Internal thread coaxiality gauge detection method based on contour scanning

Abstract

The invention provides an internal thread coaxiality gauge detection method based on contour scanning, and the method comprises the following steps: employing a self-centering clamp, taking the external diameter of an internal thread coaxiality gauge as an installation contact surface, and calculating the absolute coordinate of the theoretical axis of the gauge in the Y direction in a coordinate system of a machine tool of a contour gauge; searching the highest point of the part to ensure that the part axis is parallel to the measuring shaft of the profile tolerance instrument; selecting a bidirectional contour probe to obtain a contour profile; drawing and fitting the profile molded surface, checking Y coordinate variation of two center lines, and recording the maximum value and the minimum value of the Y coordinate variation; the axis position of the reference element is measured, and the axis of the minimum covering circle serves as the reference element of the internal thread coaxiality; and calculating the measured value of the coaxiality. The method has the advantages that the problem that the internal thread coaxiality gauge cannot directly detect or indirectly detect the large error is solved, the measured coaxiality error data is accurate and reliable, and in addition, the method can be popularized to coaxiality detection of other types of threads.

Description

Technical Field

[0001] The present invention relates to the technical field of non-standard tooling equipment measurement, and in particular to a method for detecting an internal thread coaxial measuring gauge based on profile scanning. Background Art

[0002] Internal thread coaxiality gauges are widely used in the production and manufacturing of parts such as aircraft engines. The internal thread coaxiality gauge uses the internal thread pitch diameter as the reference axis to detect the coaxiality of the gauge outer diameter relative to the internal thread pitch diameter. The thread pitch diameter is an imaginary cylinder diameter, which is the place where the cylinder's generatrix passes through the groove on the tooth profile and the solid thickness is equal. There is no solid at the generatrix, so traditional coaxiality detection methods, such as the dial method and the roundness meter method, cannot collect its features and therefore cannot measure its coaxiality.

[0003] At present, the internal thread coaxial gauge can only be measured indirectly by designing a tapered external thread mandrel that matches it. However, in the actual production process, it is found that when using a tapered external thread mandrel to indirectly detect the internal thread coaxial gauge, it is affected by the tightening force, thread matching clearance, etc., and there is an error in the detection result after each loading and unloading of the mandrel. Summary of the Invention

[0004] The purpose of the present invention is to address the problems existing in the detection of internal thread coaxial gauges. The present invention provides an internal thread coaxial gauge detection method based on contour scanning, which adopts high-precision small-size bidirectional contour probe scanning to obtain the graphic contours of the upper and lower thread tooth profiles and the outer diameter entity, and makes the internal thread mean diameter line and the outer diameter center line by fitting. The coaxiality value of the internal thread and the outer diameter is obtained by comprehensive evaluation multiple times on the circumference to realize the measurement of its coaxiality.

[0005] The present invention provides a method for detecting an internal thread coaxial gauge based on profile scanning, comprising the following steps:

[0006] Step 1: Use a self-centering fixture, use the outer diameter of the internal thread coaxial gauge as the mounting contact surface, and calculate the absolute coordinate of the theoretical axis of the gauge in the Y direction in the profilometer machine tool coordinate system;

[0007] Step 2: Find the highest point of the part and ensure that the axis of the part is parallel to the measuring axis of the profilometer;

[0008] Step 3: Select the bidirectional profile probe and adjust the measurement program to multiple measurements. Scan the upper and lower side tooth profiles of the internal thread and the upper and lower side generatrix of the outer diameter of a single cross-section to obtain the profile surface.

[0009] Step 4: Draw and fit the contour surface, make the thread pitch diameter generatrix measured in this scan, and then make the thread center line and the outer diameter center line. Check the Y coordinate changes of the two center lines and record their maximum and minimum values.

[0010] Step 5: Select 3 evenly spaced locations on the circumference and repeat steps 2 to 4.

[0011] Step 6: Measure the axis position of the reference element: Use the maximum and minimum Y coordinate values ​​of the internal thread center line obtained by multiple scanning measurements to make a minimum covering circle as discrete points, and use the axis of the minimum covering circle as the reference element for the coaxiality of the internal thread.

[0012] Step 7: Calculate the coaxiality measurement value by calculating the maximum and minimum Y coordinate values ​​on the center line of the outer diameter obtained from each scan and twice the maximum distance from the reference element.

[0013] Advantages of the present invention:

[0014] The internal thread coaxiality gauge detection method based on contour scanning described in the present invention solves the problem that the internal thread coaxiality gauge cannot be directly detected or the indirect detection error is large. The measured coaxiality error data is accurate and reliable. In addition, this method can be extended to the coaxiality detection of other types of threads.

