A method for processing diaphragm cutting knife by electric spark and femtosecond laser

Abstract

The application relates to a combined machining method of electric spark and femtosecond laser for machining a diaphragm cutter, which comprises the following steps: firstly, electric spark grinding machining is carried out on a cutter blank, so that the cutter blank obtains a machining surface with preset precision; secondly, electric spark forming machining is carried out on the ground cutter blank, and the excess part outside the cutter blade part of the cutter blank is removed; finally, the cutter blade of the cutter blank after the electric spark forming machining is machined by using the femtosecond laser, and the diaphragm cutter meeting the precision requirement is obtained. The application provides a high-precision machining method of the diaphragm cutter, the diaphragm cutter is used to form diaphragm marks with certain depth on the diaphragm under the action of the punching force of a machine tool, the machining precision of the diaphragm marks is improved, and the consistency and reliability of the diaphragm are ensured.

Description

Technical Field

[0001] This invention belongs to the field of rocket engine diaphragm processing technology, and relates to a combined electrical discharge machining and femtosecond laser machining method for processing diaphragm engraving tools. Background Technology

[0002] The diaphragm is a crucial component in the starting system of a liquid rocket engine, primarily used to isolate the liquid, gas, and high-temperature combustion gases within the container or tank from upstream and downstream pipelines. To control the diaphragm's rupture pressure and location, and to prevent debris shedding upon rupture, pre-formed notches of a specific shape are typically created on the diaphragm. Currently, diaphragm notches are often machined directly at predetermined locations on the diaphragm using a stamping process, resulting in poor consistency and reliability of the notches. Therefore, a diaphragm notching tool is needed to create notches of a certain depth on the diaphragm under the pressure of a machine tool, thereby improving the machining accuracy, consistency, and reliability of the notches.

[0003] Most engraving tools are now manufactured using CNC milling. Since diaphragm engraving tools are mostly made of difficult-to-machine materials such as titanium alloys and stainless steel, the cutting resistance of the tool is relatively large when using CNC milling, resulting in severe tool wear and seriously affecting the machining accuracy of the diaphragm engraving tool. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a combined EDM and femtosecond laser machining method for processing diaphragm cutting tools. The EDM method is used to remove most of the excess material from the diaphragm cutting tool, and the femtosecond laser is used to perform fine machining on the cutting edge of the diaphragm cutting tool. Since the EDM and femtosecond laser are not affected by the mechanical properties of the material during processing, no tool wear will occur during the machining of the cutting edge of the diaphragm cutting tool, thereby maintaining the machining accuracy of the cutting edge.

[0005] The solution of this invention is: a combined EDM and femtosecond laser machining method for processing diaphragm cutting tools, comprising three processes: EDM grinding, EDM forming, and femtosecond laser machining.

[0006] First, the engraving blank is subjected to electrical discharge grinding to obtain a machined surface with a preset precision. Second, the ground engraving blank is subjected to electrical discharge forming to remove excess material outside the cutting edge. Finally, the cutting edge of the engraving blank after electrical discharge forming is machined using a femtosecond laser to obtain a diaphragm engraving blade that meets the precision requirements.

[0007] Furthermore, the same set of EDM forming machine tool is used for both EDM grinding and EDM forming, and the EDM forming machine tool includes a pulse power supply, a machine tool spindle, and a working fluid tank;

[0008] The engraving blank is mounted on the spindle of the EDM machine tool and connected to the negative terminal of the pulse power supply through the spindle; the EDM electrode is immersed in the working fluid tank and connected to the positive terminal of the pulse power supply.

[0009] Furthermore, the electrical discharge electrode is made of POCO graphite.

[0010] Furthermore, the electrical discharge electrode is machined with an electrode grinding surface and a contoured electrode end face.

[0011] Furthermore, the contoured electrode end face is processed using an electrical discharge wire cutting method to create the shaped texture of the diaphragm cutting tool.

[0012] Furthermore, before the electrical discharge machining (EDM) process, the engraving blank is aligned with a dial indicator to ensure that the perpendicularity of the engraving blank is within 0.001mm and the coaxiality between the engraving blank and the electrode grinding surface is within 0.001mm.

[0013] Furthermore, during electrical discharge machining, the process parameters set on the electrical discharge forming machine tool include: grinding amount on the end face of the engraving tool blank is 0.1-0.3 mm, discharge gap is 0.07-0.09 mm, and surface roughness is 0.67-1.6 μm.

[0014] Furthermore, during electrical discharge machining (EDM), the process parameters set on the EDM machine tool include: a forming depth of 0.5–1.5 mm, a discharge gap of 0.07–0.09 mm, and a surface roughness of 0.67–1.6 μm.

