A method for processing deep long hole by combining hydrodynamic and electric processing

Abstract

The application relates to the technical field of special precision deep hole machining, and discloses a deep long hole machining method combining hydraulic and electric machining, which is realized based on a system comprising a hollow tubular electrode, a high-pressure water supply system, a pulse machining power supply and a feeding servo mechanism. The hollow tubular electrode with an outer wall insulation layer is connected with the high-pressure water supply system and the negative pole of the power supply, and a workpiece to be machined is connected with the positive pole; low-concentration neutral conductive water is introduced and sprayed out from the bottom end of the electrode, the servo mechanism drives the electrode to feed towards the workpiece and simultaneously performs high-frequency micro-distance tool lifting action. Under high current density between the poles, the front end of the electrode is electrically eroded to drill a through hole, and synchronously, the conductive water between the exposed area of the outer wall of the electrode and the hole wall is electrolyzed to expand the side wall; the low-pressure water flow continuously pumps and discharges the residues in the hole in cooperation with the fluid pumping effect generated by the tool lifting action until the set machining depth is reached. The application realizes synchronous composite machining of tip electric erosion and side wall electrolysis, improves the deep long hole machining efficiency, improves the residue discharge effect and reduces the comprehensive cost.

Description

Technical Field

[0001] This application relates to the field of special precision deep hole machining technology, specifically a method for machining deep and long holes using a combination of hydraulic and electrical machining. Background Technology

[0002] Currently, the mainstream processing method for micro-deep holes with diameters of 1 to 2 mm and depths of 260 to 420 mm is pure electrochemical machining. However, this process has many technical limitations in actual production.

[0003] First, traditional pure electrochemical machining relies solely on anodic dissolution to remove metal, resulting in a slow material removal rate and long single-hole machining cycles, leading to low overall processing efficiency and difficulty in meeting the capacity requirements of mass production. Second, when machining small holes with large depth-to-diameter ratios, it is difficult to remove electrolytic products from the bottom of the hole. Due to the limited internal space of deep holes, residue accumulation is prone to occur, which alters the local electric and flow field distribution, leading to dimensional defects such as out-of-tolerance hole wall taper, poor hole diameter consistency, and residual corrosion protrusions at the bottom of the hole, resulting in a low product yield.

[0004] Furthermore, traditional pure electrochemical processes rely on large amounts of highly corrosive acidic or high-salt electrolytes, resulting in wastewater containing heavy metal ions and corrosive substances. Wastewater treatment is costly and poses environmental pollution risks. Simultaneously, to maintain the processing, traditional equipment requires complex electrolyte circulation and temperature control systems that operate at continuous high power, leading to high overall energy consumption and difficulty in controlling comprehensive production costs.

[0005] There is a lack of a composite processing technology that can simultaneously solve the problems of low efficiency in deep hole processing, difficulty in removing slag from deep holes, and high pollution and high energy consumption. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides a deep hole machining method that combines hydraulic and electro-machining, aiming to solve the problems of low efficiency in pure electrochemical deep hole machining, difficulty in removing slag from deep holes leading to hole diameter quality defects, and high pollution and high energy consumption caused by the use of highly corrosive electrolytes in existing technologies.

[0007] To achieve the above objectives, this application provides the following technical solution: a deep and elongated hole machining method combining hydraulic and electrical machining, based on a hydraulic and electrical composite machining system. The system includes a hollow tubular electrode with an outer insulating layer, a high-pressure water supply system, a pulse machining power supply, a workpiece clamping table, a feed servo mechanism with high-frequency tool lifting function, and a conductive water circulation and filtration device. The deep and elongated hole machining method includes the following steps:

[0008] The upper end of the hollow tubular electrode is connected to the high-pressure water supply system and the negative terminal of the pulse processing power supply, respectively, and the workpiece to be processed is connected to the positive terminal of the pulse processing power supply. The high-pressure water supply system is activated to introduce low-concentration neutral conductive water into the hollow channel of the hollow tubular electrode. The low-concentration neutral conductive water is sprayed out at a constant speed from the bottom of the hollow tubular electrode, and the pulse processing power supply is turned on simultaneously. The feed servo mechanism drives the hollow tubular electrode to feed towards the workpiece at a constant speed, accompanied by a high-frequency micro-distance tool lifting action. Under the action of high current density between electrodes, a gas film is formed at the front end of the hollow tubular electrode and electrolytic breakdown occurs, quickly drilling out the initial through hole. Simultaneously, the low-concentration neutral conductive water between the exposed area of ​​the outer wall of the hollow tubular electrode and the hole wall undergoes electrolysis to expand the sidewall pores. The low-pressure water flow, combined with the fluid pumping effect generated by the lifting action, continuously draws out the electrolytic residue and erosion products in the initial through hole, and the hollow tubular electrode continues to feed until the set processing depth is reached.

