A post-welding processing method for lightweight thin-walled cabin

Abstract

The present invention discloses a method for post-welding processing of a lightweight thin-walled cabin body. The method comprises the following steps: fitting a post-welding scanning model of a thin-walled cabin body with a theoretical three-dimensional model, determining the offset between the actual central rib surfaces of the upper and lower ribs of a weld and the corresponding central rib surfaces of the theoretical three-dimensional model, designing a continuous rib compensation method at the weld, and generating a fitting processing digital model; designing a rough processing and fine processing numerical control program for a lightening groove at the weld according to the fitting processing digital model; designing and processing a milling cutter with unequal helical angles coated with a DLC coating; and performing post-welding processing on the lightening groove using a milling cutter in a dry cutting environment based on the numerical control program, so as to achieve uniform thickness of the lightening groove of the thin-walled cabin body and continuity of the reinforcing ribs after processing.

Description

Technical Field

[0001] The invention relates to a post-welding processing method for a lightweight thin-wall cabin body, and belongs to the technical field of numerical control processing. Background Art

[0002] The lightweight thin-walled cabin is a large lightweight thin-walled shell made of high-specific-strength aluminum alloy 5B70, and there is a strong demand for weight reduction. In order to fully reduce weight while ensuring reliability, the sealed cabin adopts an integral wall plate structure, and the skin and reinforcement are formed by integrated processing of thick plates, reducing the number of welds and using continuous rib configuration to improve sealing performance and reliability, and reduce structural mass.

[0003] 1) The thickness of the bottom skin of the grid cavity is thin, which makes processing difficult

[0004] The thinnest part of the cabin is 1.2mm, and the largest grid is 887×486mm. The wall thickness of the product is an important dimension. The stress and strain caused by machining and cutting and the stress caused by welding will have a great impact on the product size and state.

[0005] 2) Vibration during cutting is difficult to suppress

[0006] After the product is integrated into one, it adopts the process route of overall CNC machining. Different from the traditional wall panel processing that is close to the rigid mold, the lightweight and thin-walled cabin is hollow and has no rigid mold for effective support. During the cutting process, it is very easy to cause processing vibration due to the influence of resonance, cutting force changes, etc., and the processing risk is high.

[0007] 3) Cutting fluid is not allowed to be used in the whole cabin processing after welding, as the knife may get sticky during the processing.

[0008] During the processing of the entire cabin after welding, in order to avoid pollution and corrosion, it is clearly required that the use of cutting fluid is strictly prohibited. A large amount of heat is generated during the cutting process, which causes adhesion between the aluminum alloy and the cutting tool, bringing challenges to the processing.

[0009] At present, the processing of cabins mainly adopts the single-wall panel forming-rolling-welding method. This production model cannot be applied to the processing of lightweight thin-walled cabins with continuous rib configurations. Summary of the invention

[0010] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, the present invention provides a method for post-welding processing of a lightweight thin-walled cabin, designs a special vibration-damping tool, optimizes the processing route, and performs dry cutting processing on the thin-walled cabin to achieve uniform thickness of the lightening groove of the thin-walled cabin and continuity of the reinforcing ribs after processing.

[0011] The technical solution of the present invention is:

[0012] A post-welding processing method for a lightweight thin-walled cabin body, comprising:

[0013] The post-weld scanning model of the thin-walled cabin is fitted with the theoretical three-dimensional model to determine the offset between the actual center rib surface of the upper and lower ribs of the weld and the corresponding center rib surface of the theoretical three-dimensional model, design the continuous rib compensation method at the weld, and generate the fitting state processing digital model;

[0014] Design the rough machining and finishing NC program of the weld lightening groove according to the fitting state machining digital model;

[0015] Design and process DLC coated unequal helix angle milling cutters;

[0016] Based on the NC program, the lightening groove is post-welded processed by a milling cutter in a dry cutting environment.

[0017] Preferably, the continuous rib compensation method at the weld is:

[0018] If the deviation between the actual center rib surface and the theoretical center rib surface of the upper and lower ribs of the weld is less than 0.2 mm, the theoretical three-dimensional model is used for model fitting;

[0019] If the offset between the actual center rib surface and the theoretical center rib surface of the upper and lower ribs of the weld is greater than 0.2mm, take the intersection of the welds on the same side of the upper and lower ribs as the base point and sweep the offset ribs with equal rib width.

