Three-dimensional reconstruction method of internal thread of pipe fittings combined with busbar measurement specifications

Abstract

The present invention discloses a method for three-dimensional reconstruction of internal threads of pipe fittings in combination with busbar measurement specifications. The method includes: using engineering design software to generate a digital three-dimensional model of internal threads of standard pipe fittings; inputting the digital three-dimensional model of internal threads of standard pipe fittings into a three-coordinate measuring instrument; measuring the internal threads of standard pipe fittings with a three-coordinate measuring instrument in a standard environment to obtain a first set of thread busbars; measuring the internal threads of standard pipe fittings with a comparator at the production site to obtain a second set of thread busbars; associating the first set of thread busbars with the second set of thread busbars to obtain a standard association model; measuring the internal threads of product pipe fittings at the production site with a comparator to obtain a third set of thread busbars; converting the third set of thread busbars according to the standard association model to obtain a three-dimensional construction busbar set; and constructing a three-dimensional model of the internal threads according to the three-dimensional construction busbar set. The three-dimensional reconstruction method of the present invention can realize accurate three-dimensional model reconstruction of the internal threads of product pipe fittings at the production site.

Description

Technical Field

[0001] The invention relates to a three-dimensional model reconstruction technology, and in particular to a three-dimensional reconstruction method for internal threads of pipe fittings combined with busbar measurement specifications. Background Art

[0002] For manufacturing companies, it is very important to understand the quality of the products they produce. With the continuous improvement of detection technology, the use of 3D model reconstruction technology to evaluate the dimensional accuracy of products has been widely used in many companies, especially for some products with very precise dimensional requirements. The use of 3D model reconstruction technology for evaluation tests can achieve good results and is also very efficient.

[0003] The current three-dimensional model reconstruction technology mainly uses optical image processing methods.

[0004] Chinese patent (CN110044293) discloses a three-dimensional reconstruction system and a three-dimensional reconstruction method, in which the system includes a loading device, which includes a rotatable rotating frame and a loading table arranged on the rotating frame, and the rotating frame has a rotating shaft; a data acquisition device is arranged at a distance from the loading table, and is used to collect reflected light data of an object on the loading table when the rotating frame rotates to a corresponding angle, and obtain single-view data of the object at the corresponding angle; a data processing device is connected to the data acquisition device, and is used to perform three-dimensional reconstruction based on the single-view data and a reconstruction algorithm.

[0005] Chinese patent (CN109087382) discloses a 3D reconstruction method and a 3D imaging system, which discloses a 3D reconstruction method, including: using two cameras to shoot images of the same target to obtain a first image and a second image respectively; extracting feature points from the first image and the second image respectively; initializing the feature points to obtain feature point descriptors; performing the following processing on each feature point extracted from the first image: performing operations on the descriptors of each feature point extracted from the first image and the descriptors of the feature points extracted from the second image respectively to obtain the matching degree of the two feature points, calculating the parallax of the object points corresponding to the two feature points with the highest matching degree in the two cameras according to the coordinates of the two feature points with the highest matching degree, and then obtaining the depth value and 3D coordinates of the object points corresponding to the two feature points with the highest matching degree.

[0006] The three-dimensional model reconstruction technologies disclosed in the above patent documents are all implemented through optical image processing methods. Such optical image processing methods can only measure and reconstruct the three-dimensional model of the surface of an object, but cannot measure and reconstruct the three-dimensional model of the internal structure of the object.

[0007] Take the oil pipe produced by a steel pipe manufacturer as an example. Both ends of the oil pipe are provided with threads, one end is external thread and the other end is internal thread. When extracting oil, many oil pipes are connected end to end through threads, one by one to form a long oil production pipeline leading into the ground. The threaded connection is the weak link of the oil pipe, so it is very important to ensure the quality of the thread size configuration.

[0008] At present, although optical image processing methods can be used to reconstruct the 3D model of the external thread at one end of the oil pipe, this optical image processing method is not suitable for the 3D model reconstruction of the thread due to the influence of the quality of the photoelectric element itself, the surface quality of the thread and the operating environment, especially it cannot realize the 3D model reconstruction of the thread at the production site. For the internal thread at the other end of the oil pipe, the optical image processing method is completely inapplicable. Summary of the invention

[0009] The purpose of the present invention is to provide a three-dimensional reconstruction method for internal threads of pipe fittings combined with busbar measurement specifications, which can realize accurate three-dimensional model reconstruction of the internal threads of product pipe fittings at the production site.