[0015] Furthermore, the femtosecond laser processing involves layering the pre-set cutting depth, with each layer having a processing depth of 0.002–0.01 mm, thereby determining the number of layers.

[0016] Furthermore, during femtosecond laser processing, material is removed from the cutting edge by scanning layer by layer according to the set layer depth and number of layers. During scanning, the scanning path of the femtosecond laser is expanded by 0.05 to 0.15 mm on each side.

[0017] The advantages of this invention compared to the prior art are:

[0018] (1) In this invention, the removal of most of the excess material of the diaphragm cutting tool can be achieved by electrical discharge machining, which can reduce the amount of femtosecond laser processing and improve the preparation efficiency of the diaphragm cutting tool.

[0019] (2) The present invention mainly uses two methods to ensure the final forming accuracy: First, the end face with high precision is obtained by electrical discharge grinding; second, during the femtosecond laser forming process, the 0.25mm allowance is layered with a thickness of 0.002-0.01mm, and the cutting edge of the film is processed by scanning layer by layer to ensure that the final forming accuracy can reach ±0.005mm.

[0020] (3) The cutting edge of the engraving knife of the present invention is divided into an electrical discharge machining area and a femtosecond laser fine engraving area. The manufacturing accuracy of the diaphragm engraving knife is guaranteed by both electrical discharge machining and femtosecond laser processes. The combination of the two processes ensures the overall manufacturing accuracy of the diaphragm engraving knife, reducing the difficulty of engraving knife processing and reducing processing costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the electrical discharge grinding process according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the electrical discharge machining process according to an embodiment of the present invention;

[0023] Figure 3 The die cutter for the diaphragm after electrical discharge machining in an embodiment of the present invention;

[0024] Figure 4 The cutting edge of the diaphragm after femtosecond laser processing in an embodiment of the present invention;

[0025] Figure 5 This is a flowchart of the processing method according to an embodiment of the present invention.

[0026] In the diagram: 1-Pulse power supply, 2-Machine tool spindle, 3-Cut tool blank, 4-EDM electrode, 5-Working fluid tank. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figure 5 As shown, the combined EDM and femtosecond laser processing method in this embodiment can be divided into three processes: EDM grinding, EDM forming, and femtosecond laser processing.

[0029] First, such as Figure 1 As shown, the engraving blank 3 is mounted on the spindle 2 of the EDM machine, and is connected to the negative terminal of the pulse power supply 1 of the EDM machine via the spindle 2. In this embodiment, the EDM machine used is a Form series EDM machine.

[0030] The electrical discharge electrode 4 is made of fine-grained POCO graphite (3μm). The middle of the upper end face of the electrical discharge electrode 4 is the electrode grinding surface. The left and right sides of the electrical discharge electrode 4 are machined with contoured electrode end faces. The contoured electrode end faces are machined with the electrical discharge slow wire cutting method to form the shaped texture of the diaphragm scriber.

[0031] During electrical discharge machining (EDM), the engraving blank 3 is machined on the upper end of the electrode grinding surface. The parallelism between the electrode grinding surface and the X-axis of the EDM forming machine tool is within 0.002 mm. The EDM electrode 4 is placed in the machine tool's working fluid tank 5 and connected to the positive terminal of the machine tool's pulse power supply 1. Negative polarity machining is used to improve the grinding accuracy and surface quality of the end face of the engraving blank 3. When performing electrical discharge grinding on the end face of the engraving blank 3, firstly, the engraving blank 3 is aligned using a dial indicator to ensure that its perpendicularity is within 0.001mm and its coaxiality with the electrode grinding surface is within 0.001mm. Secondly, the machine tool spindle 2 rotates at a speed of 10-15 r / min, thereby driving the engraving blank 3 to rotate. During rotation, the engraving blank 3 will generate pulsed discharges with the electrical discharge electrode 4. During the machining process, the engraving blank 3 rotates and performs Z-axis feed motion under the drive of the machine tool spindle 2. The process parameters for machine tool grinding include: grinding amount on the workpiece end face of 0.1-0.3mm, discharge gap of 0.08mm, and surface roughness after grinding of 0.67-1.6μm. When the high point on the engraving blank 3 rotates to the point where the distance between it and the electric spark electrode 4 reaches the discharge gap, the high point on the engraving blank 3 is removed by discharge erosion, thereby realizing the electric spark grinding of the end face of the engraving blank and ensuring the processing quality and precision of the end face.

