Pulse dynamic electrochemical mechanical composite polishing method

Abstract

The invention discloses a pulse dynamic electrochemical mechanical composite polishing method which comprises the following steps: step 1, preparing a polishing medium with an electrochemical thickening effect, the polishing medium being formed by mixing a dispersion medium, a dispersion phase, an electrolyte, an additive and an abrasive; secondly, a polishing medium is placed in a polishing groove, and a workpiece is fixed to a connecting shaft of a polishing device through a pneumatic clamp; thirdly, the positive electrode of a pulse power source is connected with the connecting shaft through a wire, and the negative electrode of the pulse power source is connected with the polishing groove through a wire; fourthly, a multi-dimensional coupling vibration device is fixedly connected with the polishing groove through an insulation connecting body, and the vibration frequency, the vibration amplitude, the voltage, the duty ratio and the frequency of a pulse power source are set; and fifthly, the polishing medium is subjected to the directional vibration effect of the multi-dimensional coupling vibration device. By setting a programmable vibration direction, a polishing medium is directionally induced to generate a shear thickening effect and an electrochemical oxidation effect on the surface of a specific workpiece, so that localized removal of a material is realized.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-precision machining, and in particular to a pulsed electrochemical mechanical composite polishing method. Background Art

[0002] As the global technological revolution continues to make progress and breakthroughs, the requirements for ultra-precision machining of mechanical parts are constantly increasing, especially for additive manufacturing parts with complex structural features, which are more difficult to ultra-precision. On the one hand, higher surface quality and accuracy are required, and on the other hand, efficient and low-cost machining methods are required. Polishing is often the final process of the entire additive manufacturing parts process chain, which determines the performance of the parts.

[0003] The existing polishing technologies for complex surface additive manufacturing parts mainly include chemical polishing, electrochemical polishing, chemical mechanical polishing, non-Newtonian fluid polishing, vibration polishing, etc. Among them, electrochemical polishing uses viscous acidic substances to selectively dissolve the uneven areas on the surface of the workpiece under the action of an electric field to eliminate surface defects and smooth the surface; it is widely used because of its advantages such as high polishing efficiency and no influence from the processed surface; however, when polishing the surface of workpieces with surface roughness (Ra>2μm), the surface waviness cannot be effectively controlled. The patent (CN201210192915.8) discloses a method for polishing ultra-precision surfaces based on the shear thickening effect of non-Newtonian fluids. The method utilizes the nonlinear characteristics of the viscosity and shear rate of non-Newtonian fluids, relies on the extrusion and shearing of the polishing medium in the processing area to achieve a sudden increase in its viscosity, greatly improves the holding force of the abrasive, and then utilizes the micro-cutting effect of the abrasive on the workpiece surface to achieve material removal; this method achieves relative movement between the polishing liquid and the workpiece through the rotation of the polishing liquid, resulting in the workpiece to be processed being limited to rotating parts, and the material removal uniformity is poor, making it difficult to achieve uniform polishing of complex structures. Vibration polishing uses a vibration device to drive the abrasive and the workpiece to produce relative movement to achieve micro-cutting of the abrasive and the workpiece surface. However, due to the influence of amplitude and acceleration, the extrusion force and shear force of the abrasive on the workpiece surface are small, so this method is only widely used in the process of removing small excess materials such as deburring of complex parts.

[0004] In summary, the existing polishing methods cannot simultaneously meet the precision machining of additively manufactured parts with complex surfaces. In order to further enrich the ultra-precision machining technology of additively manufactured parts with complex surfaces, a pulsed electrochemical mechanical composite polishing method is developed, which has important theoretical significance and practical application value. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the problems existing in the above-mentioned existing pulsed electrochemical mechanical composite polishing method, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to provide a pulsed electrochemical mechanical composite polishing method, which sets a programmable vibration direction to directionally induce the polishing medium to undergo shear thickening effect and electrochemical oxidation effect on the surface of a specific workpiece, thereby achieving localized removal of materials.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a pulsed electrochemical mechanical composite polishing method, comprising the following steps:

[0009] Step 1: preparing a polishing medium with an electrochemical thickening effect, wherein the polishing medium is mixed with a dispersion medium, a dispersed phase, an electrolyte, an additive and an abrasive;

[0010] Step 2: Place the polishing medium in the polishing tank, fix the workpiece to the connecting shaft of the polishing device through a pneumatic clamp, and adjust the height of the workpiece through the connecting shaft so that the workpiece is completely immersed in the polishing medium;