[0010] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0011] A method for three-dimensional reconstruction of internal threads of pipe fittings combined with busbar measurement specifications comprises the following steps:

[0012] Step 1, input the digital 3D model of the standard internal thread of the pipe fitting into the three-dimensional coordinate measuring machine;

[0013] Step 2, in a standard environment, using a three-dimensional coordinate measuring instrument to measure the internal thread of a standard pipe fitting, and obtaining a three-dimensional generatrix set of the internal thread of the standard pipe fitting, wherein the three-dimensional generatrix set is a first thread generatrix set; when using the three-dimensional coordinate measuring instrument to measure the internal thread of the standard pipe fitting, the measurement is performed based on the digital three-dimensional model and in accordance with a preset generatrix measurement specification;

[0014] Step 3, importing the first thread generatrix set into a comparator;

[0015] Step 4: At the production site, use a comparator to measure the internal thread of the standard pipe fitting, and obtain a three-dimensional generatrix set of the internal thread of the standard pipe fitting, which is the second thread generatrix set; when using the comparator to measure the internal thread of the standard pipe fitting, the measurement is performed according to a preset generatrix measurement specification;

[0016] Step 5, in the comparator, associating the first thread generatrix set with the second thread generatrix set to obtain a standard association model;

[0017] Step 6, using a comparator to measure the internal threads of the product pipe fittings at the production site, and obtaining a three-dimensional generatrix set of the internal threads of the product pipe fittings, the three-dimensional generatrix set being the third thread generatrix set; when using a comparator to measure the internal threads of the product pipe fittings at the production site, the measurement is performed according to a preset generatrix measurement specification;

[0018] Step 7, in the comparator, the third thread generatrix set is converted according to the standard association model, and the converted three-dimensional generatrix set is used as the three-dimensional construction generatrix set of the internal thread of the product pipe fitting;

[0019] Step 8: construct a three-dimensional model of the internal thread of the product pipe fitting according to the three-dimensional construction generatrix set of the internal thread of the product pipe fitting.

[0020] Furthermore, the busbar measurement specification includes: placing the pipe fitting to be measured vertically in a three-dimensional measuring device, dividing the circumference of the pipe fitting into N arc segments, wherein the arc segments are busbar interval arc segments; the stylus of the three-dimensional measuring device measures the thread busbar of the internal thread of the pipe fitting to be measured, and after measuring each thread busbar, the stylus moves along the inner circumference of the pipe fitting by a busbar interval arc segment, and then measures the next thread busbar, until a three-dimensional busbar set consisting of N thread busbars is obtained after measuring N thread busbars; when measuring each thread busbar, the stylus performs point measurement on the profile of the internal thread of the pipe fitting from top to bottom, and then connects the measured points to construct a thread busbar; the measurement of the profile of the internal thread of the pipe fitting is based on a cylindrical coordinate system, and the rotation axis of the cylindrical coordinate system is consistent with the central axis of the pipe fitting to be measured.

[0021] Furthermore, the busbar measurement specification also includes: before measuring the thread busbar of the internal thread of the measured object pipe fitting, first constructing a virtual standard pipe fitting internal thread profile configuration, the axis of the virtual standard pipe fitting internal thread is consistent with the central axis of the measured object pipe fitting; when measuring the internal thread of the measured object pipe fitting, the measuring needle of the three-dimensional measuring device measures along the virtually constructed standard pipe fitting internal thread profile configuration.

[0022] Furthermore, the busbar measurement specification also includes: constructing the virtual standard pipe fitting internal thread profile configuration using a thread digitization method;

[0023] The thread digitization method comprises: defining a standard thread tooth profile contour line according to the thread configuration of the standard pipe fitting, wherein the standard thread tooth profile contour line comprises a first straight line, a first arc, a second straight line, a second arc, a third straight line, a third arc, a fourth straight line and a fourth arc; the first straight line is a straight line contour line of the thread tooth top surface, the first arc is a circular arc contour line between the thread tooth top surface and the bearing surface, the second straight line is a straight line contour line of the thread tooth bearing surface, the second arc is a circular arc contour line between the thread tooth bearing surface and the bottom surface, the third straight line is a straight line contour line of the thread tooth bottom surface, the third arc is a circular arc contour line between the thread tooth bottom surface and the guide surface, the fourth straight line is a straight line contour line of the thread tooth guide surface, and the fourth arc is a circular arc contour line between the thread tooth guide surface and the top surface; setting a two-dimensional temporary coordinate system on the defined standard thread tooth profile contour line, and setting the intersection of the second straight line and the thread mid-diameter line as the origin of the temporary coordinate system; the temporary coordinate system comprises an X-axis and a Z-axis, wherein the Z-axis is parallel to the thread axis. The X-axis is parallel to the thread axis, and the X-axis is perpendicular to the thread axis; discrete points are taken on the defined standard thread tooth profile contour line according to the preset interval distance, and the coordinate values ​​and vector directions of all the obtained discrete points are used to construct the vector set of the standard thread tooth profile contour line; on the standard thread tooth profile contour line, the intersection point of the second straight line and the thread mid-diameter line is used as the calibration point of the standard thread tooth profile contour line; on the measured object pipe fitting, the intersection point of the thread mid-diameter line and the pipe fitting end face is used as the reference point of the pipe fitting; all the discrete points obtained on the standard thread tooth profile contour line are transplanted as a whole to the measured object pipe fitting thread, and the calibration point of the standard thread tooth profile contour line coincides with the reference point of the pipe fitting, and the vector set of the standard thread tooth profile contour line is converted into a vector set of transplanted discrete points, and the transplanted vector set is a transplanted converted vector set; the discrete points represented by the transplanted converted vector set are connected to form a transplanted standard tooth profile contour line, and then the transplanted standard tooth profile contour line is spirally rotated around the thread axis to construct a virtual standard pipe fitting internal thread contour configuration.

