A high smoothness polishing method for small and medium caliber germanium window

Abstract

The present application belongs to the technical field of germanium window processing, and particularly relates to a high-surface-finish polishing method for medium and small caliber germanium windows, which has the processing route of: fine grinding, coarse polishing, fine polishing, on-disk finishing and off-disk finishing. Compared with the prior art, the present application has the beneficial effects that: on the basis of polishing germanium windows by classical optical processing method, the present application proposes the polishing process combining on-disk finishing and off-disk finishing, and improves the off-disk finishing process, effectively improves the surface finish and polishing efficiency of medium and small caliber germanium windows, and meanwhile, does not have great influence on the part surface shape, which helps to ensure the product quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of germanium window processing, in particular, relates to a high-finish polishing method for small and medium caliber germanium window. BACKGROUND

[0002] With the development of military infrared technology, the application of infrared optical system in airborne, shipborne and tank infrared imaging system is more and more widely, and the application of germanium crystal, an indispensable optical material in infrared system, is also increasing. It is the most commonly used window and lens material in 8-12um waveband. In this waveband, it has small chromatic aberration and high refractive index, and the transmittance can reach more than 97% after coating antireflection film on both sides. The optical processing of crystal material is roughly the same as that of optical glass, and the existing classical single-axis machine polishing, ring polishing machine polishing and double-sided polishing machine polishing can all complete the processing of specific germanium crystal material. Due to the low hardness of germanium crystal material, the surface finish is not easy to control during processing, and frequent rework is prone to occur, resulting in low processing efficiency. When the surface finish requirement is high, the processing cycle of this kind of material will be longer.

[0003] For small and medium caliber germanium window with an outer diameter of 50-150mm, when polishing the germanium window by using the classical optical processing method, the part surface shape and surface finish are detected in the upper disc state, and after passing the inspection, the part is lowered, cleaned and then hand polished to remove the fine lines on the surface of the part and make the surface finish meet the application requirements. During the hand polishing process, the worker directly polishes the part on the polishing cloth. This process mainly has two problems: low polishing efficiency and easy change of local irregularity index of part surface shape.

[0004] Therefore, it is urgent to provide a high-efficiency polishing method for small and medium caliber germanium window with high surface finish. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned shortcomings and provide a high-finish polishing method for small and medium caliber germanium window.

[0006] The technical solution of the present application is as follows:

[0007] A high-finish polishing method for small and medium caliber germanium window, the outer diameter of the small and medium caliber germanium window is between 50mm and 150mm, comprising the following steps:

[0008] Step one, fine grinding: fine grinding the part on a fine grinding polishing machine for 20min with W14 grit diamond, controlling the vector height difference of the part within-1um, the surface roughness is Ra1.6um, and there is no large knot with a diameter of 0.7-1mm on the part surface shape, and there is no large scratch with a length of 15-20mm and a width of 0.07-0.1mm;

[0009] Step two, rough polishing: the parts are rough polished on the fine grinding polishing machine with W1 particle size of alumina polishing solution, the part surface is controlled within 5 light circles, the surface roughness is Ra 0.012 μm, and there is no large sand eye with a diameter of 0.7 mm to 1 mm, and there is no large scratch with a length of 15 mm to 20 mm and a width of 0.07 mm to 0.1 mm.

[0010] Step three, fine polishing: the parts are further fine polished on the fine grinding polishing machine with W0.3 particle size of alumina polishing solution, the part surface is controlled within 5 light circles, the surface roughness is Ra 0.012 μm, and there is no large sand eye with a diameter of 0.7 mm to 1 mm, and there is no large scratch with a length of 15 mm to 20 mm and a width of 0.07 mm to 0.1 mm; the number of scratches within the width of 0.07 mm is not more than 10.