[0011] Step 3: Connect the positive electrode of the pulse power supply to the connecting shaft through a wire, connect the negative electrode of the pulse power supply to the polishing tank through a wire, and the pulse power supply, the connecting shaft, the workpiece, the polishing medium, the polishing tank and the wire form a closed circuit;

[0012] Step 4: The multi-dimensional coupling vibration device is fixedly connected to the polishing tank through an insulating connector, and the vibration frequency and amplitude as well as the voltage, duty cycle and frequency of the pulse power supply are set;

[0013] Step 5: The polishing medium is subjected to the directional vibration of the multi-dimensional coupled vibration device, generating shear motion on the specific surface of the workpiece, inducing the dispersed medium and the dispersed phase to rapidly cluster at the micro-peaks on the workpiece surface in the polishing area, generating flexible particle clusters. The electrolyte and abrasive are entrained in the generated particle clusters due to the clustering effect. Driven by the intermittent pulse electric field, a soft oxide film is intermittently generated at the micro-peaks on the workpiece surface in the polishing area. The flexible particle clusters remove the oxide film in the form of a plow, and the oxide film is repeatedly generated and gradually removed, thereby achieving the required polishing quality and realizing efficient localized lossless ultra-smooth polishing of the workpiece.

[0014] As a preferred embodiment of the pulsed electrochemical mechanical composite polishing method of the present invention, the dispersion medium is deionized water or an alcohol compound; the dispersed phase is hydroxypropyl starch or silicon dioxide; the electrolyte is sodium chloride or sodium nitrate; the additives include sodium polyacrylate and sodium molybdate; the abrasive includes grade I abrasive and grade II or grade III abrasive, and grade I 1-10 μm, grade II 10-500 μm and grade III 500-2000 μm diamond and alumina are selected.

[0015] As a preferred embodiment of the pulsed electrochemical mechanical composite polishing method of the present invention, the Class I abrasive removes shallow scratches and deformation layers on the surface, and the flexible particle clusters entrain Class II abrasives or Class III abrasives to remove oxide films.

[0016] As a preferred solution of the pulsed electrochemical mechanical composite polishing method described in the present invention, the multi-dimensional coupled vibration device uses electromagnetic vibration or mechanical vibration, which can realize six-degree-of-freedom coupled vibration in space, change the amplitude and direction of the multi-dimensional coupled vibration device, and thus continuously change the polishing force of the polishing area.

[0017] As a preferred scheme of the pulsed electrochemical mechanical composite polishing method described in the present invention, wherein: the vibration frequency and amplitude are set in step four, and the shear movement of the workpiece surface is used to induce the clustering effect of the dispersion medium and the dispersed phase, thereby controlling the concentration of the electrolyte in the polishing area, regulating the formation rate of the oxide film in the polishing area, regulating the thickness of the oxide film, and thereby controlling the surface hardness of the processing area.

[0018] Beneficial effects of the present invention:

[0019] 1. In the pulsed electrochemical mechanical composite polishing method described in the present invention, the polishing medium can produce a clustering effect in the polishing area under the induction of multi-dimensional vibration shear, and accurately gather electrolytes and abrasive particles to the processing area, thereby improving electrolysis efficiency and polishing quality;

[0020] 2. The pulsed electrochemical mechanical composite polishing method described in the present invention, by setting the vibration frequency and amplitude, the polishing medium undergoes shear motion on the workpiece surface, inducing the dispersed medium and the dispersed phase to produce a clustering effect, thereby controlling the concentration of the electrolyte in the polishing area and continuously changing the polishing force in the polishing area; in combination with setting the voltage, duty cycle and frequency of the pulse power supply, the intermittent generation rate of the oxide film is adjusted to improve the controllability of the material removal process;

[0021] 3. The pulsed electrochemical mechanical composite polishing method of the present invention achieves localized removal of materials by setting a programmable vibration direction to directionally induce the polishing medium to produce shear thickening effect and electrochemical oxidation effect on the surface of a specific workpiece;

[0022] 4. The pulsed electrochemical mechanical composite polishing method described in the present invention comprises a plurality of abrasives of different particle sizes in the polishing medium, wherein the grade I abrasive removes shallow scratches and deformation layers on the surface, and the flexible particle clusters carry the grade II abrasive or the grade III abrasive to remove the oxide film, thereby gradually removing the oxide film and improving the surface quality of the workpiece, achieving an ultra-smooth surface quality, and effectively avoiding the existence of micro-defects on the surface after polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0024] Figure 1 This is a schematic diagram of pulsed electrochemical mechanical composite polishing;

[0025] Figure 2 This is a microscopic diagram of the initial distribution state of the polishing medium components;

[0026] Figure 3 Generate schematic diagrams for oxide films and "flexible particle clusters";

[0027] Figure 4 It is a microscopic diagram showing the removal of micro-convex peaks at different positions of the oxide film;

[0028] Figure 5 Schematic diagram of medium composition distribution and smooth surface formation after polishing.

