Electrochemical Drilling Research Articles

Enhancing the bottom surface flatness of blind holes in electrochemical drilling by optimizing the electric and flow field with discretized electrode

Enhancing the bottom surface flatness of blind holes in electrochemical drilling by optimizing the electric and flow field with discretized electrode

Ultrasonic assisted electrochemical drilling and grinding of small holes on SLMed Hastelloy X with rotating abrasive tube electrode

Ultrasonic assisted electrochemical drilling and grinding of small holes on SLMed Hastelloy X with rotating abrasive tube electrode

The entropy method integrated RSM model to evaluate hole geometries in electrochemical blind hole drilling

ABSTRACTThe electrochemical drilling (ECD) process enables the machining of conductive materials with a wide range of hardness, yield strength, and brittleness. In this study, the ECD experiments have been conducted on blind hole drilling in high-speed steel material using a tailor-made ECD machine. The hole geometries (cross-sectional profiles) at different machining parameters have been examined for the hole depth consistency (HDC), hole cross-sectional area (HCAC) and the hole profile length (HPLC) evaluation (response; output) metrics introduced. The relationships between the hole geometry evaluation metrics and machining parameters are obtained using the response surface method (RSM). Using the Entropy method, an optimisation model is also proposed to combine multiple responses into a single objective function. The effectiveness of the Entropy method is compared with the Analytical Hierarchical Process (AHP). The comparison showed that the Entropy model provides more robust and convenient results than the AHP approach.

A sustainable, high-quality method for machining film cooling holes: Cryogenic airflow-assisted electrochemical discharge drilling

Film cooling hole is an essential part of aero-engines, necessitating without recast layer, no stray corrosion, and high machining efficiency. Its sustainable manufacturing has been at the forefront of industrial focus. Existing machining methods have problems such as low efficiency and environmental hazards. In order to achieve the production requirements of precision, quality, and green simultaneously, an external cryogenic airflow-assisted electrochemical discharge drilling (ECDD) is proposed. Compared with the current electrochemical drilling (ECD) or electrical discharge drilling (EDD), a glycol working fluid with ultra-low conductivity neutralizing salt replaces the high conductivity of acidic solution or spark oil to realize green machining without a recast layer. Compared to existing ECDD, the introduction of cryogenic gas with glycol can significantly reduce stray corrosion and achieve exceptionally high surface quality. In the theoretical part, the influence mechanism of a low-temperature environment on the electrochemical interface was analyzed by using the electrochemical analysis technique. In addition, a multi-physical field simulation model was established, which was finally verified by experiments. Finally, the surface characteristics were analyzed by using TEM. The results demonstrate that the cryogenic environment enhances the passivation effect, as evidenced by a 35% reduction in taper at 258 K and a 28.2% decrease in stray corrosion. The hole side has nano-roughness (Ra 0.512 μm). Notably, the material removal rate does not significantly diminish at low temperatures and achieves 0.1 mm/s, superior to EDD. As there is no need for an additional machining step after drilling, this method proves its characteristic to attain sustainability, efficiency, and high quality, indicating promising application prospects.

Advancing electrochemical drilling process via coupling of flow field and electric field in pulsating state generated by a novel tube tool

This paper introduces an improvement to electrochemical drilling process by coupling flow field and electric field in pulsating state. A novel tube with half-wedged shape at the end (HW-tube) is prepared, with both sidewall and wedged part of the HW-tube insulated. Only the flat part is utilized to provide electric field for electrochemical drilling. By rotating the HW-tube, both flow field and electric field in pulsating state are generated, alternating in different positions within the inter-electrode gap (IEG). The pulsating flow field enhances the mass transfer process, while pulsating electric field disperses material dissolution process and distribution of electrolytic by-products. Both pulsating fields are coupled at the same frequency, further enhancing the electrochemical drilling process. Simulation results indicate that both flow field and electric field in pulsating state are generated. Compared to the traditional tube, the HW-tube significantly reduces the number of residual particles in IEG, and this number is further reduced by increasing the rotation speed. Experimental results reveal that the surface quality and dimensional uniformity of small hole are improved with HW-tube. With feed rate of 2.22 mm/min, a small hole with diameter of 1.52 ± 0.017 mm is drilled, resulting in a surface roughness of 0.331 μm.

