Automated wet cutting and grinding processing method for ceramic covers

Abstract

The present invention discloses an automated wet cutting and grinding processing method for a ceramic cover, comprising the following steps: blank cutting, rough machining, semi-finishing of the inner shape, automated finishing of the inner shape, and automated finishing of the outer shape. In the core finishing process of the automated wet cutting and grinding processing method for the ceramic cover of the present invention, the conventional dry cutting processing method using a PCD diamond milling cutter is cancelled. Instead, high-purity water is innovatively used as the coolant, which achieves a water cooling effect without introducing metal ion impurities, and increases the upper limit of the spindle allowable speed by nearly three times. After the spindle speed is increased, sintered grinding heads and sandblasting grinding heads are used instead of the PCD diamond milling cutter, and together with a special clamping fixture, the surface roughness of the processed product is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of machining of precision structural parts of ceramic materials, and particularly relates to an automated wet cutting and grinding method for ceramic covers. Background Art

[0002] The ceramic cover (such as Figure 1 ) assembled to the warhead part of the missile is an important structural part for the missile warhead system to receive combat information. As the "retina" of the missile, the ceramic cover needs to have characteristics such as anti-electromagnetic interference, high temperature resistance, and erosion resistance. Therefore, it is necessary to use ultra-high temperature resistant ceramic matrix composite materials for processing. The ceramic material is formed after densification and has extremely high hardness. During the processing process, it is necessary to maintain a high degree of cleanliness to avoid introducing metal ion impurities. The external dimensions and apparent quality requirements are relatively high, and the processing difficulty is extremely high. Moreover, the woven fibers (such as Figure 2 ) in the ceramic material are extremely easy to break during the processing process, causing the densified matter to fall off, affecting its surface roughness, and further affecting the electrical performance of the product.

[0003] The existing domestic processing methods for ceramic covers are all dry cutting by milling. The dry cutting method can avoid introducing metal ion impurities, but the dry cutting method will generate extremely high frictional heat, the tool life is extremely low, and the damage to the woven body is relatively large, which cannot meet the requirements of stable and continuous processing and surface roughness requirements of ceramic covers. At the same time, dry cutting will generate a large amount of dust, which has a negative impact on the physical health of operators. Summary of the Invention

[0004] Aiming at the problems described in the background art, the purpose of the present invention is to provide a processing method for ceramic covers that can not only achieve stable, continuous and batch processing, but also greatly improve the surface roughness of the product, and at the same time minimize the generation of dust.

[0005] To achieve the above purpose, the automated wet cutting and grinding method for ceramic covers designed by the present invention includes the following steps:

[0006] S1, blank cutting: After the blank is densified and its hardness meets the requirements, it is cut into square materials with the length and width dimensions required for the ceramic cover.

[0007] S2, rough machining: The square material processed in step S1 is densified again, and the material hardness needs to meet the clamping requirements of the vertical machining center; mill the blank with the length, width, and height dimensions required for the ceramic cover.

[0008] S3, semi-finishing of the inner shape: After the blank processed in step S2 is continuously densified, a concave pit of the ceramic cover is roughly machined in the center of the blank.

[0009] S4, Inward automatic precision machining: The blank processed in step S3 is further densified, and the material hardness should reach the requirements for automatic machining of flexible units. Clamp the blank onto a pallet and machine the inner shape of the ceramic cover in the order of rough machining, finish machining, and filleting. During the entire inward automatic precision machining process, high-purity water should be used as the coolant.

[0010] S5, Outward automatic precision machining: Turn over the blank processed in step S4 and clamp it onto another pallet. Machine the outer shape of the ceramic cover, and the automatic machining process is the same as that in step S4.

[0011] Preferably, in S1, high-purity water is used as the coolant, and a SiC grinding wheel is used for cutting.

[0012] Preferably, in S2, the clamping contact surface of the square material should be isolated and protected with a nylon sheet to prevent metal impurities and dirt from entering the product interior.

[0013] Preferably, in S2, a PCD diamond milling cutter is used for milling. No coolant should be used during the milling process. To avoid excessive cutting heat and reduce the tool life, the feed rate during the machining process should be controlled within 3200 mm / min, the cutting amount should be controlled at 0.5 mm per layer, and the spindle speed should be controlled within 3600 rpm.

[0014] Preferably, in S3, the depth of the pit is offset 1 mm outward from the final depth of the inner shape.

[0015] Preferably, in S3, a PCD diamond milling cutter is used for milling. No coolant should be used during the milling process. To avoid excessive cutting heat and reduce the tool life, the feed rate during the machining process should be controlled within 3200 mm / min, the cutting amount should be controlled at 0.5 mm per layer, and the spindle speed should be controlled within 3600 rpm.

[0016] Preferably, in S4, after clamping the blank, use a feeler gauge to detect the gap between the workpiece and the pallet contact surface. If the gap is less than 0.02 mm, the clamping is qualified.

