A fixture and clamping method for machining thin-walled curved lenses of brittle materials

Abstract

A fixture and clamping method for machining thin-walled curved lenses made of hard and brittle materials are disclosed. The fixture includes a fixture base, a positioning mechanism, a clamping mechanism, and a zero-point positioning quick-change mechanism. The upper surface of the fixture base is a concave positioning surface, and the lower surface of the silicon block to be processed is a convex surface, with their concavity and convexity matched. The positioning mechanism is used to adjust the position of the fixture base and the silicon block. The clamping mechanism is detachably connected to the fixture base and is equipped with a push rod capable of vertical displacement that engages with the upper surface of the silicon block to be processed. The zero-point positioning quick-change mechanism is used to position the fixture base and the processing equipment. This invention provides a clamping process and a dedicated fixture suitable for machining thin-walled curved parts made of hard and brittle materials, solving the problem of difficult clamping in machining such parts.

Description

Technical Field

[0001] This invention relates to the field of tooling fixtures for manufacturing mirrors made of hard and brittle materials, and more particularly to a fixture and clamping method for processing thin-walled curved mirrors made of hard and brittle materials. Background Technology

[0002] X-ray mirrors are key components of deep-space X-ray telescopes. Their function is to reflect and focus high-energy X-rays emitted from outer space, enabling high-sensitivity detection and high-resolution imaging of celestial objects such as pulsars, supernovae, and black holes. They are widely used in GPS global positioning systems, spacecraft deep-space autonomous navigation systems, and celestial object observation. The single-crystal silicon mirror assembly method is the most promising approach for manufacturing next-generation high-performance deep-space X-ray telescopes. This method uses high-precision, high-surface-integrity single-crystal silicon curved mirrors as basic units, and manufactures multi-layered nested X-ray mirrors through layered modular assembly of these mirrors. Figure 1 As shown.

[0003] To achieve grazing incidence reflection imaging of X-rays, the concave surface of a monocrystalline silicon curved lens is an off-axis paraboloid or hyperboloid with a large off-axis angle (>87°), and the convex surface is a conical surface with a cone angle equal to the off-axis angle. The radius of curvature of the concave and convex surfaces is 100–500 mm. The aperture of a single lens is 100–300 mm, the lens thickness is less than 1 mm, and the surface shape accuracy (PV) of the concave surface of the curved lens is required to be less than 1 micrometer, and the surface roughness (Sa) is required to be less than 0.5 nanometers. Figure 2 As shown in the figure, monocrystalline silicon curved surface lenses are typical thin-walled, weakly rigid, complex curved precision optical components made of hard and brittle materials. The key to achieving ultra-precision machining of reflective lenses lies in how to properly clamp and fix these lenses while ensuring machining accuracy.

[0004] Therefore, a new method for machining and clamping curved lenses that are made of hard and brittle materials, have thin walls and weak rigidity, and require high precision is urgently needed. Summary of the Invention

[0005] To address the aforementioned problem of difficulty in clamping thin-walled curved X-ray reflecting lenses made of hard and brittle materials, this invention proposes a fixture and clamping method for processing thin-walled curved surface lenses made of hard and brittle materials. The technical means employed in this invention are as follows:

[0006] A fixture for processing thin-walled curved lenses made of hard and brittle materials includes a fixture base, a positioning mechanism, a clamping mechanism, and a zero-point positioning quick-change mechanism. The upper surface of the fixture base is a concave positioning surface, and the lower surface of the silicon block to be processed is a convex surface, with their concavity and convexity matched. The positioning mechanism is used to adjust the position of the fixture base and the silicon block. The clamping mechanism is detachably connected to the fixture base and is provided with a push rod that can move up and down and cooperates with the upper surface of the silicon block to be processed. The zero-point positioning quick-change mechanism is used to position the fixture base and the processing equipment.

[0007] Furthermore, the fixture base is provided with an adhesive injection channel, and the lower surface of the fixture base is provided with an adhesive injection hole.