Investigation of external capacitance effects on electrochemical discharge drilling

ABSTRACT Electrochemical discharge drilling (ECDD) involves a combination of electrical discharge drilling (EDD) and electrochemical drilling (ECD) to remove the recast layer while drilling at high speed. Here, a T-RC power supply similar to the EDD method is adopted. However, the solution resistance characteristics change as a result of utilizing a weak conductivity solution instead of deionized water with insulating properties. Different external capacitances will impact ECDD. In this study, through experiment and simulation, the influence of capacitance on the ECDD performance of Ni-based single-crystal alloy is investigated compared to EDD. In the open-circuit stage, the ECDD current shows an exponential relationship, and the voltage drops slightly. The highest line material removal rate reaches 326 μm/s, which is higher than EDD, and the tool wear ratio drops by 40%. The aperture and taper continue to ascend. Finally, no recast layer can be realized over 680 nF.

An empirical study of the impacts of parameters in micro electrochemical drilling of Al 7075 alloy composites with SiC and fly-ash

The Electrochemical Drilling Technique (EDT) is utilized to bore metal alloys into the desired geometric forms. The present study investigates that various typical electrochemical drilling process variables, line supply-voltage (VT), electrolytic solution (ES), and pulse-on time (PT), impact the output responses namely material extraction rate as well as surface-roughness of stir cast Al7075 alloy, SiC, and fly-ash powder mixtures. These aluminum-matrix composites could be used to construct bridges, frames, and containers that will store pollutants, dairy, as well as other corrosive compounds; they can also be used to replace stainless steel, which is used in salty areas to avoid corrosion. Taguchi's experimental design is utilized in this study to investigate the effects of every input parameter on the Material-Extraction Rate (MER) and surface-roughness. Also, the significance of each parameter has been identified using an analysis of variance.

Breakthrough detection in electrochemical discharge drilling to enhance machining stability

Film cooling holes are widely used in aero-engine turbine blades. These blades feature large numbers of holes with complex angles and require a high level of surface integrity. Electrochemical discharge drilling (ECDD) combines the high efficiency of electrical discharge drilling (EDD) with high quality of electrochemical drilling (ECD). However, due to the existence of a variety of energy for material removal, accurate and timely detection of breakthroughs is fraught with difficulties. An insufficient preset setting distance results in a tiny exit aperture, influencing the structure’s shape. In addition, the electrode is prone to bending at a large overfeeding distance, causing secondary discharge damaging sidewall surface integrity. This paper compares and analyzes the characteristics of processing waveforms using EDD and ECDD. A novel breakthrough detection method is proposed based on the variance signal of average voltage (VSAV) to increase machining stability and achieve fabrication without a recast layer. This method extracts the fluctuation transformation by calculating the variance of the average. Following signal detection, the overfeeding distance is quantified. An experiment is used to validate the breakthrough detection with 100% accuracy in all tests. The optimum overfeeding distances for hole angles of 0 °, 30 °, and 60 ° are obtained, and the stable removal of the recast layer is realized. Finally, the effectiveness of the method is verified on a typical workpiece with a double-wall structure and a nickel-based single crystal blade.

Design and implementation of an electrode feed rate control system in the electrochemical drilling process

Design and implementation of an electrode feed rate control system in the electrochemical drilling process

Theoretical and experimental study on localization improvement in ultrasonic vibration–assisted spark-assisted electrochemical drilling process

Theoretical and experimental study on localization improvement in ultrasonic vibration–assisted spark-assisted electrochemical drilling process

Experimental investigations of magnetic field-assisted high-speed electrochemical discharge drilling

ABSTRACT Owing to its promising physical, chemical, and optical properties, glass is the most widely used material in sophisticated micro-electro-mechanical systems (MEMS) devices. These devices are finding large number of applications in the fields of medical electronics, biotechnology, energy, automobiles, aerospace, etc. While manufacturing MEMS devices, micro-holes are needed to be produced in glass with high levels of accuracy. Micro-drilling in glass using the electrochemical discharge drilling (ECDD) method is an emerging technique. Enhancing the material removal rate (MRR) and lowering the entrance hole overcut in ECDD are the major challenges during this process. To address this problem, significant attention is focused on blending two or more techniques known as hybridized methods to improve the quality of the ECDD process. In the present study, a combination of magnetic flux density (MFD) and high-speed tool rotation was employed during the ECDD process for the glass. Additionally, the effect of the process variable viz. the voltage, tool rotation speed, and feed rate of the MFD around the workpiece was analyzed. Finite element analysis was employed to obtain the optimal MFD over the workpiece. For different voltages, tool rotation speeds, and feed rates; the performance analysis of MRR and entrance hole overcut were compared in the absence and presence of magnetic field-assisted high-speed ECDD.