[0009] The working principle of this application is as follows: using the aforementioned hollow tubular electrode as the processing cathode, a conductive path between the electrodes is established on the fluid medium ejected from the electrode tip, generating a combined effect of tip-hydraulic conductive pulse drilling and sidewall electrolytic hole enlargement. The pressure-conductive water column forms a concentrated conductive channel between the electrodes at the electrode tip, and the high current density between the electrodes vaporizes the water medium to form a gas film, which is then eroded through electrolytic penetration to drill the initial small hole; simultaneously, a tiny electrolytic gap is formed between the exposed area of ​​the electrode outer wall and the workpiece hole wall, where the conductive water medium simultaneously completes the sidewall electrolytic hole enlargement.

[0010] In addition, by using low-pressure water flow in conjunction with the high-frequency micro-distance tool lifting action of the feed servo mechanism, a fluid pumping effect is triggered in the confined space of deep and long holes, continuously sucking up and flushing the electrolytic residues and erosion products at the bottom of the hole, avoiding product accumulation during deep hole processing, and completing the one-time composite processing of deep and long holes.

[0011] Preferably, the low-concentration neutral conductive water is a sodium nitrate deionized water solution, with sodium citrate added as an anti-flocculation dispersant; wherein the mass fraction of sodium nitrate is 3%-5%, and the mass fraction of sodium citrate is 0.1%-0.3%. Using the above formula can avoid corrosion of equipment and workpieces by strong acids and alkalis, and sodium citrate keeps metal residues in a suspended and dispersed state, reducing the probability of residue adhesion to the pore wall.

[0012] In one specific embodiment, when the high-pressure water supply system is started, the water supply pressure of the high-pressure water supply system is adjusted to be stable at 2.0-3.0 kgf / cm². 2 .

[0013] In one specific embodiment, the voltage of the pulse processing power supply is set to 40-80V and the current to 15-35A.

[0014] In one specific embodiment, the frequency of the high-frequency micro-distance tool lifting action of the feed servo mechanism is set to 3-5Hz.

[0015] Preferably, the hollow tubular electrode with an outer insulating layer has only its front end and micro-segment sidewalls exposed, and the outer diameter of the hollow tubular electrode is 0.8-1.8 mm. This structure limits the effective range of sidewall electrolytic hole expansion to the exposed section at the front end of the electrode, maintaining the consistency of the axial dimensional distribution of the deep and long holes.

[0016] Preferably, the set processing depth is 260-420mm; the diameter of the hole formed by one-time composite processing is 1.0-2.0mm.

[0017] In one specific embodiment, the material of the workpiece to be processed is stainless steel, high-temperature alloy, or titanium alloy.

[0018] Preferably, after reaching the set processing depth, the medium is circulated, specifically including: the low-concentration neutral conductive water flows back to the conductive water circulation filter device, and is reused after the metal debris is removed by filtration.

[0019] Furthermore, before the upper end of the hollow tubular electrode is connected, the workpiece is pre-treated, specifically including: deburring and cleaning the workpiece to be processed, and clamping and fixing it on the workpiece clamping table of the feed servo mechanism; after reaching the set processing depth, post-processing is performed: the workpiece to be processed is taken out and the residual medium in the hole is rinsed with clean water.

[0020] This application provides a method for machining deep and long holes using a combination of hydraulic and electrical machining. It has the following advantages: 1. This application establishes an inter-electrode conductive path through a fluid medium ejected from the tip of a hollow tubular electrode. Under the action of a high current density between the electrodes, the water medium vaporizes to form a gas film, which is then electrolytically eroded, achieving stable initial through-hole drilling. Simultaneously, the conductive water between the exposed area of ​​the electrode outer wall and the hole wall is used for sidewall electrolytic hole enlargement. This composite processing mechanism, which involves simultaneous tip gas film electroerosion and sidewall electrolytic hole enlargement, overcomes the problem of slow anodic dissolution rate in traditional pure electrolytic processing, improves the material removal rate, and shortens the processing cycle of a single workpiece.

[0021] 2. This application utilizes a low-pressure water jet ejected from the bottom of a hollow tubular electrode, combined with the high-frequency micro-distance lifting action of the feed servo mechanism, to induce a fluid pumping effect within the confined space at the bottom of the hole. This method can continuously suck up and flush out electrolytic residues and etching products from the initial through-hole, avoiding residue accumulation inside deep holes, reducing hole wall taper and dimensional defects, and improving the consistency of hole diameter distribution and processing yield.

[0022] 3. This application uses low-concentration sodium nitrate neutral conductive water with added sodium citrate as the processing medium, replacing the traditional highly corrosive electrolyte. The neutral, low-salt formula, combined with the medium circulation filtration step, produces no strong acid waste liquid, reducing hazardous waste treatment costs. Simultaneously, the addition of sodium citrate as an anti-flocculation dispersant keeps the metal residue in a suspended and dispersed state, reducing the probability of residue adhesion to narrow pore walls. This facilitates direct recycling of metal debris after being trapped by the filtration device, thereby reducing the energy consumption and consumable costs of continuous system operation. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the composite deep hole drilling device of this application.