[0020] Preferably, the design of the lightening groove rough machining and fine machining NC program adopts layer priority mode for rough machining and fine machining of the lightening groove bottom surface; and sets a single-turn 1 / 8 area as the basic adjustment unit of the NC program.

[0021] Preferably, the design of the lightening groove roughing and finishing NC program includes:

[0022] Roughly process the side wall of the weld, leaving a 5mm margin at the bottom and a 3mm margin on the side wall;

[0023] Then process the feed groove, leaving 3mm margin at the bottom and 4mm margin on the side wall;

[0024] Machining the lightening groove bottom, leaving 3mm margin at the bottom, 3mm margin on the side wall, 2mm cutting depth, 2mm step distance;

[0025] Measure the thickness of the groove bottom surface and make tool length compensation;

[0026] Process the infeed groove again, the bottom reaches the size, and a 4mm margin is left on the side wall;

[0027] Finish the bottom of the groove to reduce the size, leaving a 3mm margin on the side wall;

[0028] Reduce the root cleaning of the groove side walls and ensure that the side walls and bottom surfaces are to size.

[0029] Preferably, a DLC coated unequal helix angle milling cutter is designed, comprising:

[0030] Design a 49°~51° high helix angle milling cutter with a rake angle of 18°, a first clearance angle of 14°, a second clearance angle of 26°, and variable pitch treatment for processing and lightening the side wall of the groove;

[0031] Design a milling cutter with a low helix angle of 8° to 10°, with a front angle of 16°, a first clearance angle of 12°, a second clearance angle of 25°, and variable pitch processing for processing and lightening the bottom of the groove;

[0032] The surfaces of the two milling cutters are coated with DLC coating.

[0033] Preferably, the post-welding processing of the lightening groove using a milling cutter in a dry cutting environment based on the numerical control program includes:

[0034] The DLC standard END16 milling cutter is used to rough-process the annular weld side wall allowance of 3mm and the bottom allowance of 5mm. The cutting parameters are speed 10000-12000r / min, feed 5000-7000mm / min, cutting depth 1mm, and cutting width 12mm.

[0035] Use 8°~10° low helix angle milling cutter END10 to process the feed groove, 10000-12000r / min, feed 3000-4500mm / min, cutting depth 0.5mm, cutting width 10mm;

[0036] Use 8°~10° low helix angle END10 milling cutter to adopt "large cutting depth, small cutting width" to reduce the bottom surface of the groove to size, and use cutting parameters of speed 10000-12000r / min, feed 5000-7000mm / min, cutting depth 3mm, cutting width 2mm;

[0037] Use END10R3 milling cutter with high helix angle of 49°~51° for root cleaning, and adopt cutting parameters of speed 10000-12000r / min, feed 4000-6000mm / min, cutting depth 1mm, and cutting width 3mm.

[0038] Preferably, in the process of performing post-weld processing of the lightening groove using a milling cutter in a dry cutting environment based on the numerical control program, supercritical carbon dioxide is used for cooling and lubrication between the tool and the lightening groove cutting part.

[0039] Preferably, the welded thin-walled cabin body is scanned, a post-weld scanned model of the thin-walled cabin body is reversely generated, a reference coordinate system consistent with the theoretical three-dimensional model is established, and the post-weld scanned model of the thin-walled cabin body is fitted with the theoretical three-dimensional model in the design three-dimensional software.

[0040] The beneficial effects of the present invention compared with the prior art are:

[0041] (1) The present invention solves the difficult problems of vibration suppression and deformation control during the post-processing of lightweight thin-walled cabin ring welding, optimizes the CNC processing process route, ensures that the product reduces the thickness of the bottom of the groove, strengthens the ribs continuously, and ensures the product processing accuracy.