[0011] Step four, on-disk finishing: the parts are respectively on-disk finished on the fine grinding polishing machine with polishing cloth and W0.25 particle size of diamond solution, the part surface is controlled within 5 light circles, the surface roughness is Ra 0.012 μm, and the surface finish is within level V; and there is no large sand eye with a diameter of 0.7 mm to 1 mm, and there is no large scratch with a length of 15 mm to 20 mm and a width of 0.07 mm to 0.1 mm.

[0012] Step five, off-disk finishing: after the parts are cleaned on the lower disk, they are placed in the clamping tool, and then off-disk finishing is performed on the fine grinding polishing machine with polishing cloth and W0.25 particle size of diamond solution, the part surface is controlled within 5 light circles, the surface roughness is Ra 0.012 μm, and the surface finish is within level V; and there is no large sand eye with a diameter of 0.7 mm to 1 mm, and there is no large scratch with a length of 15 mm to 20 mm and a width of 0.07 mm to 0.1 mm.

[0013] Preferably, in step one, the spindle speed of the fine grinding polishing machine is 70 r / min to 60 r / min; the swing shaft speed is 60 r / min to 50 r / min, and the load is 50 N to 70 N.

[0014] Preferably, in steps two, three, four and five, the spindle speed of the fine grinding polishing machine is 40 r / min to 50 r / min; the swing shaft speed is 30 r / min to 40 r / min, and the load is 50 N.

[0015] Preferably, in step four, the polishing die base material on the fine grinding polishing machine is aluminum, a 3mm-5mm thick layer of asphalt is coated on the polishing surface of the polishing die, and then a 1mm-2mm polishing cloth layer is pasted on the surface, thereby forming the polishing die, the polishing die is washed clean before use, the diamond solution is uniformly sprayed on the surface of the polishing cloth layer, and then the part to be processed is placed on the polishing die to perform on-disk polishing.

[0016] Preferably, in step five, the base material of the clamping tool is polytetrafluoroethylene, the upper part of the clamping tool is the clamping part, and the lower part is the handle part, the top end of the clamping part is processed with a corresponding groove according to the outer diameter and thickness of the part, and a layer of polishing cloth is pasted on the surface of the groove, the part to be processed is placed on the polishing die with the surface to be processed facing downward and the non-processing surface facing upward, and then the fine grinding polishing machine is operated to perform off-disk polishing.

[0017] Preferably, the rough polishing time is more than 8h, the fine polishing time is more than 4h, the single polishing time for on-disk polishing is 15min-20min, and the single polishing time for off-disk polishing is 3min-5min.

[0018] Preferably, the fine grinding polishing machine is MMP400B type precision fine grinding polishing machine.

[0019] The application also includes other components or steps that can enable it to be used normally, which are conventional means in the art, and in addition, the steps, devices or components not defined in the application all adopt the existing technology in the art.

[0020] The working principle of the present application is that, firstly, in the fine grinding step, the surface quality and the surface shape of the part can be effectively improved after single grinding for 20 minutes, and the difficulty of the polishing stage is reduced. On this basis, the sample is polished, and the polishing stage is divided into three stages according to the type and particle size of the polishing powder. The main purpose of rough polishing is to quickly correct the surface shape of the part. According to the surface shape change of the part in the polishing stage, the speed of the main shaft and the swing shaft of the equipment can be adjusted. The polishing in this stage is generally after 8 hours, and the surface shape of the part can be basically controlled within 5 channels of low aperture. At the same time, the surface of the part is polished to be very bright, and the surface roughness has been obviously improved compared with that after fine grinding, but there are a large number of fine lines on the surface, which restricts the surface roughness grade of the part. It is necessary to use polishing powder with finer particle size to correct it. When fine polishing, the part is continuously polished by using W0.3 alumina polishing powder with smaller particle size, and the equipment parameters remain unchanged. After about 4 hours of polishing, the fine lines on the surface of the part are effectively removed, and the surface roughness is further improved. However, there are still a small number of fine lines on the surface, and the surface roughness of the part still has a certain distance from the application. It is found that this is related to the polishing base. Since the hardness of germanium crystal material is relatively low, although the pitch polishing mold used for polishing has a hardness of only 60 degrees (Schall A), the hardness is still relatively high, and it is easier to cause scratches on the surface during actual polishing. Therefore, it is necessary to adjust the polishing base. The application prepares a polishing cloth base for polishing. The hardness of the base is obviously lower than that of the pitch mold, and diamond solution with higher hardness and slightly lower particle size is selected as the polishing liquid to ensure the efficiency of the part during polishing. The disc-on-disc polishing method is used, and the single polishing time is about 15-20 minutes. The equipment parameters remain unchanged. After disc-on-disc polishing, the fine lines on the surface of the part are basically removed, and the surface roughness of the part can meet the requirements. Since the polishing time is short, the surface shape of the part does not change obviously, and it can still meet the requirements of the drawing. A small number of shallow fine lines and marks will appear on the surface of the part during the disc-off cleaning and before vacuum coating. This is not conducive to vacuum coating and will affect the firmness of the film. The part needs to be polished again to improve the surface quality. Through the design of a special clamping tool, the part can be directly polished off the disc without being placed on the disc again, and the shallow fine lines and marks on the surface of the part can be effectively removed to ensure the surface roughness of the part.

