Integrated Femtosecond Laser Hybrid Machining Method for the Pendulum Assembly of a Quartz Flexible Accelerometer

Abstract

The present invention discloses a femtosecond laser composite processing method for the integrated pendulum assembly of a quartz flexible accelerometer, which includes: Step 1, turning a quartz cylindrical blank to machine two cylindrical convex structures on both sides to obtain a pendulum plate; Step 2, using femtosecond laser to process the pendulum plate to remove the middle part of the two cylindrical convex structures to obtain a framework; Step 3, using femtosecond laser to process a through hole in the center of the pendulum plate; Step 4, polishing the pendulum plate; Step 5, irradiating the front and back sides of the pendulum plate with a double-pulse Bessel beam to obtain a modified area penetrating the pendulum plate; Step 6, etching the modified area with an etching solution to obtain a U-shaped through groove; Step 7, using Gaussian laser to process the flexible beam to obtain the integrated structure of the pendulum assembly of the quartz flexible accelerometer. The present invention can realize the integrated processing and forming of the pendulum plate and the framework, reduce the error sources, will not generate residual stress during use, and at the same time has a low temperature cycle influence, high processing accuracy, and good long-term retention.

Description

Technical Field

[0001] The present invention relates to the technical field of detection instruments, and particularly to a femtosecond laser composite processing method for integrating the pendulum assembly of a quartz flexible accelerometer. Background Art

[0002] The sensitive element is not only the core of the capacitive sensor but also a part of the electromagnetic torque generator. Its stability and reliability directly determine the performance of the quartz accelerometer and are the core components of the accelerometer. Due to the hard and brittle nature of the quartz glass material, it is prone to chipping, cracking, and fragmentation during processing, and conventional optical element processing methods cannot be applied, resulting in a very low qualified rate and great processing difficulty.

[0003] The quartz pendulum piece and the two aluminum alloy coil components of the traditional split pendulum part are bonded together by adhesives. The structure of the mixture of multiple media will lead to a high environmental sensitivity coefficient of the sensitive element and unstable output of the accelerometer. At the same time, due to the different curing conditions of the adhesive and the working environment conditions, as well as factors such as the creep of the material, tensile stress or compressive stress will be generated in the pendulum piece and the adhesive layer over time or with temperature changes, causing the parts to deform and have relative displacement, resulting in poor long-term retention.

[0004] Therefore, a femtosecond laser composite processing method for integrating the pendulum assembly of a quartz flexible accelerometer is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a femtosecond laser composite processing method for integrating the pendulum assembly of a quartz flexible accelerometer, aiming to solve or improve at least one of the above technical problems.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a femtosecond laser composite processing method for integrating the pendulum assembly of a quartz flexible accelerometer, including the following steps:

[0007] Step 1: Turn a quartz cylindrical blank to process cylindrical convex structures on both sides to obtain a pendulum piece;

[0008] Step 2: Use femtosecond laser to process the pendulum piece (1) to remove the middle part of the cylindrical convex structures on both sides to obtain a skeleton (3);

[0009] Step 3: Use femtosecond laser to process a through hole in the center of the pendulum piece (1);

[0010] Step 4: Polish the pendulum piece (1);

[0011] Step 5: Irradiate the front and back sides of the pendulum piece with a double-pulse Bessel beam to obtain a modified area penetrating the pendulum piece;

[0012] Step 6: Etch the modified area with an etching solution to obtain a U-shaped through groove;

[0013] Step 7: Process the flexible beam with Gaussian laser to obtain the integrated structure of the pendulum assembly of the quartz flexible accelerometer.

[0014] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexible accelerometer provided by the present invention, in the step 5, a 4f system composed of a 2° cone lens, a 100 mm plano-convex lens, and a 20× objective lens is used to shape the Gaussian beam into a double-pulse Bessel beam in the spatial domain. The double-pulse Bessel beam is focused inside the pendulum plate and irradiates both the front and back sides of the pendulum plate.