[0042] (2) The present invention designs two milling cutters with unequal helix angles and adopts low-temperature cooling technology to suppress the vibration of the tool and the product during the processing, suppress the adhesion of the tool and the aluminum alloy in a dry cutting environment, and ensure the surface quality of the product during dry cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of a post-welding processing method for a lightweight thin-walled cabin according to an embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of a thin-walled cabin model after welding according to an embodiment of the present invention;

[0045] Figure 3 This is a flow chart of CNC machining of lightweight thin-walled cabin body after welding according to an embodiment of the present invention;

[0046] Figure 4 This is a schematic diagram of the design of a CNC machining adjustment unit for a lightweight thin-walled cabin according to an embodiment of the present invention;

[0047] Figure 5 Schematic diagram of the offset between the actual center rib surface and the theoretical center rib surface of the upper and lower ribs of the weld according to the embodiment of the present invention;

[0048] Figure 6 Schematic diagram of milling cutter design according to an embodiment of the present invention;

[0049] Figure 7 This is a schematic diagram of reducing groove processing according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0051] The present invention proposes a method for post-welding processing of a lightweight thin-walled cabin body, such as Figure 1 As shown, including:

[0052] Step 1, obtaining a theoretical three-dimensional model of the lightweight cabin product after welding;

[0053] Step 2: Use 3D scanning to obtain the real size of the cabin after welding, and reversely generate the real product after welding scanning model, such as Figure 2As shown; among them, scanning the cabin after welding requires establishing a reference coordinate system WCS (workpiece coordinate system) consistent with the theoretical three-dimensional model. At the same time, it is necessary to obtain the actual dimensions of the cabin interior and the weld at the circumferential weld to generate a post-weld scanning model of the real product.

[0054] Step 3: Fit the post-weld scanning model of the real product with the theoretical three-dimensional model of the product, formulate a continuous rib compensation method, determine the offset (i.e., misalignment) between the actual center rib surface and the theoretical center rib surface of the upper and lower ribs of the weld, and generate a fitting model;

[0055] Open the theoretical 3D model of the product in the 3D design software, set the model WCS coordinate system to be consistent with the coordinate system of the real product post-weld scan model, import the scanned model into the software, and formulate the upper and lower continuous rib compensation mechanism of the girth weld, such as Figure 5 As shown:

[0056] 1) The offset between the actual center rib surface of the upper and lower ribs and the theoretical center rib surface is less than 0.2 mm, and the theoretical model is used for model fitting;

[0057] 2) The offset between the actual center rib surface and the theoretical center rib surface of the upper and lower ribs is greater than 0.2mm. Taking the intersection of the welds on the same side of the upper and lower ribs as the base point, the offset ribs are generated by sweeping with equal rib width.

[0058] Boolean operations are used in the software to obtain a fitting processing digital model.

[0059] Step 4: According to the fitting state model, optimize the program preparation process, which is consistent with the processing sequence, such as Figure 3 As shown in the figure, the NC machining program for the lightening groove at the weld is compiled in sequence and issued to the production site. Figure 7 As shown, ① is the rough machining part, ② is the one-time machining of the cutting groove and the bottom surface (leaving a 3mm margin on the bottom surface), ③ is the fine machining of the bottom surface (bottom surface to size), and ④ is the side wall root cleaning part.

[0060] The CNC program for rough machining and finishing of the lightening groove is compiled. The lightening groove is first rough machined in layer priority mode, and then the lightening groove finishing is completed by the "large cutting depth and small cutting width" method. The "large cutting depth and small cutting width" method is a cutting method with large axial cutting depth, small radial cutting width, high speed and high feed. The constant cutting amount ensures the stability of cutting force and cutting heat. During the product processing, the cabin will produce a large deformation as the stress is released in the process. At this time, the product has spatial position deviation and thickness deviation. In order to ensure the thickness of the product, the program needs to be adjusted to ensure the thickness of the bottom of the lightening groove. In order to facilitate program adjustment during processing, the single-turn 1 / 8 area is determined as the basic adjustment unit, such as Figure 4As shown in the figure, if there are too many single-turn adjustment units, although the skin thickness accuracy is higher, the amount of NC program will increase and the processing efficiency will be low; if there are too few single-turn adjustment units, although the efficiency is high, the thickness accuracy of the bottom of the lightening groove cannot be guaranteed. Comprehensive product processing efficiency and skin thickness accuracy requirements.

[0061] Step 5: According to the tool design requirements, a DLC (DiamondLike Carbon) coated unequal helical angle milling cutter is obtained. The tool design diagram is shown in the figure below. Figure 6 shown.