[0029] In the figure: 1 pulse power supply, 2 polishing groove, 3 insulating connector, 4 multi-dimensional coupled vibration device, 5 connecting shaft, 6 pneumatic clamp, 7 workpiece, 8 polishing medium, 9 oxide film, 8-1 electrolyte, 8-2 dispersion medium, 8-3 grade I abrasive, 8-4 grade II or grade III abrasive, 8-5 dispersed phase, 8-6 additive. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0033] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0034] Reference Figure 1 - Figure 5 , provides a pulsed electrochemical mechanical composite polishing method, comprising the following steps:

[0035] Step 1: preparing a polishing medium 8 with an electrochemical thickening effect, wherein the polishing medium 8 is mixed with a dispersion medium 8-2, a dispersed phase 8-5, an electrolyte 8-1, an additive 8-6 and an abrasive;

[0036] Step 2: Place the polishing medium 8 in the polishing tank 2, fix the workpiece 7 to the connecting shaft 5 of the polishing device through the pneumatic clamp 6, and adjust the height of the workpiece through the connecting shaft 5 so that the workpiece 7 is completely immersed in the polishing medium 8;

[0037] Step 3: Connect the positive electrode of the pulse power supply 1 to the connecting shaft 5 through a wire, and connect the negative electrode of the pulse power supply 1 to the polishing tank 2 through a wire, so that the pulse power supply 1, the connecting shaft 5, the workpiece 7, the polishing medium 8, the polishing tank 2 and the wire form a closed circuit;

[0038] Step 4: The multi-dimensional coupling vibration device 4 is fixedly connected to the polishing tank 2 through the insulating connector 3, and the vibration frequency and amplitude as well as the voltage, duty cycle and frequency of the pulse power supply are set;

[0039] Step 5: The polishing medium 8 is subjected to the directional vibration of the multi-dimensional coupled vibration device 4, generating shear motion on the specific surface of the workpiece 7, inducing the dispersed medium 8-2 and the dispersed phase 8-5 to rapidly generate a clustering effect at the micro-peaks on the surface of the workpiece 7 in the polishing area, generating flexible particle clusters. The electrolyte 8-1 and the abrasive are entrained in the generated particle clusters due to the clustering effect. Driven by the intermittent pulse electric field, a soft oxide film 9 is intermittently generated at the micro-peaks on the surface of the workpiece 7 in the polishing area. The flexible particle clusters remove the oxide film 9 in the form of a plow, and the oxide film 9 is repeatedly generated and gradually removed, thereby achieving the required polishing quality and realizing efficient localized lossless ultra-smooth polishing of the workpiece 7.

[0040] Among them, the dispersion medium 8-2 is selected from deionized water or alcohol compounds; the dispersed phase 8-5 is selected from hydroxypropyl starch or silicon dioxide; the electrolyte 8-1 is selected from sodium chloride or sodium nitrate; the additive 8-6 includes sodium polyacrylate and sodium molybdate; the abrasive includes grade I abrasive 8-3 and grade II or grade III abrasive 8-4, and grade I 1-10μm, grade II 10-500μm and grade III 500-2000μm diamond and aluminum oxide are selected. The grade I abrasive 8-3 removes shallow scratches and deformation layers on the surface, and the flexible particle cluster entrains the grade II abrasive or grade III abrasive 8-4 to remove the oxide film 9.

[0041] Specifically, the multi-dimensional coupling vibration device 4 uses electromagnetic vibration or mechanical vibration, which can realize six-degree-of-freedom coupling vibration in space, change the amplitude and direction of the multi-dimensional coupling vibration device, and thus continuously change the polishing force of the polishing area.

[0042] Among them, in step 4, the vibration frequency and amplitude are set, and the shear movement of the surface of the workpiece 7 is used to induce the clustering effect of the dispersion medium 8-2 and the dispersed phase 8-5, control the concentration of the electrolyte 8-1 in the polishing area, regulate the generation rate of the oxide film 9 in the polishing area, regulate the thickness of the oxide film 9, and then control the surface hardness of the processing area.