[0021] Compared with the prior art, the present application has the beneficial effects that: on the basis of the classical optical processing method of polishing germanium window, the present application proposes a polishing process combining disc-on-disc polishing and disc-off polishing, and improves the disc-off polishing process, effectively improves the surface roughness and polishing efficiency of small and medium caliber germanium window, and does not have a great influence on the surface shape of the part, which is helpful to ensure the product quality. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The process flow chart of the present application in the embodiment.

[0023] Figure 2 Structure diagram of the polishing mold of the present application in the embodiment.

[0024] Figure 3 Structure diagram of the clamping tool of the present application in the embodiment.

[0025] Figure 4 Structure diagram of the clamping tool of the present application in the embodiment. Figure 3 Structure diagram of the clamping tool of the present application in the embodiment.

[0026] Figure 5 Structure diagram of the part one in the embodiment 1.

[0027] Figure 6 Structure diagram of the part two in the embodiment 2.

[0028] Figure 7 Structure diagram of the part two in the embodiment 2. Figure 6 Structure diagram of the part two in the embodiment 2. DETAILED DESCRIPTION

[0029] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0030] Embodiment 1:

[0031] As shown in the drawings, the present application provides a high-finish polishing method for small and medium caliber germanium window, which is used for polishing the germanium window shown in the part one, and the polishing technical index is: N=5, ΔN=1, B=Ⅴ, θ=1', effective Φ100mm (wherein N represents the number of annulus on the part surface shape, ΔN represents the adjustment amount of annulus on the part surface shape, θ represents the parallelism, B is the surface finish, and effective Φ100mm represents that the part surface shape is effective within the range of 100mm in diameter of the center point), and the method comprises the following steps. Figure 1 Figure 5 Step one, fine grinding: using W14 granularity diamond to fine grind the part on the fine grinding polishing machine for 20min, the spindle speed of the fine grinding polishing machine is 70r / min~60r / min, the swing shaft speed is 60r / min~50r / min, and the load is 50N~70N, so that the part surface quality and surface shape can be effectively improved and the difficulty of polishing stage is reduced.

[0032] Step two, rough polishing: using W12 granularity diamond to rough polish the part on the rough polishing machine for 20min, the spindle speed of the rough polishing machine is 60r / min~50r / min, the swing shaft speed is 50r / min~40r / min, and the load is 70N~90N, so that the part surface quality and surface shape can be effectively improved and the difficulty of polishing stage is reduced.

[0033] ​Step two, rough polishing: the parts are rough polished on the fine grinding polishing machine with W1 particle size of aluminum oxide polishing solution, the spindle speed of the fine grinding polishing machine is 40r / min~50r / min; the swing shaft speed is 30r / min~40r / min, and the load is 50N; after rough polishing for 8h, the surface profile of the part can be basically controlled in low aperture 5 channels. At the same time, the part surface is very bright, and the surface finish has been significantly improved compared with the fine grinding, but there are a large number of fine roads on the surface, which need to be corrected using polishing powder with finer particle size.