[0024] Furthermore, the step 8 also includes: when constructing the three-dimensional model of the internal thread of the pipe fitting according to the three-dimensional constructed generatrix set, inserting a supplementary generatrix between adjacent generatrixes of the three-dimensional constructed generatrix set.

[0025] Furthermore, the step 8 further includes: the inserted supplementary busbar is calculated based on the adjacent busbars and in accordance with the thread busbar interpolation calculation method, the thread busbar interpolation calculation method includes: setting the number t of inserted busbars between each pair of adjacent busbars; when inserting the supplementary busbar, the busbar on one side is used as the first adjacent busbar, and the busbar on the other side is used as the second adjacent busbar; determining the three-dimensional coordinates of the busbar construction points, and then connecting the busbar construction points to construct the inserted supplementary busbar;

[0026] The rule for determining the three-dimensional coordinates of the generatrix construction point is: j =Iρ j +(IIρ j -Iρ j )×t / (t+1),iθ j =Iθ j +(IIθ j -Iθ j )×t / (t+1),iZ j =IZ j +(IIZ j -IZ j) ×t / (t+1); iρ j , iθ j 、iZ j The three-dimensional coordinate value of the j-th busbar construction point of the i-th busbar inserted between adjacent buses is given by iρ j , iθ j 、iZ j Composed of (iρ j ,iθ j ,iZ j ) is the three-dimensional coordinate of the j-th busbar construction point of the i-th busbar inserted between adjacent buses; j , Iθ j , IZ j is the three-dimensional coordinate value of the jth measured point on the first adjacent busbar, given by Iρ j , Iθ j , IZ j Composed of (Iρ j ,Iθ j ,IZ j ) is the three-dimensional coordinate of the jth measured point on the first adjacent busbar; j , IIθ j , IIZ j is the coordinate value of the jth measurement point on the second adjacent busbar, given by IIρ j , IIθ j ,IIZ j Composed of (IIρ j ,IIθ j ,IIZ j ) is the three-dimensional coordinate of the jth measured point on the second adjacent generatrix; the measured point is the measured point obtained by point measuring the profile of the internal thread of the pipe fitting when the comparator measures the thread generatrix.

[0027] Furthermore, the pipe fitting is a petroleum pipe.

[0028] In the three-dimensional reconstruction method of the present invention, a three-dimensional busbar set of the internal thread of the pipe fitting is measured by combining a three-coordinate measuring instrument and a comparator, wherein the three-dimensional busbar set of the internal thread of the standard pipe fitting is measured in a standard environment by a three-coordinate measuring instrument, and the three-dimensional busbar set of the internal thread of the standard pipe fitting is measured at a production site by a comparator. After associating the two sets of three-dimensional busbar sets, a standard association model can be obtained. The internal threads of the product pipe fittings at the production site are measured by a comparator to obtain the three-dimensional busbar set of the internal threads of the product pipe fittings, which are converted according to the standard association model to obtain a three-dimensional constructed busbar set, and the three-dimensional model of the internal thread of the product pipe fitting can be constructed using the three-dimensional constructed busbar set.

[0029] Compared with the prior art, the three-dimensional reconstruction method of the present invention has the beneficial effect of being able to reconstruct the three-dimensional model of the internal thread of the product pipe fitting at the production site, and the reconstructed three-dimensional model can accurately reflect the dimensional configuration of the internal thread of the product pipe fitting in a standard environment, thereby providing strong support for the test evaluation or digital assembly of the internal thread of the product pipe fitting in a digital manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of the method for three-dimensional reconstruction of internal threads of pipe fittings combined with the busbar measurement specification of the present invention;

[0031] Figure 2 It is a schematic diagram of a three-dimensional coordinate measuring machine measuring a pipe fitting in the three-dimensional reconstruction method of the present invention;

[0032] Figure 3 It is a schematic diagram of the comparison instrument measuring the pipe fitting in the three-dimensional reconstruction method of the present invention;

[0033] Figure 4 It is a schematic diagram of a standard thread tooth profile contour line defined according to the thread configuration of a standard pipe in the three-dimensional reconstruction method of the present invention.

[0034] In the figure: 1- three-dimensional coordinate measuring machine, 2- comparison instrument, 3- pipe fitting, 4- measuring probe. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0036] See also Figures 1 to 4 This embodiment provides a three-dimensional reconstruction method for internal threads of pipe fittings combined with busbar measurement specifications. The three-dimensional reconstruction method is used to reconstruct a three-dimensional model of internal threads of pipe fittings of petroleum pipe products at a production site.