[0024] Figure 2 This is a flowchart of the processing method of this application.

[0025] The components include: 1. Hollow tubular electrode; 2. High-pressure water supply system; 3. Pulse machining power supply; 4. Workpiece clamping table; 5. Feed servo mechanism; and 6. Conductive water circulation filtration device. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0027] Reference Appendix Figure 1 This application provides a method for machining deep and long holes using a combination of hydraulic and electrical machining, which is based on a hydraulic and electrical composite machining system. The system includes: a hollow tubular electrode 1 with an outer insulating layer (only the front end and micro-segment sidewalls of the electrode are exposed), a high-pressure water supply system 2, a pulse machining power supply 3, a workpiece clamping table 4, a feed servo mechanism 5 with a high-frequency tool lifting function, and a conductive water circulation and filtration device 6.

[0028] The core working principle of this method is as follows: using the aforementioned hollow tubular electrode 1 as the processing cathode, 2-3 kgf / cm² is introduced into the hollow channel of the hollow tubular electrode 1 by the high-pressure water supply system 2. 2 The low-pressure conductive water medium, approximately 0.20-0.30 MPa, is neutral and low-pressure. A pulsed machining power supply 3 is applied between the hollow tubular electrode 1 and the workpiece. The conductive water medium is ejected from the electrode tip, forming a conductive path between the electrode tip and the workpiece. This achieves a combined effect of tip-mounted hydraulic conductive pulse drilling and sidewall electrolytic hole enlargement. The working principle is as follows: First, the pressure-conductive water column forms a relatively concentrated inter-electrode conductive channel at the front end of the electrode (its physical essence is that the high current density between the electrodes causes the water medium to vaporize and form a gas film, which is then broken down by electro-erosion). Relying on this electro-erosion effect, the workpiece is quickly broken down to create an initial small hole. Secondly, a tiny electrolytic gap is formed between the exposed area of ​​the electrode outer wall and the workpiece hole wall, where the conductive water medium simultaneously completes the electrolytic hole expansion of the sidewall. Finally, regarding the slag removal and molding mechanism, 2-3 kgf / cm³ is utilized. 2 The low-pressure water flow, approximately 0.20-0.30 MPa, combined with the fluid pumping effect generated by the high-frequency micro-distance lifting action of the feed servo mechanism 5, continuously sucks up and washes away the electrolytic residues and erosion products at the bottom of the hole; at the same time, the servo mechanism synchronously and continuously drives the electrode feed, continuously deepening the hole depth, and finally forming a precision deep hole with a diameter of 1-2 mm and a depth of 260-420 mm in one composite processing.

[0029] Examples 1-3: Example 1: This embodiment provides a method for machining deep, elongated holes using a combination of hydraulic and electrical machining, targeting a stainless steel workpiece with a hole diameter of 1.0 mm and a depth of 260 mm. Figure 2 As shown, it includes the following steps: S1. Workpiece pretreatment: Deburr and clean the stainless steel workpiece to be processed, clamp and fix it on the workpiece clamping table of the feed servo mechanism, and correct the processing datum. S2. Electrode assembly: Select a hollow tubular electrode with an outer insulating layer that is compatible with the target aperture of 1.0 mm (the outer diameter of the electrode is about 0.8 mm, with only the front end and the side wall of the micro segment exposed). The upper end of the hollow tubular electrode is connected to the high-pressure water supply system and the negative terminal of the pulse machining power supply respectively; the workpiece is connected to the positive terminal of the pulse machining power supply. S3. Medium Preparation: Prepare low-concentration neutral conductive water (specifically, a 3% (w / w) sodium nitrate deionized water solution with 0.1% (w / w) sodium citrate added as an anti-flocculation dispersant, free of strong acids and alkalis), introduce it into the high-pressure water supply system, and adjust the water supply pressure to stabilize at 2.0 kgf / cm³. 2 ; S4. Parameter settings: Set the voltage of the pulse machining power supply to 40V and the current to 15A. The upper limit of the transient peak current should not be less than 25A, and set the maximum machining depth to 260mm. S5. Pre-conduction debugging: Start the high-pressure water supply system. Low-concentration neutral conductive water is sprayed out from the bottom of the hollow tubular electrode at a uniform speed. Simultaneously connect the pulse processing power supply and check the circuit conduction status and fluid circulation status to ensure they are normal. S6. Composite Drilling Process: The feed servo mechanism drives the hollow tubular electrode to feed towards the workpiece at a uniform speed, accompanied by a 3Hz high-frequency micro-distance tool lifting action; under the action of high current density between the electrodes, a gas film is formed at the electrode tip and is eroded through by electrolysis, quickly drilling the initial through hole; simultaneously, the low-concentration neutral conductive water between the exposed area of ​​the electrode outer wall and the hole wall undergoes electrolysis to enlarge the sidewall; 2.0 kgf / cm 2 The low-pressure water flow, combined with the fluid pumping effect generated by the lifting action, continuously sucks out the electrolytic residue and erosion products from the initial through hole; the electrode continues to feed until the set machining depth of 260mm is reached. S7. Machining complete: Cut off the pulse machining power supply, shut off the high-pressure water supply system, and the feed servo mechanism retracts the hollow tubular electrode; S8. Post-processing: Remove the workpiece and rinse the residual medium in the hole with clean water. After inspection, the hole diameter is 1.0 mm, the depth is 260 mm, and the hole wall roughness meets the precision requirements. S9. Medium circulation: Low-concentration neutral conductive water flows back to the conductive water circulation filter device, where it is filtered to remove metal debris and then reused.