[0034] Step three, fine polishing: the parts are further fine polished on the fine grinding polishing machine with W0.3 particle size of aluminum oxide polishing solution, the spindle speed of the fine grinding polishing machine is 40r / min~50r / min; the swing shaft speed is 30r / min~40r / min, and the load is 50N, after fine polishing for 4h, the fine roads on the part surface are effectively removed, and the surface finish is further improved. But there are still a small amount of fine roads on the surface, and there is still a certain distance from the required surface finish.

[0035] Step four, on-disk finishing: the parts are respectively finished on the disk on the fine grinding polishing machine with polishing cloth and W0.25 particle size of diamond solution, the single finishing time is 15min~20min, the spindle speed of the fine grinding polishing machine is 40r / min~50r / min; the swing shaft speed is 30r / min~40r / min, and the load is 50N, after on-disk finishing, the fine roads on the part surface are basically removed, which can better meet the demand of the part for surface finish. At the same time, due to the short polishing time, the surface profile of the part has not changed significantly, and still meets the application requirements.

[0036] Step five, off-disk finishing: after the parts are cleaned on the lower disk, the relatively shallow fine roads on the surface are placed in the clamping tool, and the parts are respectively finished off-disk on the fine grinding polishing machine with polishing cloth and W0.25 particle size of diamond solution, the single finishing time is 3min~5min, the spindle speed of the fine grinding polishing machine is 40r / min~50r / min; the swing shaft speed is 30r / min~40r / min, and the load is 50N, the special clamping tool can be used to directly finish the parts without re-disk, effectively remove the fine roads generated during the lower disk cleaning process, and ensure the surface finish of the parts.

[0037] Specifically, as Figure 2As shown in step four, the polishing die base material on the fine grinding and polishing machine is aluminum, a 3mm-5mm thick layer of asphalt 1 is applied on the polishing surface of the polishing die, and then a 1mm-2mm polishing cloth layer 2 is pasted on the surface, thereby forming a polishing die. When used, the polishing die is cleaned, the diamond solution is uniformly sprayed on the surface of the polishing cloth layer, and then the part to be processed is placed on the polishing die to perform on-disk polishing.

[0038] Further, as shown in Figure 3 、 Figure 4 The base material of the clamping tool is polytetrafluoroethylene, the upper part of the clamping tool is a clamping part 3, and the lower part is a handle part 4. The top end of the clamping part is processed with a corresponding groove 5 according to the outer diameter and thickness of the part one. A layer of polishing cloth 6 is pasted on the surface of the groove. When used, the part to be processed is placed on the polishing die with the non-processing surface facing up, and then the fine grinding and polishing machine is operated to perform off-disk polishing.

[0039] After detection, the product has reached the requirements of the polishing technical index.

[0040] Example 2:

[0041] As shown in Figure 6 、 Figure 7 The difference between this embodiment and example 1 is only in the processing of part two. The polishing technical index is: N=5, ΔN=1, B=Ⅶ, θ=2'. After detection, the product has also reached the requirements of the polishing technical index, which again confirms the feasibility of the polishing method proposed in the application.

[0042] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for high-gloss polishing of small-to-medium diameter germanium windows, wherein the outer diameter of the small-to-medium diameter germanium window is between 50 mm and 150 mm, characterized in that: Includes the following steps: Step 1, Fine Grinding: On a fine grinding and polishing machine, use W14 grit diamond abrasive to fine grind the parts for 20 minutes, controlling the sagittal difference of the parts to be within -1μm, the surface roughness to be Ra1.6μm, and the surface of the parts to be free of large spots with a diameter between 0.7mm and 1mm, as well as large scratches with a length between 15mm and 20mm and a width between 0.07mm and 0.1mm. Step 2, Rough Polishing: On a fine polishing machine, use W1 grit alumina polishing liquid to rough polish the parts, control the surface shape of the parts within 5 light rings, the surface roughness is Ra0.012μm, and the surface shape of the parts does not have large spots with a diameter between 0.7mm and 1mm, nor large scratches with a length between 15mm and 20mm and a width between 0.07mm and 0.1mm. Step 3, Fine Polishing: On a fine polishing machine, continue fine polishing of the parts using alumina polishing slurry with a particle size of W0.