[0015] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexible accelerometer provided by the present invention, in the step 5, a flipping fixture is used to fix and rotate the pendulum plate; the double-pulse Bessel beam irradiates both the front and back sides inside the pendulum plate by means of trajectory scanning; when processing the back side, a CCD camera is used to determine the traces of the front side processing, and positioning is performed in cooperation with a high-precision six-axis translation stage, and the repeated positioning accuracy reaches ±5 microns.

[0016] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexible accelerometer provided by the present invention, the specific operation of the step 2 is: using a 20° cone lens to shape the femtosecond Gaussian laser into a long focal-depth Bessel laser, and processing the middle part of the two cylindrical convex structures on both sides to obtain the skeleton.

[0017] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexible accelerometer provided by the present invention, in the step 1, a single-point diamond turning is used for the quartz cylindrical blank; the specific steps are: moving the diamond tool tip to the processing end face of the quartz cylindrical blank, using a rotating motor to drive the three-jaw chuck and the quartz cylindrical blank to rotate, and turning to process a cylindrical convex structure on one side; then re-clamping and processing a cylindrical convex structure on the other side.

[0018] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexible accelerometer provided by the present invention, the specific operation of the step 3 is: using a 20° cone lens to shape the femtosecond Gaussian laser into a long focal-depth Bessel laser, and processing the central through-hole part of the skeleton to obtain a through-hole in the center of the pendulum plate.

[0019] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexible accelerometer provided by the present invention, in the step 4, a CO2 laser is used to polish the surface of the pendulum plate and the inner cavity of the skeleton.

[0020] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexible accelerometer provided by the present invention, in the step 6, the etching solution is a hydrofluoric acid solution with a mass fraction of 5%. The pendulum plate is placed in an ultrasonic vibrator, and the modified contour area is etched away by hydrofluoric acid to obtain a U-shaped through groove.

[0021] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexure accelerometer provided by the present invention, the flipping fixture includes:

[0022] A support base;

[0023] A rotating table, mounted on the support base;

[0024] A fixture assembly, mounted on the rotating table; the pendulum piece is detachably connected to the fixture assembly;

[0025] Wherein, the rotating table is used to drive the fixture assembly to rotate.

[0026] According to the integrated femtosecond laser composite processing method for the pendulum assembly of a quartz flexure accelerometer provided by the present invention, the fixture assembly includes a top plate and a bottom plate; the bottom plate is located directly below the top plate, and the bottom plate is mounted on the rotating table; the top plate and the bottom plate are detachably connected by a bolt assembly; the pendulum piece is press-fitted between the top plate and the bottom plate; gaskets are provided between the pendulum piece and the top plate and between the pendulum piece and the bottom plate.

[0027] The present invention discloses the following technical effects:

[0028] The quartz pendulum assembly of the present invention adopts an integral structure and is integrally processed and formed by turning; both the skeleton and the pendulum piece are made of fused quartz material, without using adhesives, and there is no error caused by the bonding of dissimilar materials; the quartz pendulum assembly will not generate residual stress during use, and at the same time has a low temperature cycle influence and good long-term retention.

[0029] The present invention uses a double-pulse Bessel beam to process the U-shaped through groove and uses a Gaussian laser to process the flexure beam, which significantly improves the processing accuracy of the U-shaped through groove and the flexure beam, improves the surface roughness, and improves the finished product quality. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a structural schematic diagram of the pendulum assembly of the quartz flexure accelerometer of the present invention;

[0032] Figure 2 It is a process flow chart of the processing of the pendulum piece of the present invention;

[0033] Figure 3 It is a structural schematic diagram of the flipping fixture of the present invention;

[0034] Among them, 1. swing piece; 2. flexible beam; 3. framework; 4. top plate; 5. gasket; 7. bottom plate; 8. rotating table; 9. support base. Specific implementation manner

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the protection scope of the present invention.

