Anti-deformation clamping method for outer cylinder of low pressure of nuclear power
By using the anti-deformation clamping method, the problem of insufficient clamping rigidity of the low-pressure outer cylinder of nuclear power plants was solved, achieving efficient and stable high-precision machining, improving machining efficiency and clamping stability, and reducing tool wear.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN MARINE DIESEL
- Filing Date
- 2025-04-30
- Publication Date
- 2026-05-29
AI Technical Summary
The existing technology for clamping the low-pressure outer cylinder of nuclear power plants lacks rigidity, making the workpiece prone to vibration during processing and resulting in poor clamping stability. This makes it difficult to meet the requirements of high-precision processing and cannot effectively counteract the deformation caused by the workpiece's own weight, leading to a large deviation between the processed surface and the theoretical design, and low processing efficiency.
The reverse deformation clamping method is adopted, which includes pre-processing the measurement reference surface at the assembly station, flipping it to a station with stronger rigidity for clamping, using low support pads and thrust pads in combination with jacks for reverse support, and using dial indicators to monitor the deformation in real time to accurately compensate for the deformation of the workpiece's own weight. Finally, a pressure plate is used to fix the workpiece.
It improves clamping rigidity, avoids machining vibration, ensures that the machining datum surface is consistent with the theoretical design, increases machining efficiency by about 30%, reduces tool wear and machining costs, and meets high precision requirements.
Smart Images
Figure CN120244654B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of clamping technology for low-pressure outer cylinders in nuclear power plants, and specifically relates to a method for anti-deformation clamping of low-pressure outer cylinders in nuclear power plants. Background Technology
[0002] The low-pressure outer cylinder of a nuclear power plant, a key component of the unit, is composed of six half-cylinders. Each half is up to 12 meters long, 3-4 meters wide, and approximately 4 meters high. Its structure is hollow, housing the inner cylinder. However, the support plates at both ends are relatively thick, while the middle area is thin and hollow, resulting in a significant reduction in overall rigidity. Especially under its own weight, the deformation in the lower middle region can reach nearly 10 mm, severely impacting machining accuracy.
[0003] Traditional processing methods require precision machining at the assembly station, but the support platform at this station is located at both ends, up to 2.7 meters above the bottom surface, requiring support pads with a height of more than 2.7 meters and a span of more than 10 meters.
[0004] Existing clamping methods for low-pressure outer cylinders in nuclear power plants suffer from the following problems: First, the support system lacks rigidity, causing workpiece vibration during machining, necessitating small cutting depths and resulting in low machining efficiency. Second, clamping stability is poor, failing to meet high-precision machining requirements. Furthermore, existing clamping methods cannot effectively counteract workpiece deformation due to its own weight, leading to significant deviations between the machined surface and the theoretical design, requiring repeated adjustments and further extending the machining cycle. Therefore, a novel clamping method is urgently needed that can improve clamping rigidity, compensate for deformation due to its own weight, and enhance machining efficiency. Summary of the Invention
[0005] This invention addresses the problems of existing nuclear power plant low-pressure outer cylinder clamping methods, which fail to effectively counteract workpiece deformation due to its own weight, resulting in large deviations between the machined surface and the theoretical design; insufficient rigidity of the support system leads to workpiece vibration during machining, poor clamping stability, difficulty in meeting high-precision machining requirements, necessitating repeated adjustments, and low machining efficiency. The invention proposes an anti-deformation clamping method for nuclear power plant low-pressure outer cylinders, comprising the following steps:
[0006] S1: Machining of the reference surface at the assembly station:
[0007] At the assembly station, place the workpiece on both sides of the table on the equal height pad, so that the workpiece is suspended in the air, process and measure the reference surface and record the distance dimension A of the first reference surface;
[0008] S2: Workpiece flipping and clamping station adjustment:
[0009] Flip the workpiece to a clamping position with the horizontal split surface facing down, place the low-pressure outer cylinder on the support pad, and measure the distance B between the second reference surface after flipping.
[0010] S3: Deformation detection and reverse compensation:
[0011] A thrust washer is installed at one end of the workpiece, and the other end is supported by a jack. A dial indicator is installed on the outer wall of the side platform of the jack and zeroed.
