Low conductivity ethylene glycol solution cut-in EDM electrolysis synchronous composite milling method

Abstract

This invention relates to a low-conductivity ethylene glycol solution-based plunge milling method for simultaneous electro-discharge and electrolytic milling. The low-conductivity ethylene glycol solution, as an amphoteric electrolyte, serves as both the dielectric fluid for EDM and the electrolyte for electrolytic machining. During the machining process, a rod-shaped tool cathode initially feeds vertically towards the workpiece. Once the gap between the cathode and the workpiece reaches the discharge gap, discharge occurs. When the downward feed distance reaches the preset depth of cut, the rod-shaped tool cathode transitions from vertical to horizontal feed, initiating the milling of the preset microstructure shape. During milling, EDM discharges on the side and front bottom of the rod-shaped tool cathode efficiently remove workpiece material, while electrolysis occurs in the rear bottom area to remove the recast layer and heat-affected zone generated by the EDM discharge. The plunge milling mode improves machining efficiency, and the polishing effect of the low-conductivity ethylene glycol solution enhances the surface quality, thereby achieving efficient and high-quality machining.

Description

Technical Field

[0001] This invention relates to a low-conductivity ethylene glycol solution-based simultaneous composite milling method using electrical discharge machining (EDM) and electrolytic cutting, belonging to the field of electrical discharge machining technology. Background Technology

[0002] Metal microstructures, such as microchannels, have been widely used in lab-on-a-chip applications, microanalytical systems, bipolar plates for fuel cells, and heat exchangers for solar cells. Microchannels, with dimensions ranging from 10 to 200 μm, require stringent fabrication techniques, demanding high surface quality and the absence of recast layers. Traditional mechanical milling typically produces burrs and residual stress on the machined surface. Electrical discharge milling (EDM) and laser milling remove material through melting and vaporization, but generate recast layers and heat-affected zones on the machined surface. Electrolytic milling avoids recast layers but is limited by low processing efficiency and precision. Similarly, ultrasonic milling and abrasive waterjet milling also have drawbacks, such as unsatisfactory dimensional accuracy and surface quality. Currently, high-quality and efficient fabrication of metal microchannels remains a significant challenge in the field of microfluidics.

[0003] Electrical discharge machining (EDM) is a composite machining technology that combines EDM micro-milling and electrolytic micro-milling. Its advantage lies in its ability to machine both metallic and non-metallic materials without considering their mechanical properties. Currently, a large body of literature focuses on EDM micro-milling of non-metallic materials, investigating aspects such as dielectric concentration and type, machining voltage waveform and amplitude, and tool electrode material and motion. Some researchers have also conducted studies on EDM micro-milling of metallic materials, elucidating the machining mechanism and material removal methods, and achieving composite EDM-electrolytic machining through small feed rates and low feed speeds. However, current EDM micro-milling primarily employs a fly-through machining mode, which results in a low material removal rate and makes it difficult to achieve an ideal balance between machining quality and efficiency; therefore, further research is needed.

[0004] Working fluid is a crucial component of electrical discharge machining (EDM) technology. Currently, almost all research utilizes water-based working fluids, including alkaline, neutral, and acidic solutions. However, when using water-based solutions, a large amount of oxygen is generated on the machined surface, which combines with metal elements to form oxides. This further hinders the electrochemical reaction and causes severe stray corrosion, ultimately leading to low machining efficiency and poor surface quality and integrity. Therefore, research into novel working fluids and machining methods is urgently needed to achieve more efficient and higher-quality machining. Summary of the Invention

[0005] To address the problem that existing technologies cannot simultaneously achieve both processing efficiency and surface quality, this invention proposes a low-conductivity ethylene glycol solution-based simultaneous composite milling method using electrical discharge electrolysis, aiming to achieve efficient and high-quality machining of metal microstructures.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method includes:

[0008] Step 1: Immerse the workpiece in an amphoteric electrolyte, which serves as both the dielectric for electrical discharge and the electrolyte for electrolytic machining. The amphoteric electrolyte is a salt solution composed of ethylene glycol solvent and solid salt, wherein the salt is one or any combination of NaCl, NaNO3, and NaClO3, and the amount added is determined by the conductivity of the amphoteric electrolyte, which ranges from 10 to 200 μS / cm. The workpiece and the rod-shaped tool cathode are connected to the positive and negative terminals of the machining power supply, respectively, with the rod-shaped tool cathode rotating around its own axis. Before machining, the rod-shaped tool determines the zero point of the machining coordinate system using a short-circuit tool setting method. After tool setting, the rod-shaped tool cathode retracts 8-20 μm as the initial machining gap.