[0043] Embodiment 1

[0044] Step 1: Deionized water is selected as the dispersion medium 8-2; hydroxypropyl starch is selected as the dispersion phase 8-5; sodium chloride is selected as the electrolyte 8-1; sodium polyacrylate and sodium molybdate are selected as the additive 8-6; Class I abrasive 1-10 microns 8-3, Class II abrasive 10-500 microns and Class III 500-2000 microns 8-4 diamond are mixed to form a combined abrasive, and deionized water, hydroxypropyl starch, sodium chloride, sodium polyacrylate, sodium molybdate and abrasive are fully mixed to form a polishing medium 8;

[0045] Step 2: Place the polishing medium 8 in the polishing tank 2, fix the workpiece 7 to the polishing device connecting shaft 5 through the pneumatic clamp 6, and adjust the height of the workpiece through the connecting shaft 5 so that the workpiece 7 is completely immersed in the polishing medium 8;

[0046] Step 3: Connect the positive electrode of the pulse power supply 1 to the connecting shaft 5 through a wire, and connect the negative electrode of the pulse power supply 1 to the polishing tank 2 through a wire, so that the pulse power supply 1, the connecting shaft 5, the workpiece 7, the polishing medium 8, the polishing tank 2 and the wire form a closed circuit;

[0047] Step 4: The multi-dimensional coupling vibration device 4 is fixedly connected to the polishing tank 2 through the insulating connector 3, and the vibration parameters are set to 20 Hz vibration frequency, 2 mm amplitude, 5 V processing voltage, 70% duty cycle, and 50 Hz frequency;

[0048] Step 5: The polishing medium 8 is subjected to the directional vibration of the multi-dimensional coupling vibration device 4, generating shear motion on the specific surface of the workpiece 7, inducing the dispersed medium 8-2 and the dispersed phase 8-5 to rapidly generate a clustering effect at the micro-convex peaks on the surface of the workpiece 7 in the polishing area, generating flexible particle clusters. The electrolyte 8-1 and the abrasives 8-3 and 8-4 are entrained in the generated particle clusters due to the clustering effect. Driven by the intermittent pulse electric field, a soft oxide film is intermittently generated at the micro-convex peaks on the surface of the workpiece 7 in the polishing area. The Class II abrasive or Class III abrasive 8-4 entrained by the flexible particle cluster removes the oxide film in the form of a plow (large material removal amount), and then the Class I abrasive 8-3 removes the shallow scratches and deformation layer on the surface. The oxide film 9 is repeatedly generated and gradually removed, thereby achieving the required polishing quality and realizing efficient localized non-destructive ultra-smooth polishing of the workpiece.

[0049] Embodiment 2

[0050] Step 1: The dispersion medium 8-2 is an alcohol compound; the dispersion phase 8-5 is silicon dioxide; the electrolyte 8-1 is sodium nitrate; the additive 8-6 is sodium polyacrylate and sodium molybdate; the grade I abrasive 1-10 microns 8-3, the grade II abrasive 10-500 microns and the grade III 500-2000 microns 8-4 of aluminum oxide are mixed to form a combined abrasive, and the alcohol compound, silicon dioxide, sodium nitrate, sodium polyacrylate, sodium molybdate and the abrasive are fully mixed to form a polishing medium 8;

[0051] Step 2: Place the polishing medium 8 in the polishing tank 2, fix the workpiece to the polishing device connecting shaft 5 through the pneumatic clamp 6, and adjust the height of the workpiece 7 through the connecting shaft 5 so that the workpiece 7 is completely immersed in the polishing medium 8;

[0052] Step 3: Connect the positive electrode of the pulse power supply 1 to the connecting shaft 5 through a wire, and connect the negative electrode of the pulse power supply 1 to the polishing tank 2 through a wire, so that the pulse power supply 1, the connecting shaft 5, the workpiece 7, the polishing medium 8, the polishing tank 2 and the wire form a closed circuit;

[0053] Step 4: The multi-dimensional coupling vibration device 4 is fixedly connected to the polishing tank 2 through the insulating connector 3, and the vibration parameters are set to 50 Hz vibration frequency, 0.5 mm amplitude, 20 V processing voltage, 70% duty cycle, and 100 Hz frequency;

