Internal thread pitch diameter in-situ measuring device and measuring method based on line laser

Abstract

The invention provides an internal thread pitch diameter in-situ measurement device and method based on line laser, and belongs to the technical field of precision measurement. The device comprises a base, a manual fine-tuning arc-shaped sliding table, a manual fine-tuning rotary sliding table, a T-shaped adapter plate, a sensor fixing plate and a linear laser displacement sensor. The base is connected with a cutter bar of a machine tool, and the angle of the linear laser displacement sensor around the X axis and the Y axis of the machine tool can be adjusted through the manual fine-tuning arc-shaped sliding table and the manual fine-tuning rotary sliding table. During measurement, the measuring device is arranged in a threaded hole, a workpiece is driven to rotate through a machine tool spindle, three-dimensional point cloud data of an internal thread contour is obtained through scanning of the line laser displacement sensor, the pitch diameter of the thread is calculated through data processing and parameter fitting, and the pitch diameter is compared with a theoretical value to obtain deviation. According to the invention, non-contact, in-place, rapid and precise measurement of the pitch diameter of the internal thread is realized, the detection efficiency and the automation degree are effectively improved, and the device is suitable for integrated application of a processing site.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement technology, specifically relating to an in-situ measuring device and method for measuring the pitch diameter of internal threads based on line laser. Background Technology

[0002] Accurate measurement of the pitch diameter of internal threads is crucial for ensuring the quality and precision of threaded connections, and is a core inspection component in the thread manufacturing process. With the rapid development of high-precision and intelligent manufacturing in the high-end equipment manufacturing industry, higher demands are placed on the efficiency, automation level, and data traceability of internal thread pitch diameter measurement. Especially in high-volume, high-paced production environments, achieving rapid, online, and non-destructive measurement of the internal thread pitch diameter is one of the significant challenges in improving the level of intelligent thread manufacturing. Currently, most domestic enterprises still rely on traditional contact-based measurement methods, which are often affected by interference from cutting fluid, oil, and metal shavings, resulting in a low level of automation.

[0003] Traditional methods for measuring the pitch diameter of internal threads often employ thread plug gauges, coordinate measuring machines (CMMs), or specialized internal thread measuring instruments. While thread plug gauges are simple to operate, they are contact-based limit measurements, unable to obtain the actual pitch diameter value, and are prone to wear and have low efficiency. CMMs offer high accuracy, but require the workpiece to be moved to a constant-temperature testing environment, making on-site measurement impossible, and they have extremely stringent dimensional requirements. For internal threads with special structures such as deep holes and blind holes, traditional measurement methods are even more difficult to implement effectively. Therefore, achieving precise on-site measurement of the pitch diameter of internal threads in deep blind holes has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide an in-situ measuring device and method for measuring the pitch diameter of internal threads based on line laser, so as to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides an in-situ measurement device for the pitch diameter of internal threads based on line laser, comprising: The base 1 is connected to the machine tool bar, and the base 1 is connected to the lower end of the manually adjustable arc slide 2; The manual fine-tuning arc slide 2 is connected at its upper end to the lower end of the manual fine-tuning rotary slide 3; the manual fine-tuning arc slide 2 is used to adjust the angle of the line laser displacement sensor 6 around the X-axis of the machine tool. The manual fine-tuning rotary slide 3 is used to adjust the angle of the line laser displacement sensor 6 around the Y-axis of the machine tool; T-shaped adapter plate 4, one end of which is connected to the upper end of the manual fine-tuning rotary slide 3, and the other end of which is connected to the sensor fixing plate 5; Sensor mounting plate 5; A linear laser displacement sensor 6 is fixed on the sensor mounting plate 5.

[0006] Furthermore, in the above-mentioned device, the base 1 is threadedly connected to the lower end of the manually adjustable arc-shaped slide 2.

[0007] Furthermore, in the above-mentioned device, the lower end of the manual fine-tuning rotary slide 3 is threadedly connected to the upper end of the manual fine-tuning arc slide 2.

[0008] Furthermore, in the above-mentioned device, one end of the T-shaped adapter plate 4 is threadedly connected to the upper end of the manual fine-tuning rotary slide 3, and the other end of the T-shaped adapter plate 4 is threadedly connected to the sensor fixing plate 5.

