Micro-circular pit array electric spark machining method

Abstract

The invention relates to a micro-circular pit array electric spark machining method, which belongs to the technical field of electric spark machining process, and specifically comprises the following steps: preparing an initial micro-prism array electrode; the initial micro-prism array electrode is adopted for electric spark machining loss, and a loss micro-prism array electrode is obtained; and preparing the micro-circular pit array by adopting the loss micro-prism array electrode. When an initial micro-prism array electrode is prepared through wire cut electrical discharge machining, firstly, a thin-wall array is machined on a workpiece according to a snake-shaped wire moving path, and then the workpiece is rotated according to a set angle; according to the reciprocating wire moving path, an array structure is machined on the thin-wall array; and multiple times of machining are conducted through electric spark machining loss. According to the method, the characteristic that the loss of the section of the front end of the electrode is in an ellipsoid shape after the micro-prism array electrode is used for electric spark machining of a micro-hole array is utilized, and the lost micro-prism array electrode is used for preparing the micro-array circular pit on a workpiece in a repeated reflecting mode. The method is high in machining efficiency, high in precision and easy and convenient to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of electric spark machining, and in particular relates to an electric spark machining method for a micro-circular pit array. Background Art

[0002] With the advancement of science and technology, microarray circular dimple structures have demonstrated tremendous potential in friction reduction / increase, vibration reduction, loss reduction, and anti-adhesion applications, and are widely used in fluid dynamics, tribology, biomedicine, and bionics. However, due to the small size, large number, and high precision requirements of microarray circular dimples, current processing methods primarily include mechanical machining, laser machining, ultrasonic machining, electrical discharge machining (EDM), and electrochemical machining (ECM). EDM, with its advantages of no cutting force, wide range of process materials, and excellent surface integrity, presents broad application prospects in the field of microarray circular dimple machining.

[0003] Currently, the main method used is to electrospark machine micro-circular dimples one by one using a single cylindrical electrode. However, this method suffers from low efficiency and difficulty in manufacturing micro-circular electrodes. Therefore, it is urgent to develop new machining methods to achieve efficient and highly consistent machining of micro-array circular dimple structures.

[0004] A Chinese patent application (publication number: CN108746899A, publication date: November 6, 2018) discloses a device and method for processing micro-dimple arrays on metal surfaces. The patent proposes a strategy for fabricating micro-array circular dimples and a method for fabricating micro-cylindrical array electrodes based on ultrasonic electrochemical processing of metal surface micro-dimple arrays. The patent's technical solution utilizes a combination of ultrasonic and electrofluidic mechanisms, using a microporous template in conjunction with a nozzle. The template is brought into contact with the workpiece surface, and after properly connecting the positive and negative electrodes, an electrical current is applied to produce the micro-dimple array. However, this solution requires microarray holes with precise dimensions, making the micro-through-hole template difficult to prepare. Furthermore, the electrochemical processing suffers from low efficiency and material removal rate, resulting in poor processing quality. Furthermore, it can cause environmental pollution, making efficient and green processing of micro-circular dimple arrays difficult. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a method for EDM machining micro-circular dimple arrays. After EDM machining a microhole array using a microprismatic array electrode, the electrode's front end undergoes a circular cross-section loss. The lost microprismatic array electrode is then used to re-image the microarray circular dimples onto the workpiece. This method offers high machining efficiency, high precision, and ease of operation.

[0006] A method for electrospark machining of a micro-circular dimple array, comprising the following steps:

[0007] preparing an initial micro-prism array electrode;

[0008] The initial micro-prismatic array electrode is subjected to electrospark machining to obtain a consumed micro-prismatic array electrode;

[0009] Micro-circular pit arrays were prepared using lossy micro-prism array electrodes.

[0010] The initial micro-prism array electrodes were prepared using a low-speed wire-cut electrical discharge machine.

[0011] The specific process steps for preparing the initial micro-prism array electrode are:

[0012] Install the rotating mechanism;

[0013] Two initial micro-prismatic array electrodes were obtained by wire electrospark machining.

[0014] The process steps for obtaining two initial micro-prismatic array electrodes by wire EDM are the same, as follows:

[0015] Install the workpiece;

[0016] A thin-wall array is machined on the workpiece according to a serpentine wire path;

[0017] Rotate the workpiece according to the set angle;

[0018] According to the reciprocating wire feeding path, an array micro-prism structure is processed on the thin-wall array. The cross section of the micro-prism is a regular polygon, and the diameter of the inscribed circle of the regular polygon is larger than the diameter of the target micro-circular pit.