Electrochemical drilling and multi response optimization using different methods of assigning weights to the responses for sustainable machining of AA6061-TiB2 in-situ composites

Electrochemical drilling and multi response optimization using different methods of assigning weights to the responses for sustainable machining of AA6061-TiB2 in-situ composites

Electrochemical drilling of small holes by regulating in real-time the electrolyte flowrate in multiple channels

Electrochemical drilling (ECD) provides an alternative technique for drilling multiple small holes in difficult-to-machine materials in numerous industrial applications such as for aeroengines. The value and fluctuation of electrolyte flowrate can seriously affect the machining stability and hole quality in ECD. In particular, when drilling multiple holes, the distribution and fluctuations of the electrolyte flowrate in each channel could influence the uniformity of the electrolyte flowrate among multiple tube electrodes, thereby affecting the machining stability and the maximum feed rate. Thus, an eight-channel flow control system was developed to measure and regulate in real time the electrolyte flowrate supplied into each individual tube electrode. This paper proposes ECD of small holes with real-time flowrate control to improve the uniformity of electrolyte flowrate in each tube electrode and reduce the fluctuations in the electrolyte flowrate. In single-hole drilling, when the electrolyte flowrate was regulated in real time, the hole quality and machining stability were considerably better than without regulation. This is because the electrolyte flowrate remains basically constant, which stabilizes the flow field. Moreover, by considering the hole profile, it was found that an electrolyte flowrate of 200.0 mL/min can be acceptable for ECD of small holes. When the eight-channel flow control system was used in multiple-hole drilling, the uniformity of the electrolyte flowrate in each tube electrode was obviously improved, which led to a more stable process. Additionally, the maximum feed rate can attain 2.40 mm/min in multiple-hole drilling. Based on these findings, a matrix (5 × 32) of multiple small holes was successfully fabricated with a satisfactory diameter consistency, as the machining stability and machining efficiency had been enhanced.

Study on Ultrasonic Assisted Electrochemical Drill-Grinding of Superalloy

Electrochemical grinding (ECG) technique composed of electrochemical machining (ECM) and mechanical grinding is a proper method for machining of difficult-to-cut alloys. This paper presents a new ultrasonic assisted electrochemical drill-grinding (UAECDG) technique which combines electrochemical drilling, mechanical grinding, and ultrasonic vibration to fabricating high-quality small holes on superalloy. By applying ultrasonic vibration to high-speed rotating electrode in ECG, machining stability, efficiency, and surface quality can be obviously improved. Firstly, the electrochemical passive behavior of superalloy is studied, the mathematical model and simulation of gap electric field are established. Then, several experiments are conducted to investigate the influence of applied voltage, feed rate and ultrasonic amplitude on the machining quality. The balance of material removal between electrochemical reaction and mechanical grinding is achieved by optimizing the machining parameters. It reveals that the surface quality as well as machining stability and efficiency can be significantly improved by applying rotating ultrasonic vibration to the ECG process. Finally, several small holes of high quality have been machined successfully along with surface roughness of hole sidewall decreases from Ra 0.99 μm to Ra 0.14 μm by UAECDG.

Research on Improving the Taper of Hole Processing by Insulation Coating of ECM Cathode

Electrochemical machining (ECM) is widely used in metal parts processing because of its high processing speed, good surface quality, no stress and deformation of the workpiece after processing, and no tool loss. However, when using electrochemical drilling, the taper of the hole is large due to the secondary electrolysis phenomenon. Therefore, this paper aims to reduce the taper of the anode workpiece hole by studying the degree of insulation of the cathode sidewall. The processing of the holes is performed by insulating coating the cathode structures to form different conductive radial heights h0. A multiphysics (electric field, flow field, temperature field and mathematical field) model for simulating ECM machining process using a moving cathode tool is proposed in different modes of conductive radial height h0. The mathematical relationship between the height h0 and the taper of the machined hole is established to obtain the optimum machining method.