[0036] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0037] Refer to Figures 1-3 , the present invention provides a femtosecond laser composite processing method for the integrated swing assembly of a quartz flexible accelerometer, including the following steps:

[0038] Step 1: Turn the quartz cylindrical blank to process the cylindrical convex structures on both sides to obtain the swing piece 1.

[0039] Step 2: Use femtosecond laser to process the swing piece 1 to remove the middle part of the cylindrical convex structures on both sides to obtain the framework 3.

[0040] Step 3: Use femtosecond laser to process the through hole in the center of the swing piece 1.

[0041] Step 4: Polish the swing piece 1.

[0042] Step 5: Irradiate the front and back surfaces of the swing piece 1 with double-pulse Bessel beams to obtain a U-shaped modified area penetrating the swing piece 1 and a non-penetrating modified area of the flexible beam part.

[0043] Step 6: Etch the modified area with etching solution to obtain a U-shaped through groove, a rectangular through groove, and four blind grooves in the flexible beam part.

[0044] Step 7: Use Gaussian laser to continue processing the flexible beam 2 to obtain the integrated structure of the swing assembly of the quartz flexible accelerometer; since the thickness of the flexible beam 2 part is only 0.02 mm, after using Bessel laser-assisted etching, and then using Gaussian laser to scan multiple times to process the flexible beam 2 part, the processing depth of a single Gaussian laser scan can be accurately controlled to 10 microns, realizing high-precision processing.

[0045] With such arrangement, the quartz pendulum assembly of the present invention adopts an integrated structure and is integrally formed by turning; the frame 3 and the pendulum piece 1 are both made of fused quartz material, and no adhesive is used, so there is no error caused by bonding of dissimilar materials; the quartz pendulum assembly does not generate residual stress during use, and the temperature cycle has a low impact, and the long-term retention is good;

[0046] The present invention adopts a double-pulse Bessel beam to process the U-shaped through groove and processes the flexible beam 2 by Gaussian laser, thereby significantly improving the processing accuracy of the U-shaped through groove and the flexible beam 2, improving the surface roughness, and improving the quality of the finished product.

[0047] To further optimize the solution, in step five, a 4f system consisting of a 2° conical lens, a 100mm plano-convex lens and a 20x objective lens is used to shape the Gaussian beam into a double-pulse Bessel beam in the spatial domain. The double-pulse Bessel beam is focused inside the pendulum 1 to irradiate the front and back sides of the pendulum 1; a double-pulse Bessel beam is used, and a suitable double-pulse delay is selected, which is preferably 15.42ps in this embodiment; compared with a single-pulse Bessel beam, the processing depth can be significantly improved while improving the processing quality and accuracy; the 4f system is used to double the frequency of the femtosecond laser, which can significantly improve the absorption efficiency of fused quartz for photons, and at the same time, it can realize the shaping of the spatial shape and energy distribution, control the degree of material structure modification, etc., thereby achieving high-efficiency and selective etching in the modified area.

[0048] The use of a low-magnification objective lens can increase the processing range of the Bessel beam, and the entire area can be modified by only one positive and negative processing. In conjunction with a flip fixture, the processing efficiency of the quartz pendulum 1 can be greatly improved. At the same time, the use of positive and negative processing can significantly reduce the processing path deviation caused by the refraction of the laser inside the molten quartz, and improve the consistency of the trajectories of the upper and lower surfaces of the pendulum 1.

[0049] To further optimize the solution, in step five, a flip fixture is used to fix and rotate the pendulum 1; a double-pulse Bessel beam is used to irradiate the front and back surfaces of the inside of the pendulum 1 by trajectory scanning, so as to obtain U-shaped and rectangular modified areas that penetrate the upper and lower surfaces of the quartz material; when processing the flexible beam part, the laser focus is moved to 200μm above the pendulum 1 for processing, so as to ensure that the modified area will not penetrate the pendulum 1; when processing the back side, a CCD camera is used to determine the traces of the front side processing, and a high-precision six-axis translation stage is used for positioning, and the repeated positioning accuracy reaches ±5 microns.