[0009] Furthermore, in the above-mentioned device, the linear laser displacement sensor 6 is threadedly connected to the sensor fixing plate 5.

[0010] According to another aspect of the present invention, a method for in-situ measurement of the pitch diameter of internal threads based on line laser is also provided, using the above-described line laser-based in-situ measurement device for the pitch diameter of internal threads, the method comprising: The line laser-based in-situ internal thread pitch diameter measuring device is mounted on the machine tool holder via a base; Based on the parameters of the internal thread being measured, the first angle of the laser displacement sensor around the X-axis and the second angle of the linear laser displacement sensor around the Y-axis are obtained. Adjust the laser displacement sensor to the first angle around the X-axis by manually fine-tuning the arc-shaped slide 2; adjust the laser displacement sensor to the second angle around the Y-axis by manually fine-tuning the rotary slide 3. The machine tool bar is moved to move the line laser-based internal thread pitch diameter in-situ measuring device to the inside of the thread so that the internal thread being measured is within the measurement range of the line laser sensor. The machine tool spindle is controlled to rotate around the Z-axis, which drives the internal thread to rotate synchronously, enabling the line laser position sensor to complete the data acquisition of the thread profile, and the three-dimensional point cloud data of the internal thread is obtained based on the acquired data; Calculate the thread pitch diameter based on the aforementioned three-dimensional point cloud data; The calculated thread pitch diameter is compared with the thread pitch diameter marked on the drawing to obtain the deviation result.

[0011] Furthermore, in the above method, the first angle makes the scanning plane of the linear laser emitted by the linear laser displacement sensor parallel to the tooth profile section of the internal thread; the second angle makes the projection direction of the linear laser emitted by the linear laser displacement sensor perpendicular to the axis of the internal thread.

[0012] Furthermore, in the above method, the line laser position sensor completes the data acquisition of the thread profile, and based on the acquired data, obtains the three-dimensional point cloud data of the internal thread, including: Based on the machine tool encoder information, the Z-axis rotation angle information θ of the machine tool is obtained. i And the first timestamp information, where i represents the angle sequence number of the machine tool's Z-axis rotation; The measured contour data (x) is obtained from the linear laser displacement sensor. ij , z ij ) and second timestamp information, where j represents the sequence number of the contour point under a single angle i; The Z-axis rotation angle θ of the machine tool is obtained using the first and second timestamp information. i The measured profile data (x) of the linear laser displacement sensor 6 ij , z ij Corresponding to these, we obtain the three-dimensional point cloud data of the internal thread (θ). i x ij , z ij ).

[0013] Furthermore, in the above method, calculating the thread pitch diameter based on the aforementioned three-dimensional point cloud data includes: Based on the aforementioned 3D point cloud data, the profile of each internal thread is obtained; based on each thread profile, the linear equations of the left and right sides of the thread teeth are fitted. By simultaneously solving the equations on the left and right sides of the thread tooth, the intersection point of the thread tooth is obtained; Based on the thread tooth intersection points of multiple thread profile data, a preliminary thread pitch diameter equation is fitted. By simultaneously establishing the preliminary equations for the thread pitch diameter and the straight lines on the left and right sides of the thread teeth, the intersection points on the left and right sides are obtained. Redefine the left and right intersection points in sequence, and calculate the distance between adjacent points between the redefined points; The pitch diameter is defined as being parallel to and equidistant from both sides of the thread profile; the objective function is then constructed. The pitch diameter point of each thread profile is determined by making the optimization objective function less than a preset minimum value; based on the pitch diameter points of each thread profile, the pitch diameter of the thread is finally calculated using the Levenberg-Marquardt algorithm.

[0014] Furthermore, in the above method, based on each thread profile, fitting the linear equations on both sides of the thread teeth includes: The equation of the straight line on the left side of the thread tooth for: ; The equation of the straight line on the right side of the thread tooth for: ; in, The serial number representing the thread profile of a specific measurement section; , The x and y coordinates of a point on the left side profile of the thread tooth are represented. , The x and y coordinates of a point on the right side profile of the thread tooth are represented. , The slope , This is the intercept.

