Electric spark and electrolysis combined machining method for long and narrow slit structure

Abstract

The invention discloses an electric spark and electrolysis combined machining method for a long and narrow slit structure, and particularly relates to the technical field of electric spark and electrolysis machining. The method comprises the following steps that a workpiece is installed on a tool setting of an electric spark machining electrode wire; the electric spark machining electrode wire performs feeding motion in an XY plane; tool setting is conducted on the machined workpiece and the electrolytic machining linear electrode; turning on a power supply and an electrolysis control system, and carrying out secondary processing; the electrolytic machining linear electrode does feeding motion on a preset track in an XY plane; and after secondary machining is completed, the power source is disconnected, the electrolyte circulating system is closed, the electrolytic machining linear electrode and the workpiece are detached, the electrolytic machining linear electrode and the workpiece are cleaned, and machining is completed. By the adoption of the technical scheme, the problem that high-quality machining of the ultra-thin sheet-shaped long and narrow slit structure is difficult to achieve through an existing machining method is solved, and the machining quality and efficiency of the ultra-thin sheet-shaped long and narrow slit structure are improved.

Description

Technical Field

[0001] The invention relates to the technical field of electric spark electrolytic machining, and in particular to an electric spark electrolytic combined machining method for a long narrow slot structure. Background Art

[0002] With the continuous improvement of the process of industrial modernization, various high-end manufacturing technology fields have higher and higher requirements for the performance of metal materials. In the fields of aerospace, automobile manufacturing, weapons and equipment, etc., high-temperature alloys, titanium alloys, aluminum-based composite materials and other difficult-to-process materials have been increasingly used. In the field of aerospace, thin-walled parts refer to parts with a wall thickness to height ratio in the range of 1 / 5 to 1 / 8. If it is less than this value, it can be called an ultra-thin wall part. In the design structure of aviation parts, there are a large number of ultra-thin sheet parts. Thin sheet parts are widely used in aircraft engine rotors, flexible pendulum accelerometers, laser gyroscopes and platform inertial navigation. For example, the contact fingertip seal structure in the engine rotor, the pendulum in the accelerometer, the gasket in the gyroscope, etc. The assembly accuracy of many tiny precision devices needs to be better than 25 to 30μm. Taking the fingertip seal structure as an example, its wall thickness to height ratio has even reached 1 / 50 or less. Compared with general thin-walled parts, its processing is more difficult, especially in the finishing stage, the rigidity of the workpiece or structure is already very poor. High-precision and rapid processing and manufacturing of such parts is of great benefit to improving product quality and production capacity.

[0003] At present, for various difficult-to-process ultra-thin sheet structures of metal materials, the existing processing technologies mainly include precision forging, CNC precision milling, partition cycle layer-by-layer cutting, etc. However, the following common problems are prone to occur in the precision processing stage: the ultra-thin workpiece is subjected to the clamping force and cutting force to produce elastic tool release, causing large size and shape errors; the workpiece has poor processing stability, and elastic flutter is generated when subjected to cutting force, resulting in the inability to process normally, causing the surface quality of the workpiece to fail to meet the design requirements. The main optimization methods currently include optimizing the tool processing path, tool position compensation, designing a special vibration suppression fixture, and optimizing the CNC system program design. However, based on the consensus of industry practitioners, there is no non-contact special processing method for ultra-thin sheet long narrow slit structures. How to achieve precise, high-quality, efficient and low-cost processing for ultra-thin sheet long narrow slit structures has become a difficult problem in the industry. Therefore, it is necessary to propose an innovative processing method for ultra-thin sheet long narrow slit structures of difficult-to-process metal materials to promote the further application of special processing technology. Summary of the invention

[0004] The present invention aims to provide a method for combined electric spark electrolysis machining of a long narrow slot structure, which solves the problem that the existing machining methods are difficult to achieve high-quality machining of ultra-thin sheet-like long narrow slot structures.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows: a method for combined electric spark electrolysis machining of a long narrow slit structure, comprising the following steps:

[0006] S1. Load the workpiece to be processed into the EDM system and complete the tool alignment between the workpiece to be processed and the EDM electrode wire;

[0007] S2, turning on the coolant circulation system to cool the workpiece to be processed, turning on the power supply and the EDM control system, and the EDM electrode wire feeds along a predetermined trajectory in the XY plane to complete the preliminary processing;

