In-situ measurement method for large-span screw hole position and scraping flatness of part

Abstract

The invention discloses an in-situ measurement method for a large-span screw hole position and scraping flatness of a part, and belongs to the field of measurement. According to the method, a composite target seat is manufactured to serve as a laser tracker measuring target seat, a spherical pyramid mirror is fixed through three positioning balls at the upper end of the composite target seat, meanwhile, it is guaranteed that the sphere center of the pyramid mirror is concentric with a threaded rod at the lower end, and the laser tracker is combined with the composite target seat to measure and analyze the position degree of a screw hole. The threaded rod is taken down, and the bottom of the composite target seat is in contact with the scraping surface to complete scraping flatness measurement. By means of the method, it can be ensured that the spherical pyramid lens has good centering and repeatability precision when being repeatedly placed and rotated, threaded rods of different specifications can be replaced for the target base, and the method is suitable for rapid detection of threaded holes of different specifications. Meanwhile, flatness measurement is not affected by scraped points, the measured surface can be effectively protected, and the device has the advantages of being high in efficiency, simple in structure, easy to achieve, low in cost and the like.

Description

Technical Field

[0001] The invention belongs to the field of detection, and in particular discloses an on-site measurement method for the position of a large-span screw hole of a component and the scraping flatness. Background Art

[0002] The position accuracy of large-span threaded holes and the flatness of the mounting base of large precision parts in aerospace products are important indicators of product assembly performance. The error of this indicator affects the connection strength, assembly accuracy, safety and reliability of parts. How to quickly and accurately measure the position of large-span threaded holes and the flatness of the mounting base also determines the final performance of the system.

[0003] At present, laser trackers have been widely used in the measurement of large-scale geometric parameters in aerospace products. For the measurement of the position of large-span screw holes, the circle measuring accessory can be used to indirectly measure the center of the multi-point fitting circle of the threaded hole, or the screw tooling can be made to match the screw hole for measurement. The implementation process requires the operator to hold the target ball. When facing the high-altitude installation of large components, the actual operation is cumbersome and difficult to implement.

[0004] At present, there are many technical studies on the detection of large-scale installation flatness in China. Among them, the laser tracker combined with the air-floating target realizes rapid scanning measurement, which improves the measurement speed and the protection of the measured surface. When facing the high-precision scraping surface of aerospace products, the surface scraping points will affect the normal use of the air-floating target. Therefore, the measurement process is not affected by the scraping plane points, no scratches are generated, and the completion of in-situ rapid scanning measurement is also a technology worth studying. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of rapid and accurate measurement of screw hole positions during high-altitude debugging of large parts and the in-situ measurement of scraping flatness of large-size installations, and to provide an in-situ measurement method for the positions of screw holes with large spans and the scraping flatness of parts. The method is to manufacture a composite target seat as a target seat for laser tracker measurement, fix a spherical conic mirror by positioning balls at three locations on the upper end of the composite target seat, ensure that the center of the conic mirror is concentric with the threaded rod at the lower end, and use a laser tracker to measure and analyze the positional relationship between the screw holes; remove the threaded rod and use the bottom of the composite target seat to contact the scraping surface to complete the flatness measurement.

[0006] The implementation of the method of the present invention comprises the following steps:

[0007] Step 1: Construct a composite target base, which consists of a base, a magnetic positioning ball, a threaded rod, a locking mechanism, and a spherical corner cone. An internal cone is machined on the upper surface of the base, and three magnetic positioning balls are installed in the internal cone. The magnetic positioning balls are used for placement and centering of the spherical corner cone and provide a suitable magnetic force to adsorb the spherical corner cone. Two symmetrical through holes on the base are used for auxiliary locking and loosening adjustment when the composite target base is matched with the measured screw hole. The threaded rod is connected to the bottom of the base through a locking mechanism. The threaded rod is used as a standard threaded rod to match the measured screw hole to realize the measurement of the center coordinate of the screw hole.

[0008] Step 2: Use a composite target seat as a measuring target seat for a laser tracker, fix a spherical conic mirror on the upper end of the target seat, and use a magnetic positioning ball to center the spherical conic mirror. The center of the spherical conic mirror is concentric and perpendicular to the threaded rod at the lower end of the composite target seat. The threaded rod is used as a standard rod to cooperate with the threaded hole to reproduce the coordinates of the center point of the threaded hole to be measured. Use a laser tracker to collect the coordinates of the center point of the threaded hole to be measured by the spherical conic mirror to analyze the positional relationship between the threaded holes to be measured.