[0015] Figures in the specification

[0016] Figure 1 This is a schematic diagram of the structure of a commonly used internal thread coaxial gauge;

[0017] Figure 2 Schematic diagram of the internal thread coaxial gauge detection fixture; 1-mounting plate, 2-pressing block, 3-internal thread coaxial gauge, 4-locating pin;

[0018] Figure 3 Schematic diagram of the calculated theoretical axis; where L is the center distance of the locating pin, φd is the diameter of the cylindrical pin, φD is the theoretical outer diameter, Y is the absolute coordinate value of the locating pin on the machine tool, and Y0 is the absolute coordinate value of the calculated theoretical axis.

[0019] Figure 4 Schematic diagram for finding the highest point of a part; 5-contour stylus, 6-internal thread coaxial gauge;

[0020] Figure 5 Schematic diagram of contour scanning and mapping fitting;

[0021] Figure 6 Schematic diagram of coaxiality error value; among them, A-Y1max, A'-Y1min, B-Y2max, B'-Y2min, C-Y3max, C'-Y3min, y1max, a'-y1min, b-y2max, b'-y2min, c-y3max, c'-y3min. DETAILED DESCRIPTION

[0022] The present invention will be further explained below in conjunction with specific implementation plans, but the present invention is not limited thereto. The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0023] The commonly used internal thread coaxial gauge structure can be seen in the attached Figure 1 A method for detecting an internal thread coaxial gauge based on profile scanning comprises the following steps:

[0024] Step 1: Use a self-centering fixture, see the attached Figure 2 Place the internal thread coaxial gauge on two positioning pins and self-center them with the outer diameter. The fixture is required to strictly control the position of the two cylindrical pins to ensure the center distance L. Measure the absolute coordinate of the high point of the cylindrical pin in the Y direction of the machine tool coordinate system with the profile gauge. Combined with the theoretical outer diameter D of the internal thread coaxial gauge, calculate the theoretical axis Y0 of the gauge. According to the formula For details, please see the attached Figure 3 .

[0025] Step 2: Move the stylus to the approximate high point of the outer diameter of the coaxial gauge and start the program to automatically find the highest point of the part. Figure 4 , ensure that the part axis is parallel to the profilometer measuring axis (X axis);

[0026] Step 3: Use a bidirectional profile stylus and adjust the measurement program to multiple measurements. Scan A1-outer diameter upper side, A2-outer diameter lower side, B1-tooth profile upper side, and B2-tooth profile lower side respectively. See attached. Figure 5 , obtain a single cross-section profile surface;

[0027] Step 4: Use A1, A2, B1, and B2 profiles to draw a fitting diagram, and make the thread median line of this scan measurement, and then make the thread center line, and the outer diameter center line. Record the upper absolute coordinate Y maximum and minimum values ​​Ymax / Ymin of the single-section thread center line, and record the absolute coordinate Y maximum and minimum values ​​ymax / ymin of the single-section outer diameter center line. See the attached diagram for details. Figure 5 ;

[0028] Step 5: Select 3 evenly spaced spots on the circumference and repeat steps 2 to 4.

[0029] Step 6: Determination of datum elements: With Y0 as the center point, make a discrete point diagram of Ymax / Ymin recorded in each cross-section measurement, and make a minimum covering circle containing all discrete points. The center Y0' of the minimum covering circle is used as the datum element of the internal thread coaxial gauge, see the attached Figure 6 ;

[0030] Step 7: Determine the measured element: With Y0 as the center point, make a discrete point diagram of ymax / ymin recorded for each cross-section measurement, and measure the distance △ between each point and Y0' in step 6. The 2 times of △max is the measured coaxiality error value, see the attached Figure 6 .

[0031] Matters not covered by the present invention are known technologies.

[0032] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for detecting an internal thread coaxial gauge based on profile scanning, characterized in that: The internal thread coaxial gauge detection method based on profile scanning comprises the following steps: Step 1: Use a self-centering fixture, use the outer diameter of the internal thread coaxial gauge as the mounting contact surface, and calculate the absolute coordinate of the theoretical axis of the gauge in the Y direction in the profilometer machine tool coordinate system; Step 2: Find the highest point of the part and ensure that the axis of the part is parallel to the measuring axis of the profilometer; Step 3: Select the bidirectional profile probe and adjust the measurement program to multiple measurements. Scan the upper and lower side tooth profiles of the internal thread and the upper and lower side generatrix of the outer diameter of a single cross-section to obtain the profile surface. Step 4: Draw and fit the contour surface, make the thread pitch diameter generatrix measured in this scan, and then make the thread center line and the outer diameter center line. Check the Y coordinate changes of the two center lines and record their maximum and minimum values. Step 5: Select 3 evenly spaced spots on the circumference and repeat steps 2 to 4. Step 6: Measure the axis position of the reference element: Use the maximum and minimum Y coordinates of the internal thread centerline obtained by multiple scanning measurements as discrete points to make a minimum covering circle, and use the axis of the minimum covering circle as the reference element for the coaxiality of the internal thread; Step 7: Calculate the coaxiality measurement value by calculating the maximum and minimum Y coordinate values ​​on the center line of the outer diameter obtained from each scan and twice the maximum distance from the reference element.

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