[0012] S4: Workpiece clamping and accuracy verification:
[0013] Slowly press the workpiece against the outer wall of the jack side platform using a jack, and observe the change in the percentage indicator value. Stop pressing when the value reaches BA. At this time, the deformation of the workpiece due to its own weight is offset in the opposite direction.
[0014] Use a pressure plate to press and fix the low-pressure outer cylinder onto the support pad of the machine tool worktable to complete the clamping.
[0015] According to the above-described method for anti-deformation clamping of a low-pressure outer cylinder for nuclear power plants, the material of the equal-height pad in step S1 is high-hardness alloy steel with a surface roughness ≤ Ra1.6.
[0016] According to the above-described method for anti-deformation clamping of a low-pressure outer cylinder for nuclear power plants, the machining of the measurement reference surface in step S1 is performed using a vertical milling machine with a milling depth ≤ 0.2 mm.
[0017] According to the above-described anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant, the distribution spacing of the support pads in step S2 is ≤500mm to enhance the uniformity of support on the bottom surface of the workpiece.
[0018] According to the above-described anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant, the dial indicator in step S3 has a range ≥15mm and an accuracy class of 0.01mm.
[0019] According to the above-described anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant, the contact surface of the thrust pad in step S3 is provided with anti-slip texture, and the fit with the end face of the workpiece is ≥95%.
[0020] According to the above-described anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant, the lifting speed of the jack in step S4 is ≤0.5mm / s to ensure the accuracy of deformation compensation.
[0021] According to the above-described method for anti-deformation clamping of a low-pressure outer cylinder for nuclear power plants, the clamping force of the pressure plate in step S4 is controlled by a torque wrench, with a torque value of 200-300 N·m.
[0022] According to the above-described method for anti-deformation clamping of a low-pressure outer cylinder for nuclear power plants, step S4 further includes real-time acquisition of dial gauge data during the top-pressing process, and automatic adjustment of the jack stroke through the control system.
[0023] According to the above-described anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant, after step S4 is completed, the deformation of the workpiece reference surface is re-measured using a laser tracker to ensure that the error is ≤0.05mm.
[0024] The beneficial effects of the present invention are as follows:
[0025] 1. This invention pre-processes a measurement reference surface at a less rigid assembly station to provide a basis for subsequent deformation detection; secondly, the workpiece is flipped to a more rigid station for clamping, and combined with a low support pad and thrust pad, the clamping stability is greatly improved and machining vibration is avoided.
[0026] 2. This invention uses a jack for reverse support and a dial indicator to monitor the deformation in real time, accurately compensating for the deformation caused by the workpiece's own weight. After the deformation is reduced to zero, it is then pressed and fixed, ensuring that the machining reference surface is consistent with the theoretical design.
[0027] This method overcomes the limitations of traditional processes, allowing for efficient finishing at non-assembly stations. Cutting parameters can be increased by approximately 30%, significantly improving machining efficiency. Simultaneously, the enhanced clamping rigidity reduces tool wear, extends tool life, and lowers machining costs. Practical verification shows that the nuclear power plant low-pressure outer cylinder machined using this method achieves dimensional accuracy fully meeting drawing requirements and exhibits stable surface quality. It effectively solves the deformation control problem in machining large, thin-walled parts, demonstrating significant engineering application value. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the assembly and use station of the nuclear power low-pressure outer cylinder according to the present invention, which describes a method for anti-deformation clamping of the outer cylinder of a nuclear power plant.
[0029] Figure 2 This is a schematic diagram of the anti-deformation workstation of the low-pressure outer cylinder of a nuclear power plant, which is a method for anti-deformation clamping of the low-pressure outer cylinder of a nuclear power plant according to the present invention.
