An ultra-precision turning method for NiP modified reflector

Abstract

The invention discloses an ultra-precision turning method for a NiP modified reflector, comprising: preparing a NiP modified layer on the surface of a reflector substrate, testing the NiP modified layer until its quality meets the index requirements, performing ultra-precision turning on the NiP modified layer to obtain the NiP modified reflector, and performing white light interference detection on the NiP modified reflector until the index requirements are met. The method of the invention can effectively improve the processing efficiency, processing quality and process repeatability of the NiP modified reflector by improving the material properties of the NiP modified layer and optimizing the process parameters, can make up for the deficiency in improving the quality when processing light metal materials into reflectors, can realize high-quality and low-defect processing of the NiP modified layer on the surface of the reflector, can obtain a high-quality reflector surface, has important engineering practical application value, and is of great significance to promoting the wide application of NiP modified reflectors in the field of optics.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-precision machining of optical elements, and in particular relates to an ultra-precision turning method for a NiP modified reflector. Background Art

[0002] Optical systems in aerospace applications have many strict restrictions on system weight, volume, and performance. The reflectors in the optical system play a critical role in the performance of the optical system and need to meet the requirements of high lightweight rate, high precision, and high surface quality. It is difficult to use materials such as single crystal silicon and glass to process reflectors in a lightweight manner. In the optical system, multiple fixed structures need to be added for assembly and adjustment, which increases the complexity of the system. Light metals represented by aluminum and beryllium have the advantages of high lightweight rate, easy to realize complex surface manufacturing, and athermal optical-mechanical integrated homogeneous design. Therefore, metal reflectors are increasingly used in aerospace equipment. However, aluminum materials are composed of multiple elements and are soft in texture. During processing, defects such as scratches and pits are very likely to occur. The chemical properties of aluminum are active and it is easy to form an oxide layer on the surface. Beryllium materials are sensitive to processing damage and are prone to cracking, breaking, and slag during processing. The quality of metal reflectors directly processed from aluminum, beryllium and other materials is difficult to meet the application requirements of shorter wavelengths such as visible light. To solve this problem, aluminum or beryllium metal is usually used as a substrate, and a NiP modified layer with better processing performance is covered on the substrate. The modified layer is then processed to obtain a higher quality optical reflector.

[0003] NiP modified reflectors have many advantages. The NiP modified layer is plated on the substrate surface by chemical nickel plating. The deposition method is equal thickness deposition. A modified layer with uniform thickness can be obtained on the surface of workpieces with complex surfaces. NiP modified layers with different phosphorus contents and thicknesses can also be obtained by controlling the rate and time of chemical plating. The surface roughness of the NiP modified reflector obtained by polishing is much better than the surface roughness that can be achieved by polishing aluminum, beryllium and other materials. Therefore, for applications with shorter wavelength spectra such as visible light, metal materials such as aluminum and beryllium are usually used as substrates, and NiP modified layers are plated on the substrates by chemical nickel plating, and then the NiP modified layers are ultra-precision processed to obtain high-quality reflectors, thereby meeting the application requirements of short-wave optical systems.

[0004] Compared with traditional processing methods, ultra-precision turning can realize the processing of various complex curved surfaces, with high processing efficiency, good processing accuracy and repeat processing accuracy, and a smooth reflective mirror surface at the nanometer level can be obtained in one processing. At the same time, ultra-precision turning has high production efficiency, is suitable for mass production, and has low processing costs. When processing metal reflectors, the manufacturing cycle and manufacturing cost of the entire system are greatly reduced. The assembly accuracy of the processed optical elements and mounting brackets is high enough, the installation and adjustment are simple, and the calibration is convenient. Through ultra-precision turning, the NiP modified reflector blank can directly obtain an optical reflective mirror surface, and the processing quality can meet the application requirements of the infrared band. After ultra-precision turning, the NiP modified reflector can also be combined with other polishing processing technologies to form a combined process to obtain a NiP modified reflector with higher surface accuracy and surface quality. However, when the NiP modified reflector is processed by ultra-precision turning, if the material properties of the NiP modified layer are poor or the ultra-precision turning process parameters are not selected properly, the processed reflector surface is prone to cracks, cavities, scratches, pits, peeling and other defects, which affect the processing quality. At the same time, the existence of the above-mentioned shortcomings is not conducive to obtaining a higher quality NiP modified reflector through the polishing process, and will increase the difficulty of the subsequent polishing process, making the processing efficiency of the polishing process very low. Therefore, obtaining an ultra-precision turning method for high-quality NiP modified reflectors is of great significance for the processing and production of advanced optical reflectors. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an ultra-precision turning method for a NiP modified reflector, which can effectively improve the processing efficiency and processing quality of the NiP modified reflector while also improving the process repeatability.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] An ultra-precision turning method for a NiP modified reflector comprises the following steps:

[0008] Step S1, preparing a NiP modified layer on the surface of the reflector substrate; the phosphorus content in the NiP modified layer is 9 wt % to 14 wt %;

[0009] Step S2, inspecting the NiP modified layer. If the NiP modified layer has quality defects, the NiP modified layer on the surface of the reflector substrate is removed, and the process jumps to step S1 until the quality of the NiP modified layer meets the index requirements, and then the next step is executed;

[0010] Step S3, heat treating the NiP modified layer;

[0011] Step S4, using a diamond turning tool to perform ultra-precision turning on the NiP modified layer, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirement, and a NiP modified reflector is obtained; the rake angle of the diamond turning tool is 0°; the radius of the tool tip arc of the diamond turning tool is 0.5 mm to 2 mm; the blunt radius of the cutting edge of the diamond turning tool is 20 nm to 50 nm; the process parameters of the ultra-precision turning are: the machine tool spindle speed is 1200 rpm to 1600 rpm, the feed rate is 1 μm / r to 2 μm / r, and the cutting depth is 1 μm to 2 μm;

[0012] Step S5, performing white light interference detection on the NiP modified reflector, if the index requirements are not met, jump to step S4, otherwise the processing is terminated, and the ultra-precision turning processing of the NiP modified reflector is completed.

[0013] The above-mentioned ultra-precision turning method of the NiP modified reflector is further improved. In step S2, a microscope is used to detect the NiP modified layer, and the detection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether there are holes, whether there are gaps, and whether there are cracks.

[0014] The above-mentioned ultra-precision turning method of the NiP modified reflector is further improved, in step S3, the quality of the NiP modified layer meets the index requirements, including meeting the following indicators: the surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, without holes, gaps and cracks.

[0015] The above-mentioned ultra-precision turning method of the NiP modified reflector is further improved, in which in step S1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating; the thickness of the NiP modified layer is 80 μm to 120 μm.

[0016] The ultra-precision turning method of the NiP modified reflector is further improved in that, in step S1, the material of the reflector substrate is a light metal; the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

[0017] The ultra-precision turning method of the NiP modified reflector is further improved in that, in step S3, a heat treatment method is selected according to relevant standards and the type of the reflector substrate, and the NiP modified layer is heat treated to reduce hydrogen embrittlement and improve bonding strength.

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] In the present invention, the ultra-precision turning mechanism and process of NiP modified reflector are studied and explored, and an ultra-precision turning method of NiP modified reflector is proposed. First, a high-phosphorus content NiP modified layer that meets the processing requirements is prepared on the surface of the reflector substrate. The NiP modified layer has a flat and smooth surface, is uniform and dense, has no impurity deposition, no holes, no gaps, no cracks, and has strong bonding with the substrate. On this basis, the NiP modified layer is ultra-precision turned to achieve mirror processing of the NiP modified layer, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirement, thereby obtaining a low-defect, high-quality NiP modified reflector. The NiP modified reflector can not only meet the application requirements of the infrared band, but also can be combined with other polishing processing technologies to form a combined process to obtain a NiP modified reflector with higher surface accuracy and surface quality, which is conducive to achieving the application requirements of the NiP modified reflector in high-quality optical systems. The ultra-precision turning method of the NiP modified reflector of the present invention can effectively improve the processing efficiency and processing quality of the NiP modified reflector while also improving the process repeatability, and can also make up for the deficiencies in improving the surface quality when light metal materials are processed into reflectors, and can achieve high-quality, low-defect processing of the NiP modified layer on the surface of the reflector, and obtain a high-quality reflector surface, which has important practical engineering application value and is of great significance for promoting the widespread application of NiP modified reflectors in the optical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0021] Figure 1 This is a process flow chart of ultra-precision turning of a NiP modified reflector in an embodiment of the present invention.