[0009] Step 3: Use the composite target as the target for measuring the spherical conic mirror of the laser tracker, remove the threaded rod, make the bottom of the composite target contact with the scraping plane, use the laser tracker SA software scanning measurement mode, with a scanning interval of 5mm and a scanning speed of 100mm / s. When moving the composite target at a constant speed, always keep it in contact with the scraping plane of the workpiece, collect sampling points on the scraping plane of the workpiece, and complete the measurement and analysis of the flatness error of the scraping plane.

[0010] The advantages of the present invention compared with the prior art are:

[0011] (1) The method of the present invention has good centering and repeatability accuracy when repeatedly fixing the spherical corner cube and rotating the corner cube in multiple directions by using the positioning ball with adsorption force at the three locations on the conical surface at the upper end of the composite target holder;

[0012] (2) The method of the present invention is a measurement method for reproducing the center of a threaded hole by using a standard threaded rod and a threaded hole to simulate the assembly state of a screw and a threaded hole. The laser tracker can be remotely operated to automatically aim and measure the center point of the threaded hole, thereby reducing the fatigue intensity of personnel. The method has a simple structure, good measurement repeatability, convenient operation, and low cost.

[0013] (3) The detection method of the present invention can be applied to the rapid measurement of the center coordinates of symmetrically or asymmetrically distributed deep and shallow threaded holes on precision parts of large and small products made of various materials;

[0014] (4) The present invention uses tetrafluoroethylene (PTFE) as a substrate, which has the characteristics of high and low temperature resistance, corrosion resistance, wear resistance, high lubricity, etc. It can be measured in contact with the scraped surface without being affected by the scraping point. At the same time, it can well protect the surface from being scratched. It is suitable for contact measurement of smooth surfaces or scraped surfaces with high requirements for finish. In addition, it has a data averaging effect on the measurement points in the local area, thereby improving the accuracy of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a flow chart of the laser tracker combined with the composite target base measurement method of the present invention;

[0016] Figure 2 This is a schematic diagram of the composite target base structure of the method of the present invention;

[0017] Figure 3 This is a schematic diagram of the laser tracker combined with the composite target base for measuring the position of the screw hole in the method of the present invention;

[0018] Figure 4 It is a schematic diagram of the method of the present invention in which the laser tracker is combined with the composite target stand to measure the scraping plane;

[0019] Figure 5 A schematic diagram of the sampling point path for measuring the flatness of a square workpiece by a laser tracker combined with a composite target holder according to the method of the present invention;

[0020] Figure 6 The present invention is a schematic diagram of the sampling point path for measuring the flatness of a circular workpiece using a laser tracker combined with a composite target holder.

[0021] The reference numerals in the drawings are: base 1 , magnetic positioning ball 2 , threaded rod 3 , locking mechanism 4 , spherical conic mirror 5 . DETAILED DESCRIPTION

[0022] In order to facilitate a better understanding of the method of the present invention, each link involved in the present invention is described in detail below by means of drawings and implementation examples.

[0023] like Figure 1 As shown, the implementation process of the method for on-site measurement of the position and scraping flatness of a large-span screw hole of a component of the present invention is as follows: a laser tracker is used in combination with a composite target mount to remotely complete the automatic measurement of 8 threaded holes of different specifications on 3 workpieces at high altitude, as well as the relative position adjustment between the 3 workpieces, and at the same time complete the on-site measurement of the flatness of the 4m×2m installation reference surface on the ground after scraping.