[0030] In the diagram: 1-Low-pressure outer cylinder, 2-Equal height pad, 3-Support pad, 4-Thrust pad, 5-Jack, 6-Dial indicator. Detailed Implementation
[0031] Preferred Implementation
[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0033] like Figure 1 , Figure 2 As shown: In this embodiment, a method for anti-deformation clamping of a low-pressure outer cylinder for nuclear power plants includes the following steps:
[0034] S1: Machining of the reference surface at the assembly station:
[0035] At the assembly station, place the workpiece on both sides of the table surface on the equal height pad 2, so that the workpiece is suspended in the air, process and measure the reference surface and record the distance dimension A of the first reference surface;
[0036] S2: Workpiece flipping and clamping station adjustment:
[0037] Flip the workpiece to the clamping position with the horizontal split surface facing down, place the low-pressure outer cylinder 1 on the support pad 3, and measure the distance B of the second reference surface after flipping.
[0038] S3: Deformation detection and reverse compensation:
[0039] A thrust pad 4 is set at one end of the workpiece, and the other end is supported by a jack 5. A dial indicator 6 is installed on the outer wall of the side platform of the jack and zeroed.
[0040] S4: Workpiece clamping and accuracy verification:
[0041] Use jack 5 to slowly press the outer wall of the jack side platform of the workpiece and observe the change of the percentage indicator value. When the indicated value reaches BA, stop pressing. At this time, the deformation of the workpiece due to its own weight is offset in the opposite direction.
[0042] Use a pressure plate to press and fix the low-pressure outer cylinder onto the support pad of the machine tool worktable to complete the clamping.
[0043] In step S1, the material of the medium height pad 2 is high hardness alloy steel with a surface roughness ≤ Ra1.6.
[0044] In step S1, the measurement reference surface is machined using a vertical milling machine with a milling depth ≤ 0.2 mm.
[0045] In step S2, the distribution spacing of the support pads 3 is ≤500mm to enhance the uniformity of support on the bottom surface of the workpiece.
[0046] In step S3, the dial indicator 6 has a range of ≥15mm and an accuracy class of 0.01mm.
[0047] In step S3, the contact surface of the stop pad 4 is provided with anti-slip texture, and its fit with the end face of the workpiece is good.
[0048] ≥95%.
[0049] In step S4, the lifting speed of jack 5 is ≤0.5mm / s to ensure the accuracy of deformation compensation.
[0050] In step S4, the clamping force of the pressure plate is controlled by a torque wrench, with a torque value of 200-300 N·m.
[0051] Step S4 also includes collecting dial gauge data in real time during the pressing process and automatically adjusting the jack stroke through the control system.
[0052] After step S4 is completed, use a laser tracker to re-measure the deformation of the workpiece reference surface to ensure that the error is ≤0.05mm.
[0053] The implementation process of the present invention is described in detail below with reference to the accompanying drawings:
[0054] Step 1: Machining of the reference surface at the assembly station
[0055] like Figure 1 As shown, the low-pressure outer cylinder 1 is hoisted to the assembly and use station, and the two side platforms are placed on the leveling pad 2 with a height of 2.8 meters to ensure that the workpiece is horizontal. A vertical milling machine is used to machine the measurement reference surface, and the distance A from the reference surface to the reference point is recorded. During machining, the milling depth is controlled within 0.2 mm to avoid additional deformation caused by cutting force.
[0056] Step 2: Workpiece flipping and clamping position adjustment
[0057] The workpiece is rotated 180° so that the horizontal split surface is facing down and transferred to a non-assembly station. This station uses a 50mm high support pad 3 made of hardened steel with a ground surface roughness of Ra1.6. The support pads 3 are evenly spaced at 500mm intervals to ensure uniform distribution of support force on the bottom surface of the workpiece. The workpiece position is adjusted so that one end is close to the thrust pad (4). The contact surface of the thrust pad 4 is designed with cross-shaped anti-slip patterns to enhance friction.
[0058] Step 3: Deformation Detection and Reverse Compensation
[0059] A hydraulic jack (5) is installed at the other end of the workpiece, and a dial indicator (6) is installed on the reference surface on the side of the jack. The dial indicator has a range of 15 mm and an accuracy of 0.01 mm. After zeroing the dial indicator, the jack is slowly started to lift the workpiece at a speed of 0.5 mm / s. The deformation is monitored in real time by the dial indicator 6. When the change in the indicated value reaches BA, that is, the height difference between the reference surfaces of the assembly station and the non-assembly station, the lifting is stopped. At this time, the sinking deformation of the workpiece caused by its own weight has been compensated in the reverse direction, and the whole is restored to the theoretical geometric state.