[0019] The initial micro-prismatic array electrode is subjected to electrospark machining to obtain a worn micro-prismatic array electrode. The process steps include:

[0020] Installing the base plate on the EDM machine;

[0021] The initial micro-prism array electrode is used to process a plurality of micro-array square holes on a substrate to prepare a lossy micro-prism array electrode, wherein the polarity of the substrate is positive and the polarity of the initial micro-prism array electrode is negative.

[0022] Before using an initial micro-prism array electrode to process a plurality of micro-array square holes on a substrate, the axial loss length or the maximum loss length of the initial micro-prism array electrode in a stable loss state is obtained based on processing one of the two initial micro-prism array electrodes with the substrate, and then the other initial micro-prism array electrode is used to prepare a lossy micro-prism array electrode.

[0023] The specific process steps for processing several microarray square holes are as follows:

[0024] The EDM process is repeated multiple times, with the same machining depth each time, until the front end of the initial micro-prismatic electrode reaches a stable wear state and takes on an ellipsoidal shape.

[0025] Each processing depth is greater than the sum of the substrate thickness and the axial loss length or the maximum loss length of the initial micro-prism array electrode in a stable loss state.

[0026] When using a lossy micro-prismatic array electrode to prepare a micro-circular pit array, first measure the front end diameter of the lossy micro-prismatic array electrode to determine the axial length of the position where the cross-section is circular. Based on the axial length, the processing depth of the micro-circular pit array is determined. The processing depth of the micro-circular pit array is less than the axial length of the position where the cross-section is circular. Based on the determined processing depth of the micro-circular pit array, an electric spark forming machine is used to process the workpiece. The polarity of the workpiece is positive and the polarity of the lossy micro-prismatic array electrode is negative.

[0027] The working fluids in the process include kerosene and deionized water.

[0028] By means of the above technical solution, the present invention has at least the following beneficial effects:

[0029] Compared to existing methods of producing micro-circular dimple arrays using single-electrode electrospark machining or micro-ball-end milling cutters, the present invention proposes using a micro-prismatic array electrode for multi-projection fabrication of micro-circular dimple arrays. The resulting micro-dimple arrays have improved dimensional accuracy, are simpler to operate, and can significantly reduce production costs. The reliability of this method has been verified through preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the process flow of an electrospark machining method for a micro-circular dimple array provided by the present invention;

[0031] Figure 2 A schematic diagram of machining a thin-wall array in an electrospark machining method for a micro-circular dimple array provided by the present invention;

[0032] Figure 3 A schematic diagram of the process of machining an initial micro-prismatic array electrode in a micro-circular dimple array electrospark machining method provided by the present invention;

[0033] Figure 4 A schematic diagram of an initial micro-prismatic array electrode machined in a micro-circular dimple array electrospark machining method provided by the present invention;

[0034] Figure 5 A schematic diagram of a consumable micro-prism array electrode after the first machining process in a micro-circular pit array electrospark machining method provided by the present invention;

[0035] Figure 6 A schematic diagram of a lossy micro-prism array after machining in a micro-circular dimple array electrospark machining method provided by the present invention;

[0036] Figure 7 Scanning electron microscope image 1 of the copper-tungsten alloy lossy micro-prismatic array electrode provided by an embodiment of the present invention;

[0037] Figure 8 Scanning electron microscope image 2 of the copper-tungsten alloy lossy micro-prismatic array electrode provided by an embodiment of the present invention;

[0038] Figure 9 A three-dimensional display of the copper-tungsten alloy lossy micro-prism array electrode provided by an embodiment of the present invention under an ultra-depth-of-field microscope;

[0039] Figure 10 A diagram showing the dimensional measurement results of the copper-tungsten alloy lossy micro-prismatic array electrode provided in an embodiment of the present invention;

[0040] Figure 11 This is a scanning electron microscope image of a micro-circular pit array processed according to an embodiment of the present invention;

[0041] In the picture:

[0042] 1-initial micro-prism array electrode, 2-depleted micro-prism array electrode, 3-substrate. DETAILED DESCRIPTION

[0043] In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention are described in detail below with reference to the accompanying drawings through specific implementation methods.

[0044] Combine Figure 1 As shown, the present invention provides a method for electrospark machining of a micro-circular dimple array, which utilizes a consumable micro-prismatic array electrode to re-image onto a workpiece to prepare a micro-array of circular dimples. This embodiment takes machining a micro-circular dimple array with a target diameter of 240 μm on a workpiece made of a high-temperature alloy material, grade IN718, as an example, and specifically includes the following steps:

[0045] S1: The initial micro-prism array electrode 1 is prepared by low-speed wire-cut electrospark cutting.