[0024] The implementation steps are as follows:

[0025] Step 1: construct a composite target base;

[0026] like Figure 2As shown: the composite target seat consists of a base 1, a magnetic positioning ball 2, a threaded rod 3, a locking mechanism 4, and a spherical conic mirror 5. The base 1 is divided into an upper and lower cylindrical section. The diameter of the upper section of the cylinder is Φ18mm and the height is 14mm. The diameter of the lower section of the cylinder is Φ20mm and the height is 10mm. The interior of the upper cylinder of the base 1 is a conical surface with a cone angle of 40°. The center of the cone must be concentric with the mounting hole at the bottom of the base. Three magnetic positioning balls 2 are installed at an even distribution of 120° on the conical surface for placement and centering of the spherical corner frustum 5, and at the same time, a magnetic force of appropriate size is provided to adsorb the spherical corner frustum 5, and the diameter of the spherical corner frustum 5 is 0.5 inches; two through holes with a diameter of Φ4mm are symmetrically distributed at the center of the lower cylinder of the base 1. When the composite target seat is fitted into the measured screw hole, a cylindrical tool with a diameter of less than Φ4mm is used to be fitted into the through hole to assist in rotating the composite target seat to complete locking and loosening adjustment; the upper end of the locking mechanism 4 cooperates with the screw hole at the bottom of the base 1 through a thread, and the upper end of the threaded rod 3 cooperates with the bottom of the locking mechanism 4, and finally the threaded sleeve is fixed, and the threaded rod 3 is used as a standard threaded rod to precisely cooperate with the measured threaded hole to realize the measurement of the center coordinates of the measured threaded hole.

[0027] The base 1 of the composite target is made of tetrafluoroethylene (PTFE), which has the characteristics of high and low temperature resistance, corrosion resistance, wear resistance, lubrication, etc.

[0028] Step 2: Use a laser tracker combined with a composite target to measure the screw hole position information;

[0029] Among them, Figure 3 As shown: Using a laser tracker and a spherical conic mirror combined with a composite target to measure the coordinates of the center point of the threaded hole on a part;

[0030] The application process is as follows: Figure 3 As shown, workpiece 1#, workpiece 2#, and workpiece 3# need to debug the relative positions of 8 screw holes at a height of 10m, among which the screw hole measured for workpiece 1# is M5, the screw hole measured for workpiece 2# is M12, and the screw hole measured for workpiece 3# is M6.

[0031] First, before measuring, make sure all the screw holes to be measured are on the ground. 1、 a 2… a8 is cleaned inside, and composite target holders of different specifications are placed in the 8 screw holes corresponding to workpieces 1#, 2#, and 3#. Next, 8 0.5-inch spherical conic mirrors 5 are adsorbed on the center of the magnetic positioning ball 3 of the composite target holder. The light receiving port of the spherical conic mirror 5 is adjusted to face the laser tracker installed on the ground. Workpiece 1# is moved to a height of 10m to the connection point of the main mechanism through the hoist. The workpiece 1# and the main mechanism model are imported into the laser tracker SA measurement software. The workpiece coordinate system is established on the main mechanism as required, and the laser tracker motor is manually controlled to remotely find the screw hole a of workpiece 1# to be measured. 1、Spherical conic mirror 5 on a2, using single point acquisition to measure screw hole a 1、 a2 center point coordinates, obtain the actual deviation value between the center coordinates of the measured screw hole of workpiece 1# and the theoretical center coordinates, and according to the deviation value, use the real-time coordinate values ​​(X, Y, Z) of the laser tracker to guide and debug the relative position correction of the workpiece in horizontal, up and down, left and right directions until the requirements are met. Finally, complete the measurement of the center coordinates of the measured screw holes of workpiece 2# and workpiece 3# according to the above method, and guide and debug the relative position to meet the requirements.

[0032] Step 3: Use a laser tracker combined with a composite target to measure the scraping flatness;

[0033] Among them, Figure 1 As shown: the spherical conic mirror 5 is placed in the center of the magnetic positioning ball 2 at 3 places inside the composite target seat, and the threaded rod 3 and the locking mechanism 4 at the bottom of the base 1 are removed; and Figure 4 As shown, the bottom surface of the base is placed on the scraping plane, and the laser tracker on the side frame is combined with the composite target seat to measure the scraping plane, wherein the flatness of the bottom surface of the base is less than 2 microns, the laser tracker is in scanning mode, the spacing is 5mm, and the scanning speed is 100mm / s. During the measurement process, the composite target seat is moved at a constant speed to always keep the bottom surface of the composite target seat in contact with the scraping plane of the workpiece, and according to Figure 5 or Figure 6 The planned measurement path shown in the figure completes the collection of sampling points on the scraping plane of the workpiece, fits the collected points to the flatness according to the least squares method and generates a high and low point error map, marks the local high points and repair amount of the scraping plane of the workpiece under the real-time coordinates of the laser tracker, and guides the scraping plane of the workpiece to be repaired until the flatness meets the requirements. The sampling points of square workpieces are distributed according to the rectangular measurement path, and the sampling points of circular workpieces are distributed according to the radial point measurement path. The scanning measurement mode is used in the early stage of rough processing of the scraping surface to improve the detection efficiency, and the stable point measurement mode is used in the later stage of fine processing to improve the detection accuracy.