[0030] Example 2: This embodiment provides a method for machining deep and long holes using a combination of hydraulic and electrical machining, targeting a high-temperature alloy (gas turbine blade) workpiece with a hole diameter of 1.5 mm and a depth of 350 mm. Figure 2 As shown, it includes the following steps: S1. Workpiece pretreatment: Deburr and clean the high-temperature alloy workpiece to be processed, clamp and fix it on the workpiece clamping table of the feed servo mechanism, and correct the processing datum. S2. Electrode assembly: Select a hollow tubular electrode with an outer insulating layer that is compatible with the target aperture of 1.5mm (the outer diameter of the electrode is about 1.3mm, with only the front end and the side wall of the micro segment exposed). The upper end of the hollow tubular electrode is connected to the high-pressure water supply system and the negative terminal of the pulse machining power supply respectively; the workpiece is connected to the positive terminal of the pulse machining power supply. S3. Medium Preparation: Prepare low-concentration neutral conductive water (specifically, a 4% (w / w) sodium nitrate deionized water solution with 0.2% (w / w) sodium citrate added as an anti-flocculation dispersant, free of strong acids and alkalis), introduce it into the high-pressure water supply system, and adjust the water supply pressure to stabilize at 2.5 kgf / cm³. 2 Approximately 0.25 MPa; S4. Parameter settings: Set the voltage of the pulse machining power supply to 60V and the current to 25A, set the high-frequency micro-pitch lifting frequency of the feed servo mechanism to 4Hz, and set the maximum machining depth to 350mm. S5. Pre-conduction debugging: Start the high-pressure water supply system. Low-concentration neutral conductive water is sprayed out from the bottom of the hollow tubular electrode at a uniform speed. Simultaneously connect the pulse processing power supply and check the circuit conduction status and fluid circulation status to ensure they are normal. S6. Composite Drilling Process: The feed servo mechanism drives the hollow tubular electrode to feed towards the workpiece at a uniform speed, accompanied by a 4Hz high-frequency micro-distance tool lifting action; under the action of high current density between the electrodes, a gas film is formed at the electrode tip and is eroded through by electrolysis, quickly drilling the initial through hole; simultaneously, the low-concentration neutral conductive water between the exposed area of ​​the electrode outer wall and the hole wall undergoes electrolysis to enlarge the sidewall; 2.5kgf / cm 2 The low-pressure water flow, combined with the fluid pumping effect generated by the lifting action, continuously sucks out the electrolytic residue and erosion products from the initial through hole; the electrode continues to feed until the set machining depth of 350mm is reached. S7. Machining complete: Cut off the pulse machining power supply, shut off the high-pressure water supply system, and the feed servo mechanism retracts the hollow tubular electrode; S8. Post-processing: Remove the workpiece and rinse the residual medium in the hole with clean water. After inspection, the hole diameter is 1.5mm, the depth is 350mm, and the hole wall roughness meets the precision requirements. S9. Medium circulation: Low-concentration neutral conductive water flows back to the conductive water circulation filter device, where it is filtered to remove metal debris and then reused.