[0022] Figure 2 This is a surface pit morphology image of the NiP modified layer with impurities on the surface after ultra-precision turning in an embodiment of the present invention.

[0023] Figure 3 This is a surface scratch morphology of the NiP modified layer with impurities on the surface after ultra-precision turning in an embodiment of the present invention.

[0024] Figure 4 This is a surface peeling morphology of the NiP modified layer that meets the quality requirements in the embodiment of the present invention after ultra-precision turning.

[0025] Figure 5 This is a surface morphology of the NiP modified layer with insufficient bonding strength after ultra-precision turning in an embodiment of the present invention.

[0026] Figure 6 This is a surface morphology of the NiP modified layer after heat treatment and ultra-precision turning in an embodiment of the present invention.

[0027] Figure 7 This is a graph showing the surface roughness results of the NiP modified reflector prepared in an embodiment of the present invention.

[0028] Figure 8 This is the surface roughness result diagram of the NiP modified reflector made by the existing conventional ultra-precision turning process.

[0029] Fig. 9 Graph showing the elastic recovery rate of the NiP modified layer prepared in an embodiment of the present invention under different loading loads.

[0030] Fig.10 3. The tapered groove morphology of the NiP modified layer prepared in the embodiment of the present invention under different maximum scratching depth conditions.

[0031] Fig.11 This is a graph showing the surface roughness of the NiP modified layer when the rake angle of the diamond turning tool is 10° in an embodiment of the present invention.

[0032] Fig.12 Graph showing the surface roughness of the NiP modified layer when the rake angle of the diamond turning tool is 0° in an embodiment of the present invention.

[0033] Fig.13 This is a graph showing the surface roughness results of the NiP modified layer when the rake angle of the diamond turning tool is -10° in an embodiment of the present invention.

[0034] Fig.14 Graph showing the relationship between the arc radius of the turning tool tip and the blunt radius of the cutting edge and the surface roughness of the NiP modified layer in an embodiment of the present invention.

[0035] Fig.15 Graph showing the relationship between feed rate, cutting depth and surface roughness of the NiP modified layer in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] The workpiece to be processed in this embodiment is a NiP modified plane reflector with a diameter of 100 mm, and the substrate is 6061 aluminum alloy. The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, and the processing method used in the present invention is further explained.

[0038] like Figure 1 As shown, the ultra-precision turning method of the NiP modified reflector of this embodiment comprises the following steps:

[0039] Step S1, preparing a NiP modified layer on the surface of a reflector substrate.

[0040] Step S2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate, and jump to step S1 until the quality of the NiP modified layer meets the index requirements and execute the next step.

[0041] Step S3, heat treating the NiP modified layer.

[0042] Step S4, performing ultra-precision turning on the NiP modified layer, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirement, and obtaining a NiP modified reflector.

[0043] Step S5, performing white light interference detection on the NiP modified reflector, if the index requirements are not met, jump to step S4, otherwise the processing is terminated, and the ultra-precision turning processing of the NiP modified reflector is completed.

[0044] In this embodiment, the material properties of the NiP modified layer directly affect the processing performance of ultra-precision turning. For example, in the process of chemical nickel plating in step S1, if the plating process is not properly controlled, impurities are easily deposited on the surface of the NiP modified layer. At the same time, since the binding force between the impurities and the NiP modified layer is relatively small, when the NiP modified layer is subjected to ultra-precision turning, the impurities are driven by the turning tool to separate from the surface of the NiP modified layer, forming pit defects (such as pits) on the surface of the NiP modified layer. Figure 2 As shown in the figure), or the turning tool drives impurities to form scratches on the surface of the modified layer (as shown in the figure). Figure 3 as shown).