[0015] Furthermore, in the above method, the intersection point of the thread teeth is obtained by simultaneously solving the equations on the left and right sides of the thread teeth, including: By combining the equations for the left and right sides of the thread teeth above, we can obtain the intersection point of the thread teeth. , ), Furthermore, in the above method, by simultaneously establishing the preliminary equation for the thread pitch diameter and the equations for the straight lines on the left and right sides of the thread teeth, the intersection points on the left and right sides are obtained, including: By simultaneously establishing the preliminary equations for the thread pitch diameter L and the straight lines on the left and right sides of the thread teeth, the intersection point on the left side is obtained. , ) and the intersection on the right ( , ),in, The preliminary equation for the thread pitch diameter L is: ; The intersection point of the thread pitch diameter line and the left side straight line of the thread tooth is: ( , ); The intersection point of the thread pitch diameter line and the right side straight line of the thread tooth is: ( , ); ; .

[0016] Furthermore, in the above method, the left and right intersection points are redefined in sequence, and the distance between adjacent points between the redefined points is calculated, including: The left intersection point ( , The intersection point with the right side ( , ) be redefined in order as ( , ), calculate the distance between two adjacent points between the redefined points. , ; in, The intersection point is the serial number; It is the first The intersection point and the first The distance between adjacent intersection points.

[0017] Furthermore, in the above method, based on the definition that the pitch diameter is parallel to and equidistant from both sides of the thread profile, an objective function is constructed, including: Since the pitch diameter line is a straight line parallel to and equidistant from both sides of the thread profile, we get d1=d2, where d1 and d2 are the distances from the pitch diameter line to the left and right sides of the thread. The objective function is defined as follows: Where d1 and d2 are the distances from the median diameter to the left and right sides of the tooth, respectively; , It is the parameter of the thread pitch diameter equation L; , It is the distance between the intersections of adjacent median diameter lines and the two sides of the tooth, calculated using the method corresponding to the distance between two adjacent points. Compared with existing technologies, this invention applies a line laser displacement sensor to the precise in-situ measurement of internal threads, integrating the measuring device onto the machine tool holder. Based on the principle of non-contact optical measurement, it can achieve point cloud acquisition of the thread profile. Combined with the machine tool motion system, it can complete the three-dimensional scanning of the internal thread, and accurately calculate the thread pitch diameter through point cloud data processing and fitting. This method has advantages such as non-contact operation, high measurement speed, and in-situ measurement. Its overall structure is compact and easily integrated into machining centers or flexible manufacturing units. Attached Figure Description

[0018] Figure 1 This is a general three-dimensional diagram of the present invention; Figure 2 This is a schematic diagram illustrating the calculation of the mean diameter of the internal thread in this invention; Figure 3 This is a flowchart of the in-situ measurement method for the pitch diameter of internal threads based on line laser of the present invention; The components include: 1. Base; 2. Manually adjustable arc-shaped slide; 3. Manually adjustable rotary slide; 4. T-shaped adapter plate; 5. Sensor mounting plate; and 6. Linear laser displacement sensor. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Reference Figure 1 This invention discloses an in-situ measurement device for the pitch diameter of internal threads based on line laser, comprising: Base 1 is connected to the machine tool bar, and the lower end of the manually adjustable arc slide 2 is connected to the base 1; the manually adjustable arc slide 2 is used to adjust the angle of the line laser displacement sensor 6 around the X-axis of the machine tool; The manual fine-tuning rotary slide 3 is connected at its lower end to the upper end of the manual fine-tuning rotary slide 2; the manual fine-tuning rotary slide 3 is used to adjust the angle of the line laser displacement sensor 6 around the Y-axis of the machine tool. The T-shaped adapter plate 4 is connected at one end to the upper end of the manual fine-tuning rotary slide 3 and at the other end to the sensor fixing plate 5. A linear laser displacement sensor 6 is fixed on a sensor mounting plate 5.

[0021] In use, the measuring device is integrated onto the machine tool holder. Based on the principle of non-contact optical measurement, it can achieve high-density point cloud acquisition of the thread profile. Combined with the machine tool motion system, it can complete the three-dimensional scanning of the internal thread, and accurately calculate the thread pitch diameter through point cloud data processing and fitting. This method has advantages such as non-contact operation, high measurement speed, and in-situ measurement. The overall structure is compact and easy to integrate into machining centers or flexible manufacturing units.