[0031] Example 3: This embodiment provides a method for machining deep and long holes using a combination of hydraulic and electrical machining, targeting a titanium alloy workpiece with a hole diameter of 2.0 mm and a depth of 420 mm. Figure 2 As shown, it includes the following steps: S1. Workpiece pretreatment: Deburr and clean the titanium alloy workpiece to be processed, clamp and fix it on the workpiece clamping table of the feed servo mechanism, and correct the processing datum. S2. Electrode assembly: Select a hollow tubular electrode with an outer insulating layer that is compatible with the target aperture of 2.0mm (the outer diameter of the electrode is about 1.8mm, with only the front end and the side wall of the micro segment exposed). The upper end of the hollow tubular electrode is connected to the high-pressure water supply system and the negative terminal of the pulse machining power supply respectively; the workpiece is connected to the positive terminal of the pulse machining power supply. S3. Medium Preparation: Prepare low-concentration neutral conductive water (specifically, a 5% (w / w) sodium nitrate deionized water solution with 0.3% (w / w) sodium citrate added as an anti-flocculation dispersant, free of strong acids and alkalis), introduce it into the high-pressure water supply system, and adjust the water supply pressure to stabilize at 3.0 kgf / cm³. 2 Approximately 0.30 MPa; S4. Parameter settings: Set the voltage of the pulse machining power supply to 80V and the current to 35A, set the high-frequency micro-pitch lifting frequency of the feed servo mechanism to 5Hz, and set the maximum machining depth to 420mm. S5. Pre-conduction debugging: Start the high-pressure water supply system. Low-concentration neutral conductive water is sprayed out from the bottom of the hollow tubular electrode at a uniform speed. Simultaneously connect the pulse processing power supply and check the circuit conduction status and fluid circulation status to ensure they are normal. S6. Composite Drilling Process: The feed servo mechanism drives the hollow tubular electrode to feed towards the workpiece at a uniform speed, accompanied by a 5Hz high-frequency micro-distance tool lifting action; under the action of high current density between the electrodes, a gas film is formed at the electrode tip and is eroded through by electrolysis, quickly drilling the initial through hole; simultaneously, the low-concentration neutral conductive water between the exposed area of ​​the electrode outer wall and the hole wall undergoes electrolysis to enlarge the sidewall; 3.0 kgf / cm 2 The low-pressure water flow, combined with the fluid pumping effect generated by the lifting action, continuously sucks out the electrolytic residue and erosion products in the initial through hole; the electrode continues to feed until the set machining depth of 420mm is reached. S7. Machining complete: Cut off the pulse machining power supply, shut off the high-pressure water supply system, and the feed servo mechanism retracts the hollow tubular electrode; S8. Post-processing: Remove the workpiece and rinse the residual medium in the hole with clean water. After inspection, the hole diameter is 2.0 mm, the depth is 420 mm, and the hole wall roughness meets the precision requirements. S9. Medium circulation: Low-concentration neutral conductive water flows back to the conductive water circulation filter device, where it is filtered to remove metal debris and then reused.

[0032] Comparative Examples 1-4: Comparative Example 1: Compared with Example 2, the difference is that the hollow tubular electrode used does not have an outer wall insulation layer (i.e., the entire outer wall of the electrode is completely exposed), but all other aspects are the same.

[0033] Comparative Example 2: Compared with Example 2, the difference is that the pulse processing power supply is replaced with a common constant voltage DC power supply, and the output voltage of the constant voltage DC power supply is kept at 60V and the stable operating current is controlled at about 25A. All other aspects are the same.

[0034] Comparative Example 3: Compared with Example 2, the difference is that the feed servo mechanism only performs uniform linear downward feed and the high-frequency micro-distance tool lifting action is turned off, while the rest are the same.

[0035] Comparative Example 4: Compared with Example 2, the difference is that no anti-flocculation dispersant was added to the conductive water (only pure sodium nitrate aqueous solution was used), and all other aspects are the same.

[0036] Test Examples 1-4: Test Example 1: Electrical Signal Test for Dual-Circuit Composite Machining Experimental steps: (1) Using a high-temperature alloy workpiece with a hole diameter of 1.5 mm and a depth of 350 mm as the test object, according to the parameter requirements of Example 2, Comparative Example 1 and Comparative Example 2, the workpiece is clamped on the feed servo mechanism and the corresponding hollow tubular electrode is assembled.

[0037] (2) Connect a current monitoring element to the positive and negative circuits of the processing power supply output terminal, the hollow tubular electrode, and the workpiece, and connect the signal output terminal to the data acquisition channel of the oscilloscope.

[0038] (3) Start the high-pressure water supply system, processing power supply and feed servo mechanism according to the preset processing parameters. After the electrode is fed to a depth of 50mm and maintains a stable feeding state, record the current signal between the two electrodes with an oscilloscope.

[0039] (4) Set the sampling time window of the oscilloscope to 20ms, obtain the current characteristics within this period, and extract the transient current discrete data between the two poles of each processing scheme at the corresponding time node. The transient current discrete data is the transient peak value or transient effective sampling value collected by the oscilloscope, which is not the same as the stable processing average current set by the pulse processing power supply.

[0040] Experimental data: Table 1. Sampling data of transient current between the two poles during a local time period in the composite drilling process.

[0041] Note: "-" indicates that due to factors such as the sampling triggering mechanism or signal noise, no exact discrete data points with analytical value were extracted at this sampling time point.

[0042] Conclusion section: According to the data in Table 1, the inter-electrode current under different processing conditions exhibits differentiated distribution characteristics. When processing using the scheme of Example 2, the inter-electrode current shows a high-low distribution: at time nodes such as 1.34ms and 5.12ms, it exhibits a basic current range of 14.8A to 15.5A, while at time nodes such as 2.87ms and 7.65ms, it exhibits a pulse current range of 27.8A to 29.1A. The basic current characterizes the continuous electrochemical reaction loop established between the exposed area of ​​the electrode outer wall and the pore wall by conductive water, representing a sidewall pore expansion state; the pulse current characterizes the discharge signal generated by the instantaneous breakdown of the gas film formed by the vaporization of the water medium at the electrode tip. This data characteristic of alternating overlap between the basic current and the pulse current reflects the combined process of front-end breakdown discharge and sidewall electrochemical dissolution.