[0045] In view of the above problems, in steps S1 and S2 of the present embodiment, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating. After the chemical nickel plating is completed, the NiP modified layer is inspected by a microscope. The inspection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether it has holes, whether it has gaps, and whether it has cracks. If the NiP modified layer has any of the above quality defects, the NiP modified layer on the surface of the reflector substrate is removed, and the process jumps to step S1, and the NiP modified layer is continuously prepared on the surface of the reflector substrate by chemical nickel plating until the quality of the NiP modified layer meets the index requirements. Specifically, by observing under a strong light and using an ultra-depth of field microscope, it is ensured that the surface of the NiP modified layer is free of impurity deposition, is flat and smooth, uniform and dense, and has no defects such as holes, gaps, and cracks. Figure 4As shown. In this step, the quality of the NiP modified layer meets the index requirements, which can be determined according to the actual situation. For example, impurity-free deposition means that there are no impurities on the surface of the NiP modified layer. Generally speaking, chemical plating is an equal thickness deposition, so the preparation by chemical nickel plating can basically ensure that the NiP modified layer is flat and smooth. Uniform density requires that the Ni element and the P element are randomly and evenly distributed. Since the NiP modified layer is an amorphous NiP modified layer, it is also easier to achieve. Voids and cracks are usually easy to observe. They belong to very bad conditions and are scrapped when they appear. Therefore, once defects such as voids and cracks appear, the modified layer needs to be re-plated. The holes are formed by hydrogen generated in chemical nickel plating, and their size and depth are required not to exceed the value of the cutting depth during ultra-precision turning.

[0046] In step S2 of this embodiment, the NiP modified layer plated on the 6061 aluminum alloy substrate meets the quality requirements, has a thickness of 100 μm, and a phosphorus content of 11 wt %, which is a high-phosphorus-content amorphous NiP modified layer.

[0047] In addition, during the chemical nickel plating process in step S1, not all chemical reaction products are beneficial to the formation of the NiP modified layer. For example, hydrogen will be generated during the chemical nickel plating, and hydrogen will form pores in the NiP modified layer, reducing the toughness and load capacity of the modified layer, affecting the bonding strength between the NiP modified layer and the reflector substrate, and then when the NiP modified layer is subjected to ultra-precision turning, the NiP modified layer is prone to peeling and falling off. Figure 5 shown.

[0048] In order to eliminate hydrogen embrittlement and enhance the bonding strength between the NiP modified layer and the substrate, it is also necessary to select a heat treatment method according to relevant standards and the type of reflector substrate, and heat treat the NiP modified layer whose quality meets the index requirements in step S1 to reduce hydrogen embrittlement and improve the bonding strength. Specifically: in step S3 of this embodiment, the NiP modified layer whose quality meets the index requirements plated on the 6061 aluminum alloy substrate is heat treated to reduce hydrogen embrittlement and improve the bonding strength. After testing by a tensile testing machine, the bonding strength between the substrate and the modified layer can reach 40 MPa after heat treatment to reduce hydrogen embrittlement and heat treatment to improve the bonding strength, which meets the requirements.

[0049] In step S4 of this embodiment, the NiP modified layer obtained after heat treatment in step S3 is subjected to ultra-precision turning. When the modified layer is subjected to ultra-precision turning, a diamond turning tool is used, wherein the rake angle of the diamond turning tool is 0°, the radius of the tool tip arc is 0.5 mm, the radius of the cutting edge blunt circle is 20 nm, and at the same time, the feed rate range is 1 μm / r, and the cutting depth is 1 μm; the spindle speed of the machine tool is 1500 rpm, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirement, and a NiP modified reflector is obtained. The result is as shown in FIG. Figure 6 As shown. Figure 6 It can be seen that in the present invention, after ultra-precision turning, the surface of the NiP modified layer has no defects such as scratches, pits, peeling, etc.

[0050] In this embodiment, in step S5, after the ultra-precision turning process is completed, the surface quality is measured using a white light interferometer. Figure 7 As shown in FIG. 1 , the surface roughness Ra of the NiP modified reflector is 0.695 nm, and the processed surface has no defects. However, in the existing ultra-precision turning method for the NiP modified layer, after ultra-precision turning, the surface roughness Ra of the NiP modified reflector is 1.335 nm, and there are pit defects on the processed surface, such as Figure 8 shown.

[0051] In this embodiment, the influence of different process parameters on the ultra-precision turning processing effect is also investigated, as follows:

[0052] (1) The effects of different rake angles of diamond turning tools on ultra-precision turning processing were investigated.