[0022] As an optional implementation, the base 1 is threadedly connected to the lower end of the manually adjustable arc-shaped slide 2.

[0023] As an optional implementation, the lower end of the manually adjustable rotary slide 3 is threadedly connected to the upper end of the manually adjustable arc slide 2.

[0024] As an optional implementation, one end of the T-shaped adapter plate 4 is threadedly connected to the upper end of the manual fine-tuning rotary slide 3, and the other end of the T-shaped adapter plate 4 is threadedly connected to the fixing plate of the line laser displacement sensor 6.

[0025] As an optional implementation, the linear laser displacement sensor 6 is threadedly connected to the sensor mounting plate 5.

[0026] This invention proposes an in-situ measurement device for the pitch diameter of internal threads based on line laser. The device consists of a base 1, a manually adjustable arc-shaped slide 2, a manually adjustable rotary slide 3, a T-shaped adapter plate 4, a sensor fixing plate 5, and a line laser displacement sensor 6.

[0027] The base 1 is threadedly connected to the manually adjustable arc-shaped slide 2. The base 1 has an M4 threaded hole, and the lower end of the manually adjustable arc-shaped slide 2 has an M4 countersunk hole, connected using M4 bolts. The manually adjustable arc-shaped slide 2 is threadedly connected to the manually adjustable rotary slide 3. The upper end of the manually adjustable arc-shaped slide 2 has an M4 threaded hole, and the lower end of the manually adjustable rotary slide 3 has an M4 countersunk hole, connected using M4 bolts. One end of the T-shaped adapter plate 4 is threadedly connected to the manually adjustable rotary slide 3. The T-shaped adapter plate 4 has a Ф4 countersunk hole, and the upper end of the manually adjustable rotary slide 3 has an M4 threaded hole, connected using M4 bolts. The other end of the sensor fixing plate 5 is threadedly connected to the T-shaped adapter plate 4. The sensor fixing plate 5 has a Ф6 through hole, and the T-shaped adapter plate 4 has a Ф6 threaded hole, connected using M6 threads. The linear laser displacement sensor 6 is threadedly connected to the sensor mounting plate 5. The linear laser displacement sensor 6 has an M5 threaded hole, and the sensor mounting plate 5 has a Ф5 through hole, which is connected by an M5 thread.

[0028] During measurement, simply control the movement of the machine tool bar to move the measuring device inside the thread, ensuring that the thread being measured is within the measurement range of the online laser displacement sensor 6. Then, rotate the machine tool spindle around the Z-axis to make the internal thread being measured slowly rotate around the machine tool Z-axis, thereby enabling the online laser displacement sensor 6 to scan the contour of the internal thread and obtain the three-dimensional point cloud data of the internal thread.

[0029] Furthermore, the thread pitch diameter D is obtained through point cloud data processing and parameter fitting.

[0030] Furthermore, the base 1 and the line laser displacement sensor 6 are movable parts. At the end of each measurement, this entire part can be removed to continue internal thread turning. The base 1 is mounted on the machine tool holder.

[0031] Furthermore, the manual fine-tuning rotary slide 3 and the manual fine-tuning arc slide 2 can be used to fine-tune the pose of the line laser displacement sensor 6 by adjusting the knobs. The manual fine-tuning arc slide 2 can fine-tune the angle of rotation of the line laser displacement sensor around the X-axis of the machine tool, and the manual fine-tuning rotary slide 3 can fine-tune the angle of rotation of the line laser displacement sensor around the Y-axis of the machine tool. By jointly adjusting the manual fine-tuning rotary slide 3 and the manual fine-tuning arc slide 2, the pose of the line laser displacement sensor can be brought into a suitable measurement state.