[0043] When processed using the scheme of Comparative Example 1, the current distribution between the two electrodes ranged from 36.5A to 38.2A, and no instantaneous large current surge node similar to that in Example 2 was extracted. Because the hollow tubular electrode in Comparative Example 1 lacked an outer insulating layer, the current was laterally dispersed along the conductive water towards the hole wall over a large area. Although the total current between the two electrodes was high, the increased current distribution area resulted in insufficient local current density at the electrode tip. This shunting weakened the current concentration at the electrode tip, preventing the tip from meeting the triggering requirements for gas film formation and breakdown.

[0044] When processed using the scheme in Comparative Example 2, the current between the two electrodes fluctuated slightly within the range of 20.8A to 21.6A, which is consistent with the characteristics of anodic dissolution current under constant voltage DC power supply, and failed to induce discharge pulse phenomena of a specific frequency. Analysis of the comparative data shows that the combination of the electrode structure with the insulating layer and the pulse processing power supply provides the necessary conditions for realizing the composite processing of front-end discharge drilling and sidewall electrochemical hole enlargement.

[0045] Test Example 2: Fluid Pump Suction Transient Gauge Pressure Test Experimental steps: (1) A high-temperature alloy workpiece with a blind hole depth of 150 mm was used as the test object. According to the parameter requirements of Example 2 and Comparative Example 3, a hollow tubular electrode, a high-pressure water supply system and a feed servo mechanism were assembled.

[0046] (2) A miniature dynamic pressure sensor is arranged on the side wall of the fluid channel at the bottom of the blind hole of the workpiece, and the signal output terminal of the sensor is connected to the data acquisition and analysis instrument.

[0047] (3) Start the high-pressure water supply system, processing power supply, and feed servo mechanism according to the preset parameters, and introduce a set pressure of 2.5 kgf / cm into the hollow tubular electrode. 2 The conductive water drives the hollow tubular electrode to feed into the workpiece.

[0048] (4) After all the operating conditions are stable, set the data acquisition time to 1000ms, obtain the dynamic change data of the fluid dynamic pressure at the bottom of the hole, and extract the transient dynamic pressure discrete values ​​at specific sampling time nodes.

[0049] Experimental data: Table 2. Transient Gauge Pressure Sampling Data at the Bottom of Fluid Pump Suction and Discharge Holes

[0050] Note: "-" indicates that the sensor did not extract any exact discrete data points with analytical value due to transient disturbances in the fluid inside the orifice at that sampling time point. The data in the table are representative peak, valley and transition point data extracted from the continuous sampling curve.

[0051] Conclusion section: According to the data in Table 2, the transient gauge pressure of the fluid at the bottom of the hole under different feed modes exhibits differentiated distribution characteristics. When machining using the scheme of Example 2, the transient gauge pressure inside the hole shows alternating fluctuations between positive and negative pressure: at time nodes such as 125.4ms, 374.8ms, and 625.3ms, the transient gauge pressure of the fluid is in the negative pressure range of -12.6kPa to -18.4kPa; at time nodes such as 248.9ms, 501.2ms, and 748.5ms, the transient gauge pressure of the fluid is in the positive pressure range of 82.4kPa to 89.1kPa. Because the feed servo mechanism is set with a high-frequency micro-pitch lifting action of 4Hz, the hollow tubular electrode reciprocates inside the hole. When the electrode is lifted upwards, the local space at the bottom of the hole increases instantaneously, creating an outward fluid suction force that causes the transient gauge pressure at the bottom of the hole to enter the negative pressure range. When the electrode is fed downwards, the space at the bottom of the hole is compressed, creating an inward fluid pushing force that causes the transient gauge pressure at the bottom of the hole to enter the positive pressure range. This data characteristic of periodic switching between positive and negative pressure reflects the fluid pumping effect caused by intermittent lifting actions within a confined space.

[0052] When processing using the scheme in Comparative Example 3, the transient gauge pressure inside the hole was distributed within a positive pressure range of 37.8 kPa to 41.6 kPa. Because the high-frequency micro-prying action was disabled in Comparative Example 3, the feed servo mechanism only performed unidirectional uniform linear feed, and the fluid inside the hole was only driven unidirectionally by a water supply pressure of 2.5 kg. Due to the constraint of fluid resistance along the deep and long hole, it was difficult for the fluid at the bottom of the hole to flow back, and no negative pressure data points were extracted; the overall flow field exhibited a unidirectional positive compression state. Comparison with the transient gauge pressure test data shows that the prying action of the feed servo mechanism, combined with the low-pressure water supply, changed the unidirectional pressure state of the flow field at the bottom of the hole, providing dynamic suction conditions to overcome fluid resistance and extract the residue and erosion products from the bottom of the hole.