[0062] The unequal helix angle vibration-damping tool is designed for dry cutting environment. The tool body is made of cemented carbide and the milling cutter is coated with DLC coating. The DLC coating solves the problem that aluminum alloy is easy to stick to ordinary tools during dry cutting, affecting the product processing quality.

[0063] Changing the helix angle of the same cutting edge of the milling cutter, using unequal spacing between the cutting edges, changing the resonant frequency of the tool during continuous cutting, and suppressing the occurrence of vibration from a mechanism perspective. Design two milling cutters with unequal helix angles:

[0064] The total contact edge of the high helix angle milling cutter is long, the axial projection is longer, the side wall finish is better, the cutting is stable, and the axial cutting force is larger, which is suitable for processing the lightened groove side wall;

[0065] The total contact edge length axial projection of the low helix angle milling cutter is relatively short, which is suitable for cutting the bottom of the groove.

[0066] Through a large number of cutting tests in production, it is known that when the lead angle of a high helix angle milling cutter is greater than 51°, the surface roughness of the groove side wall is reduced. When the lead angle is less than 49°, the cutting force increases during the side wall cutting process, which easily leads to overcutting of the product and quality problems. When the angle of a low helix angle milling cutter is greater than 10°, the cutting force is too large when cutting the bottom surface, and the bottom surface quality is poor. When the lead angle is less than 8°, the cutting edge is too small and the product cannot be processed.

[0067] Design a 49°~51° high helix angle milling cutter with a front angle of 18°, a first back angle of 14°, and a second back angle of 26°, and perform variable pitch processing, such as Figure 6 (a) is used for processing the side wall of the lightening groove;

[0068] Design a milling cutter with a low helix angle of 8° to 10°, with a front angle of 16°, a first back angle of 12°, and a second back angle of 25°, and perform variable pitch processing, such as Figure 6 As shown in (b), it is used to process the bottom of the lightening groove to ensure the bottom thickness of the product.

[0069]

[0070] Step six: The DLC coated unequal helix angle milling cutter uses a low-temperature cooling and lubrication device in a dry cutting environment to perform lightening groove processing at the weld after welding to achieve precise processing of the lightweight cabin.

[0071] The DLC standard END16 milling cutter is used to rough-process the annular weld side wall allowance of 3mm and the bottom allowance of 5mm. The cutting parameters are speed 10000-12000r / min, feed 5000-7000mm / min, cutting depth 1mm, and cutting width 12mm.

[0072] Use 8° low helix angle END10 milling cutter to process the feed groove, 10000-12000r / min, feed 3000-4500mm / min, cutting depth 0.5mm, cutting width 10mm;

[0073] Use 8° low helix angle END10 milling cutter to process the bottom surface of the skin to size with "large cutting body and small cutting width". The cutting parameters are 10000-12000r / min, feed 5000-7000mm / min, cutting depth 3mm, and cutting width 2mm.

[0074] Finally, a 49° high helix angle END10R3 milling cutter was used for root cleaning, with cutting parameters of speed 10000-12000r / min, feed 4000-6000mm / min, cutting depth 1mm, and cutting width 3mm.

[0075] During the machining process, supercritical carbon dioxide is used for cooling and lubrication of the tool and the cabin cutting part. After the machining is completed, the cabin post-weld annular weld processing is realized. Carbon dioxide is a gas at room temperature. It can condense into liquid (or even solid) under a certain pressure at room temperature. When the pressure is removed, carbon dioxide evaporates (sublimates) quickly, taking away a lot of heat and achieving the purpose of cooling. It effectively ensures the quality of dry cutting processing of products and prolongs the life of tools.

[0076] For the thin-walled cabin after girth welding, the scanning model was fitted with the theoretical model, the continuous rib adjustment method was formulated, and the unequal helical angle end mills were designed. The product processing flow was optimized and low-temperature lubrication cooling technology was used. Finally, the thickness range of the groove bottom was reduced to 1.15-1.32mm, meeting the design index of 1.2 (-0.1, +0.2) mm.