[0046] The initial micro-prismatic array electrode 1 is prepared by low-speed wire-cut EDM, which removes localized material through electric sparks. The principle is as follows: First, the tool electrode and the workpiece are connected to the electrodes of a pulse power supply to form two electrodes, which are then immersed in an insulating fluid. When the gap between the two electrodes reaches a certain distance, the pulse voltage applied to the two electrodes breaks through the insulating fluid and generates spark discharge, achieving localized material removal. The specific process is as follows:

[0047] S1.1: Install a rotating mechanism on a low-speed wire EDM machine to rotate the workpiece. In this embodiment, the rotating mechanism and machine platform for low-speed wire EDM micro-tool electrodes disclosed in Patent No. ZL201610851598.4 are used to achieve workpiece rotation.

[0048] S1.2: Preparation of the first initial micro-prism array electrode 1:

[0049] The workpiece is mounted on a low-speed wire-cut EDM machine, and a thin-walled array is machined on the workpiece according to a serpentine wire path. The electrode wire movement adopts a uniform feed mode, and the feed speed parameter selection range is between 0.8-2mm / min. The workpiece is then rotated according to the set angle. According to the reciprocating wire path, an array micro-prism structure is machined on the thin-walled array, where the inscribed circle radius of the micro-prism is larger than the diameter of the target micro-circular pit, and the first initial micro-prism array electrode 1 is obtained. The electrode wire adopts a servo feed mode, and the low-speed wire-cut EDM machine adjusts the feed speed of the motor wire in real time according to the discharge state to ensure the stability of the EDM process and avoid short circuit caused by too fast feed or reduced processing efficiency due to too slow feed.

[0050] S1.3: Repeat steps S1.1 to S1.2 to prepare a second initial microprism array electrode 1.

[0051] The first initial micro-prismatic array electrode 1 and the second initial micro-prismatic array electrode 1 are identical and are used to obtain the axial loss length or maximum loss length of the initial micro-prismatic array electrode 1 in a stable loss state and to prepare the lossy micro-prismatic array electrode 2 .

[0052] The workpiece in this embodiment is a cylindrical electrode made of copper-tungsten alloy. The same process steps are used to successively produce the first initial micro-prism array electrode 1 and the second initial micro-prism array electrode 1. The specific preparation process is as follows: first, the cylindrical electrode is mounted on the three-jaw chuck of the low-speed wire-cut EDM machine, the workpiece is clamped by the three-jaw chuck, and a thin-walled array is machined on the cylindrical structure according to the serpentine wire cutting path, such as Figure 2 As shown; then the workpiece is rotated 90° by the rotating mechanism for the low-speed wire cutting micro tool electrode, as shown Figure 3 As shown; according to the reciprocating wire feeding path, a micro regular quadrangular prism array electrode is processed on the thin-wall array, that is, the cross section of the micro prism is a regular quadrilateral, as shown Figure 4 As shown, the first initial micro-prism array electrode 1 and the second initial micro-prism array electrode 1 of this embodiment are both micro-regular quadrangular prism array electrodes, and the inscribed circle diameter of the regular quadrangular micro-prism is 300 μm, which is larger than the target diameter of the micro-circular pit array to be processed, 240 μm.

[0053] S2: The initial micro-prismatic array electrode 1 is subjected to electrospark machining to produce a worn micro-prismatic array electrode 2.

[0054] S2.1: Install substrate 3 on the EDM machine for subsequent loss processing. The conductivity of substrate 3 is greater than 35×10 6 S / m, materials with high conductivity and low melting point and melting point less than 1100℃, such as aluminum, copper, and silver, so that the discharge energy required for EDM is low and energy consumption is more saved.

[0055] In this embodiment, a pure copper substrate 3 with a thickness of 500 μm is used.

[0056] S2.2: According to the first initial micro-prism array electrode 1 obtained in step S1 and the substrate 3 selected in step S2.1, the axial loss length or the maximum loss length of the initial micro-prism array electrode 1 in a stable loss state is obtained.

[0057] In this embodiment, a copper-tungsten alloy initial micro-prismatic array electrode 1 with an inscribed circle radius of 300 μm is used to process a pure copper substrate 3 with a thickness of 500 μm. The axial loss length of the initial micro-prismatic array electrode 1 in a stable loss state is 130 μm.