[0017] Preferably, in S4, a sintered grinding head is used for rough machining to quickly remove the surplus material, machining to leave a 0.2 mm surplus on each side of the final size, and the set cutting amount for rough machining is 0.2 mm per layer. A sandblasting grinding head is used for finish machining the inner shape to the final size, and the set cutting amount for finish machining is 0.05 mm per layer. A PCD diamond milling cutter is required for interpolation machining of the filleting.

[0018] Compared with the prior art, the present invention has the following advantages: In the core finishing process of the automated wet cutting and grinding method for ceramic covers, the conventional dry cutting method using PCD diamond milling cutters is cancelled. Instead, high-purity water is innovatively used as the coolant, which achieves a water cooling effect without introducing metal ion impurities, and increases the upper limit of the permitted spindle speed by nearly three times. After the spindle speed is increased, sintered grinding heads and abrasive blasting grinding heads are used instead of PCD diamond milling cutters, and together with a special clamping fixture, the surface roughness of the processed product is greatly improved.

[0019] At the same time, the upgrade from "air cooling" to "water cooling" enables the tool life to be extended by 5 to 10 times, eliminating the need for frequent manual tool changes and meeting the requirements of automated production. Fast feeding is achieved through an automatic feeding tray and a wedge-shaped pressing block, automatic detection is realized through a built-in probe of the machine tool, and automatic tool compensation for unprocessed dimensions can be carried out by setting logical judgments in the processing program, ultimately achieving full automation of the finishing process. Compared with manual finishing, the dimensional consistency of the product is greatly improved, and human quality problems are eliminated. Since actual production was put into operation for one year, more than 2,000 ceramic covers have been processed, and none of them exceeded the tolerance, achieving a processing qualification rate of 100%.

[0020] The automated wet cutting and grinding method for ceramic covers of the present invention solves the deficiencies of the conventional dry cutting method for milling, such as low tool life and poor surface quality of the product. It can not only effectively extend the tool life and reduce production costs, but also improve the surface quality of the product. This method is applicable to the processing of various ceramic covers with rectangular flanges.

[0021] Based on the material characteristics of the ceramic cover, the present invention reasonably designs different forming processes such as cutting, milling, and grinding. By innovatively using high-purity water for "wet cutting" and replacing the milling cutter with a grinding head for high-speed grinding, the surface quality of the product is improved, dust generation is reduced, and further introduction of an automated processing method greatly enhances the quality stability of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a three-dimensional schematic diagram of the ceramic cover;

[0023] Figure 2 is a schematic diagram of the woven body fibers in the ceramic material;

[0024] Figure 3 is a schematic diagram of the T-shaped chute fixture structure of the present invention;

[0025] Figure 4 is Figure 3 the cross-sectional view of A-A in

[0026] Figure 5 is a schematic diagram of the T-shaped key block structure of the present invention;

[0027] Figure 6 It is a schematic diagram of the semi-finishing structure of the ceramic cover of the present invention;

[0028] Figure 7 It is the present invention Figure 6 Cross-sectional view B-B in the present invention;

[0029] Figure 8 It is the front view schematic diagram of the automatic loading pallet clamping and tooling structure of the present invention;

[0030] Figure 9 It is the top view schematic diagram of the automatic loading pallet clamping and tooling structure of the present invention;

[0031] Figure 10 It is the schematic diagram of the wedge-shaped pressing block tooling structure of the present invention;

[0032] Figure 11 It is the cross-sectional view of the wedge-shaped pressing block tooling of the present invention;

[0033] Figure 12 It is the schematic diagram of the internal profile finishing structure of the ceramic cover of the present invention;

[0034] Figure 13 It is the cross-sectional schematic diagram of the internal profile finishing structure of the ceramic cover of the present invention;

[0035] Figure 14 It is the schematic diagram of the external profile finishing structure C-C of the ceramic cover of the present invention;

[0036] Figure 15 It is the schematic diagram of the external profile finishing structure D-D of the ceramic cover of the present invention. Specific embodiments

[0037] The technical solutions (including the preferred technical solutions) of the present invention will be further described in detail below by means of the accompanying drawings and by listing some optional 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 creative efforts shall fall within the scope of protection of the present invention.

[0038] The automated wet cutting and grinding processing method for the ceramic cover designed by the present invention includes the following steps:

[0039] 1) Blank cutting: The initial blank is in a fabric state and cannot be machined. After three densification processes, the hardness of the blank reaches the cutting requirement. The blank is clamped on a numerically controlled sawing machine, and high-purity water is used as the coolant (high-purity water can achieve a refrigeration effect and will not introduce metal ion impurities). The stainless steel pneumatic fixture is installed on the T-slot tooling 1 through the T-shaped key block 2. The tooling is as Figures 3 to 5As shown, start the stainless - steel pneumatic fixture to compress the blank, and use a SiC grinding wheel to cut it into a square material with a length of 265 mm and a width of 235 mm, without machining in the thickness direction.

