A method of adjusting the intermediate overlap of a coupling thread

Abstract

The application discloses a method for adjusting intermediate overlapping buckle of coupling thread, and belongs to the technical field of oil casing coupling processing. The method collects parameters such as actual total length of the coupling and thread pitch through benchmark positioning, establishes a quantitative compensation algorithm based on length difference and pitch, calculates the axial compensation amount of a single-end cutter, realizes accurate alignment of the intermediate thread profile through synchronous and equal axial adjustment of two ends, and eliminates the problems of intermediate overlapping buckle, disorderly buckle and meshing interference caused by pitch cumulative error and axial positioning deviation in the processing. The method has high adjustment precision, strong universality, does not need to modify equipment, can significantly improve the processing qualified rate of the coupling thread, reduces the production rework cost, and is suitable for automatic processing and error compensation of the butt thread of various oil casing couplings.

Description

Technical Field

[0001] This invention belongs to the field of oil casing coupling processing technology, and particularly relates to a method for adjusting the intermediate overlapping threads of the coupling thread. Background Technology

[0002] Oil casing couplings are core components used in oil and gas extraction to connect oil pipes and casing. They typically employ a two-end internal tapered thread machining structure, with the threads formed by CNC lathe machining from both ends. During actual machining, factors such as coupling blank length tolerances, machine tool positioning errors, tool zero-position drift, and cumulative pitch errors can easily lead to defects such as thread overlap, misalignment, and meshing interference at the midpoint of the coupling's thread connection. These defects are collectively referred to in the industry as intermediate overlap threads.

[0003] Existing processing technologies largely rely on operators' experience for manual trial cutting and repeated adjustments, lacking standardized and quantifiable compensation schemes. This results in problems such as low adjustment accuracy, poor consistency, and high time and labor costs. Intermediate overlap defects can directly lead to problems such as sticking, seizing, and sealing failure during on-site coupling installation, reducing the strength and service life of the threaded connection, seriously affecting the safety of oil and gas extraction operations, and causing high product scrap rates, large rework volumes, and increased production costs for enterprises.

[0004] Therefore, developing a quantifiable, automated, and highly adaptable method for adjusting the intermediate overlapping threads of couplings has become a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for adjusting the intermediate overlapping threads of coupling threads, so as to achieve precise quantitative compensation for overlapping thread errors, eliminate intermediate thread overlap, random threading and interference problems, and improve the machining accuracy and product qualification rate of coupling threads.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] The present invention discloses a method for adjusting the intermediate overlapping threads of a coupling, comprising the following steps:

[0008] 1) Benchmark positioning and parameter acquisition

[0009] Using the outer circular end faces of both ends of the coupling as the axial machining reference, after the coupling is fixedly clamped, the actual total length L of the coupling, the standard thread pitch P, the theoretical effective thread engagement length and the alignment position parameters of the intermediate target are collected by the machine tool measurement system.

[0010] 2) Overlapping error compensation calculation

[0011] Establish the formula for axial compensation calculation:

[0012] Δ = (L − n×P) / 2

[0013] in:

[0014] Δ represents the axial compensation amount for a single-ended tool;

[0015] L is the measured total length of the coupling;

[0016] P is the thread pitch;

[0017] n is a positive integer, and the value is chosen such that |L − n×P| is the minimum value;

[0018] 3) Axial synchronous adjustment of the tool

[0019] Perform tool adjustment based on the calculated compensation amount Δ:

[0020] When Δ > 0, the two cutting tools at both ends move Δ distance towards the inside of the coupling simultaneously;

[0021] When Δ < 0, the two cutting tools at both ends move synchronously outward of the coupling by a distance of |Δ|.

[0022] During the adjustment process, the movement at both ends should be equal and symmetrical to ensure that the middle thread is centered and aligned.

[0023] Furthermore, it also includes 4) trial cutting and precision verification:

[0024] Complete the thread trial cutting process according to the adjusted parameters. Use thread plug gauges and axial measuring tools to check the overlap of intermediate tooth profiles and the smoothness of meshing. Confirm that there is no overlap, no cross-threading, and no meshing interference to be considered qualified.