[0077] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0078] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A method for post-welding processing of a lightweight thin-walled cabin, characterized in that: include: The post-weld scanning model of the thin-walled cabin is fitted with the theoretical three-dimensional model to determine the offset between the actual center rib surface of the upper and lower ribs of the weld and the corresponding center rib surface of the theoretical three-dimensional model, design the continuous rib compensation method at the weld, and generate the fitting state processing digital model; Design the rough machining and finishing NC program of the weld lightening groove according to the fitting state machining digital model; Design and process DLC coated unequal helix angle milling cutters, including: designing a 49° to 51° high helix angle milling cutter, with a front angle of 18°, a first clearance angle of 14°, a second clearance angle of 26°, and a variable pitch treatment for processing and reducing the side wall of the groove; designing an 8° to 10° low helix angle milling cutter, with a front angle of 16°, a first clearance angle of 12°, a second clearance angle of 25°, and a variable pitch treatment for processing and reducing the bottom of the groove; coating the surfaces of the two unequal helix angle milling cutters with DLC coating; Based on the NC program, the lightening groove is post-welded processed by a milling cutter in a dry cutting environment.

2. A method for post-welding processing of a lightweight thin-walled cabin according to claim 1, characterized in that: The continuous reinforcement compensation method at the weld is: If the deviation between the actual center rib surface and the theoretical center rib surface of the upper and lower ribs of the weld is less than 0.2 mm, the theoretical three-dimensional model is used for model fitting; If the offset between the actual center rib surface and the theoretical center rib surface of the upper and lower ribs of the weld is greater than 0.2mm, take the intersection of the welds on the same side of the upper and lower ribs as the base point and sweep with equal rib width to generate offset ribs.

3. A method for post-welding processing of a lightweight thin-walled cabin according to claim 1, characterized in that: The design of the lightening groove rough machining and fine machining NC program adopts the layer priority mode for rough machining and fine machining of the lightening groove bottom surface; and sets the single-turn 1 / 8 area as the basic adjustment unit of the NC program.

4. A method for post-welding processing of a lightweight thin-walled cabin according to claim 1, characterized in that: The design lightening groove roughing and finishing NC program includes: Roughly process the side wall of the weld, leaving a 5mm margin at the bottom and a 3mm margin on the side wall; Then process the feed groove, leaving 3mm margin at the bottom and 4mm margin on the side wall; Machining the lightening groove bottom, leaving 3mm margin at the bottom, 3mm margin on the side wall, 2mm cutting depth, 2mm step distance; Measure the thickness of the groove bottom surface and make tool length compensation; Process the infeed groove again, the bottom reaches the size, and a 4mm margin is left on the side wall; Finish the bottom of the groove to reduce the size, leaving a 3mm margin on the side wall; Reduce the root cleaning of the groove side walls and ensure that the side walls and bottom surfaces are to size.

5. A lightweight thin-walled cabin post-welding processing method according to claim 1, characterized in that: Based on the numerical control program, post-welding processing of the lightening groove using a milling cutter in a dry cutting environment includes: The DLC standard END16 milling cutter is used to rough-process the annular weld side wall allowance of 3mm and the bottom allowance of 5mm. The cutting parameters are speed 10000-12000r / min, feed 5000-7000mm / min, cutting depth 1mm, and cutting width 12mm. Use 8°~10° low helix angle milling cutter END10 to process the feed groove, 10000-12000r / min, feed 3000-4500mm / min, cutting depth 0.5mm, cutting width 10mm; Use END10 milling cutter with low helix angle of 8°~10° to adopt "large cutting depth and small cutting width" to reduce the bottom surface of the groove to size. The cutting parameters are speed 10000-12000r / min, feed 5000-7000mm / min, cutting depth 3mm, and cutting width 2mm. Use END10R3 milling cutter with high helix angle of 49°~51° for root cleaning, and adopt cutting parameters of speed 10000-12000r / min, feed 4000-6000mm / min, cutting depth 1mm, and cutting width 3mm.

6. A method for post-welding processing of a lightweight thin-walled cabin according to claim 1, characterized in that: In the process of post-welding processing of the lightening groove by a milling cutter in a dry cutting environment based on the numerical control program, supercritical carbon dioxide is used for cooling and lubrication between the cutter and the lightening groove cutting part.

7. A method for post-welding processing of a lightweight thin-walled cabin according to claim 1, characterized in that: Scan the welded thin-walled cabin, reversely generate the post-weld scan model of the thin-walled cabin, establish a reference coordinate system consistent with the theoretical 3D model, and fit the post-weld scan model of the thin-walled cabin with the theoretical 3D model in the design 3D software.

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