Theoretical and experimental study on micro ultrasonic-assisted electrochemical drilling with high speed electrode

Metal micro-holes structures have been widely used in aerospace and biomedical fields, such as aero engine, medical vaporizer, and so on. In this paper, a micro rotating ultrasonic-assisted electrochemical drilling (UA-ECD) method was proposed to improve the machining localization, efficiency, and stability. Firstly, a numerical simulation of the flow field in the machining gap is carried out, the simulation results show that the rotating electrode with ultrasonic vibration can renew the electrolyte in the machining gap and homogenize the flow field. Secondly, a mathematical model is established to study the effect of ultrasonic vibration and key machining parameters on machining results, which illustrate that the rotating ultrasonic-assisted electrochemical drilling method can improve the machining quality, machining efficiency, and stability sufficiently. Finally, after optimization of several groups of contrast experiments, a micro holes array with good quality is fabricated successfully on a 510-μm-thick 304 stainless steel workpiece. It is proved that the proposed rotating ultrasonic-assisted micro electrochemical drilling method has considerable potential and broad application prospects.

Effects of a Magnetic Field on the Machining Accuracy for the Electrochemical Drilling of Micro Holes

Effects of a Magnetic Field on the Machining Accuracy for the Electrochemical Drilling of Micro Holes

Electrode insulation layer for electrochemical machining fabricated through hot-dip aluminizing and microarc oxidation on a stainless-steel substrate

Insulation of an electrode for use with an electrochemical machining (ECM) was achieved through hot-dip aluminizing and microarc oxidation techniques. To form an effective insulation layer on a stainless-steel substrate and achieve high precision in ECM, an electrode was processed through microarc oxidation, and the aluminum-rich layer was converted into an aluminum oxide insulating layer. The withstand voltage of the tool was evaluated through sodium chloride electrolysis, and the surface and cross-section were observed. The ECM performance of various tools with and without aluminum oxide insulating layer was examined by drilling on a stainless-steel workpiece. A precise and robust insulation layer must be produced. Precision can be achieved by reducing the stray effects of ECM.Experimental results indicated that the optimal parameters were aluminum dipping were 4 min, microarc voltage of 475 V for 10 min with a withstand voltage of 9.3 V. Electrochemical drilling was used to examine electrodes with and without an insulation layer. Improvement of variation between entrance and exit could be 64.58 %. The differences between the entrance and exit values indicated that the electrochemical insulating layer considerably reduces stray current and improves drilling accuracy.

Electrochemical corrosion assisted laser drilling of micro-hole without recast layer

High-power pulsed laser is an efficient tool for drilling micro-holes on metal, but due to the melt ejection dominated material removal mechanism, recast layer can hardly be avoided. This paper proposes to use electrochemical corrosion as a kind of postprocessing technique to remove the laser induced recast layer. A tungsten steel wire-electrode based electrochemical machining head was designed. During the research, it was discovered that the laser and electrochemical corrosion (ECC) processes may interact due to the assist gas used in the laser drilling process. Although ECC can theoretically dissolve all kinds of metal as ions, the laser induced recast layer showed special characteristics. By comparative study, it was found that oxidative assist gas would lead to oxidizing thermal reaction on the surface of the molten metal during laser drilling, resulting in an insulating layer of oxide, which disabled the ECC to fulfil its validity on recast layer dissolving. When non-oxidative assist gas was used, the recast layer on the hole wall could easily be removed, and ideal micro hole can be produced, with smooth side wall, rounded entrance and decreased taper. After optimization of the overall drilling efficiency, the efficiency of the presented method is over 4 times higher in contrast to the conventional electrochemical drilling.

Experimental Parametric Investigation of Electrochemical Drilling of AA6061-TiB2 In Situ Composites

The composite material manufacturing via in situ route is a popular method for developing the greater mechanical properties by reinforcing smaller volume of the ceramic phases. Electrochemical machining is widely employed for drilling smaller hole, machining the micro-slots and intricate shape on any material without considering its hardness. The present paper describes the electrochemical drilling of the composites reinforced with TiB2 ceramics under various reinforcement and volume contents of TiB2. Analysis of the experimental results indicates that the electrical parameters and electrolyte concentration offer significant effect on rate of material removal, delamination and radial overcut of drilled hole. The composite has minimum rate of material removal and maximum delamination and radial overcut than unreinforced alloy under ideal machining condition. Further, the effect of electrical parameters, electrolyte concentration and volume content of TiB2 on hole qualities are investigated via scanning electron microscopy and reported.