[0054] Step 5: The polishing medium 8 is subjected to the directional vibration of the multi-dimensional coupling vibration device 4, generating shear motion on the specific surface of the workpiece 7, inducing the dispersed medium 8-2 and the dispersed phase 8-5 to rapidly generate a clustering effect at the micro-convex peaks on the surface of the workpiece 7 in the polishing area, generating flexible particle clusters. The electrolyte 8-1 and the abrasives 8-3 and 8-4 are entrained in the generated particle clusters due to the clustering effect. Driven by the intermittent pulse electric field, a soft oxide film is intermittently generated at the micro-convex peaks on the surface of the workpiece 7 in the polishing area. The Class II abrasive or Class III abrasive 8-4 entrained by the flexible particle cluster removes the oxide film in the form of a plow (large material removal amount), and then the Class I abrasive 8-3 removes the shallow scratches and deformation layer on the surface. The oxide film 9 is repeatedly generated and gradually removed, thereby achieving the required polishing quality and realizing efficient localized non-destructive ultra-smooth polishing of the workpiece.

[0055] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A pulsed electrochemical mechanical composite polishing method, characterized in that: The following steps are involved: Step 1: preparing a polishing medium (8) having an electrochemical thickening effect, wherein the polishing medium (8) is mixed with a dispersion medium (8-2), a dispersed phase (8-5), an electrolyte (8-1), an additive (8-6) and an abrasive; Step 2: placing the polishing medium (8) in the polishing tank (2), fixing the workpiece (7) to the connecting shaft (5) of the polishing device through the pneumatic clamp (6), and adjusting the height of the workpiece through the connecting shaft (5) so that the workpiece (7) is completely immersed in the polishing medium (8); Step 3: Connect the positive electrode of the pulse power supply (1) to the connecting shaft (5) through a wire, and connect the negative electrode of the pulse power supply (1) to the polishing tank (2) through a wire, so that the pulse power supply (1), the connecting shaft (5), the workpiece (7), the polishing medium (8), the polishing tank (2) and the wire form a closed circuit; Step 4: The multi-dimensional coupling vibration device (4) is fixedly connected to the polishing tank (2) via the insulating connector (3), and the vibration frequency and amplitude as well as the voltage, duty cycle and frequency of the pulse power supply are set; Step 5: The polishing medium (8) is subjected to the directional vibration of the multi-dimensional coupling vibration device (4), generating shear motion on a specific surface of the workpiece (7), inducing the dispersed medium (8-2) and the dispersed phase (8-5) to rapidly generate a clustering effect at the micro-convex peaks on the surface of the workpiece (7) in the polishing area, generating flexible particle clusters. The electrolyte (8-1) and the abrasive are entrained in the generated particle clusters due to the clustering effect. Under the drive of the intermittent pulse electric field, a soft oxide film (9) is intermittently generated at the micro-convex peaks on the surface of the workpiece (7) in the polishing area. The flexible particle cluster removes the oxide film (9) in the form of a plow, and the oxide film (9) is repeatedly generated and gradually removed, thereby achieving the required polishing quality and realizing efficient localized lossless ultra-smooth polishing of the workpiece (7).

2. The pulsed electrochemical mechanical composite polishing method according to claim 1, characterized in that: The dispersion medium (8-2) is selected from deionized water or alcohol compounds; the dispersion phase (8-5) is selected from hydroxypropyl starch or silicon dioxide; the electrolyte (8-1) is selected from sodium chloride or sodium nitrate; the additive (8-6) includes sodium polyacrylate and sodium molybdate; the abrasive includes grade I abrasive (8-3) and grade II or grade III abrasive (8-4), and grade I 1-10 μm, grade II 10-500 μm and grade III 500-2000 μm diamond and aluminum oxide are selected.

3. The pulsed electrochemical mechanical composite polishing method according to claim 2, characterized in that: The class I abrasive (8-3) removes shallow scratches and deformation layers on the surface, and the flexible particle clusters entrain class II abrasives or class III abrasives (8-4) to remove oxide films (9).

4. The pulsed electrochemical mechanical composite polishing method according to claim 3 is characterized in that: The multi-dimensional coupling vibration device 4 uses electromagnetic vibration or mechanical vibration, which can realize six-degree-of-freedom coupling vibration in space, change the amplitude and direction of the multi-dimensional coupling vibration device, and then continuously change the polishing force of the polishing area.

5. The pulsed electrochemical mechanical composite polishing method according to claim 1, characterized in that: In step 4, the vibration frequency and amplitude are set, and the shearing motion of the surface of the workpiece (7) is used to induce the clustering effect of the dispersion medium (8-2) and the dispersed phase (8-5), thereby controlling the concentration of the electrolyte (8-1) in the polishing area, regulating the generation rate of the oxide film (9) in the polishing area, regulating the thickness of the oxide film (9), and thus controlling the surface hardness of the processing area.

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