[0032] like Figure 3As shown, the present invention also provides a method for in-situ measurement of the pitch diameter of internal threads based on line laser, using the aforementioned in-situ measurement device for the pitch diameter of internal threads based on line laser. The method includes the following steps: Step S1: The in-situ measurement device for the pitch diameter of the internal thread based on line laser is mounted on the machine tool holder via a base; Step S2: Based on the parameters of the internal thread being measured, obtain the first angle of the laser displacement sensor around the X-axis and the second angle of the line laser displacement sensor around the Y-axis. The first angle makes the scanning plane of the line laser emitted by the line laser displacement sensor parallel to the tooth profile section of the internal thread; the second angle makes the projection direction of the line laser emitted by the line laser displacement sensor perpendicular to the axis of the internal thread. Here, the laser displacement sensor is adjusted to the first angle around the X-axis by the arc-shaped slide 2. The purpose is to make the scanning plane of the line laser parallel to the tooth profile section of the internal thread. The tooth profile of the internal thread has a fixed tilt angle (for example, the tooth profile angle of a normal thread is 60°). It is necessary to adjust the angle of the sensor around the X-axis so that the line projected by the line laser can just cover a complete tooth profile section (from the tooth crest to the tooth bottom), ensuring that the acquired two-dimensional contour data contains complete tooth profile information.

[0033] Adjust the laser displacement sensor to the second angle around the Y-axis by rotating the slide 3. The purpose is to make the projection direction of the line laser perpendicular to the axis of the internal thread. The internal thread is a helical structure distributed along the Z-axis (machine tool spindle). It is necessary to adjust the angle of the sensor around the Y-axis so that the line laser line is in a plane perpendicular to the Z-axis. Only in this way can the contour data obtained by scanning accurately reflect the true shape of the thread in that cross section.

[0034] The core of these two angles is to match the projection direction / plane of the line laser with the tooth profile and axial direction of the internal thread, ensuring that complete and accurate thread profile data can be acquired. In actual operation, it can usually be fine-tuned by combining the parameters of the thread being tested or by observing the data integrity through pre-scanning.

[0035] Step S3: Adjust the laser displacement sensor to the first angle around the X-axis by manually fine-tuning the arc-shaped slide 2; adjust the laser displacement sensor to the second angle around the Y-axis by manually fine-tuning the rotary slide 3. Step S4: Control the machine tool bar to move and move the line laser-based internal thread pitch diameter in-situ measuring device to the inside of the thread so that the measured internal thread is within the measurement range of the line laser sensor. Step S5: Control the machine tool spindle to rotate around the Z-axis, driving the internal thread to rotate synchronously, so that the line laser position sensor can complete the data acquisition of the thread profile, and obtain the three-dimensional point cloud data of the internal thread based on the acquired data.

[0036] Here, when measuring internal threads, the measuring device is first installed on the machine tool bar, and then the machine tool bar is moved to make the internal thread to be measured within the measurement range of the online laser displacement sensor 6. Then, the machine tool spindle is slowly rotated around the Z-axis to make the internal thread to be measured slowly rotate around the Z-axis of the machine tool, so that the measuring device scans the internal thread profile and obtains the three-dimensional point cloud data of the internal thread.

[0037] Further, in step S5, the line laser position sensor completes the data acquisition of the thread profile, and based on the acquired data, obtains the three-dimensional point cloud data of the internal thread, including: Step S51: Based on the machine tool encoder information, obtain the Z-axis rotation angle information θ of the machine tool. i And first timestamp information; Step S52: Obtain the measured contour data (x) from the line laser displacement sensor. ij , z ij ) and second timestamp information; Step S53: Using the first and second timestamp information, the angle information θ of the machine tool's Z-axis rotation is obtained. i The measured profile data (x) of the linear laser displacement sensor 6 ij , z ij Corresponding to these, we obtain the three-dimensional point cloud data of the internal thread (θ). i x ij , z ij ).

[0038] Here, 'i' corresponds to the rotation angle sequence number of the machine tool's Z-axis. When the machine tool spindle drives the internal thread to rotate around the Z-axis, data will be collected at different angles (e.g., the 1st angle, the 2nd angle, etc.). 'i' is the sequence number of this angle batch (e.g., i=1 represents the 1st rotation angle, θ...). i It is the specific value of the i-th angle.

[0039] j corresponds to the sequence number of the profile point at a single angle i. At a certain rotation angle (i.e., a certain i), the line laser sensor will collect a set of point data of the thread profile, such as multiple profile points within a cross-section. j is the sequence number of this single set of profile points. For example, j=1 represents the first profile point at the i-th angle. (x ij , z ij () are the coordinates of that point.

[0040] Step S6: Calculate the thread pitch diameter based on the aforementioned three-dimensional point cloud data; Here, because the machine tool spindle drives the internal thread to rotate around the Z-axis during measurement, the sensor will rotate at different rotation angles (corresponding to different θ). iThe contour data of multiple cross sections are collected. These two-dimensional contours from different angles are combined to form a three-dimensional point cloud that covers the overall shape of the internal thread.