[0053] Test Example 3: Processing Parameters and Operating Status Test Experimental steps: (1) Based on the parameter settings of Examples 1 to 3, Comparative Examples 2 and 3, clamp the workpieces to be processed made of stainless steel, high temperature alloy and titanium alloy of corresponding materials, and assemble hollow tubular electrodes that are adapted to the target aperture.

[0054] (2) Connect an energy parameter measuring instrument to the total power input terminal of the whole machine to record the cumulative power consumption, and connect a displacement sensor to the side of the guide rail of the feed servo mechanism to obtain the feed position information of the electrode.

[0055] (3) Start the water circulation and processing control program to feed the hollow tubular electrode into the workpiece for drilling.

[0056] (4) Record the terminal status of each processing group when it reaches the preset target depth or when it stops due to a fault, and extract the processing time of a single hole, the actual depth reached, and the cumulative power consumption of a single hole. The processing time of a single hole is the effective processing time from the formation of stable discharge to the time when the set depth is reached or when the machine stops due to a fault, excluding the time for workpiece clamping, processing positioning, pre-conduction debugging and post-processing.

[0057] Experimental data: Table 3. Processing Parameters and Operating Status Test Data

[0058] Note: "-" indicates that the single-hole machining process was not completed due to an abnormal interruption during the machining process, and its power consumption data cannot be used as a reference benchmark for quantitative comparison at the same depth; the voltage and current parameters in Examples 1 to 3 are the set peak values ​​or stable machining average parameters of the pulse machining power supply, and the actual cumulative power consumption is affected by the pulse duty cycle, effective machining time and auxiliary system operating status.

[0059] Conclusion section: According to the data in Table 3, the equipment operating parameters at the same target depth show a certain variation pattern among different processing groups. Under the condition of completing a 350.0 mm deep hole, Example 2's single-hole processing time was 6.05 min, and the cumulative power consumption per hole was 0.258 kWh; Comparative Example 2's single-hole processing time was 12.42 min, and the cumulative power consumption per hole was 0.365 kWh. The comparison shows that Example 2's processing time is shorter than Comparative Example 2, and its overall energy consumption is lower. Example 2 adopts a combined working mode of front-end gas film discharge electro-erosion and sidewall electrochemical dissolution, while Comparative Example 2 adopts a single anodic dissolution working mode. The combined working mode increases the amount of metal material removed per unit time, reducing the single-hole processing time by approximately 50% compared to Comparative Example 2. Simultaneously, due to the shortened single-hole processing cycle, the total power consumption of the equipment during operation is reduced by approximately 29%.

[0060] In addition, in Comparative Example 3, the equipment experienced a short circuit and power failure after 1.76 minutes of processing time, and the actual depth reached was stuck at 47.6 mm, failing to reach the target depth of 350.0 mm. Because Comparative Example 3 did not activate the high-frequency micro-tool lifting action, the metal residue generated at the bottom of the hole was only discharged outwards by unidirectional low-pressure water flow. As the drilling depth increased, the residue locally accumulated within the narrow processing gap, causing a short circuit due to direct contact between the electrode and the workpiece. Comparing the operating states of each group, it can be seen that Examples 1 to 3 all achieved the set target depth. By introducing periodic tool lifting displacement at the mechanical level in conjunction with low-pressure water flow, fluid suction conditions can be created within the hole, which is beneficial for the discharge of metal residue and etching products, meeting the processing requirements of large depth-to-diameter holes and maintaining the continuity of the processing process.

[0061] Test Example 4: Dimensional Accuracy and Medium Indicators Test Experimental steps: (1) Collect the high-temperature alloy workpieces processed using the parameters of Example 2, Comparative Example 1 and Comparative Example 4, cut the workpieces along the axis, and clean the residual processing residue in the section area.

[0062] (2) Fix the cut workpiece on the platform of the coordinate measuring machine and control the probe to collect the boundary coordinate data of both ends of the hole wall along the hole depth direction.

[0063] (3) Use a surface roughness tester to scan a fixed area 150 mm away from the hole on the workpiece profile and extract the arithmetic mean deviation (Ra) value of the hole wall surface.

[0064] (4) Extract the system circulating filtrate after processing 100 wells in each test group, measure the pH value of the liquid medium using an acid-base tester, and collect the solid precipitate trapped in the filtration equipment. After drying and dehydration, weigh and record the dimensional yield rate. The yield rate is the average value of the test results of multiple batches of processing, with 100 wells processed in each batch.

[0065] Experimental data: Table 4. Test Data of Deep Hole Dimensional Accuracy and Media Indicators

[0066] Note: "-" indicates that in this test group, continuous burns and residue fusion occurred on the inner surface of the workpiece, which did not meet the initial test conditions for hole wall quality and is not included in the statistical scope of dimensional yield.