[0058] S2.3: Use the second initial micro-prismatic array electrode 1 to machine a plurality of micro-array square holes on a pure copper substrate 3 using an EDM machine to prepare a lossy micro-prismatic array electrode 2. The pure copper substrate 3 has a positive polarity, while the initial micro-prismatic array electrode 1 has a negative polarity. The working fluid includes, but is not limited to, kerosene or deionized water. The machining depth is greater than the sum of the thickness of the pure copper substrate 3 and the axial loss length in a stable loss state or the maximum loss length.

[0059] The EDM is repeatedly performed multiple times using an EDM forming machine until the front end of the initial micro-prismatic electrode reaches a stable loss state and is ellipsoidal, thereby preparing a lossy micro-prismatic array electrode 2. The depth of each processing is the same. The schematic diagram after the first processing is shown in FIG. Figure 5 As shown, the final lossy micro-prism array electrode 2 is as shown in FIG. Figure 6 shown.

[0060] In EDM, the tip discharge phenomenon of EDM is utilized, and the electrode will be damaged by electrical corrosion due to pulse discharge. According to the skin effect and the tip discharge phenomenon, the current density and electric field intensity at the corners of the initial micro-prismatic electrode are greater than those at the edges. The loss rate of the corners during EDM is greater than that of the edges. When the initial micro-prismatic array electrode 1 is first processed, the morphology of the front end of the electrode changes little. When the number of processing times reaches a certain value, the front end of the initial micro-prismatic array electrode 1 reaches a stable loss state and is ellipsoidal. Specifically, during processing, the processing time used each time or the axial loss length of the initial micro-prismatic array electrode 1 during each processing is recorded. When the processing time or the axial loss length of the initial micro-prismatic array electrode 1 during each processing remains unchanged, it indicates that the micro-prismatic array electrode has entered a stable loss state. Observing the morphology of the micro-prismatic array electrode, the shape of the front end has changed from a micro-prism with a regular polygonal cross-section to an ellipsoid. It should be noted that during the EDM wear process, the depth of each machining needs to be greater than the sum of the thickness of the substrate 3 and the axial wear length or the maximum wear length of the initial micro-prismatic array electrode 1 in the stable wear state, ensuring that when the initial micro-prismatic array electrode 1 reaches the stable wear state and becomes the wear micro-prismatic array electrode 2, the end of the electrode changes from a polygonal plane to a point.

[0061] In this embodiment, the polarity of the pure copper substrate 3 is positive, the polarity of the initial micro-prism array electrode 1 is negative, the working fluid is kerosene, and the processing depth is 800 μm, which is greater than the sum of the thickness of the substrate 3 of 500 μm and the axial loss length of the initial micro-prism array electrode 1 in the stable loss state of 130 μm. During the preparation process of the lossy micro-prism array electrode 2 in this embodiment, the number of times the initial micro-prism electrode enters the stable loss state is 2. The positioning accuracy of the X-direction, Y-direction, and Z-direction of the electric spark forming machine is 3 μm, 3 μm, and 2 μm respectively; the repeat positioning accuracy in the X-direction, Y-direction, and Z-direction is 1 μm, 1 μm, and 1 μm respectively. The copper-tungsten alloy lossy micro-prism array electrode 2 prepared in this embodiment is as follows Figure 7 and Figure 8 shown.

[0062] S3: Prepare a micro-circular pit array using a lossy micro-prism array electrode 2.

[0063] S3.1: Measure the front end diameter of the lossy micro-prism array electrode 2 obtained in step S2, determine the axial length of the portion where the cross section is circular, and determine the processing depth of the micro-circular dimple array based on the axial length. The processing depth of the micro-circular dimple array is less than the axial length of the portion where the cross section is circular.

[0064] S3.2: Using the lossy micro-prismatic array electrode 2, a micro-circular dimple array is machined onto the workpiece using an electrospark die-sinking machine, based on the micro-circular dimple array obtained in step S3.1. The workpiece is positively charged, the lossy micro-prismatic array electrode 2 is negatively charged, and the working fluid is kerosene.