[0009] Step 2: Adjust the machining parameters and turn on the machining power. The rod-shaped tool cathode is fed vertically towards the workpiece. When the gap between the rod-shaped tool cathode and the workpiece reaches the discharge gap, spark discharge occurs to remove the material. The bottom of the rod-shaped tool cathode generates an electric spark discharge to efficiently remove the workpiece material. Electrolysis occurs on the side wall of the rod-shaped tool cathode to remove the recast layer and heat-affected zone generated by the spark discharge. As the rod-shaped tool cathode feeds, the workpiece material is continuously eroded away.

[0010] When the bar-shaped tool cathode feeds downward a distance D, it switches from vertical to horizontal feed and begins synchronous composite electrical discharge machining (EDM). During machining, EDM discharge occurs on the side and front bottom of the bar-shaped tool cathode to efficiently remove workpiece material, while electrolysis occurs in the rear bottom of the bar-shaped tool cathode to remove the recast layer and heat-affected zone generated by the spark discharge. D is the depth of cut in the EDM milling. Machining stops when the bar-shaped tool cathode completes the preset milling trajectory.

[0011] The workpiece is immersed in a low-conductivity ethylene glycol solution to a depth of 2-8 mm.

[0012] The rod-shaped tool cathode is made of a metal material resistant to electrolytic corrosion.

[0013] The rotational speed range of the rod-shaped tool cathode is 500-50000 r / min.

[0014] The processing power supply is an RC power supply or a transistor pulse power supply.

[0015] The cutting depth D is in the range of 5-60 μm.

[0016] The downward feed speed range of the rod-shaped tool cathode is 1-5 μm / s, and the horizontal feed speed range is 5-20 μm / s.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. This invention overcomes the limitations of previous electrical discharge machining (EDM) processes that could not balance machining efficiency and quality. It proposes a low-conductivity ethylene glycol solution-based simultaneous composite EDM milling method. This method improves machining efficiency through the entry-milling machining mode and enhances the surface quality of the machined surface by utilizing the polishing effect of the low-conductivity ethylene glycol solution, thereby achieving efficient and high-quality machining.

[0019] 2. This invention achieves the simultaneous combined effect of electrical discharge machining (EDM) and electrolysis. In previous EDM-electrolysis composite machining processes, only one of the discharge waveform and electrolysis waveform could be displayed under a single pulse waveform. However, in this invention, both EDM and electrolysis waveforms are displayed under the same pulse waveform. This results in higher removal efficiency of the recast layer generated during the machining process, higher surface quality, and further improves the process capability and applicability of EDM-electrolysis composite machining technology.

[0020] 3. This invention eliminates the need to change the working fluid, tool cathode, and processing power supply during the processing. Electric spark discharge and electrolytic etching occur simultaneously under the same solution and electrode, resulting in low process cost, simple procedures, and convenient operation. Furthermore, the intensity of electric spark discharge and electrolytic etching can be controlled and adjusted by preparing ethylene glycol solutions with different conductivity. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the processing principle of the present invention;

[0022] Figure 2 This is a partial enlarged view of the processing area in this invention;

[0023] Figure 3 This is a microscopic morphology diagram of the rod-shaped tool cathode used in this invention;

[0024] Figure 4 These are voltage and current waveforms during the processing of this invention.

