than titanium was applied to the surface to mitigate stray corrosion at the hole edges. Simulation and experimental results show that compared to ECD, VA-ECD can increase flow velocity in the side inter-electrode gap (IEG) by 10.6%, reduce the width of the low-velocity zone by 33.87%, decrease hole diameter by 21.86%, and reduce sidewall roughness <i>Ra</i> by 54.96%. Additionally, the SUS-SL significantly improved the edge quality of the DSHs, with no noticeable stray corrosion. Further experimental findings indicate that hole diameter decreases with increasing outlet vacuum pressure and feed rate, while it increases with higher voltage. However, overall sidewall roughness <i>Ra</i> initially decreases and then rises. With optimized parameters of 25 V applied voltage, -0.03 MPa outlet vacuum pressure, and a feed rate of 0.84 mm/min, DSHs were successfully machined, achieving an average diameter of 1.262 mm, a standard deviation of 0.017 mm, a sidewall roughness <i>Ra</i> of 2.203 μm, and an aspect ratio of 7.9.</p>

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Investigation on vacuum-assisted electrochemical drilling of deep-small hole

  • 期刊论文

  • 发表日期：

    2025年6月17日

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  • Xuanning Wang,
  • Xiaolei Chen,
  • Zhisen Ye,
  • Yongjun Zhang

摘要

Deep-small holes (DSHs), with diameters ranging from 1 to 3 mm and depth-to-diameter ratios greater than 5, are widely used in applications such as aero-engines, molds, and medical devices. Electrochemical drilling (ECD) is an advanced technique for machining DSHs, offering advantages such as no tool wear, no cutting force, and high surface quality. However, electrolyte flow resistance increases as machining depth grows, reducing flow velocity and hindering the removal of electrolytic by-products. Additionally, electrolyte tends to accumulate near the DSH’s edges, diminishing machining accuracy and quality. To address these issues, this study proposes a vacuum-assisted electrochemical drilling (VA-ECD) method for DSH machining. In this approach, vacuum pressure is applied at the hole entrance to accelerate electrolyte flow, facilitating electrolytic by-products removal and improving machining quality. Titanium alloy TC4 was chosen as the workpiece material, and a stainless-steel sacrificial layer (SUS-SL) with a lower dissolution voltage than titanium was applied to the surface to mitigate stray corrosion at the hole edges. Simulation and experimental results show that compared to ECD, VA-ECD can increase flow velocity in the side inter-electrode gap (IEG) by 10.6%, reduce the width of the low-velocity zone by 33.87%, decrease hole diameter by 21.86%, and reduce sidewall roughness Ra by 54.96%. Additionally, the SUS-SL significantly improved the edge quality of the DSHs, with no noticeable stray corrosion. Further experimental findings indicate that hole diameter decreases with increasing outlet vacuum pressure and feed rate, while it increases with higher voltage. However, overall sidewall roughness Ra initially decreases and then rises. With optimized parameters of 25 V applied voltage, -0.03 MPa outlet vacuum pressure, and a feed rate of 0.84 mm/min, DSHs were successfully machined, achieving an average diameter of 1.262 mm, a standard deviation of 0.017 mm, a sidewall roughness Ra of 2.203 μm, and an aspect ratio of 7.9.