[0008] Furthermore, the fixture substrate is made of microcrystalline glass or ceramic, which has a similar coefficient of thermal expansion to monocrystalline silicon, thus reducing lens deformation during hot melt adhesive bonding. The fixture substrate is machined with adhesive flow channels, concave positioning surfaces, and zero-point positioning grooves using ultrasonic milling.

[0009] Furthermore, the positioning mechanism comprises multiple components, including a positioning base, a laser displacement sensor, and a fine-tuning device. The fine-tuning device includes a fine-tuning motor and a push rod connected to it. The positioning base is mounted on the fixture base, and the output end of the push rod can contact the silicon block. The laser displacement sensor is used to measure the relative position of the side of the silicon block and the side of the fixture base in real time. The fine-tuning motor pushes the push rod to move the silicon block. The laser displacement sensor is mounted on the side of the fixture base. When the relative positions of the silicon block and the front / back and left / right sides of the fixture base are the same, the geometric center of the silicon block and the fixture base is aligned. At this point, it is convenient for subsequent processing to establish the geometric center of the single-crystal silicon lens as the processing coordinate system, using the four sides of the fixture base as a reference.

[0010] Furthermore, the clamping mechanism includes a bracket, a support plate, and a threaded push rod. The bracket is fixed to the fixture base via a threaded connection, and the support plate is fixed to the bracket via a threaded connection. A threaded hole is formed in the center of the support plate, and the threaded push rod moves up and down through this hole. After the silicon block is centered with the fixture base, the threaded push rod is rotated to press the silicon block downwards, thus clamping and fixing the silicon block to the fixture base. At this point, inverting the fixture base will not cause the silicon block to shift, completing the clamping of the silicon block to the fixture base. Molten hot melt adhesive is poured into the injection port at the bottom of the fixture base. After the hot melt adhesive cools and solidifies, the positioning mechanism and clamping mechanism are removed.

[0011] Furthermore, a conical positioning groove is provided at the bottom of the fixture base, and the zero-point positioning quick-change mechanism includes a zero-point positioning mother plate. Rapid positioning is achieved through the cooperation of the conical positioning groove at the bottom of the fixture base and the conical positioning block on the zero-point positioning mother plate. Vacuuming is performed through the air duct on the positioning mother plate to clamp the fixture base. Relying on the zero-point positioning quick-change mechanism, consistent processing benchmarks can be achieved for multiple processes such as curved surface cutting, grinding, and polishing, and vacuum suction and release enables quick changes of parts at multiple workstations.

[0012] Furthermore, the glue injection channel has various shapes, including but not limited to spiral, cross, and square shapes.

[0013] Furthermore, the hot melt adhesive includes, but is not limited to, paraffin wax, sealing wax, asphalt, rubber, epoxy resin, etc.

[0014] This invention also discloses a method for clamping thin-walled curved mirrors made of hard and brittle materials based on the above-mentioned fixture, comprising the following steps: First, the concave positioning surface of the fixture base and the convex surface of the silicon block are used as the main reference surface. Then, the four sides of the fixture base and the four sides of the silicon block are used as secondary reference surfaces to achieve centering and clamping through a positioning and clamping mechanism. Second, hot melt adhesive is poured into the fixture body from the back of the fixture through the flow channel inside the fixture to achieve bonding between the fixture base and the silicon block. Then, through the zero-point positioning quick-change mechanism of the fixture body, the same 1mm thin sheet cutting, off-axis parabolic grinding, and reflective surface polishing are carried out sequentially on a cutting machine, a grinding machine, and a polishing machine. Finally, the fixture base and the reflective mirror are heated together to decompose the hot melt adhesive and achieve separation of the mirror from the fixture, resulting in a high-precision curved reflective mirror.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. A clamping process and special clamping fixture are provided for machining thin-walled curved parts made of hard and brittle materials, which solves the problem of difficult clamping in machining thin-walled curved parts made of hard and brittle materials.