[0008] S3, turn off the power supply and remove the workpiece that has been preliminarily processed from the EDM system;

[0009] S4, open the electrolyte circulation system, connect the workpiece that has completed the preliminary processing to the positive pole of the power supply, connect the electrolytic processing linear electrode to the negative pole of the power supply, and complete the tool alignment between the workpiece and the electrolytic processing linear electrode; turn on the power supply and the electrolytic control system for secondary processing; the electrolytic processing linear electrode performs feed motion along a predetermined trajectory in the XY plane;

[0010] S5. After the secondary processing is completed, the power supply is disconnected, the electrolyte circulation system is closed, the electrolytic processing linear electrode and the workpiece are removed, the electrolytic processing linear electrode and the workpiece are cleaned, and the processing is completed.

[0011] Furthermore, in steps S2 and S4, the coolant and the electrolyte are supplied by external spraying and are sprayed out from the spray holes below the multiple nozzles.

[0012] Through the above settings, the liquid supply methods are mainly divided into external spraying and internal spraying. Compared with the internal spraying method, the external spraying method reduces the cost. The traditional wire electrode processing requires pre-grooving holes inside the workpiece, which will increase the processing cost. The external spraying method is beneficial to the discharge of products in the processing area, thereby improving the processing localization and processing quality.

[0013] Furthermore, the operating voltage range in step S2 and step S4 is controlled within 20-25V.

[0014] Through the above settings, the voltage will affect the width of the processed seam. Through multiple experiments to study the influence of processing voltage on electrolytic processing, it is found that increasing the voltage can significantly increase the seam width, and the voltage of 20-25V can meet the gap processing requirements.

[0015] Furthermore, the feed speed range of step S4 is set to 2.0 mm / min-20.0 mm / min.

[0016] Through the above settings, the seam width decreases with the increase of feed speed. If low-speed feeding is adopted, more material can be removed per unit time, and vice versa. After the voltage is controlled, the feed speed within this range can achieve the processed seam width. However, in order to improve the processing efficiency, the feed speed can be set to 20.0mm / min.

[0017] Furthermore, in step S4, the initial machining gap between the workpiece and the electrolytic machining linear electrode is 150 μm.

[0018] Through the above settings, there is a certain relationship between the initial processing gap and the diameter length of the wire electrode, so the initial gap is determined according to the electrode diameter; under this gap condition, the corresponding seam width can be processed.

[0019] Furthermore, the EDM electrode wire and the electrolytic machining wire electrode are both made of stainless steel, and the wire diameter is 0.3 mm.

[0020] Through the above settings, the selection of electrodes of the same material can reduce costs, and the stainless steel material is not easily corroded when immersed in coolant and electrolyte; the selection of electrodes of this diameter meets the seam width design requirements. If the diameter is too large, the processing seam width is too large; otherwise, the seam width is too small.

[0021] Furthermore, the material of the workpiece to be processed is high temperature alloy GH536, and the thickness does not exceed 150 μm.

[0022] Compared with the prior art, this solution has the following beneficial effects:

[0023] 1. This solution solves the problem in the prior art that ultra-thin sheet structures with a thickness of less than 150μm are prone to elastic chatter and residual stress in the cutting processing method. This solution uses a two-step process. During the processing, electric spark wire cutting is first used to remove large excesses, and then wire electrode electrolytic processing is used to perform size finishing and remelting layer removal. The points on the long and narrow slit structure can obtain a surface with good processing quality after combined processing, and finally a multi-channel long and narrow slit structure with an aspect ratio of more than 100 is processed.

[0024] 2. This solution aims at the problem that the ultra-thin sheet metal workpiece is subjected to the clamping force and cutting force at the same time, which causes the elasticity of the cutter and the elastic flutter, resulting in the inability to process normally, and the surface quality of the workpiece does not meet the design requirements. The present invention proposes an electrospark-electrolysis combined processing method. In the process of completing the preliminary material removal in the first process, the electrode wire has no contact with the workpiece to be processed throughout the process, and there is no problem of elastic flutter caused by the cutting force. The preliminary material removal of the ultra-thin sheet metal material that is difficult to process can be completed quickly. The heat-affected zone and the remelting layer generated by the first process can be very effectively removed by the second process. If only electrospark slow wire cutting is used, although there is flushing of coolant, there will still be a relatively serious heat-affected zone in the processing area. And through the electrospark-electrolysis combined processing method proposed by the present invention, it can be seen in the subsequent embodiments that the long and narrow groove structure finally processed by this method has the same crystal structure and element composition as the unprocessed area, has good physical properties, and does not affect the performance of the processing area after processing.