[0037] See also Figure 1 The three-dimensional reconstruction method of this embodiment includes the following steps 1 to 8:

[0038] Step 1: Input the digital 3D model of the internal thread of the standard petroleum pipe fitting into the three-dimensional coordinate measuring machine.

[0039] In this embodiment, the digital three-dimensional model is generated by using CAD software. In other embodiments according to the present invention, other engineering design software may also be used to generate the digital three-dimensional model.

[0040] Step 2: In a standard environment, use a three-dimensional coordinate measuring instrument to measure the internal threads of the standard oil pipe parts, and obtain a three-dimensional generatrix set of the internal threads of the standard oil pipe parts, which is a first thread generatrix set. When using the three-dimensional coordinate measuring instrument to measure the internal threads of the standard oil pipe parts, the measurement is performed based on the digital three-dimensional model and in accordance with the preset generatrix measurement specification.

[0041] The process of measuring the internal threads of oil pipe fittings with a three-coordinate measuring instrument is as follows: Figure 2 As shown, the pipe fitting 3 is placed in the three-dimensional coordinate measuring machine 1, and the measuring needle 4 of the three-dimensional coordinate measuring machine 1 is inserted into the pipe fitting 3 to measure the internal thread of the petroleum pipe fitting.

[0042] The standard environment mentioned here usually refers to the laboratory environment. In order to make the measured data as accurate as possible, it is necessary to create an environment in the laboratory where the temperature, humidity, air pressure and other physical and chemical indicators meet the data measurement standards and are stable. The data measured in such an environment will be more accurate and meet the standards.

[0043] Step 3: import the first thread generatrix set into the comparator.

[0044] Step 4, at the production site, use a comparator to measure the internal threads of the oil pipe standard parts, and obtain a three-dimensional generatrix set of the internal threads of the oil pipe standard parts, which is the second thread generatrix set; similarly, when using a comparator to measure the internal threads of the oil pipe standard parts, the measurement is performed according to the preset generatrix measurement specifications.

[0045] Step 5, in the comparator, associate the first thread generatrix set with the second thread generatrix set to obtain a standard association model.

[0046] The correlation process in step 5 is actually to calibrate the comparator. After the correlation with the comparator, the correlation model obtained can reflect the mapping relationship between the dimensional data measured under the standard environment and the dimensional data measured at the production site.

[0047] Step 6, using a comparator to measure the internal threads of the petroleum pipe fittings at the production site, and obtain a three-dimensional generatrix set of the internal threads of the petroleum pipe fittings, which is the third thread generatrix set; similarly, when using a comparator to measure the internal threads of the petroleum pipe fittings at the production site, the measurement is performed according to a preset generatrix measurement specification.

[0048] The process of measuring the internal threads of petroleum pipe fittings with a comparator is as follows: Figure 3 As shown, the pipe fitting 3 is placed in the aligner 2, the measuring needle 4 of the three-dimensional coordinate measuring machine 1 is inserted into the pipe fitting 3, and the internal thread of the petroleum pipe fitting is measured.

[0049] Step 7: In the comparison instrument, the third thread generatrix set is converted according to the standard association model, and the converted three-dimensional generatrix set is used as the three-dimensional construction generatrix set of the internal thread of the oil pipe product pipe fitting. The three-dimensional construction generatrix set is equivalent to the three-dimensional generatrix set of the thread under the standard environment.

[0050] Step 8: construct a three-dimensional model of the internal threads of the oil pipe product fittings according to the three-dimensional construction generatrix set of the internal threads of the oil pipe product fittings.

[0051] In step 8, when constructing the three-dimensional model of the internal thread of the petroleum pipe fitting according to the three-dimensional constructed busbar set, a supplementary busbar is inserted between adjacent busbars of the three-dimensional constructed busbar set, and the inserted supplementary busbar can be calculated according to the adjacent busbars and the thread busbar interpolation calculation method. The thread busbar interpolation calculation method includes: setting the number t of inserted busbars between each pair of adjacent busbars; when inserting the supplementary busbar, the busbar on one side is the first adjacent busbar, and the busbar on the other side is the second adjacent busbar; determining the three-dimensional coordinates of the busbar construction points, and then connecting the busbar construction points to construct the inserted supplementary busbar.