[0017] 2. This clamping method can achieve multiple processing steps such as lens cutting, grinding, and polishing with a single clamping. The processing datum is consistent, which can ensure that the workpiece can be quickly and repeatedly disassembled between multiple processes. Multiple clamping does not change the processing datum, shortening tool setting time and improving processing efficiency.

[0018] 3. Based on the characteristics of hot melt adhesive, which heats and fuses and solidifies at room temperature, the adhesive method is used to completely fix thin-walled curved parts made of hard and brittle materials. This method eliminates the traditional mechanical clamping method, which is prone to causing hard and brittle materials to break. It is convenient to operate and economical.

[0019] 4. The fixture base adopts an internal flow channel design, which prevents hot melt adhesive from overflowing onto the positioning surface through back-side glue injection. This does not affect the tight fit of the convex and concave curved surfaces, ensuring positioning accuracy. The novel structure reduces the bonding area and minimizes the deformation of thin-walled parts during the bonding process. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The background technology describes the assembly method for monocrystalline silicon reflective lenses.

[0022] Figure 2 This is a schematic diagram of the structure of a single monocrystalline silicon curved lens as described in the background art.

[0023] Figure 3 This is an assembly drawing of the fixture described in this invention.

[0024] Figure 4 This is an exploded view of the fixture described in this invention.

[0025] Figure 5 This is a flowchart of the clamping method for processing thin-walled curved lenses made of hard and brittle materials according to the present invention.

[0026] Figure 6 This is a schematic diagram of the shape of the glue injection channel in the fixture substrate of the present invention.

[0027] In the diagram: 1. Fixture base; 2. Positioning mechanism; 3. Clamping mechanism; 4. Zero-point positioning quick-change mechanism; 5. Silicon block; 101. Glue injection channel; 102. Concave positioning surface; 103. Positioning groove; 201. Laser displacement sensor; 202. Positioning base; 203. Push rod; 204. Fine-tuning motor; 301. Threaded push rod; 302. Support plate; 303. Support rod; 401. Positioning block; 402. Positioning mother plate; 403. Air passage. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] like Figure 3 , Figure 4 As shown in the figure, this invention discloses a fixture for processing thin-walled curved lenses made of hard and brittle materials. The fixture includes a fixture base 1, a positioning mechanism 2, a clamping mechanism 3, and a zero-point positioning quick-change mechanism 4. The upper surface of the fixture base is a concave positioning surface 102, and the lower surface of the silicon block 5 to be processed is a convex surface; the concavity and convexity of the two are matched. The positioning mechanism is used to adjust the position of the fixture base and the silicon block. The clamping mechanism is detachably connected to the fixture base and is equipped with a push rod capable of vertical displacement that engages with the upper surface of the silicon block to be processed. The zero-point positioning quick-change mechanism is used to position the fixture base and the processing equipment. In this embodiment, both the upper surface of the silicon block and the lower surface of the fixture base are planar.

[0032] The fixture base is provided with an adhesive injection channel 101, and the lower surface of the fixture base is provided with an adhesive injection hole.

[0033] The fixture substrate is made of microcrystalline glass or ceramic, which has a similar coefficient of thermal expansion to monocrystalline silicon, thus reducing lens deformation during hot melt adhesive bonding. The fixture substrate is machined using ultrasonic milling to create adhesive flow channels, concave positioning surfaces, and zero-point positioning grooves.