[0050] To further optimize the solution, the specific operation of step 2 is: use a 20° conical lens to shape the femtosecond Gaussian laser into a long-focus deep Bessel laser, and process the middle part of the cylindrical protruding structures on both sides to obtain skeleton 3.

[0051] For a further optimized solution, in step one, a single-point diamond turning process is used for the quartz cylindrical blank. The specific steps are as follows: Move the diamond tool tip to the machining end face of the quartz cylindrical blank. Use a rotary motor to drive the three-jaw chuck and the quartz cylindrical blank to rotate. The tool tip feeds from the inside of the symmetry axis to the outermost specified wall thickness, and then gradually feeds inward along the axis from the end face, thereby turning to machine a cylindrical convex structure on one side. Then re-clamp and machine the cylindrical convex structure on the other side. The size of the diamond tool tip is set according to the actual working conditions.

[0052] The rotation angle of the rotary motor can be set through a control system. The control system (not shown in the figure) is electrically connected to the rotary motor.

[0053] After the all-quartz integrated sensitive element blank is formed, the whole blank needs to be finely processed to improve the dimensional accuracy of the sensitive element. Considering that the sensitive element blank is a rotating body and the inner cavity and through-hole dimensions of the skeleton 3 are very small, femtosecond laser is used for processing to improve the processing accuracy.

[0054] For a further optimized solution, the specific operation of step three is as follows: Use a 20° cone lens to shape the femtosecond Gaussian laser into a long focal-depth Bessel laser, and process the central through-hole part of the skeleton 3 to obtain the through-hole at the center of the swing piece 1.

[0055] For a further optimized solution, in step four, use a CO2 laser to polish the surface of the swing piece 1 and the inner cavity of the skeleton 3. After the above steps of processing are completed, the dimensional accuracy of the integrated quartz swing piece blank can reach 0.02 mm, and the surface roughness can reach 0.012 μm.

[0056] For a further optimized solution, in step six, the etching solution uses a hydrofluoric acid solution with a mass fraction of 5%. Place the swing piece 1 in an ultrasonic vibrator, and etch away the modified contour area through hydrofluoric acid to obtain a U-shaped through groove. Significantly improve the etching speed and at the same time reduce the etching of the non-modified area.

[0057] For a further optimized solution, in step seven, perform Gaussian laser processing on the swing piece 1 sample after hydrofluoric acid etching to improve the roughness of the bottom of the groove in the flexible beam 2 part, and at the same time, the thickness of the flexible beam 2 can be accurately adjusted.

[0058] For a further optimized solution, the flipping fixture includes:

[0059] A support base 9; the support base 9 is fixed on a high-precision six-axis translation stage;

[0060] A rotating table 8, installed on the support base 9;

[0061] A fixture assembly, installed on the rotating table 8; the swing piece 1 is detachably connected to the fixture assembly;

[0062] Among them, the rotating table 8 is used to drive the fixture assembly to rotate; the switching between the front and back sides of the swinging piece 1 is realized through the rotating table 8; the internal structure and working principle of the rotating table 8 are both prior arts and will not be elaborated here.

[0063] In a further optimized solution, the fixture assembly includes a top plate 4 and a bottom plate 7; the bottom plate 7 is located directly below the top plate 4, and the bottom plate 7 is installed on the rotating table 8; the top plate 4 and the bottom plate 7 are detachably connected by a bolt assembly; the swinging piece 1 is press-fitted between the top plate 4 and the bottom plate 7; gaskets 5 are provided between the swinging piece 1 and the top plate 4 and between the swinging piece 1 and the bottom plate 7.