[0052] In the thread generatrix interpolation calculation method, the three-dimensional coordinates of the generatrix construction points are determined as follows: j =Iρ j +(IIρ j -Iρ j )×t / (t+1),iθ j =Iθ j +(IIθ j -Iθ j )×t / (t+1),iZ j =IZ j +(IIZ j -IZ j) ×t / (t+1), where: iρ j , iθ j 、iZ j The three-dimensional coordinate value of the j-th busbar construction point of the i-th busbar inserted between adjacent buses is given by iρ j , iθ j 、iZ j Composed of (iρ j ,iθ j ,iZ j) is the three-dimensional coordinate of the j-th busbar construction point of the i-th busbar inserted between adjacent buses. j , Iθ j , IZ j is the three-dimensional coordinate value of the jth measured point on the first adjacent busbar, given by Iρ j , Iθ j , IZ j Composed of (Iρ j ,Iθ j ,IZ j ) is the three-dimensional coordinate of the jth measured point on the first adjacent busbar. j , IIθ j ,IIZ j is the coordinate value of the jth measurement point on the second adjacent busbar, given by IIρ j , IIθ j ,IIZ j Composed of (IIρ j ,IIθ j ,IIZ j ) is the three-dimensional coordinate of the jth measured point on the second adjacent generatrix. Both i and j are sequential natural numbers. The measured point is the measured point obtained by point measuring the profile of the internal thread of the oil pipe fitting when the comparator measures the thread generatrix. The three-dimensional coordinates are all based on a cylindrical coordinate system, and the rotation axis of the cylindrical coordinate system is consistent with the central axis of the oil pipe fitting to be measured.

[0053] According to the thread busbar interpolation calculation method, supplementary busbars are inserted between adjacent busbars in the three-dimensional constructed busbar set. The purpose is twofold: on the one hand, the number of busbars in the three-dimensional busbar set can be increased, thereby making the constructed three-dimensional model more coherent and realistic; on the other hand, the inserted supplementary busbars can be used to replace a part of the busbars that originally needed to be obtained through measurement. In this way, a relatively complete three-dimensional model can be constructed by measuring only a few busbars, thereby saving busbar measurement time, speeding up the construction of the three-dimensional model, and effectively improving work efficiency.

[0054] The busbar measurement specification in step 2, step 4 and step 6 includes: placing the measured object petroleum pipe fitting vertically in a three-dimensional measuring device, and the three-dimensional measuring device mentioned here refers to a three-dimensional coordinate measuring instrument or a comparator. Divide the circumference of the petroleum pipe fitting into N arc segments, and the arc segments are busbar interval arc segments. The probe of the three-dimensional measuring device measures the thread busbar of the internal thread of the measured object petroleum pipe fitting. After measuring each thread busbar, the probe moves along the inner circumference of the petroleum pipe fitting by a busbar interval arc segment, and then measures the next thread busbar, until the N thread busbars are measured, and a three-dimensional busbar set consisting of N thread busbars is obtained. When measuring each thread busbar, the probe performs point measurement on the contour of the internal thread of the petroleum pipe fitting from top to bottom, and then connects the measured points to construct a thread busbar.

[0055] It should be noted that, in this embodiment, the measurement of the internal thread profile of the petroleum pipe fitting is based on the cylindrical coordinate system, and the rotation axis of the cylindrical coordinate system is consistent with the central axis of the petroleum pipe fitting to be measured. The description of the cylindrical coordinate system in this article is in accordance with the convention established by the International Organization for Standardization (ISO 31-11). According to this convention, the radial distance, azimuth, and altitude in the cylindrical coordinate system are marked as ρ, θ, and Z, respectively.

[0056] The busbar measurement specification in step 2, step 4 and step 6 also includes: when measuring the busbar of the internal thread of the petroleum pipe fitting to be measured, the three-dimensional measuring device uses a cross probe to measure the internal thread of the petroleum pipe fitting to be measured, and the four probe heads of the cross probe respectively measure one-fourth of the circumference of the petroleum pipe fitting to be measured, and each probe head measures N / 4 busbars.

[0057] The generatrix measurement specification in step 2, step 4 and step 6 also includes: before measuring the thread generatrix of the internal thread of the measured object petroleum pipe fitting, first construct a virtual internal thread profile configuration of the petroleum pipe standard part, the axis of the virtual internal thread of the petroleum pipe standard part is consistent with the central axis of the measured object petroleum pipe fitting. When measuring the internal thread of the measured object petroleum pipe fitting, the probe of the three-dimensional measuring device measures along the virtually constructed internal thread profile configuration of the petroleum pipe standard part, thereby improving the speed of measuring the thread generatrix, thereby greatly improving the work efficiency.

[0058] The busbar measurement specification in step 2, step 4 and step 6 also includes: using a thread digitization method to construct a virtual internal thread profile configuration of a petroleum pipe standard part.