[0034] The parts not described in detail in the present invention belong to the well-known technology in the art.

[0035] The above descriptions are only some specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims

1. An in-situ measurement method for the position of large-span screw holes and the flatness of scraping of parts, characterized in that: The following steps are involved: Step 1: Construct a composite target base, which consists of a base, a magnetic positioning ball, a threaded rod, a locking mechanism, and a spherical corner cone. An internal cone is machined on the upper surface of the base, and three magnetic positioning balls are installed in the internal cone. The magnetic positioning balls are used for placement and centering of the spherical corner cone and provide a suitable magnetic force to adsorb the spherical corner cone. Two symmetrical through holes on the base are used for auxiliary locking and loosening adjustment when the composite target base is matched with the measured screw hole. The threaded rod is connected to the bottom of the base through a locking mechanism. The threaded rod is used as a standard threaded rod to match the measured screw hole to realize the measurement of the center coordinate of the screw hole. Step 2: Use a composite target as a measuring target for a laser tracker. A spherical conic mirror is fixed on the upper end of the target. The spherical conic mirror is centered by a magnetic positioning ball. The center of the spherical conic mirror is concentric and perpendicular to the threaded rod at the lower end of the composite target. The threaded rod is used as a standard rod to cooperate with the threaded hole to reproduce the coordinates of the center point of the threaded hole to be measured. The laser tracker is used to collect the coordinates of the center point of the threaded hole to be measured using the spherical conic mirror, and the positional relationship between the threaded holes to be measured is analyzed. Step 3: Use the composite target as the target for measuring the spherical conic mirror of the laser tracker, remove the threaded rod, make the bottom of the composite target contact with the scraping plane, use the laser tracker SA software scanning measurement mode, with a scanning interval of 5mm and a scanning speed of 100mm / s. When moving the composite target at a constant speed, always keep it in contact with the scraping plane of the workpiece, collect sampling points on the scraping plane of the workpiece, and complete the measurement and analysis of the flatness error of the scraping plane.

2. The in-situ measurement method for the position of large-span screw holes and the flatness of scraping of parts according to claim 1 is characterized by: In step 1, the centers of the graduation circles of the three positioning balls in the conical surface at the upper end of the composite target seat are adjusted to be concentric with the threaded rod.

3. The in-situ measurement method for the position of large-span screw holes and the scraping flatness of a component according to claim 1 is characterized by: In step one, threaded rods of different specifications are made. The threaded rods can be disassembled and changed in specifications for the matching measurement of different threaded holes. The installation and locking are performed to ensure that the bottom of the base is connected to the threaded rod vertically. The threaded rods can also be replaced with cylindrical pins of different specifications for the reproducible measurement of the center of the through hole of the workpiece.

4. The in-situ measurement method for the position of large-span screw holes and the scraping flatness of components according to claim 1 is characterized by: The locking mechanism is fixed to the bottom of the base as a threaded sleeve, so that the threaded rod is connected to the bottom of the base.

5. The in-situ measurement method for the position of large-span screw holes and the scraping flatness of a component according to claim 1 is characterized in that: The base is made of tetrafluoroethylene, and its appearance is divided into upper and lower cylindrical sections. The diameter of the upper section is Φ18mm and the height is 14mm, while the diameter of the lower section is Φ20mm and the height is 10mm.

6. The in-situ measurement method for the position of large-span screw holes and the scraping flatness of a component according to claim 1 is characterized by: The sampling points of square workpieces are distributed according to the rectangular measurement path, and the sampling points of circular workpieces are distributed according to the radial point measurement path. The scanning measurement mode is used in the early stage of rough processing of the scraped surface to improve the detection efficiency, and the stable point measurement mode is used in the later stage of fine processing to improve the detection accuracy.

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