[0067] Conclusion section: According to the data in Table 4, the aperture size and surface quality parameters differ under different parameter configurations. Regarding the aperture wall profile, the workpiece processed using the parameters of Comparative Example 1 has an aperture of 3.41 mm at 10 mm from the aperture opening and 1.48 mm at 340 mm from the aperture opening, with a diameter difference of 1.93 mm between the two ends. The axial cross-section of the aperture exhibits an inward taper. The hollow tubular electrode used in Comparative Example 1 was not coated with an outer insulating layer, allowing conductive water to conduct through the sidewall region. The material at the shallow end of the aperture underwent a longer period of electrochemical dissolution, resulting in aperture expansion. The workpiece processed using the parameters of Example 2 had an aperture difference of less than 0.01 mm between the two ends, with a dimensional yield of 82.5%. The insulating layer covering the outer wall of the hollow tubular electrode confines the aperture expansion effect to the exposed section at the electrode tip, maintaining a consistent dimensional distribution along the axial direction of the deep aperture.

[0068] Regarding the surface roughness of the pore wall and the medium properties, the surface roughness Ra value measured in Comparative Example 4 was 3.72 μm, while the Ra value measured in Example 2 was 0.84 μm. Because sodium citrate dispersant was not added to the conductive medium in Comparative Example 4, the metal etched material agglomerated and adhered to the pore wall surface within the chip removal channel. Some etched products remained inside the pores or adhered to the pore walls, failing to fully enter the filtration device with the circulating liquid. Solid particles triggered localized secondary discharges during processing, increasing the surface roughness of the pore walls. The conductive medium prepared in Example 2 contained a dispersant, keeping the metal residue in a suspended and dispersed state, reducing the probability of particle adhesion and secondary discharge. After the continuous processing task was completed, Example 2 retained 45.3 g of solid waste in the filtration device, while Comparative Example 4 retained 14.6 g. The pH value of the circulating liquid in each test group was between 6.9 and 7.2, with no acid-base deviation. No acidic waste liquid was generated during the entire processing process, which met the processing requirements of a neutral and environmentally friendly medium environment.

Claims

1. A method for machining deep and long holes using a combination of hydraulic and electrical machining, characterized in that, Includes the following steps: The upper end of the hollow tubular electrode (1) is connected to the negative terminal of the high-pressure water supply system (2) and the pulse processing power supply (3), respectively, and the workpiece to be processed is connected to the positive terminal of the pulse processing power supply (3). Start the high-pressure water supply system (2) and introduce low-concentration neutral conductive water into the hollow channel of the hollow tubular electrode (1). The low-concentration neutral conductive water is sprayed out from the bottom end of the hollow tubular electrode (1) and the pulse processing power supply (3) is turned on simultaneously. The feed servo mechanism (5) drives the hollow tubular electrode (1) to feed towards the workpiece to be processed, accompanied by a high-frequency micro-distance tool lifting action; The hollow tubular electrode (1) forms a gas film at its front end and is punctured by electrical erosion, thus quickly drilling out the initial through hole; The low-concentration neutral conductive water between the exposed area of ​​the outer wall of the hollow tubular electrode (1) and the hole wall undergoes electrolysis to expand the sidewall pores. The low-pressure water flow, combined with the fluid pumping effect generated by the lifting action, continuously draws out the electrolytic residue and erosion products in the initial through hole, and the hollow tubular electrode (1) is continuously fed until the set processing depth is reached.

2. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, The low-concentration neutral conductive water is a sodium nitrate deionized water solution, with sodium citrate added as an anti-flocculation dispersant. The sodium nitrate has a mass fraction of 3%-5%, and the sodium citrate has a mass fraction of 0.1%-0.3%.

3. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, After starting the high-pressure water supply system (2), adjust the water supply pressure of the high-pressure water supply system (2) to stabilize at 2.0-3.0 kgf / cm². 2 .

4. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, The voltage of the pulse processing power supply (3) is set to 40-80V and the current to 15-35A.

5. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, The frequency of the high-frequency micro-distance tool lifting action of the feed servo mechanism (5) is set to 3-5Hz.

6. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, The hollow tubular electrode (1) has an outer wall insulation layer, with only the front end and micro-segment sidewalls exposed, and the outer diameter of the hollow tubular electrode (1) is 0.8-1.8 mm.

7. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, The set processing depth is 260-420mm; The aperture of the hole formed by one-time composite processing is 1.0-2.0mm.

8. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, The workpiece to be processed is made of stainless steel, high-temperature alloy or titanium alloy.

9. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, After reaching the set processing depth, media circulation is performed, and the process includes: The low-concentration neutral conductive water flows back to the conductive water circulation filter device (6), where it is filtered to remove metal debris and then reused.

10. The deep and long hole machining method combining hydraulic and electrical machining according to claim 1, characterized in that, Before connecting the upper end of the hollow tubular electrode (1) to the high-pressure water supply system (2) and the negative terminal of the pulse processing power supply (3), respectively, the workpiece is pre-treated, specifically including: The workpiece to be processed is deburred, degreased and cleaned, and then clamped and fixed on the workpiece clamping table (4) on the feed servo mechanism (5). After reaching the set processing depth, post-processing is performed: the workpiece to be processed is removed, and the residual medium in the hole is rinsed with clean water.

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