[0053] In ultra-precision turning, the material properties of the workpiece material determine the turning process parameters and the selection of diamond turning tools. There are different opinions on whether the NiP modified layer is a brittle material or a plastic material. The present invention first analyzes the brittle plasticity of the NiP modified layer. When the applied load does not exceed its elastic limit, the elastic recovery rate of brittle materials and plastic materials is close to 100%. If the applied load is removed, they can completely recover to the shape and size before loading. However, once the applied load exceeds the elastic limit, the brittle material will suddenly break without an obvious plastic deformation stage. Plastic materials are different from brittle materials. When the applied load exceeds the elastic limit, the plastic material will first undergo plastic deformation. Plastic deformation is irreversible. After the applied load is removed, the material cannot completely recover to its original shape and size. Therefore, in the plastic deformation stage, the elastic recovery rate of the plastic material will be less than 100%. Elastic recovery rate R e Maximum penetration depth h max Residual indentation depth hp The difference between the maximum penetration depth h max Calculate the ratio of:

[0054] (1).

[0055] Through experiments and calculations, the elastic recovery rate of the NiP modified layer after heat treatment under different loading loads is as follows: Fig. 9 As shown. Fig. 9 It can be seen that the elastic recovery rate of the NiP modified layer is between 39.77% and 43.35%, which indicates that during the unloading process, the modified layer mainly undergoes plastic deformation and has less elastic recovery.

[0056] In the ultra-precision turning of NiP modified reflectors, the material removal method plays a vital role in obtaining a low-defect surface. Due to the scale effect in ultra-precision turning, if a high-quality cutting surface is to be obtained, the chips generated during processing need not have material breakage or cracks extending to the processed surface. Based on this, in the present invention, a taper scratching experiment is used to further analyze the ultra-precision turning of NiP modified reflectors. In order to better fit the actual processing conditions of NiP modified reflectors, a taper scratching experiment is performed on an ultra-precision turning machine with a diamond turning tool used in actual processing.

[0057] During the experiment, the cutting speed, starting point and end point of the diamond tool were set, and the turning tool was controlled to perform continuous variable depth cutting at a constant speed in the Z direction. The tip of the turning tool continuously scratched along the surface of the workpiece to the deepest part of the bottom of the groove. The scratching depth changed continuously from zero to the set maximum depth, and taper scratching could be achieved.

[0058] In order to ensure the reliability of the experimental results, a total of 4 tapered grooves were engraved, each with a length of 10 mm, the engraving speed of the turning tool was 1000 mm / min, and the tool tip arc radius was 0.5 mm. Considering that the thickness of the NiP modified reflector is generally tens of microns to hundreds of microns, the cutting depth of the ultra-precision turning NiP modified reflector generally does not exceed 10 μm. Therefore, the maximum engraving depth of the 4 tapered grooves was set to 2 μm, 5 μm, 8 μm and 10 μm respectively to observe whether there was material breakage or cracks in the tapered groove.

[0059] Four taper grooves were engraved on the surface of the NiP modified reflector sample using a diamond turning tool according to the set turning parameters. Fig.10 Figure 1 is a groove morphology diagram of the NiP modified layer prepared in the embodiment of the present invention under different maximum scratching depth conditions. Fig.10It can be observed that there is a black area at the end of each tapered groove, which is a bulge formed by the accumulation of NiP modified layer material at the end of the tapered groove. At the same time, it can be observed that the inner wall surface of each tapered groove is smooth, and the junction between the groove edge and the surface is flat. No material breakage or cracks are observed inside and at the edge of each tapered groove, indicating that at a cutting depth of 10 μm, the material removal method of the NiP modified reflector is still plastic removal.