[0040] 2) Rough machining: Continue to perform three densification processes on the square material processed in step 1). After densification is completed, the hardness of the material reaches the clamping requirement of the vertical machining center. Clamp the workpiece with an ordinary vise, and use nylon sheets to isolate and protect the clamping contact surface to prevent rust or dirt of the vise from entering the product interior. Use a PCD diamond milling cutter for milling. During the milling process, do not use any coolant. To avoid excessive cutting heat and reduce the tool life, the feed rate during the machining process needs to be controlled within 3200 mm / min, the cutting amount is controlled at 0.5 mm per layer, and the spindle speed is controlled within 3600 rpm. Finally, machine the product to a size of length 261 mm, width 231 mm, and height 65 mm.

[0041] 3) Inner - shape semi - finishing: Continue to perform three densification processes on the workpiece processed in step 2). At this time, the densification effect of the densification process begins to decrease, and it is necessary to increase the contact area between the outer surface of the workpiece and the densified material. Therefore, inner - shape semi - finishing is carried out. The inner - shape semi - finishing also uses a PCD diamond milling cutter for machining. During the process, do not use any coolant, and the cutting parameters are the same as those in step 2). Finally, a pit with a length of 216 mm and a width of 186 mm is machined in the center of the product. The depth of the pit is offset 1 mm outward from the final depth of the inner - shape. See the semi - finishing structure diagram in Figure 6 、 Figure 7 。

[0042] 4) Inner - shape automatic finishing: Due to the high requirements for product consistency and cleanliness of the ceramic cover 5, manual machining is likely to lead to discrete machining results, and impurities are easily introduced during the production preparation process. Therefore, the finishing process needs to achieve automatic machining. The specific process of inner - shape automatic finishing is as follows: Continue to perform 3 densification processes on the workpiece processed in step 3). After densification is completed, the hardness of the material reaches the automatic machining requirement of the flexible unit. Clamp the workpiece on the automatic loading tray. See the tray clamping schematic diagram in Figure 8 、 Figure 9 and fix it through four wedge - shaped pressing blocks 3 and baffles 4. See the wedge - shaped pressing blocks in Figure 10 、 Figure 11, after the fixation is completed, use a feeler gauge to detect the gap between the workpiece and the pallet contact surface. If the gap is less than 0.02 mm, the clamping is qualified. The operator places the qualified pallet on the loading station of the automatic magazine, and the manipulator forks the pallet to the machining station to be processed. Repeat the above operations until the machining station to be processed is full. Start the flexible unit and call the automatic machining main program to start automatic machining. The main program includes a detection program and a machining program. The detection program takes points through a three-coordinate probe. After obtaining the point position data, it executes the logic judgment in the program, and can realize dimension detection, automatic centering and automatic tool compensation; the machining program is divided into rough machining, finish machining and filleting. The rough machining uses a sintered grinding head to quickly remove the surplus material, and leaves a 0.2 mm surplus on each side when machining to the final size. The cutting amount set for rough machining is 0.2 mm per layer. The finish machining uses a sandblasting grinding head to machine the inner shape to the final size. The cutting amount set for finish machining is 0.05 mm per layer. Since the dimensional discreteness of the sintered grinding head and the sandblasting grinding head is relatively large during the production and manufacturing process, and the deviation of the actual tool diameter is relatively large, the sintered grinding head and the sandblasting grinding head cannot be used for filleting. PCD diamond milling cutters need to be used for interpolation machining for filleting to ensure that the sizes of the 4 inner shape fillets are qualified. See the structure diagram of the inner shape finish machining in Figure 12 , Figure 13 .

[0043] During the entire automatic finish machining of the inner shape, high-purity water needs to be used as the coolant (since high-purity water cooling has no rust prevention ability, all components of the entire water circulation cooling system in the machine tool need to be made of stainless steel). In the water-cooled state, the tool life of each tool can be greatly extended. According to the actual machining data statistics, compared with dry cutting, the tool life of water-cooled cutting can be extended by 5 to 10 times, which can meet the requirements of stable and continuous machining of ceramic covers. On the premise of water cooling, the spindle speed can be further increased to 12,000 rpm. The microscopic effect of low-speed cutting is "tearing off" the braid, while the microscopic effect of high-speed cutting is "grinding off" the braid. Therefore, the surface roughness of the ceramic cover machined by high-speed grinding has been greatly improved, and no surface manual repair is required.

[0044] 5) Automatic finish machining of the outer shape: After step 4) is completed, directly turn the product over and clamp it on another set of pallets. The positions of the wedge-shaped pressing blocks and baffles on this set of pallets are adapted to the size of the machined flange. After the clamping is completed, start the flexible unit for machining. The principle, program and tools of automatic machining are the same as those in step 4). See the structure diagram of the outer shape finish machining in Figure 10 .