[0034] The positioning mechanism comprises multiple components, including a positioning base 202, a laser displacement sensor 201, and a fine-tuning device. The fine-tuning device includes a fine-tuning motor 204 and a push rod 203 connected to it. The positioning base is mounted on the fixture base. The output end of the push rod can contact the silicon block. The laser displacement sensor is used to measure the relative position of the side of the silicon block and the side of the fixture base in real time. The fine-tuning motor pushes the push rod to move the silicon block. The laser displacement sensor is mounted on the side of the fixture base. When the relative positions of the silicon block and the front-back and left-right sides of the fixture base are the same, the geometric center of the silicon block and the fixture base is aligned. This facilitates subsequent processing by establishing the geometric center of the single-crystal silicon lens as the processing coordinate system, using the four sides of the fixture base as a reference. Specifically, in this embodiment, the positioning base is mounted on the side of the fixture base. In this embodiment, there are four positioning mechanisms. The fixture base includes four side portions, and the four positioning mechanisms are respectively located at the upper part of the four side portions. The two opposite fixture bases are set at the same height.

[0035] The clamping mechanism includes a bracket 303, a support plate 302, and a threaded push rod 301. The bracket is fixed to the fixture base via a threaded connection, and the support plate is fixed to the bracket via a threaded connection. A threaded hole is formed in the center of the support plate, through which the threaded push rod moves up and down. After the silicon block is centered with the fixture base, the threaded push rod is rotated to press the silicon block downwards, clamping it securely to the fixture base. At this point, inverting the fixture base will not cause the silicon block to shift, completing the clamping of the silicon block to the fixture base. Melted hot melt adhesive is poured into the injection port at the bottom of the fixture base. After the hot melt adhesive cools and solidifies, the positioning mechanism and clamping mechanism are removed. The bracket includes four support rods 303 connected to the support plate.

[0036] The fixture base has a conical positioning groove 103 at its bottom. The zero-point positioning quick-change mechanism includes a zero-point positioning mother plate 402, which achieves rapid positioning by cooperating with the conical positioning groove at the bottom of the fixture base and the conical positioning block 401 on the zero-point positioning mother plate. The positioning mother plate has multiple through holes arranged in an array as air vents 403. Vacuuming is achieved through these air vents to clamp the fixture base. The zero-point positioning quick-change mechanism enables consistent processing benchmarks for multiple processes such as curved surface cutting, grinding, and polishing, and allows for quick changes of parts between multiple workstations via vacuum suction and release.

[0037] The glue injection channel has various shapes, such as spiral, cross, and meander, as shown in the following examples. Figure 6As shown. In this embodiment, the injection port of the spiral-shaped glue channel is located at the center starting point of the spiral channel, and the outlet is located at the tail end of the spiral channel; the cross-shaped channel is composed of several arrayed protrusions, with the injection port located at the center point and the outlet located at the four corners of the array; the U-shaped channel includes a center point and horizontal and vertical channels extending from the center point, as well as rectangular (or other graphic) U-shaped channels connecting the horizontal and vertical channels at preset intervals, wherein the center point is the injection port, and the outlet is located at the four corners of the outermost U-shaped channel. It should be noted that this embodiment only provides several optional implementation types. In the specific processing process, adjustments can be made according to the actual working scenario. Other channel settings that can achieve glue injection are all within the protection scope of this invention.

[0038] The hot melt adhesive can be selected from various types depending on the actual working conditions, including paraffin wax, sealing wax, asphalt, rubber, epoxy resin, etc.

[0039] like Figure 5 As shown, this invention also discloses a method for clamping thin-walled curved mirrors made of hard and brittle materials based on the above-mentioned fixture, including the following steps: First, the concave positioning surface of the fixture base and the convex surface of the silicon block are used as the main reference surface. Then, the four sides of the fixture base and the four sides of the silicon block are used as secondary reference surfaces to achieve centering and clamping through a positioning and clamping mechanism. Second, hot melt adhesive is poured into the fixture body from the back of the fixture through the flow channel inside the fixture to achieve bonding between the fixture base and the silicon block. Then, through the zero-point positioning quick-change mechanism of the fixture body, the same 1mm thin sheet cutting, off-axis parabolic grinding, and reflective surface polishing are carried out sequentially on a cutting machine, a grinding machine, and a polishing machine. Finally, the fixture base and the reflective mirror are heated together to decompose the hot melt adhesive and achieve separation of the mirror from the fixture, resulting in a high-precision curved reflective mirror.