[0059] The thread digitization method comprises: defining a standard thread profile according to the thread configuration of the oil pipe standard part, such as Figure 4As shown, the standard thread tooth profile includes a first straight line, a first arc, a second straight line, a second arc, a third straight line, a third arc, a fourth straight line and a fourth arc. The first straight line is a straight line profile of the thread tooth top surface, such as Figure 4 The first arc is the arc contour line between the thread tooth top surface and the load-bearing surface, such as Figure 4 The second straight line is the straight line contour line of the thread tooth bearing surface, such as Figure 4 The second arc is the arc contour line between the thread tooth bearing surface and the bottom surface, such as Figure 4 The third straight line is the straight line contour line of the bottom surface of the thread tooth, such as Figure 4 The third arc is the arc contour line between the bottom surface of the thread tooth and the guide surface, such as Figure 4 The fourth straight line is the straight line contour line of the thread tooth guide surface, such as Figure 4 The fourth arc is the arc contour line between the thread tooth guide surface and the top surface, such as Figure 4 Pointed by the arrow h. Set a two-dimensional temporary coordinate system on the defined standard thread tooth profile contour line. The temporary coordinate system is a plane rectangular coordinate system. Set the intersection of the second straight line and the thread median line as the origin of the temporary coordinate system. The temporary coordinate system includes the X-axis and the Z-axis, wherein the Z-axis is parallel to the thread axis and the X-axis is perpendicular to the thread axis. The definitions of the first straight line, the first arc, the second straight line, the second arc, the third straight line, the third arc, the fourth straight line and the fourth arc based on the temporary coordinate system are as follows:

[0060] First straight line: X=k 11 *Z+a 11 , domain Z∈[d 11min , d 11max ];

[0061] The first arc: (Xb 12 ) 2 =(Zc 12 ) 2 +a 12 , domain Z∈[d 12min , d 12max ];

[0062] Second straight line: X=k 21 *Z+a 21 , domain Z∈[d 21min , d 21max ];

[0063] The second arc: (Xb 22 ) 2 =(Zc 22) 2 +a 22 , domain Z∈[d 22min , d 22max ];

[0064] The third straight line: X=k 31 *Z+a 31 , domain Z∈[d 31min , d 31max ];

[0065] The third arc: (Xb 32 ) 2 =(Zc 32 ) 2 +a 32 , domain Z∈[d 32min , d 32max ];

[0066] Fourth straight line: X=k 41 *Z+a 41 , domain Z∈[d 41min , d 41max ];

[0067] The fourth arc: (Xb 42 ) 2 =(Zc 42 ) 2 +a 42 , domain Z∈[d 42min , d 42max ].

[0068] In the formula, k 11 、a 11 、b 12 、c 12 、a 12 , k 21 、a 21 、b 22 、c 22 、a 22 , k 31 、a 31 、b 32 、c 32 、a 32 , k 41 、a 41 、b 42 、c 42 、a 42 is the function coefficient of the definition formula, d 11min d 12min d 21min d 22min d 31min d 32min d41min d 42min is the Z-axis coordinate of the starting point of each line segment, d 11max d 12max d 21max d 22max d 31max d 32max d 41max d 42max is the Z-axis coordinate of the endpoint of each line segment.

[0069] The thread digitization method also includes: taking discrete points on the defined standard thread tooth profile contour line according to a preset interval distance, and constructing a vector set of the standard thread tooth profile contour line using the coordinate values ​​and vector directions of all the obtained discrete points. The interval distance includes an interval distance preset for a straight line segment and an interval distance preset for an arc segment. On the defined standard thread tooth profile contour line, the intersection point of the second straight line and the thread mid-diameter line is used as a calibration point of the standard thread tooth profile contour line, that is, the origin of the temporary coordinate system. On the measured object petroleum pipe fitting, the intersection point of the thread mid-diameter line and the end face of the petroleum pipe fitting is used as the reference point of the petroleum pipe fitting. All the discrete points obtained on the standard thread tooth profile contour line are transplanted as a whole to the thread of the measured object petroleum pipe fitting, and the calibration point of the standard thread tooth profile contour line coincides with the reference point of the petroleum pipe fitting, and the vector set of the standard thread tooth profile contour line is converted into a vector set of transplanted discrete points, and the transplanted vector set is a transplanted and converted vector set. The formula for converting the vector set of standard thread tooth profile contour lines into the transplanted conversion vector set is TA´=TA•C, where TA´ is the transplanted conversion vector set, TA is the vector set of standard thread tooth profile contour lines, and C is the transplant conversion factor. Connecting the discrete points represented by the transplanted conversion vector set constitutes the transplanted standard tooth profile contour line, and then the transplanted standard tooth profile contour line is spirally rotated around the thread axis of the oil pipe fitting to construct the virtual internal thread profile configuration of the oil pipe standard fitting.

[0070] In the three-dimensional reconstruction method of this embodiment, a three-dimensional generatrix set of the internal threads of the petroleum pipe fittings is measured by combining a three-coordinate measuring instrument and a comparator, wherein the three-dimensional generatrix set of the internal threads of the petroleum pipe standard parts is measured in a standard environment by a three-coordinate measuring instrument, and the three-dimensional generatrix set of the internal threads of the petroleum pipe standard parts is measured at a production site by a comparator. After associating the two sets of three-dimensional generatrix sets, a standard association model can be obtained. The internal threads of the petroleum pipe product fittings at the production site are measured by a comparator to obtain the three-dimensional generatrix set of the internal threads of the petroleum pipe product fittings, and the three-dimensional construction generatrix set is converted according to the standard association model to obtain the three-dimensional construction generatrix set. The three-dimensional model of the internal threads of the petroleum pipe product fittings can be constructed using the three-dimensional construction generatrix set.