[0041] A 3D point cloud is a collection of individual profiles from multiple angles. The profiles from each angle will be extracted from these point clouds to calculate the pitch diameter. Specifically, profile data of a single cross-section can be extracted from the 3D point cloud, such as a 2D profile at a certain angle, to fit the linear equation of the thread teeth.

[0042] Step S61: Based on the three-dimensional point cloud data, obtain the thread profile of each internal thread; based on each thread profile, fit the straight line equations on both sides of the thread tooth and the straight line equation on the left side of the thread tooth. for: ; The equation of the straight line on the right side of the thread tooth for: ; in, The serial number representing the thread profile of a specific measurement section; , The x and y coordinates of a point on the left side profile of the thread tooth are represented. , The x and y coordinates of a point on the right side profile of the thread tooth are represented. , The slope , The intercept; Step S62, combine the equations for the left and right sides of the thread teeth to obtain the thread tooth intersection point ( , ), Here, the thread intersection ( , The vertex near the crest or root of the corresponding thread tooth; Step S63, based on the thread tooth intersection point of multiple thread profile data ( , The preliminary equation L for the thread pitch diameter is obtained by fitting the following: Step S64: Simultaneously establish the preliminary thread pitch diameter equation L with the straight line equations on the left and right sides of the thread tooth to obtain the intersection point on the left side. , ) and the intersection on the right ( , ); The intersection point of the thread pitch diameter line and the left side straight line of the thread tooth is: ( , ).

[0043] The intersection point of the thread pitch diameter line and the right side straight line of the thread tooth is: ( , ).

[0044] Step S65, intersect the left side ( , The intersection point with the right side ( , ) be redefined in order as ( , ), calculate the distance between two adjacent points between the redefined points. : Here, the intersection on the left ( , The intersection point with the right side ( , The points are arranged alternately. To facilitate subsequent calculations, these points are redefined as ( , If the distance between two adjacent points is 0, then the distance between the two adjacent points is 0. for: ; Here, The intersection point is the serial number; It is the first The intersection point and the first The distance between adjacent intersection points.

[0045] Step S66, to obtain the fitted thread pitch diameter equation L: Given that the pitch diameter line is a straight line parallel to and equidistant from both sides of the thread profile (i.e., d1=d2), construct the objective function: ; Where d1 and d2 are the distances from the median diameter to the left and right sides of the tooth, respectively; , It is the parameter of the thread pitch diameter equation L; , It is the distance between the intersections of adjacent median diameter lines and the two sides of the tooth, calculated using the method corresponding to the distance between two adjacent points. ; Here, the objective function aims to minimize the sum of the absolute values ​​of the differences between these distances, ideally to be 0, i.e., d1=d2.

[0046] Here, as Figure 2 As shown, according to the definition of the pitch diameter line of a thread: the pitch diameter line is a straight line that is parallel to both sides of the thread profile and is equidistant from them, so d1=d2, where d1 and d2 are the distances from the pitch diameter line to the left and right sides of the thread. The objective function is defined as follows: Step S67, Method for solving the pitch diameter: By making the optimization objective function less than the preset minimum value ε (ε>0), the pitch diameter point of each thread profile is determined; based on the pitch diameter points of each thread profile, the Levenberg-Marquardt algorithm (a nonlinear least squares fitting algorithm) is used to finally calculate the pitch diameter of the thread.

[0047] Here, the pitch diameter point of each thread profile is solved by making the objective function less than ε (ε>0), and then the thread pitch diameter is calculated using the Levenberg-Marquardt Algorithm. The Levenberg-Marquardt algorithm is a nonlinear least squares fitting algorithm.

[0048] Further, in step S7, the calculated thread pitch diameter is compared with the thread pitch diameter marked on the drawing to obtain the deviation result.

[0049] Here, the in-situ measurement system for internal thread pitch diameter can be implemented using C++ and integrated as a functional module into the control system of the machine tool. This system processes 3D point cloud data collected by a line laser sensor to calculate the actual thread pitch diameter and compares it with the theoretical value on the drawing. The deviation results can be displayed in real time through a graphical interface written in QT, and compensation commands can be generated and fed back to the machine tool, thus forming a closed-loop control of "measurement-feedback-compensation" to achieve intelligent machining driven by digital technology.