Claims

1. A fixture for machining thin-walled curved lenses made of hard and brittle materials, characterized in that, The device includes a fixture base, a positioning mechanism, a clamping mechanism, and a zero-point positioning quick-change mechanism. The upper surface of the fixture base is a concave positioning surface, and the lower surface of the silicon block to be processed is a convex surface, with their concavity and convexity matched. The positioning mechanism is used to adjust the position of the fixture base and the silicon block. The clamping mechanism is detachably connected to the fixture base and is equipped with a push rod that can move up and down and cooperates with the upper surface of the silicon block to be processed. The zero-point positioning quick-change mechanism is used to position the fixture base and the processing equipment. The fixture base is provided with an adhesive injection channel, and the lower surface of the fixture base is provided with an adhesive injection hole.

2. The fixture for processing thin-walled curved lenses made of hard and brittle materials according to claim 1, characterized in that, The fixture substrate is made of microcrystalline glass or ceramic material.

3. The fixture for processing thin-walled curved lenses made of hard and brittle materials according to claim 1, characterized in that, The positioning mechanism comprises multiple components, including a positioning base, a laser displacement sensor, and a fine-tuning device. The fine-tuning device includes a fine-tuning motor and a push rod connected thereto. The positioning base is mounted on the fixture base, and the output end of the push rod can contact the silicon block. The laser displacement sensor is used to measure the relative position between the side of the silicon block and the side of the fixture base in real time. The push rod is pushed by the fine-tuning motor to move the silicon block against the fixture base. The laser displacement sensor is mounted on the side of the fixture base.

4. The fixture for processing thin-walled curved lenses made of hard and brittle materials according to claim 1, characterized in that, The clamping mechanism includes a bracket, a support plate, and a threaded push rod. The bracket is fixed to the fixture base by a threaded connection, and the support plate is fixed to the bracket by a threaded connection. A threaded hole is opened in the center of the support plate, and the threaded push rod moves up and down through the threaded hole of the support plate. After the silicon block and the fixture base are centered, the threaded push rod is rotated to push the silicon block downward, so that the silicon block is clamped and fixed to the fixture base.

5. The fixture for processing thin-walled curved lenses made of hard and brittle materials according to claim 1, characterized in that, The bottom of the fixture base is provided with a conical positioning groove. The zero-point positioning quick-change mechanism includes a zero-point positioning mother plate. The fast positioning is achieved by the cooperation of the conical positioning groove at the bottom of the fixture base and the conical positioning block on the zero-point positioning mother plate. The fixture base is clamped by drawing a vacuum through the air port on the positioning mother plate.

6. The fixture for processing thin-walled curved lenses of hard and brittle materials according to claim 1, characterized in that, The shape of the glue injection channel includes spiral, cross, and square.

7. A method for clamping thin-walled curved surface lenses of hard and brittle materials using the clamp described in any one of claims 1 to 6, characterized in that, Includes the following steps: The main reference surface is obtained by the combination of the concave positioning surface of the fixture substrate and the convex surface of the silicon block. The positioning and clamping mechanism achieves centering and clamping by relying on the secondary reference surfaces of the four sides of the fixture base and the four sides of the silicon block; Hot melt adhesive is poured into the fixture body from the back of the fixture through the internal flow channel to achieve bonding between the fixture substrate and the silicon block. By using the zero-point positioning quick-change mechanism of the clamping body, the same datum 1mm thin sheet cutting, off-axis parabolic grinding, and reflective surface polishing are realized sequentially on the cutting machine tool, grinding machine tool, and polishing machine tool; The fixture substrate and the reflective lens are heated together, and the hot melt adhesive is decomposed to separate the lens from the fixture, resulting in a high-precision curved reflective lens.

8. The clamping method according to claim 7, characterized in that, The hot melt adhesives used include paraffin wax, sealing wax, asphalt, rubber, and epoxy resin.

Images