[0025] Figure 5 This is a microscopic morphology diagram of the microchannel structure processed according to the present invention;

[0026] Figure 6 Metallographic micrograph of the cross-section of the microchannel processed according to the present invention;

[0027] Figure 7 This is a microscopic morphology diagram of the microgroove structure processed according to the present invention when the solution conductivity is 9 μs / cm;

[0028] Figure 8 This is a microscopic morphology diagram of the microgroove structure processed according to the present invention when the solution conductivity is 10 μs / cm;

[0029] Figure 9 This is a microscopic morphology diagram of the microgroove structure processed according to the present invention when the solution conductivity is 200 μs / cm;

[0030] Figure 10 This is a microscopic morphology diagram of the microgroove structure processed according to the present invention when the solution conductivity is 205 μs / cm;

[0031] Their designations are as follows: 1. Machining power source; 2. Rod-shaped tool cathode; 2-1. Side of rod-shaped tool cathode; 2-2. Front area of ​​bottom of rod-shaped tool cathode; 2-3. Rear area of ​​bottom of rod-shaped tool cathode; 3. Workpiece; 4. Low conductivity ethylene glycol solution; 5. Working fluid tank. Detailed Implementation

[0032] The following will refer to the appendices in the embodiments of the present invention. Figure 1 To be continued Figure 6 The technical solutions in the embodiments of the present invention are clearly and in detail described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To address the problems existing in the prior art, this invention provides a low-conductivity ethylene glycol solution-based cut-in electro-discharge electrolysis synchronous composite milling method, using a rod-shaped tool cathode 2 with a diameter of 91 μm and a rotation speed of 42000 r / min, and an ethylene glycol-NaNO3 solution with a conductivity of 50 μs / cm as an example for illustration:

[0034] Step 1: Immerse workpiece 3 in ethylene glycol-NaNO3 solution 4. Workpiece 3 and rod-shaped tool cathode 2 are connected to the positive and negative terminals of processing power supply 1, respectively. Rod-shaped tool cathode 2 rotates around its own axis. Rod-shaped tool electrode 2... Figure 3 As shown. Before machining, the rod-shaped tool cathode 2 determines the zero point of the machining coordinate system by short-circuit tool setting method. After tool setting, the rod-shaped tool electrode 2 retracts 10 μm as the initial machining gap;

[0035] Step 2: Set the processing parameters of the processing power supply 1 to a pulse voltage of 50V, a pulse frequency of 50000Hz, a pulse width of 10μs, and a duty cycle of 50%. Then turn on the power supply. The rod-shaped tool cathode 2 is fed vertically towards the workpiece 3. When the gap between the rod-shaped tool cathode 2 and the workpiece 3 reaches the discharge gap, a spark discharge occurs to erode the material. As the rod-shaped tool cathode 2 feeds, the material of the workpiece 3 is continuously eroded. When the downward feed distance of the rod-shaped tool cathode 2 reaches 30μm, the rod-shaped tool cathode 2 changes from vertical feed to horizontal feed, and milling begins. When the rod-shaped tool cathode 2 completes the preset S-shaped microchannel trajectory, the processing stops. The processed S-shaped microchannel is as follows: Figure 5 As shown, the surface of the fabricated microchannels is very smooth and has excellent surface quality. Furthermore, Figure 6 The metallographic micrograph of the microchannel cross-section shown also indicates that there is no recast layer structure on the processed surface, thus confirming that the cut-in EDM electrolytic synchronous composite milling method can achieve the preparation of microstructures with high surface quality and no defects.

[0036] The preferred immersion depth of workpiece 3 in the ethylene glycol-NaNO3 solution is 4 mm.

[0037] The preferred rod-shaped tool cathode 2 is made of pure tungsten material.

[0038] The preferred rotational speed of the rod-shaped tool cathode 2 is 42000 r / min.

[0039] The preferred processing power source 1 is a transistor pulse power source.

[0040] The preferred cutting depth D is 30 μm.

[0041] The preferred speed range for the downward feed of the rod-shaped tool cathode 2 is 3 μm / s, and the speed range for the horizontal feed is 8 μm / s.