[0025] Furthermore, it also includes 5) batch automated processing:

[0026] The verified compensation parameters are written into the CNC system to achieve automated batch compensation processing of couplings of the same specification.

[0027] Furthermore, specifically:

[0028] Processing specifications: Φ177.8mm oil casing coupling

[0029] Thread parameters: Pitch P = 3.175mm

[0030] The total length of the coupling was measured to be L=254.10mm using a machine tool measuring system;

[0031] Calculate the integer n=80, the theoretical length n×P=80×3.175=254.00mm;

[0032] The compensation amount is calculated as Δ = (254.10 − 254.00) / 2 = 0.05 mm;

[0033] The cutters at both ends move 0.05mm inward towards the coupling simultaneously.

[0034] Furthermore, after trial cutting and testing, the intermediate thread profiles were found to be completely aligned, with no overlap or cross-threading, and the meshing was smooth.

[0035] Furthermore, specifically:

[0036] Processing specifications: Φ139.7mm oil casing coupling

[0037] Thread parameters: Pitch P = 3.175mm

[0038] 1. The actual measured total length of the coupling, L = 202.38 mm;

[0039] 2. Taking n=64, the theoretical length is 64×3.175=203.20mm;

[0040] 3. Calculate the compensation amount Δ = (202.38 − 203.20) / 2 = −0.41 mm;

[0041] 4. The cutters at both ends move 0.41mm outward simultaneously towards the outside of the coupling;

[0042] 5. After the trial cut is successful, batch processing will begin.

[0043] Furthermore, after trial cutting and testing, the intermediate thread profiles were found to be completely aligned, with no overlap or cross-threading, and the meshing was smooth.

[0044] Key points of the invention:

[0045] 1. A quantitative compensation algorithm for intermediate overlap threads based on the measured total length of the coupling and the pitch;

[0046] 2. The cutting tools at both ends are adjusted synchronously and equally in an axial direction;

[0047] 3. A lightweight implementation method that requires no tooling modifications and relies solely on program compensation.

[0048] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0049] 1. Thorough Defect Elimination: Precisely compensates for cumulative errors in length and pitch, completely eliminating issues such as overlapping threads, random threads, and meshing interference.

[0050] 2. High adjustment accuracy: Axial compensation error ≤0.01mm, thread engagement accuracy meets API and special airtight thread standards;

[0051] 3. High versatility: Applicable to the machining of various coupling threads, such as API round threads, trapezoidal threads, and special airtight threads;

[0052] 4. Significant cost reduction and efficiency improvement: No need for repeated manual trial cutting, scrap rate is greatly reduced, and processing efficiency is increased by more than 30%;

[0053] 5. Low implementation cost: It can be achieved without changing the machine tool structure or adding special tooling, and only through CNC programs. Attached Figure Description

[0054] The present invention will be further described below with reference to the accompanying drawings.

[0055] Figure 1 This is a schematic diagram of the overall structure of the coupling's top thread;

[0056] Figure 2 This is a schematic diagram of the morphology of the overlapping buckle defect in the middle;

[0057] Figure 3 This is a schematic diagram illustrating the compensation and adjustment principle of the present invention;

[0058] Figure 4 The flowchart is shown in the example. Detailed Implementation

[0059] Example 1

[0060] Processing specifications: Φ177.8mm oil casing coupling

[0061] Thread parameters: Pitch P = 3.175mm

[0062] 1. The total length of the coupling, measured using a machine tool measuring system, is L = 254.10 mm.

[0063] 2. Calculate the integer n=80, the theoretical length n×P=80×3.175=254.00mm;

[0064] 3. Calculate the compensation amount Δ = (254.10 − 254.00) / 2 = 0.05 mm;

[0065] 4. The cutters at both ends move synchronously 0.05mm inward towards the coupling;

[0066] 5. After trial cutting and inspection, the middle thread profile is completely aligned, with no overlap or cross-threading, and the meshing is smooth;

[0067] 6. Write the compensation value into the system for batch processing.