[0025] 3. The EDM electrode wire and the linear electrolytic machining cathode structure of this scheme are very simple, with a short manufacturing cycle, low processing cost, and easy assembly and disassembly; any conductive metal material can be removed through arc ablation and electrochemical anode removal, which improves the scope of application of the innovative processing method of the present invention.

[0026] 4. In the combined processing process using this solution, the CNC system controls the feed motion of the linear processing electrode and the linear processing cathode to form the contour generating line, which has the characteristics of high processing flexibility, high processing efficiency, low tool cost, and high processing stability. Compared with the CNC machine tool processing of ultra-thin sheet metal parts, the technology of using the combined electrospark-electrolysis processing of long narrow slits proposed in the present invention is easier to design and replace the cathode, which can better ensure the flatness and verticality of the structure obtained by processing, and there is no influence of the remelting layer and the heat-affected zone. There is no problem of suppressing elastic flutter and elastic tool yielding during processing, which can improve the processing efficiency of parts of difficult-to-cut materials, reduce costs, and shorten the processing cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the contact fingertip seal structure mentioned in the background technology;

[0028] Figure 2 It is a schematic diagram of workpiece changes in an electrospark electrolytic combined machining method of a long narrow slit structure of the present invention;

[0029] Figure 3 This is a microscopic morphology image of the workpiece magnified 1000 times using a scanning electron microscope after preliminary processing in the embodiment;

[0030] Figure 4This is a 35-fold magnified macroscopic morphology image of the long narrow slit structure after preliminary processing in the embodiment;

[0031] Figure 5 yes Figure 3 The elemental composition diagram obtained by elemental spectrum analysis at two different positions in the

[0032] Figure 6 This is a microscopic morphology image of the workpiece in the embodiment after secondary processing using a scanning electron microscope to magnify it 1000 times;

[0033] Figure 7 This is a macroscopic morphology image of the long narrow slit structure after secondary processing in the embodiment, which is magnified 35 times;

[0034] Figure 8 is a practical schematic diagram of the long narrow slit structure after secondary processing in the embodiment;

[0035] Fig. 9 yes Figure 6 The elemental composition diagram obtained by elemental energy spectrum analysis at two different positions in the image. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below through specific embodiments:

[0037] Example

[0038] The ultra-thin sheet long narrow slit structure targeted by this embodiment is Figure 1 For example, Figure 1 This is a schematic diagram of a typical ultra-thin sheet-like long narrow slit structure - a contact fingertip seal structure. Figure 1 It can be seen that the thickness of the metal part is 0.20mm, and there are multiple long narrow slit structures with complex shapes on it. The entrance width of the long narrow slit structure is 0.40mm, and the width of the curved section is only 0.16mm.

[0039] The electric spark electrolytic combined machining method of a long narrow gap structure of the present embodiment comprises the following steps:

[0040] S1. Load the workpiece to be processed into the EDM system and align the workpiece to be processed with the EDM electrode wire. In this embodiment, the EDM electrode wire is made of stainless steel with a wire diameter of 0.3 mm. The material of the workpiece to be processed is high-temperature alloy GH536 with a thickness not exceeding 150 μm.

[0041] S2. Turn on the coolant circulation system to cool down the workpiece to be processed. In this embodiment, the coolant is supplied by external spraying, and is sprayed from the spray holes under the multiple coolant nozzles. The purpose of supplying coolant is to fill the space between the EDM electrode wire and the workpiece to be processed with coolant by circulating coolant flushing. In the field of special processing, the use of coolant flushing can fully flush away the products in the processing area and improve the quality of the structure obtained by workpiece processing. Then turn on the power supply and the EDM control system, and the working voltage range is controlled at 20-25V. The EDM electrode wire feeds along a predetermined trajectory in the XY plane to complete the preliminary processing.

[0042] S3. Turn off the power supply, remove the workpiece that has completed preliminary processing from the EDM system, clean the workpiece with anhydrous ethanol and an ultrasonic cleaner to remove the coolant on the surface of the workpiece.