[0071] By adopting the three-dimensional reconstruction method of the present embodiment, it is possible to realize the three-dimensional model reconstruction of the internal threads of the oil pipe product fittings at the production site, and the reconstructed three-dimensional model can accurately reflect the size configuration of the internal threads of the oil pipe product fittings in the standard environment, thereby providing strong support for the use of digital methods to test and evaluate the internal threads of the oil pipe product fittings, thereby greatly shortening the test cycle and reducing the test cost. In addition, it can also realize the digital assembly of the internal threads of the oil pipe fittings, directly calculate the close distance of the threads, ensure the make-up quality of each thread, and thus ensure the safety, reliability and service life of oil and gas wells.

[0072] In other embodiments of the present invention, the three-dimensional reconstruction method of the present invention is also used to reconstruct the three-dimensional model of the internal threads of other types of pipe fittings.

[0073] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-dimensional reconstruction method for internal threads of pipe fittings combined with busbar measurement specifications, Features: The steps include: Step 1, input the digital 3D model of the standard internal thread of the pipe fitting into the three-dimensional coordinate measuring machine; Step 2, in a standard environment, using a three-dimensional coordinate measuring instrument to measure the internal thread of a standard pipe fitting, and obtaining a three-dimensional generatrix set of the internal thread of the standard pipe fitting, wherein the three-dimensional generatrix set is a first thread generatrix set; when using the three-dimensional coordinate measuring instrument to measure the internal thread of the standard pipe fitting, the measurement is performed based on the digital three-dimensional model and in accordance with a preset generatrix measurement specification; Step 3, importing the first thread generatrix set into a comparator; Step 4: At the production site, use a comparator to measure the internal thread of the standard pipe fitting, and obtain a three-dimensional generatrix set of the internal thread of the standard pipe fitting, which is the second thread generatrix set; when using the comparator to measure the internal thread of the standard pipe fitting, the measurement is performed according to a preset generatrix measurement specification; Step 5, in the comparator, associating the first thread generatrix set with the second thread generatrix set to obtain a standard association model; Step 6, using a comparator to measure the internal threads of the product pipe fittings at the production site, and obtaining a three-dimensional generatrix set of the internal threads of the product pipe fittings, the three-dimensional generatrix set being the third thread generatrix set; when using a comparator to measure the internal threads of the product pipe fittings at the production site, the measurement is performed according to a preset generatrix measurement specification; Step 7, in the comparator, the third thread generatrix set is converted according to the standard association model, and the converted three-dimensional generatrix set is used as the three-dimensional constructed generatrix set of the internal thread of the product pipe fitting; Step 8: construct a three-dimensional model of the internal thread of the product pipe fitting according to the three-dimensional construction generatrix set of the internal thread of the product pipe fitting.

2. According to the method for three-dimensional reconstruction of internal threads of pipe fittings combined with busbar measurement specifications according to claim 1, Features: The busbar measurement specification includes: placing the pipe fitting to be measured vertically in a three-dimensional measuring device, dividing the circumference of the pipe fitting into N arc segments, wherein the arc segments are busbar interval arc segments; the stylus of the three-dimensional measuring device measures the thread busbar of the internal thread of the pipe fitting to be measured, and after measuring each thread busbar, the stylus moves along the inner circumference of the pipe fitting by a busbar interval arc segment, and then measures the next thread busbar, until a three-dimensional busbar set consisting of N thread busbars is obtained after measuring N thread busbars; when measuring each thread busbar, the stylus performs point measurement on the profile of the internal thread of the pipe fitting from top to bottom, and then connects the measured points to construct a thread busbar; the measurement of the profile of the internal thread of the pipe fitting is based on a cylindrical coordinate system, and the rotation axis of the cylindrical coordinate system is consistent with the central axis of the pipe fitting to be measured.

3. According to the method for three-dimensional reconstruction of internal threads of pipe fittings combined with busbar measurement specifications as described in claim 2, Features: The busbar measurement specification also includes: before measuring the thread busbar of the internal thread of the measured object pipe fitting, first constructing a virtual standard pipe fitting internal thread profile configuration, the axis of the virtual standard pipe fitting internal thread is consistent with the central axis of the measured object pipe fitting; when measuring the internal thread of the measured object pipe fitting, the measuring needle of the three-dimensional measuring device measures along the virtually constructed standard pipe fitting internal thread profile configuration.