[0064] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0065] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A femtosecond laser composite processing method for the integrated pendulum assembly of a quartz flexure accelerometer, characterized in that, It includes the following steps: Step 1: Turn a quartz cylindrical blank to machine two cylindrical convex structures on both sides to obtain a pendulum piece (1). Step 2: Use femtosecond laser to machine the pendulum piece (1) to remove the middle part of the two cylindrical convex structures to obtain a framework (3). Step 3: Use femtosecond laser to machine a through hole in the center of the pendulum piece (1). Step 4: Polish the pendulum piece (1). Step 5: Irradiate the front and back sides of the pendulum piece (1) with a double-pulse Bessel beam to obtain a modified area penetrating the pendulum piece (1). Step 6: Etch the modified area with an etching solution to obtain a U-shaped through groove. Step 7: Use Gaussian laser to machine the flexible beam (2) to obtain an integrated structure of the pendulum assembly of the quartz flexible accelerometer. In the said Step 5, a flipping fixture is used to fix and rotate the pendulum piece (1); the double-pulse Bessel beam irradiates the front and back sides inside the pendulum piece (1) by means of trajectory scanning; when machining the back side, a CCD camera is used to determine the traces of the front side machining, and positioning is carried out in cooperation with a high-precision six-axis translation stage, and the repeated positioning accuracy reaches ±5 microns. The said flipping fixture includes: A support base (9); A rotating table (8) installed on the support base (9); A fixture assembly installed on the rotating table (8); the pendulum piece (1) is detachably connected to the fixture assembly; Wherein, the rotating table (8) is used to drive the fixture assembly to rotate; The fixture assembly includes a top plate (4) and a bottom plate (7); the bottom plate (7) is located directly below the top plate (4), and the bottom plate (7) is installed on the rotating table (8); the top plate (4) and the bottom plate (7) are detachably connected by a bolt assembly; the pendulum piece (1) is press-fitted between the top plate (4) and the bottom plate (7); gaskets (5) are provided between the pendulum piece (1) and the top plate (4) and between the pendulum piece (1) and the bottom plate (7).

2. The integrated femtosecond laser composite processing method for the pendulum assembly of the quartz flexure accelerometer according to claim 1, characterized in that: In the said Step 5, a 4f system composed of a 2° cone lens, a 100mm plano-convex lens and a 20x objective lens is used to shape the Gaussian beam into a double-pulse Bessel beam in the spatial domain, and the double-pulse Bessel beam is focused inside the pendulum piece (1) to irradiate the front and back sides of the pendulum piece (1).

3. The integrated femtosecond laser composite processing method for the pendulum assembly of the quartz flexible accelerometer according to claim 1, characterized in that: The specific operation of the said Step 2 is: use a 20° cone lens to shape the femtosecond Gaussian laser into a long focal-depth Bessel laser to machine the middle part of the two cylindrical convex structures to obtain a framework (3).

4. The integrated femtosecond laser composite processing method for the pendulum assembly of the quartz flexure accelerometer according to claim 1, wherein: In the said Step 1, a single-point diamond is used to turn the quartz cylindrical blank; the specific steps are: move the diamond tool tip to the machining end face of the quartz cylindrical blank, use a rotating motor to drive the three-jaw chuck and the quartz cylindrical blank to rotate, and machine a unilateral cylindrical convex structure; then re-clamp and machine the cylindrical convex structure on the other side.

5. The integrated femtosecond laser composite processing method for the pendulum assembly of the quartz flexure accelerometer according to claim 1, characterized in that: The specific operation of the said Step 3 is: use a 20° cone lens to shape the femtosecond Gaussian laser into a long focal-depth Bessel laser to machine the center through hole part of the framework (3) to obtain a through hole in the center of the pendulum piece (1).

6. The integrated femtosecond laser composite processing method for the pendulum assembly of the quartz flexible accelerometer according to claim 1, characterized in that: In the said Step 4, a CO2 laser is used to polish the surface of the pendulum piece (1) and the inner cavity of the framework (3).

7. The integrated femtosecond laser composite processing method for the pendulum assembly of the quartz flexible accelerometer according to claim 1, characterized in that: In the sixth step, the etching solution is a hydrofluoric acid solution with a mass fraction of 5%. The wafer (1) is placed in an ultrasonic vibrator, and the modified contour area is etched away by hydrofluoric acid to obtain a U-shaped through groove.

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