[0043] S4. Connect the workpiece that has completed the preliminary processing to the positive pole of the power supply, connect the electrolytic machining linear electrode to the negative pole of the power supply, and complete the tool alignment between the workpiece and the electrolytic machining linear electrode. In this embodiment, the initial processing gap between the workpiece and the electrolytic machining linear electrode is 150μm, and the electrolytic machining linear electrode material is stainless steel with a wire diameter of 0.3mm. Turn on the electrolyte circulation system, use an external liquid spraying method to fill the space between the wire-shaped electrolytic machining cathode and the workpiece to be processed with electrolyte, then turn on the power supply and electrolytic control system for secondary processing, and the working voltage range is controlled at 20-25V; the electrolytic machining linear electrode feeds along a predetermined trajectory in the XY plane, and the feed speed range is set to 2.0mm / min-20.0mm / min. Use secondary processing to complete the removal of the remelting layer and fine processing of long narrow slits.

[0044] S5. After completing the secondary processing, disconnect the power supply, close the electrolyte circulation system, remove the electrolytically processed linear electrode and workpiece, and use anhydrous ethanol and an ultrasonic cleaner to clean the electrolytically processed linear electrode and workpiece. The processing is completed. The purpose of cleaning is to remove the electrolyte and residual electrolysis products on the workpiece and cathode surface for subsequent storage and use for further research.

[0045] Figure 2 The figure is a schematic diagram of the related changes that occur when the workpiece is processed by the processing method of this embodiment. The diameter of the EDM electrode wire used in this embodiment is 0.3mm, and the material is 316L stainless steel; the thickness of the ultra-thin workpiece to be processed in the embodiment of the present invention is 0.30mm, and the material is GH536 high-temperature alloy. The EDM electrode wire feeds along a given trajectory along the XY direction on the ultra-thin sheet part to be processed. As the processing proceeds, due to the large amount of arcs and heat generated during the EDM process, remelting layers and ablation pits will appear on both sides of the long and narrow grooves, such as Figure 3 The part marked with dotted lines is shown in FIG.

[0046] By using a scanning electron microscope (Hitachi Regulus 8100, Tokyo, Japan) to observe the remelted layer at a magnification of 1000 times, it can be seen that there is no obvious grain structure and intergranular boundary at the yellow dotted line. Based on the general consensus in this field, this is the remelted layer formed by the arc and heat action of the base GH536 material. Figure 5 As shown, two sampling points, point A (in the remelting layer) and point B (non-remelting layer), were selected for element spectrum detection. The mass fraction percentage of C element at point A was 53.05%, the mass fraction percentage of O element was 8.25%, and the mass fraction percentages of Ni element, Fe element, and Cr element belonging to the GH536 matrix did not exceed 25%. The mass fraction percentage of C element at point B was 21.44%, and the O element was not detected. The mass fraction percentage of Ni element belonging to the GH536 matrix was 52.24%, the mass fraction percentage of Fe element was 17.70%, and the mass fraction percentage of Cr element was 18.23%. It can be seen that the closer to the remelting layer area, the higher the proportion of C element and O element, and the less the proportion of metal elements belonging to the matrix. This will cause the physical properties of the remelting layer area to deteriorate, the structure to become loose, and affect the final processing quality of the long narrow slit structure. Figure 4 This is a 35-fold magnified macroscopic image of the long narrow slit structure after preliminary processing; Figure 4 As shown in the figure, the long narrow slit structure after preliminary processing is affected by the remelting layer and ablation pits, and there is a need to further improve the processing quality.

[0047] pass Figure 2 In the processing process of step 4, the workpiece to be processed in this embodiment is further processed. The electrolytic salt solution used in the electrolytic processing in this embodiment is a sodium chloride electrolytic salt solution with a mass fraction of 20%; the diameter of the linear electrode used in the electrolytic processing is 0.2 mm, and the material is 316L stainless steel; the linear electrode used in the electrolytic processing continues to feed along the XY direction on the workpiece that has completed the preliminary processing. A given trajectory.