3. Control the surface shape of the parts within 5 polishing rings, the surface roughness to be Ra0.012μm, and the surface shape of the parts should not have large sand holes with a diameter between 0.7mm and 1mm, nor large scratches with a length between 15mm and 20mm and a width between 0.07mm and 0.1mm; the number of scratches within 0.07mm in width should not exceed 10. Step 4, Disc Polishing: On a fine polishing machine, use a polishing cloth with a diamond solution of W0.25 particle size to perform disc polishing on the parts, controlling the surface shape of the parts within 5 passes, the surface roughness to Ra0.012μm, and the surface finish to Grade V or below; and the surface shape of the parts should not have large sand holes with a diameter between 0.7mm and 1mm, nor large scratches with a length between 15mm and 20mm and a width between 0.07mm and 0.1mm; The base material of the polishing mold on the fine grinding and polishing machine is aluminum. A 3mm to 5mm thick layer of asphalt is applied to the polishing surface of the polishing mold, and then a 1mm to 2mm polishing cloth layer is pasted on its surface to make a polishing mold. When using it, the polishing mold is cleaned, diamond solution is evenly sprayed on the surface of the polishing cloth layer, and then the parts to be processed are placed on it for on-disc polishing. Step 5, Under-plate polishing: After cleaning the under-plate, the parts are placed in the clamping fixture. On the fine polishing machine, polishing cloth is used with diamond solution of W0.25 particle size to polish the parts individually under-plate. The surface shape of the parts is controlled within 5 passes, the surface roughness is Ra0.012μm, the surface finish is within Grade V, and there are no large sand holes with a diameter between 0.7mm and 1mm, nor large scratches with a length between 15mm and 20mm and a width between 0.07mm and 0.1mm.

2. The method for high-gloss polishing of small-to-medium diameter germanium windows according to claim 1, characterized in that: In step one, the spindle speed of the fine grinding and polishing machine is 70 r / min to 60 r / min; the swing shaft speed is 60 r / min to 50 r / min; and the load is 50 N to 70 N.

3. The method for high-gloss polishing of small-to-medium diameter germanium windows according to claim 2, characterized in that: In steps two, three, four, and five, the spindle speed of the fine grinding and polishing machine is 40 r / min to 50 r / min; the swing shaft speed is 30 r / min to 40 r / min; and the load is 50 N.

4. The method for high-gloss polishing of small-to-medium diameter germanium windows according to claim 1, characterized in that: In step five, the base material of the clamping fixture is polytetrafluoroethylene, and the upper part of the clamping fixture is the clamping part, and the lower part is the handle part. The top of the clamping part is machined with a corresponding groove according to the outer diameter and thickness of the part. A layer of polishing cloth is pasted on the surface of the groove. When using it, the part to be machined is placed with the non-machined side facing down and the non-machined side facing up, and it is pressed on the polishing mold. Then, the fine grinding and polishing machine is run for under-plate polishing.

5. A method for high-gloss polishing of small-to-medium diameter germanium windows according to any one of claims 1 to 4, characterized in that: The coarse polishing time is more than 8 hours, the fine polishing time is more than 4 hours, the single polishing time on the disc is 15 min to 20 min, and the single polishing time under the disc is 3 min to 5 min.

6. The method for high-gloss polishing of small-to-medium diameter germanium windows according to claim 5, characterized in that: The precision grinding and polishing machine is the MMP400B model.

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