[0050] In summary, this invention provides an in-situ measurement device and method for the pitch diameter of internal threads based on line laser technology. Through non-contact in-situ measurement, it achieves rapid and high-precision measurement of internal threads, effectively improving the measurement accuracy and efficiency. The measuring device can be adapted to different machine tool holders via mounting holes on the base, enabling in-situ measurement. Using a line laser displacement sensor as the measurement method, it has no special requirements for ambient lighting conditions, and the measurable thread length can be flexibly adjusted according to the tool holder's movement distance. Furthermore, this device is also suitable for the geometric dimension detection of other shaft-type parts, exhibiting strong versatility. Non-contact in-situ measurement not only avoids errors introduced by secondary clamping but also effectively protects the workpiece surface, meeting the development requirements of modern advanced manufacturing for precision and efficiency. The above description is only a preferred embodiment of the invention and is not intended to limit the scope of the invention. Various modifications and improvements made to the technical solutions of this invention by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims.

Claims

1. A device for in-situ measurement of the pitch diameter of internal threads based on line laser, characterized in that, include: The base (1) is connected to the machine tool bar, and the base (1) is connected to the lower end of the manually adjustable arc slide (2); The upper end of the manually fine-tuning arc slide (2) is connected to the lower end of the manually fine-tuning rotary slide (3); the manually fine-tuning arc slide (2) is used to adjust the angle of the line laser displacement sensor (6) around the X-axis of the machine tool. The manual fine-tuning rotary slide (3) is used to adjust the angle of the line laser displacement sensor (6) around the Y-axis of the machine tool; T-shaped adapter plate (4), one end of which is connected to the upper end of the manual fine-tuning rotary slide (3), and the other end of which is connected to the sensor fixing plate (5); Sensor mounting plate (5); A linear laser displacement sensor (6) is fixed on the sensor mounting plate (5).

2. A method for in-situ measurement of the pitch diameter of internal threads based on line laser, employing the in-situ measurement device for the pitch diameter of internal threads based on line laser as described in claim 1, characterized in that, The method includes: The line laser-based in-situ internal thread pitch diameter measuring device is mounted on the machine tool holder via a base; Based on the parameters of the internal thread being measured, the first angle of the laser displacement sensor around the X-axis and the second angle of the linear laser displacement sensor around the Y-axis are obtained. Adjust the laser displacement sensor to the first angle around the X-axis by manually fine-tuning the arc-shaped slide (2); adjust the laser displacement sensor to the second angle around the Y-axis by manually fine-tuning the rotary slide (3); The machine tool bar is moved to move the line laser-based internal thread pitch diameter in-situ measuring device to the inside of the thread so that the internal thread being measured is within the measurement range of the line laser sensor. The machine tool spindle is controlled to rotate around the Z-axis, which drives the internal thread to rotate synchronously, enabling the line laser position sensor to complete the data acquisition of the thread profile, and the three-dimensional point cloud data of the internal thread is obtained based on the acquired data; Calculate the thread pitch diameter based on the aforementioned three-dimensional point cloud data; The calculated thread pitch diameter is compared with the thread pitch diameter marked on the drawing to obtain the deviation result.

3. The in-situ measurement method for the pitch diameter of internal threads based on line laser as described in claim 2, characterized in that, The first angle makes the scanning plane of the linear laser emitted by the linear laser displacement sensor parallel to the tooth profile section of the internal thread; the second angle makes the projection direction of the linear laser emitted by the linear laser displacement sensor perpendicular to the axis of the internal thread.

4. The in-situ measurement method for the pitch diameter of internal threads based on line laser as described in claim 2, characterized in that, The line laser position sensor completes the data acquisition of the thread profile, and based on the acquired data, obtains the three-dimensional point cloud data of the internal thread, including: Based on the machine tool encoder information, the Z-axis rotation angle information θ of the machine tool is obtained. i And the first timestamp information, where i represents the angle sequence number of the machine tool's Z-axis rotation; The measured contour data (x) is obtained from the linear laser displacement sensor. ij , z ij ) and second timestamp information, where j represents the sequence number of the contour point under a single angle i; The Z-axis rotation angle θ of the machine tool is obtained using the first and second timestamp information. i The measured profile data (x) of the linear laser displacement sensor (6) ij , z ij Corresponding to these, we obtain the three-dimensional point cloud data of the internal thread (θ). i x ij , z ij ).