4. According to claim 3, the method for three-dimensional reconstruction of internal threads of pipe fittings combined with busbar measurement specifications, Features: The busbar measurement specification also includes: constructing the virtual standard pipe fitting internal thread profile configuration using a thread digitization method; The thread digitization method comprises: defining a standard thread tooth profile contour line according to the thread configuration of the standard pipe fitting, wherein the standard thread tooth profile contour line comprises a first straight line, a first arc, a second straight line, a second arc, a third straight line, a third arc, a fourth straight line and a fourth arc; the first straight line is a straight line contour line of the thread tooth top surface, the first arc is a circular arc contour line between the thread tooth top surface and the bearing surface, the second straight line is a straight line contour line of the thread tooth bearing surface, the second arc is a circular arc contour line between the thread tooth bearing surface and the bottom surface, the third straight line is a straight line contour line of the thread tooth bottom surface, the third arc is a circular arc contour line between the thread tooth bottom surface and the guide surface, the fourth straight line is a straight line contour line of the thread tooth guide surface, and the fourth arc is a circular arc contour line between the thread tooth guide surface and the top surface; setting a two-dimensional temporary coordinate system on the defined standard thread tooth profile contour line, and setting the intersection of the second straight line and the thread mid-diameter line as the origin of the temporary coordinate system; the temporary coordinate system comprises an X-axis and a Z-axis, wherein the Z-axis is parallel to the thread axis. The X-axis is parallel to the thread axis, and the X-axis is perpendicular to the thread axis; discrete points are taken on the defined standard thread tooth profile contour line according to the preset interval distance, and the coordinate values ​​and vector directions of all the obtained discrete points are used to construct the vector set of the standard thread tooth profile contour line; on the standard thread tooth profile contour line, the intersection point of the second straight line and the thread mid-diameter line is used as the calibration point of the standard thread tooth profile contour line; on the measured object pipe fitting, the intersection point of the thread mid-diameter line and the pipe fitting end face is used as the reference point of the pipe fitting; all the discrete points obtained on the standard thread tooth profile contour line are transplanted as a whole to the measured object pipe fitting thread, and the calibration point of the standard thread tooth profile contour line coincides with the reference point of the pipe fitting, and the vector set of the standard thread tooth profile contour line is converted into a vector set of transplanted discrete points, and the transplanted vector set is a transplanted converted vector set; the discrete points represented by the transplanted converted vector set are connected to form a transplanted standard tooth profile contour line, and then the transplanted standard tooth profile contour line is spirally rotated around the thread axis to construct a virtual standard pipe fitting internal thread contour configuration.

5. According to claim 1, the method for three-dimensional reconstruction of internal threads of pipe fittings combined with busbar measurement specifications, Features: The step 8 also includes: when constructing the three-dimensional model of the internal thread of the pipe fitting according to the three-dimensional constructed generatrix set, inserting a supplementary generatrix between adjacent generatrixes of the three-dimensional constructed generatrix set.

6. According to claim 5, the method for three-dimensional reconstruction of internal threads of pipe fittings combined with busbar measurement specifications, Features: The step 8 also includes: the inserted supplementary busbar is calculated according to the adjacent busbars and in accordance with the thread busbar interpolation calculation method, the thread busbar interpolation calculation method includes: setting the number t of inserted busbars between each pair of adjacent busbars; when inserting the supplementary busbar, the busbar on one side is used as the first adjacent busbar, and the busbar on the other side is used as the second adjacent busbar; determining the three-dimensional coordinates of the busbar construction points, and then connecting the busbar construction points to construct the inserted supplementary busbar; The rule for determining the three-dimensional coordinates of the generatrix construction point is: j =Iρ j +(IIρ j -Iρ j )×t / (t+1),iθ j =Iθ j +(IIθ j -Iθ j )×t / (t+1),iZ j =IZ j +(IIZ j -IZ j) ×t / (t+1); iρ j 、iθ j 、iZ j The three-dimensional coordinate value of the j-th busbar construction point of the i-th busbar inserted between adjacent buses is given by iρ j , iθ j 、iZ j Composed of (iρ j ,iθ j ,iZ j ) is the three-dimensional coordinate of the j-th busbar construction point of the i-th busbar inserted between adjacent buses; j , Iθ j , IZ j is the three-dimensional coordinate value of the jth measured point on the first adjacent busbar, given by Iρ j , Iθ j , IZ j Composed of (Iρ j ,Iθ j ,IZ j ) is the three-dimensional coordinate of the jth measured point on the first adjacent busbar; j , IIθ j , IIZ j is the coordinate value of the jth measurement point on the second adjacent busbar, given by IIρ j , IIθ j , IIZ j Composed of (IIρ j ,IIθ j ,IIZ j ) is the three-dimensional coordinate of the jth measured point on the second adjacent generatrix; the measured point is the measured point obtained by point measuring the profile of the internal thread of the pipe fitting when the comparator measures the thread generatrix.

7. According to claim 1, the method for three-dimensional reconstruction of internal threads of pipe fittings combined with busbar measurement specifications, Features: The pipe fitting is a petroleum pipe.

Images