[0042] Furthermore, this invention also conducted experimental processing using ethylene glycol-NaNO3 solutions with conductivity of 9 μs / cm, 10 μs / cm, 200 μs / cm, and 205 μs / cm as working solutions. The parameters and operating steps used in the processing were the same as in the first embodiment, and the processing results were as follows. Figures 7 to 10As shown in the figure, the processing results show that under the conditions of conductivity of 10 μS / cm and 200 μS / cm, the workpiece surface is processed with a microgroove structure that has high surface quality and is smooth and defect-free internally. However, when the conductivity drops to 9 μS / cm, the spark protrusions at the bottom of the microgroove are not completely removed, which is due to insufficient electrolysis. When the conductivity rises to 205 μS / cm, the spark protrusion structure at the bottom of the microgroove is completely removed, but electrochemical pitting occurs. This is due to excessive electrolysis. Therefore, the conductivity of ethylene glycol-NaNO3 solution can only produce microstructures with high surface quality when it is within a suitable range.

[0043] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present technical solutions, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method, characterized in that... Includes the following processes: Step 1: Immerse the workpiece in an amphoteric electrolyte, which serves as both the dielectric for electrical discharge and the electrolyte for electrolytic machining. The amphoteric electrolyte is a salt solution composed of ethylene glycol solvent and solid salt, wherein the salt is composed of one or any combination of NaCl, NaNO3 and NaClO3, and the amount added is determined by the conductivity of the amphoteric electrolyte, wherein the conductivity range is 10-200 μS / cm; the workpiece (3) and the rod-shaped tool cathode (2) are respectively connected to the positive and negative terminals of the processing power supply (1), wherein the rod-shaped tool cathode (2) rotates around its own axis; before processing, the rod-shaped tool cathode (2) determines the zero point of the processing coordinate system by short-circuit tool setting method, and after tool setting is completed, the rod-shaped tool cathode (2) retracts 8-20 μm as the initial processing gap; Step 2: Adjust the machining parameters and turn on the machining power supply (1). The rod-shaped tool cathode (2) is fed vertically towards the workpiece (3). When the gap between the rod-shaped tool cathode (2) and the workpiece (3) reaches the discharge gap, spark discharge occurs to remove the material. The bottom end of the rod-shaped tool cathode undergoes electric spark discharge to efficiently remove the workpiece material. Electrolysis occurs on the side wall of the rod-shaped tool cathode to remove the recast layer and heat-affected zone generated by the spark discharge. As the rod-shaped tool cathode (2) feeds, the material of the workpiece (3) is continuously eroded. When the rod-shaped tool cathode (2)... When the downward feed distance reaches D, the rod-shaped tool cathode (2) changes from vertical feed to horizontal feed and starts synchronous composite milling of electrical discharge and electrolysis. During the machining process, the side (2-1) and bottom front area (2-2) of the rod-shaped tool cathode undergo electrical discharge to efficiently remove the workpiece material. The bottom rear area (2-3) of the rod-shaped tool cathode undergoes electrolysis to remove the recast layer and heat-affected zone generated by the electrical discharge. D is the cutting depth of the electrical discharge and electrolysis milling. When the rod-shaped tool cathode (2) completes the preset milling trajectory, the machining stops.

2. The low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method according to claim 1, characterized in that: The workpiece (3) is immersed in a low-conductivity ethylene glycol solution (4) to a depth of 2-8 mm.

3. The low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method according to claim 1, characterized in that: The rod-shaped tool cathode (2) is made of a metal material resistant to electrolytic corrosion.

4. The low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method according to claim 1, characterized in that: The rotational speed range of the rod-shaped tool cathode (2) is 500-50000 r / min.

5. The low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method according to claim 1, characterized in that: The processing power supply (1) is an RC power supply or a transistor pulse power supply.

6. The low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method according to claim 1, characterized in that: The cutting depth D is in the range of 5-60 μm.

7. The low-conductivity glycol solution-based cut-in EDM / electrolytic synchronous composite milling method according to claim 1, characterized in that: The downward feed speed range of the rod-shaped tool cathode (2) is 1-5 μm / s, and the horizontal feed speed range is 5-20 μm / s.

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