A method for in-situ measurement of large-span screw hole position and scraping flatness of parts

Abstract

The application discloses a kind of in-situ measurement methods of large-span screw hole position and scraping flatness of parts, belong to the field of measurement.This method is through making composite target, as laser tracker measurement target, through the positioning ball fixed spherical corner mirror on the upper end 3 of composite target, while ensuring the spherical center of corner mirror and the concentricity of lower end threaded rod, using laser tracker combined with composite target measurement and analysis screw hole position degree;Remove threaded rod and complete scraping flatness measurement using the contact between the bottom of composite target and scraping surface.The method of the application can ensure that spherical corner mirror has good centering and repeatability accuracy when repeatedly placed and rotated, and the target can replace threaded rods of different specifications, suitable for rapid detection of threaded holes of different specifications.At the same time, the flatness measurement is not affected by scraping dots, can effectively protect the measured surface, with the characteristics of high efficiency, simple structure, easy to realize, low cost and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of detection, and particularly discloses a method for in-situ measurement of large-span threaded hole position and scraping flatness of a part. BACKGROUND

[0002] The large-span threaded hole position and the mounting surface flatness of a large and precise part in an aerospace product are important indexes of product assembly performance, and the index error affects the connection strength, assembly precision, safety reliability and the like of the part. How to quickly and accurately measure the large-span threaded hole position and the mounting flatness in-situ is also, in a certain sense, to determine the final performance of the system.

[0003] At present, a laser tracker is widely applied to the measurement of geometric parameters of large size in an aerospace product. For the measurement of the large-span threaded hole position, a circle accessory can be applied to indirectly measure the circle center of the threaded hole through multi-point fitting, or a screw tool can be made to cooperate with the threaded hole for measurement. The implementation process needs an operator to hold a target ball. When facing the high-altitude installation of a large part, the actual operation is relatively complicated, and the implementation is difficult.

[0004] At present, there are various domestic technologies for the detection of large mounting flatness. A laser tracker combined with an air-floating target realizes rapid scanning measurement, improves the measurement speed and protection of the measured surface. When facing the high-precision scraping surface of an aerospace product, the scraping points on the surface will affect the normal use of the air-floating target. Therefore, it is worth studying a technology that can realize in-situ rapid scanning measurement without being affected by the scraping points on the flat surface and without producing scratches. SUMMARY

[0005] The application aims to solve the problems of quick and accurate measurement of the threaded hole position of a large part in high-altitude debugging and in-situ measurement of the large-size mounting scraping flatness, and provides a method for in-situ measurement of the large-span threaded hole position and the scraping flatness of a part. The method is to make a composite target base as a measurement target base of a laser tracker, fix a spherical corner mirror through three positioning balls on the upper end of the composite target base, ensure the concentricity between the spherical center of the corner mirror and the threaded rod on the lower end, measure and analyze the position relationship between threaded holes by using the laser tracker, and then remove the threaded rod to complete the flatness measurement by using the contact between the bottom of the composite target base and the scraping surface.

[0006] The implementation of the method includes the following steps:

[0007] Step one: construct a composite target, the composite target is composed of a base, a magnetic positioning ball, a threaded rod, a locking mechanism, and a spherical corner mirror, the upper surface of the base is processed with an internal taper, three magnetic positioning balls are installed in the internal taper, the magnetic positioning balls are used for placing and centering the spherical corner mirror and providing appropriate magnetic force to attract the spherical corner mirror; the base has two symmetrical through holes for auxiliary locking and loosening adjustment when the composite target is matched with the measured screw hole; the threaded rod is connected with the bottom of the base through the locking mechanism, and the threaded rod is matched with the measured threaded hole as a standard threaded rod to realize the measurement of the center coordinates of the threaded hole;

[0008] Step two: use the composite target as the measurement target of the laser tracker, the spherical corner mirror is fixed on the upper end of the target, the centering of the spherical corner mirror is realized through the magnetic positioning ball, the spherical center of the spherical corner mirror is concentric and perpendicular to the lower end threaded rod of the composite target, the threaded rod is matched with the measured threaded hole as a standard rod to reproduce the center point coordinates of the measured screw hole, and the laser tracker is used to collect the spherical corner mirror to obtain the center point coordinates of the measured threaded hole and analyze the positional relationship between the measured threaded holes;

[0009] Step three: use the composite target as the spherical corner mirror measurement target of the laser tracker, remove the threaded rod, make the bottom of the composite target contact with the scraping plane, use the scanning measurement mode of the laser tracker SA software, the scanning interval is 5mm, the scanning speed is 100mm / s, the composite target is always kept in contact with the workpiece scraping plane during uniform movement, the sampling points of the workpiece scraping plane are collected, and the planeness error of the scraping plane is measured and analyzed.

[0010] Compared with the prior art, the advantages of the present application are:

[0011] (1) The method of the present application can repeatedly fix the spherical corner mirror and the multi-directional rotating corner mirror through the three positioning balls with adsorption force on the upper end taper of the composite target, and has good centering and repeatability precision;

[0012] (2) The method of the present application is a measurement method for simulating the assembly state of the screw and the threaded hole, using the standard threaded rod to match with the measured screw hole to reproduce the center of the threaded hole, which can remotely operate the laser tracker to automatically aim and measure the center point of the screw hole, reduce the fatigue strength of personnel, and has the advantages of simple structure, good measurement repeatability, convenient operation and low cost;

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

[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 smoothness. 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 screw holes in the method of the present invention;

[0018] Figure 4 Schematic diagram of the method of the present invention for measuring and scraping a plane using a laser tracker combined with a composite target holder;

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

[0020] Figure 6 This 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 according to the method of the present invention.