[0045] 6) Cleaning of the cooling system: During the original dry cutting process, dust would disperse throughout the processing area. A high-power exhaust fan had to be used throughout the process to extract the dust, resulting in serious air pollution and a heavy burden on the operator's body. In the present invention, "water cooling" is adopted using high-purity water in the above-mentioned processes 1), 4), and 5). All the dust generated during the processing would dissolve into the high-purity water, greatly improving the air quality in the processing area. However, as more dust dissolves, the pH value of the high-purity water would be affected by acidic components such as silica sol in the dust, changing from neutral to acidic. The acidic high-purity water has a weak corrosive effect on the stainless-steel fittings of the cooling system. Therefore, it is necessary to filter out the dust in the high-purity water. In the present invention, a three-stage filtering method is adopted, namely: filtering with a high-mesh filter screen, sedimentation filtering in the water tank, and filtering with a high-speed centrifuge, comprehensively realizing the filtering requirements of the high-purity water coolant.

[0046] The automated wet cutting and grinding method for ceramic covers of the present invention is applied to the processing of ceramic covers of a certain engineering warhead. More than 2,000 ceramic covers are processed in total, and the qualified rate reaches 100%. The processed products have good apparent quality and do not require manual repair. The tool life is increased by 5 to 10 times, greatly reducing the production cost. The important processing procedures are fully automated, with high product consistency, and no powder is generated during the processing, greatly reducing the damage to the environment and the operator's body.

[0047] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and do not limit the present invention. Any modifications, combinations, substitutions, improvements, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. An automated wet cutting and grinding processing method for ceramic covers, characterized in that, It includes the following steps: S1, blank cutting: After densifying the blank and reaching the required hardness, cut it into square materials with the required length and width dimensions for the ceramic cover; use high-purity water as the coolant and a SiC grinding wheel for cutting; S2, rough machining: Densify the square material processed in step S1 again, and the material hardness should reach the clamping requirement of the vertical machining center; mill the blank with the required length, width, and height dimensions for the ceramic cover; S3, semi-finishing of the inner shape: After continuing to densify the blank processed in step S2, rough machine a concave pit for the ceramic cover in the center of the blank; S4, automatic finishing of the inner shape: Continuously densify the blank processed in step S3, and the material hardness should reach the automatic processing requirement of the flexible unit; clamp the blank to a pallet and machine the inner shape of the ceramic cover in the order of rough repair, fine repair, and rounding of the fillet; During the entire automatic finishing process of the inner shape, high-purity water should be used as the coolant; for rough repair, use a sintered grinding head to quickly remove the surplus, machine to the final size with a 0.2 mm allowance on each side, and set the cutting amount to 0.2 mm per layer for rough repair; for fine repair, use a sandblasting grinding head to machine the inner shape to the final size, and set the cutting amount to 0.05 mm per layer for fine repair; for rounding of the fillet, interpolation machining should be carried out using a PCD diamond milling cutter; S5, automatic finishing of the outer shape: Turn over the blank processed in step S4 and clamp it to another pallet; machine the outer shape of the ceramic cover, and the automatic processing procedure is the same as that in step S4.

2. The automated wet cutting and grinding processing method for ceramic covers according to claim 1, characterized in that: In S2, the clamping contact surface of the square material should be isolated and protected with a nylon sheet to prevent metal impurities and dirt from entering the product interior.

3. The automated wet cutting and grinding processing method for ceramic covers according to claim 1 or 2, characterized in that: In S2, a PCD diamond milling cutter is used for milling. No coolant should be used during the milling process. To avoid excessive cutting heat and reduce the tool life, the feed rate during the processing should be controlled within 3200 mm / min, the cutting amount should be controlled at 0.5 mm per layer, and the spindle speed should be controlled within 3600 rpm.

4. The automated wet cutting and grinding processing method for ceramic covers according to claim 1, characterized in that: In S3, the depth of the concave pit is offset 1 mm outward from the final depth of the inner shape.

5. The automated wet cutting and grinding processing method for ceramic covers according to claim 1 or 4, characterized in that: In S3, a PCD diamond milling cutter is used for milling. No coolant should be used during the milling process. To avoid excessive cutting heat and reduce the tool life, the feed rate during the processing should be controlled within 3200 mm / min, the cutting amount should be controlled at 0.5 mm per layer, and the spindle speed should be controlled within 3600 rpm.

6. The automated wet cutting and grinding processing method for ceramic covers according to claim 1, characterized in that: In S4, after clamping the blank, use a feeler gauge to detect the gap between the workpiece and the pallet contact surface. If the gap is less than 0.02 mm, the clamping is qualified.

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