[0048] The workpiece of the embodiment was observed at 1000 times magnification using a scanning electron microscope (Hitachi Regulus 8100, Tokyo, Japan). Figure 6 shown. Figure 6 and Figure 3 Compared with , there is no longer a remelted layer with no obvious grain structure and intergranular boundary area. Figure 6 Select two sampling points, point C (close to the processing surface) and point B (far away from the processing surface), to perform element spectrum detection. The results are as follows: Fig. 9As shown. At point C, the mass fraction percentage of C element is 2.95%, the mass fraction percentage of O element is 0.32%, the mass fraction percentage of Ni element belonging to the GH536 matrix is ​​53.73%, the mass fraction percentage of Fe element is 18.23%, and the mass fraction percentage of Cr element is 22.06%. At point D, the C element and O element were not detected, and the mass fraction percentage of Ni element belonging to the GH536 matrix is ​​52.34%, the mass fraction percentage of Fe element is 18.12%, and the mass fraction percentage of Cr element is 19.23%. It can be seen from the results of element energy spectrum detection that after secondary processing, the original remelting layer structure has been completely removed, and the long narrow slit structure obtained by processing has the same element composition and crystal structure in the processing area and the non-processing area, and there is no problem affecting the physical properties and structural strength. Figure 7 This is a 35-fold magnified macroscopic morphology of the long narrow slit structure after secondary processing; Figure 7 and Figure 8 As shown, the long narrow slit structure processed by the method proposed in the present invention has high surface quality and good size controllability, which can meet the processing requirements of long narrow slit structures of ultra-thin sheet-shaped difficult-to-process metal materials. Compared with traditional laser cutting and ultra-precision wire cutting methods, the method proposed in the present invention overcomes the defects of the traditional laser cutting and ultra-precision wire cutting methods and improves the quality of the product; traditional laser cutting has high cost and cutting material restrictions, laser cutting will produce heat effects in the cutting area, and its cutting speed is slow, thus affecting the processing efficiency; while the ultra-precision wire cutting processing speed is slow, resulting in low processing efficiency and low surface quality.

[0049] The electric spark electrolysis combined processing method for the long narrow slot structure of ultra-thin sheet-like difficult-to-process metal materials proposed in the present invention can realize non-contact processing of the long narrow slot structure of ultra-thin sheet-like difficult-to-process materials through a special processing combined processing method, and finally obtain a long narrow slot structure that meets the design requirements and is not affected by cutting stress, elastic deformation, remelting layer, etc. on the ultra-thin sheet metal parts, thereby increasing the processing flexibility and operability.

[0050] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and / or characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for combined electric spark electrolysis machining of a long narrow gap structure, characterized in that: The following steps are involved: S1. Load the workpiece to be processed into the EDM system and complete the tool alignment between the workpiece to be processed and the EDM electrode wire; S2, turning on the coolant circulation system to cool the workpiece to be processed, turning on the power supply and the EDM control system, and the EDM electrode wire feeds along a predetermined trajectory in the XY plane to complete the preliminary processing; S3, turn off the power supply and remove the workpiece that has been preliminarily processed from the EDM system; S4, open the electrolyte circulation system, connect the workpiece that has completed the preliminary processing to the positive pole of the power supply, connect the electrolytic processing linear electrode to the negative pole of the power supply, and complete the tool alignment between the workpiece and the electrolytic processing linear electrode; turn on the power supply and the electrolytic control system for secondary processing; the electrolytic processing linear electrode performs feed motion along a predetermined trajectory in the XY plane; S5. After the secondary processing is completed, the power supply is disconnected, the electrolyte circulation system is closed, the electrolytic processing linear electrode and the workpiece are removed, the electrolytic processing linear electrode and the workpiece are cleaned, and the processing is completed.

2. The method for combined electrospark electrolytic machining of a long narrow slit structure according to claim 1, characterized in that: In steps S2 and S4, the coolant and the electrolyte are supplied by external spraying and are sprayed from the spray holes below the multiple nozzles.

3. The method for combined electrospark electrolytic machining of a long narrow slit structure according to claim 1, characterized in that: In step S2 and step S4, the operating voltage range is controlled within 20-25V.

4. The method for combined electrospark electrolytic machining of a long narrow slit structure according to claim 3, characterized in that: The feed speed range of step S4 is set to 2.0 mm / min-20.0 mm / min.

5. The method for combined electrospark electrolytic machining of a long narrow slit structure according to claim 3, characterized in that: In step S4, the initial machining gap between the workpiece and the electrolytic machining linear electrode is 150 μm.

6. The method for combined electrospark electrolytic machining of a long narrow slit structure according to claim 1, characterized in that: The EDM electrode wire and the electrolytic machining wire electrode are both made of stainless steel, and the wire diameter is 0.3 mm.

7. The method for combined electrospark electrolytic machining of a long narrow slit structure according to claim 6, characterized in that: The material of the workpiece to be processed is high temperature alloy GH536, and the thickness does not exceed 150 μm.

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