[0060] In ultra-precision turning, the tool rake angle is an important factor affecting surface generation and chip formation. The selection of the tool rake angle plays a vital role in the surface quality of the NiP modified metal reflector. At the same time, when ultra-precision turning the NiP modified metal reflector, the selection of the tool rake angle needs to comprehensively consider the processing efficiency, the surface quality of the modified layer and the service life of the turning tool to achieve the best processing effect. In this embodiment, diamond turning tools with rake angles of 10°, 0°, and -10° are selected. The tool tip arc radius is 0.5 mm, and the blunt radius of the turning tool cutting edge is 20 nm. The turning process parameters of spindle speed, feed speed and cutting depth are kept consistent in the experiment. The NiP modified reflector is subjected to ultra-precision turning. After the processing experiment is completed, the surface roughness of the NiP modified reflector is measured using a white light interferometer. The measurement results are shown in the figure. Figure 11 to Figure 13 shown. Figures 11 to 13 The right picture is the height profile of the left picture at the center line. Figures 11 to 13 It can be seen that the surface roughness Ra of the NiP modified reflector processed by the -10° rake angle turning tool is 2.509 nm, which is slightly better than the surface roughness of the NiP modified reflector surface processed by 10° rake angle turning, but much worse than the surface roughness of the NiP modified reflector processed by 0° rake angle turning. This is because when the rake angle of the turning tool is too small, the cutting edge will directly contact the workpiece surface when the turning tool cuts into the workpiece surface, resulting in a decrease in the surface quality of the processed NiP modified reflector and an increase in surface roughness. At the same time, if the rake angle is too small, the cutting force during turning will increase, and the heat dissipation volume will also be reduced, which is not conducive to heat dissipation, and the wear of the turning tool will be aggravated, reducing the durability of the tool. Therefore, in the ultra-precision turning method of the NiP modified reflector of the present invention, a 0° rake angle turning tool is selected, which is conducive to obtaining a high-quality NiP modified reflector.

[0061] (2) Investigate the influence of the tool tip radius and cutting edge blunt radius of the diamond turning tool on the ultra-precision turning processing effect.

[0062] like Fig.14 It can be seen that when the tool parameters are in the trend of increasing the radius of the turning tool nose arc and decreasing the radius of the cutting edge blunt circle, the surface roughness is in a decreasing trend. Fig.14It can be found that the slope of the turning tool tip arc radius increasing direction is smaller than the slope of the cutting edge blunt radius decreasing direction, indicating that in the ultra-precision turning of NiP modified metal reflectors, the influence of the turning tool tip arc radius on the surface roughness is smaller than the cutting edge blunt radius. Fig.14 It can be seen that as the radius of the tool tip increases, the surface roughness decreases. However, the larger the radius of the tool tip, the greater the radial cutting force, which will cause vibration between the turning tool and the workpiece, making the surface roughness worse. Fig.14 It can be seen that as the blunt radius of the cutting edge increases, the surface roughness will also increase. This is because as the blunt radius of the cutting edge increases, the cutting load of the tool increases, burrs are easily generated on the workpiece and an uneven surface is formed. When the blunt radius of the cutting edge decreases, the contact area between the tool and the workpiece becomes smaller, the cutting force decreases, and the chips are easily discharged, thereby obtaining a smooth machined surface. However, if the blunt radius of the cutting edge is too small, the tool will be easily worn or broken, affecting the processing efficiency and quality. Therefore, in actual processing, the tool tip arc radius and the cutting edge blunt radius should be reasonably selected according to the processing conditions and surface roughness requirements. Specifically, in the present invention, when the tip arc radius of the diamond turning tool is 0.5 mm to 2 mm and the cutting edge blunt radius of the diamond turning tool is 20 nm to 50 nm, it is conducive to obtaining a high-quality NiP modified reflector.

[0063] (3) Investigate the effects of feed rate and cutting depth on ultra-precision turning processing results.