[0065] In this embodiment, the front end diameter of the lossy micro-prism array electrode 2 obtained in step S2 is measured using an ultra-depth of field microscope, as shown in FIG. Figure 9 As shown, a three-dimensional view of the top of the lossy micro-prismatic array electrode 2 is measured. From the three-dimensional display of the ultra-depth microscope, two line contours are extracted through the center point of the top of the lossy micro-prismatic array electrode 2. The contours are extracted along the edge direction and the corner direction respectively and curves are drawn. The overlapping part of the image shows that different positions are equidistant from the center point, that is, the overlapping part of the lossy micro-prismatic array electrode 2 has a circular cross-section. Figure 10 As shown, the axial length of the position where the cross section of the lossy micro-prism array electrode 2 of this embodiment is circular is 76.27μm. Based on the axial length, the processing depth of the micro-circular pit array is determined to be 55μm, which is less than 76.27μm. Then, the copper-tungsten alloy lossy micro-prism array electrode 2 obtained in step S2 is used to prepare a circular pit array with a micro-target diameter of 240μm on a workpiece made of a high-temperature alloy material with the grade IN718. The processing depth is 55μm. The average values ​​of the diameter and depth of the processed micro-circular pit array are 257μm and 62.1μm, respectively. Figure 11 As shown, the error is only 7% compared with the theoretical value of 240μm.

Claims

1. A method for electrospark machining of a micro-circular pit array, characterized in that: The specific steps include: preparing an initial micro-prism array electrode; The initial micro-prismatic array electrode is subjected to electrospark machining to obtain a consumed micro-prismatic array electrode; Micro-circular pit arrays were prepared using lossy micro-prism array electrodes.

2. The method for electrospark machining of a micro-circular dimple array according to claim 1, wherein: The initial micro-prism array electrodes were prepared using a low-speed wire-cut electrical discharge machine.

3. The method for electrospark machining of a micro-circular dimple array according to claim 1, wherein: The specific process steps for preparing the initial micro-prism array electrode are: Install the rotating mechanism; Two initial micro-prismatic array electrodes were obtained by wire electrospark machining.

4. The method for electrospark machining of a micro-circular dimple array according to claim 3, wherein: The process steps for obtaining two initial micro-prismatic array electrodes by wire EDM are the same, as follows: Install the workpiece; A thin-wall array is machined on the workpiece according to a serpentine wire path; Rotate the workpiece according to the set angle; According to the reciprocating wire feeding path, an array micro-prism structure is processed on the thin-wall array. The cross section of the micro-prism is a regular polygon, and the diameter of the inscribed circle of the regular polygon is larger than the diameter of the target micro-circular pit.

5. The method for electrospark machining of a micro-circular dimple array according to claim 1, wherein: The initial micro-prismatic array electrode is subjected to electrospark machining to obtain a worn micro-prismatic array electrode. The process steps include: Installing the base plate on the EDM machine; The initial micro-prism array electrode is used to process a plurality of micro-array square holes on a substrate to prepare a lossy micro-prism array electrode, wherein the polarity of the substrate is positive and the polarity of the initial micro-prism array electrode is negative.

6. The method for electrospark machining of a micro-circular dimple array according to claim 5, characterized in that: Before using an initial micro-prism array electrode to process a plurality of micro-array square holes on a substrate, the axial loss length or the maximum loss length of the initial micro-prism array electrode in a stable loss state is obtained based on processing one of the two initial micro-prism array electrodes with the substrate, and then the other initial micro-prism array electrode is used to prepare a lossy micro-prism array electrode.

7. The method for electrospark machining of a micro-circular dimple array according to claim 6, wherein: The specific process steps for processing several microarray square holes are as follows: The EDM process is repeated multiple times, with the same machining depth each time, until the front end of the initial micro-prismatic electrode reaches a stable wear state and takes on an ellipsoidal shape.

8. The method for electrospark machining of a micro-circular dimple array according to claim 7, wherein: Each processing depth is greater than the sum of the substrate thickness and the axial loss length or the maximum loss length of the initial micro-prism array electrode in a stable loss state.

9. The method for electrospark machining of a micro-circular dimple array according to claim 1, wherein: When using a lossy micro-prismatic array electrode to prepare a micro-circular pit array, first measure the front end diameter of the lossy micro-prismatic array electrode to determine the axial length of the position where the cross-section is circular. Based on the axial length, the processing depth of the micro-circular pit array is determined. The processing depth of the micro-circular pit array is less than the axial length of the position where the cross-section is circular. Based on the determined processing depth of the micro-circular pit array, an electric spark forming machine is used to process the workpiece. The polarity of the workpiece is positive and the polarity of the lossy micro-prismatic array electrode is negative.

10. The method for electrospark machining of a micro-circular dimple array according to claim 1, characterized in that: The working fluids in the process include kerosene and deionized water.

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