[0068] Example 2

[0069] Processing specifications: Φ139.7mm oil casing coupling

[0070] Thread parameters: Pitch P = 3.175mm

[0071] 1. The actual measured total length of the coupling, L = 202.38 mm;

[0072] 2. Taking n=64, the theoretical length is 64×3.175=203.20mm;

[0073] 3. Calculate the compensation amount Δ = (202.38 − 203.20) / 2 = −0.41 mm;

[0074] 4. The cutters at both ends move 0.41mm outward simultaneously towards the outside of the coupling;

[0075] 5. After trial cutting and inspection, the intermediate thread profiles are completely aligned, with no overlap or cross-threading, and the meshing is smooth.

[0076] 6. Write the compensation value into the system for batch processing.

[0077] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for adjusting the overlapping threads in the middle of a coupling thread, characterized in that, Includes the following steps: 1) Benchmark positioning and parameter acquisition Using the outer circular end faces of both ends of the coupling as the axial machining reference, after the coupling is fixedly clamped, the actual total length L of the coupling, the standard thread pitch P, the theoretical effective thread engagement length and the alignment position parameters of the intermediate target are collected by the machine tool measurement system. 2) Overlapping error compensation calculation Establish the formula for axial compensation calculation: Δ = (L − n×P) / 2; in: Δ represents the axial compensation amount for a single-ended tool; L is the measured total length of the coupling; P is the thread pitch; n is a positive integer, and the value is chosen such that |L − n×P| is the minimum value; 3) Axial synchronous adjustment of the tool Perform tool adjustment based on the calculated compensation amount Δ: When Δ > 0, the two cutting tools at both ends move Δ distance towards the inside of the coupling simultaneously; When Δ < 0, the two cutting tools at both ends move synchronously outward of the coupling by a distance of |Δ|. During the adjustment process, the movement at both ends should be equal and symmetrical to ensure that the middle thread is centered and aligned.

2. The method for adjusting the intermediate overlapping threads of a coupling according to claim 1, characterized in that, It also includes 4) Trial cutting and precision verification: Complete the thread trial cutting process according to the adjusted parameters. Use thread plug gauges and axial measuring tools to check the overlap of intermediate tooth profiles and the smoothness of meshing. Confirm that there is no overlap, no cross-threading, and no meshing interference to be considered qualified.

3. The method for adjusting the intermediate overlapping threads of a coupling according to claim 1 or 2, characterized in that, It also includes 5) Batch automated processing: The verified compensation parameters are written into the CNC system to achieve automated batch compensation processing of couplings of the same specification.

4. The method for adjusting the intermediate overlapping threads of a coupling according to claim 1, characterized in that, Specifically: Processing specifications: Φ177.8mm oil casing coupling Thread parameters: Pitch P = 3.175mm The total length of the coupling was measured to be L=254.10mm using a machine tool measuring system; Calculate the integer n=80, the theoretical length n×P=80×3.175=254.00mm; The compensation amount is calculated as Δ = (254.10 − 254.00) / 2 = 0.05 mm; The cutters at both ends move 0.05mm inward towards the coupling simultaneously.

5. The method for adjusting the intermediate overlapping threads of a coupling according to claim 4, characterized in that, After trial cutting and testing, the middle thread profile was found to be perfectly aligned, with no overlap or cross-threading, and the meshing was smooth.

6. The method for adjusting the intermediate overlapping threads of a coupling according to claim 1, characterized in that, Specifically: Processing specifications: Φ139.7mm oil casing coupling Thread parameters: Pitch P = 3.175mm The measured total length of the coupling is L = 202.38 mm; Taking n=64, the theoretical length is 64×3.175=203.20mm; The compensation amount is calculated as Δ = (202.38 − 203.20) / 2 = −0.41 mm; The two cutting tools at both ends move 0.41mm outwards from the coupling simultaneously; After passing the trial cut, mass production will commence.

7. The method for adjusting the intermediate overlapping threads of a coupling according to claim 6, characterized in that, After trial cutting and testing, the middle thread profile was found to be perfectly aligned, with no overlap or cross-threading, and the meshing was smooth.

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