[0060] Step 4: Workpiece clamping and accuracy verification
[0061] Use a clamping plate to press the workpiece onto the machine tool table. The clamping force is controlled by a torque wrench with a torque value of 250 N·m to avoid overtightening and causing workpiece deformation. After clamping, use a laser tracker to re-measure the deformation of the reference surface, ensuring the error is ≤0.05 mm. If the error exceeds the tolerance, the jack stroke needs to be finely adjusted and the workpiece re-clamped.
[0062] Finally, finishing process
[0063] After clamping, the CNC machine tool is started to perform finishing machining on all surfaces and holes of the outer cylinder. Due to the high clamping rigidity and zero deformation, large cutting parameters can be used, such as increasing the feed rate to 1.3 times the conventional rate, which increases machining efficiency by about 30%. During machining, the machine tool vibration amplitude is significantly reduced, and tool life is extended by more than 15%.
[0064] The contour pad 2 and support pad 3 adopt a modular design, which can be quickly adjusted according to the workpiece size.
[0065] The thrust pad 4 has a built-in pressure sensor that can provide real-time feedback of contact force data to the control system.
[0066] Jack 5 is equipped with a servo motor drive, supporting remote control and automatic stroke adjustment.
[0067] Through the above steps, this invention achieves efficient and high-precision machining of large thin-walled workpieces, and is especially suitable for manufacturing parts with weak rigidity and easy deformation, such as low-pressure outer cylinders for nuclear power plants.
[0068] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for anti-deformation clamping of a low-pressure outer cylinder for nuclear power plants, characterized in that, Includes the following steps: S1: Machining of the reference surface at the assembly station: At the assembly station, place the workpiece on both sides of the table on the equal height pad, so that the workpiece is suspended in the air, process and measure the reference surface and record the distance dimension of the reference surface - A; S2: Workpiece flipping and clamping station adjustment: Flip the workpiece to the clamping position with the horizontal split surface facing down, place the low-pressure outer cylinder on the support pad, and measure the distance dimension B between the reference surface after flipping. S3: Deformation detection and reverse compensation: A thrust washer is installed at one end of the workpiece, and the other end is supported by a jack. A dial indicator is installed on the outer wall of the side platform of the jack and zeroed. S4: Workpiece clamping and accuracy verification: Slowly press the workpiece against the outer wall of the jack side platform using a jack, and observe the change in the percentage indicator value. Stop pressing when the value reaches BA. At this time, the deformation of the workpiece due to its own weight is offset in the opposite direction. Use a pressure plate to press and fix the low-pressure outer cylinder onto the support pad of the machine tool worktable to complete the clamping.
2. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 1, characterized in that: The contour pad mentioned in step S1 is made of high-hardness alloy steel with a surface roughness ≤ Ra1.
6.
3. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 2, characterized in that: The measurement reference surface described in step S1 is machined using a vertical milling machine with a milling depth ≤ 0.2 mm.
4. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 3, characterized in that: The distribution spacing of the support pads in step S2 is ≤500mm to enhance the uniformity of support on the bottom surface of the workpiece.
5. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 4, characterized in that: The dial indicator mentioned in step S3 has a measuring range of ≥15mm and an accuracy class of 0.01mm.
6. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 5, characterized in that: The contact surface of the thrust pad mentioned in step S3 is provided with anti-slip texture, and the fit with the end face of the workpiece is ≥95%.
7. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 6, characterized in that: The lifting speed of the jack in step S4 is ≤0.5mm / s to ensure the accuracy of deformation compensation.
8. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 7, characterized in that: The clamping force of the pressure plate in step S4 is controlled by a torque wrench, with a torque value of 200-300 N·m.
9. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 8, characterized in that: Step S4 also includes collecting dial gauge data in real time during the pressing process and automatically adjusting the jack stroke through the control system.
10. The anti-deformation clamping method for a low-pressure outer cylinder of a nuclear power plant according to claim 9, characterized in that: After step S4 is completed, use a laser tracker to re-measure the deformation of the workpiece reference surface to ensure that the error is ≤0.05mm.