5. The method for in-situ measurement of the pitch diameter of internal threads based on line laser as described in claim 4, characterized in that, Based on the aforementioned three-dimensional point cloud data, the thread pitch diameter is calculated, including: Based on the aforementioned 3D point cloud data, the profile of each internal thread is obtained; based on each thread profile, the linear equations of the left and right sides of the thread teeth are fitted. By simultaneously solving the equations on the left and right sides of the thread tooth, the intersection point of the thread tooth is obtained; Based on the thread tooth intersection points of multiple thread profile data, a preliminary thread pitch diameter equation is fitted. By simultaneously establishing the preliminary equations for the thread pitch diameter and the straight lines on the left and right sides of the thread teeth, the intersection points on the left and right sides are obtained. Redefine the left and right intersection points in sequence, and calculate the distance between adjacent points between the redefined points; The pitch diameter is defined as being parallel to and equidistant from both sides of the thread profile; the objective function is then constructed. The pitch diameter point of each thread profile is determined by making the optimization objective function less than a preset minimum value; based on the pitch diameter points of each thread profile, the pitch diameter of the thread is finally calculated using the Levenberg-Marquardt algorithm.

6. The in-situ measurement method for the pitch diameter of internal threads based on line laser as described in claim 5, characterized in that, Based on each thread profile, the equations of the straight lines on both sides of the thread teeth are fitted, including: The equation of the straight line on the left side of the thread tooth for: ； The equation of the straight line on the right side of the thread tooth for: ； in, The serial number representing the thread profile of a specific measurement section; , The x and y coordinates of a point on the left side profile of the thread tooth are represented. , The x and y coordinates of a point on the right side profile of the thread tooth are represented. , The slope , This is the intercept.

7. The in-situ measurement method for the pitch diameter of internal threads based on line laser as described in claim 6, characterized in that, The intersection point of the thread teeth is obtained by simultaneously solving the equations on the left and right sides of the thread teeth, including: By combining the equations for the left and right sides of the thread teeth above, we can obtain the intersection point of the thread teeth. , ), 。 8. The method for in-situ measurement of the pitch diameter of internal threads based on line laser as described in claim 7, characterized in that, By simultaneously establishing the preliminary equations for the thread pitch diameter and the straight lines on the left and right sides of the thread teeth, the intersection points on the left and right sides are obtained, including: By simultaneously establishing the preliminary equations for the thread pitch diameter L and the straight lines on the left and right sides of the thread teeth, the intersection point on the left side is obtained. , ) and the intersection on the right ( , ),in, The preliminary equation for the thread pitch diameter L is: ; The intersection point of the thread pitch diameter line and the left side straight line of the thread tooth is: ( , ); The intersection point of the thread pitch diameter line and the right side straight line of the thread tooth is: ( , ); ； 。 9. The method for in-situ measurement of the pitch diameter of internal threads based on line laser as described in claim 8, characterized in that, Redefine the left and right intersection points in sequence, and calculate the distance between adjacent points of the redefined points, including: The left intersection point ( , The intersection of the right and the left side ( , ) be redefined in order as ( , ), calculate the distance between two adjacent points between the redefined points. , ； in, The intersection point is the serial number; It is the first The intersection point and the first The distance between adjacent intersection points.

10. The in-situ measurement method for the pitch diameter of internal threads based on line laser as described in claim 8, characterized in that, Based on the definition that the pitch diameter is parallel to and equidistant from both sides of the thread profile, an objective function is constructed, including: Since the pitch diameter line is a straight line parallel to and equidistant from both sides of the thread profile, we get d1=d2, where d1 and d2 are the distances from the pitch diameter line to the left and right sides of the thread. The objective function is defined as follows: Where d1 and d2 are the distances from the median diameter to the left and right sides of the tooth, respectively; , It is the parameter of the thread pitch diameter equation L; , It is the distance between the intersections of adjacent median diameter lines and the two sides of the tooth, calculated using the method corresponding to the distance between two adjacent points. .

Images