[0032] Next, the engraving blank 3 is subjected to electrical discharge machining (EDM). During EDM, the engraving blank 3 is machined above the contoured electrode end faces on both sides of the EDM electrode 4. For example... Figure 2 As shown, the EDM electrode 4 is installed in the working fluid tank 5 of the EDM forming machine tool, and the positive terminal of the pulse power supply 1 is connected to it. The engraving blank 3, which has been EDM ground, and the contoured electrode end faces on the left and right sides of the electrode 4 are subjected to EDM forming under the action of the pulse power supply 1. The process parameters for forming of the machine tool are set as follows: forming depth is 1 mm, EDM discharge gap is 0.08 mm, and surface roughness is 0.67-1.6 μm. Figure 3 The middle image shows the diaphragm cutting tool after EDM (Electrical Discharge Machining). The tip of the tool was not machined after EDM. EDM is mainly used to quickly remove excess material.

[0033] Finally, the cutting edge of the diaphragm scriber is processed using a femtosecond laser. The depth of the femtosecond laser processing on the cutting edge is 0.25 mm. To ensure the final forming accuracy of the diaphragm scriber, a layer-by-layer scanning method is used to remove material. The 0.25 mm processing depth is divided into layers. The thickness of each layer is selected within the range of 0.002 to 0.01 mm based on the actual processing accuracy of the cutting edge, thus determining the number of layers. During femtosecond laser processing, the material on the cutting edge is removed layer by layer according to the set scanning thickness and number of scanning layers. To ensure thorough material removal, in this embodiment, the scanning path of the femtosecond laser is expanded by 0.1 mm on each side during scanning. Figure 4 This is a cutting tool for a membrane after it has been processed by a femtosecond laser.

[0034] The diaphragm cutting tool obtained by the method of the present invention forms diaphragm markings of a certain depth on the diaphragm under the action of machine tool punching pressure.

[0035] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. An electro-discharge, femtosecond laser integrated machining method for processing diaphragm cutting knives, characterized in that, The process comprises electrical discharge grinding, electrical discharge forming and femtosecond laser processing. First, the electrical discharge grinding is performed on the cutter blank to obtain a preset precision processing surface; second, the electrical discharge forming is performed on the ground cutter blank to remove the excess part of the cutter blade; and finally, the femtosecond laser is used to process the cutter blade of the cutter blank after the electrical discharge forming to obtain a diaphragm cutter meeting the precision requirements. The electrical discharge grinding and the electrical discharge forming use the same electrical discharge forming machine tool, which comprises a pulse power source, a machine tool spindle and a working liquid tank. The cutter blank is mounted on the machine tool spindle of the electrical discharge forming machine tool and connected to the negative pole of the pulse power source; the electrical discharge electrode is immersed in the working liquid tank and connected to the positive pole of the pulse power source. The upper end surface of the electrical discharge electrode is the electrode grinding surface, and the left and right sides of the electrical discharge electrode are the profiled electrode end surfaces. During the electrical discharge grinding, the cutter blank is processed on the upper end of the electrode grinding surface; during the electrical discharge forming, the cutter blank is processed above the profiled electrode end surfaces on the left and right sides of the electrical discharge electrode. The profiled electrode end surfaces are processed by the electrical discharge slow wire cutting method to form the forming lines of the diaphragm cutter.

2. The method according to claim 1, wherein the method is characterized by, The electrical discharge electrode is made of POCO graphite.

3. The method according to claim 1, wherein the method is characterized by, Before the electrical discharge grinding, the cutter blank is aligned by using a dial indicator to ensure that the perpendicularity of the cutter blank is within 0.001 mm and the coaxiality of the cutter blank and the electrode grinding surface is within 0.001 mm.

4. The method according to claim 1, wherein the method is characterized by, During the electrical discharge grinding, the process parameters of the electrical discharge forming machine tool include: the cutter blank end surface grinding amount is 0.1-0.3 mm, the discharge gap is 0.07-0.09 mm, and the surface roughness is 0.67-1.6 μm.

5. The method according to claim 1, wherein the method is characterized by, During the electrical discharge forming, the process parameters of the electrical discharge forming machine tool include: the forming processing depth is 0.5-1.5 mm, the discharge gap is 0.07-0.09 mm, and the surface roughness is 0.67-1.6 μm.

6. The method according to claim 1, wherein the method is characterized by, The preset blade processing depth is processed layer by layer by the femtosecond laser, and the processing depth of each layer of the femtosecond laser is 0.002-0.01 mm, thereby determining the number of layers.

7. The method according to claim 6, wherein the method is characterized by, The femtosecond laser scans and removes the material of the blade part layer by layer according to the set layering depth and the number of layers, and the scanning path of the femtosecond laser is expanded by 0.05-0.15 mm on one side during scanning.

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