[0064] like Fig.15 As shown in the figure, with the increase of feed rate and cutting depth, the surface roughness is in an increasing trend, but the slope in the direction of increasing feed rate is greater than the slope in the direction of increasing cutting depth, indicating that in the ultra-precision turning of NiP modified metal reflectors, the influence of feed rate on surface roughness is greater than that of cutting depth. Fig.15 It can be seen that as the feed rate increases, the surface roughness also increases. The larger the feed rate, the faster the cutting speed, but this will also increase the cutting force and cutting temperature, resulting in a worse surface roughness. Therefore, increasing the feed rate appropriately can improve production efficiency. However, if the feed rate is too large, it may cause vibration and impact between the tool and the workpiece, which in turn causes the deterioration of the surface quality. On the contrary, reducing the feed rate can reduce the cutting force and cutting temperature, which is conducive to obtaining a smoother machined surface. In addition, when the feed rate is too small, the machine tool is prone to low-speed creeping and other phenomena, which increases the surface roughness. From Fig.15It can be seen that the surface roughness increases with the increase of cutting depth. The increase of cutting depth will lead to an increase in cutting force, and the contact area between the tool and the workpiece will increase, which will easily cause surface extrusion deformation and cutting heat concentration, resulting in a deterioration in the roughness of the machined surface. Therefore, reducing the cutting depth can reduce the cutting force, reduce the cutting heat concentration, and is conducive to the discharge of chips, thereby obtaining a smoother machined surface. However, when the cutting depth is too small, the tool has an extrusion effect on the workpiece surface and the rebound effect of the material is large, which will also cause the surface roughness to deteriorate. Therefore, in actual processing, the feed rate and cutting depth should be reasonably selected according to the processing conditions and surface roughness requirements. Specifically, in the present invention, when the feed rate is 1 μm / r~2 μm / r and the cutting depth is 1 μm~2 μm, it is conducive to obtaining a high-quality NiP modified reflector.

[0065] It can be seen from the above results that, compared with the conventional ultra-precision turning method, the ultra-precision turning method of the NiP modified reflector of the present invention can realize low-defect, high-quality ultra-precision turning of the NiP modified reflector, and the prepared NiP modified reflector can not only meet the application requirements of the infrared band, but also can be combined with other polishing techniques to form a combined process, obtain a NiP modified reflector with higher surface accuracy and surface quality, which is conducive to realizing the application requirements of the NiP modified reflector in high-quality optical systems. Therefore, the ultra-precision turning method of the NiP modified reflector of the present invention can effectively improve the processing efficiency and processing quality of the NiP modified reflector while also improving the process repeatability, and can make up for the deficiencies in improving the surface quality when the light metal material is processed into a reflector, and can realize the high-quality, low-defect processing of the NiP modified layer on the reflector surface, and obtain a high-quality reflector surface without scratches, pits and other surface defects, which can meet the use requirements of the optical system, have important engineering practical application value, and are of great significance to promoting the wide application of NiP modified reflectors in the optical field.

[0066] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. An ultra-precision turning method for a NiP modified reflector, characterized in that: The following steps are involved: Step S1, preparing a NiP modified layer on the surface of the reflector substrate; the phosphorus content in the NiP modified layer is 9 wt % to 14 wt %; Step S2, using a microscope to detect the NiP modified layer, the detection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether it has holes, whether it has gaps, whether it has cracks, if the NiP modified layer has quality defects, then remove the NiP modified layer on the surface of the reflector substrate, and jump to step S1, until the quality of the NiP modified layer meets the index requirements, and then execute the next step; the quality of the NiP modified layer meets the index requirements, including meeting the following indicators: the surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, without holes, gaps and cracks; Step S3, selecting a heat treatment method according to relevant standards and the type of the reflector substrate, and heat treating the NiP modified layer to reduce hydrogen embrittlement and improve bonding strength; Step S4, using a diamond turning tool to perform ultra-precision turning processing on the NiP modified layer, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirement, and a NiP modified reflector is obtained; the rake angle of the diamond turning tool is 0°; the radius of the tool tip arc of the diamond turning tool is 0.5 mm to 2 mm; the blunt radius of the cutting edge of the diamond turning tool is 20 nm to 50 nm; the process parameters of the ultra-precision turning processing are: the machine tool spindle speed is 1200 rpm to 1600 rpm, the feed rate is 1 μm / r to 2 μm / r, and the cutting depth is 1 μm to 2 μm; Step S5, performing white light interference detection on the NiP modified reflector, if the index requirements are not met, jump to step S4, otherwise the processing is terminated, and the ultra-precision turning processing of the NiP modified reflector is completed.

2. The ultra-precision turning method of the NiP modified reflector according to claim 1, characterized in that: In step S1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating; the thickness of the NiP modified layer is 80 μm to 120 μm.

3. The ultra-precision turning method of the NiP modified reflector according to claim 2, characterized in that: In step S1, the material of the reflector substrate is light metal; the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

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