[0021] The reference numerals 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 through the drawings and implementation examples.

[0023] like Figure 1 The figure shows the implementation process of the method for in-situ measurement of the position and scraping flatness of large-span screw holes in a component of the present invention. Specifically, a laser tracker is used in combination with a composite target mount to remotely complete the automatic measurement of eight threaded holes of different specifications on three workpieces at high altitude, as well as the relative position adjustment between the three workpieces. At the same time, the in-situ flatness measurement of the 4m×2m installation reference surface on the ground after scraping is completed.

[0024] The implementation steps are as follows:

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

[0026] like Figure 2As shown: the composite target seat is composed of base 1, magnetic positioning ball 2, threaded rod 3, locking mechanism 4, spherical corner mirror 5, base 1 is divided into upper and lower section cylinders, the upper section cylinder diameter size is Φ18mm, height size is 14mm, the lower section cylinder diameter is Φ20mm, height size is 10mm. The inner part of the upper section cylinder of the base 1 is a conical surface, the conical angle is 40°, the conical center is concentric with the base bottom mounting hole, the conical surface is uniformly distributed with 3 magnetic positioning balls 2 for the placement and centering of the spherical corner mirror 5, and provides appropriate size magnetic force to adsorb the spherical corner mirror 5, the diameter of the spherical corner mirror 5 is 0.5 inch; the lower section cylinder of the base 1 is symmetrically distributed with two Φ4mm through holes at the center, which is used for the composite target seat to be matched into the measured screw hole, and a cylindrical tool with diameter <Φ4mm is matched into the through hole to assist in rotating the composite target seat to complete locking, loosening and adjusting; the upper end of the locking mechanism 4 is matched with the bottom screw hole of the base 1 through threads, the upper end of the threaded rod 3 is matched with the bottom of the locking mechanism 4, and finally the threaded sleeve is fixed, the threaded rod 3 is a standard threaded rod which is precisely matched with the measured threaded hole to realize the measurement of the center coordinate of the measured threaded hole.

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

[0028] Step two: measure the screw hole position information using a laser tracker combined with a composite target seat;

[0029] Among them, as shown in Figure 3 The laser tracker and the spherical corner mirror are combined with the composite target seat to measure the center point coordinate of the threaded hole on the part;

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

[0031] First, measure the front on the ground 1、 a 2… a8 interior cleaning, different specifications of composite target seat into the workpiece 1#, workpiece 2#, workpiece 3# corresponding 8 measured screw hole, secondly, 8 0.5 inch spherical corner mirror 5 is adsorbed in the center of the magnetic positioning ball 3 of the composite target seat, adjust the light port of the spherical corner mirror 5 to face the laser tracker installed on the ground, use the lifting tool to move the workpiece 1# to the main mechanism connection at a height of 10m, import the workpiece 1# and the main mechanism model into the laser tracker SA measurement software, establish the workpiece coordinate system on the main mechanism as required, and manually control the laser tracker motor to remotely find the measured screw hole a 1、Spherical corner cube mirror 5 on a2, using single-point collection of measured screw hole a 1、 a2 center point coordinates, obtain the actual deviation value of the measured screw hole center coordinates of workpiece 1# from the theoretical center coordinates, according to the deviation value, guide the debugging of the workpiece level, up and down, left and right direction correction relative position until the requirement is met, and finally complete the measurement of the measured screw hole center coordinates of workpiece 2# and workpiece 3# according to the above method and guide the debugging of the relative position to meet the requirements.

[0032] Step three: use laser tracker combined with composite target to measure the scraping flatness;

[0033] As shown in Figure 1 : Place the spherical corner cube mirror 5 inside the composite target 3 with the magnetic positioning ball 2 center, remove the threaded rod 3 at the bottom of the base 1 and the locking mechanism 4; and as shown in Figure 4 : Place the base bottom surface on the scraping plane, so that the laser tracker combined with the composite target on the side frame measures the scraping plane, wherein the base bottom surface flatness is <2 microns, the laser tracker is in scanning mode, the interval is 5mm, the scanning speed is 100mm / s, and the composite target is moved at a constant speed during the measurement process to keep the composite target bottom surface in contact with the workpiece scraping plane, and the measurement path is planned according to Figure 5 Or Figure 6 : Complete the collection of sampling points of the workpiece scraping plane, fit the flatness of the collected points according to the least square method and generate a high-low point error map, mark the local high points and repair amount of the workpiece scraping plane under the real-time coordinates of the laser tracker, and guide the workpiece scraping plane to be repaired until the flatness meets the requirements. The sampling point distribution of the square workpiece is completed according to the rectangular measurement path, and the sampling point distribution of the circular ring workpiece is completed according to the radial point measurement path. The scanning measurement mode is used before rough machining of the scraping surface to improve the detection efficiency, and the stable point measurement mode is used after fine machining to improve the detection accuracy.

[0034] The part of the application not described in detail belongs to the technology known in the art.

[0035] The above is only part of the specific embodiments of the application, but the protection scope of the application is not limited thereto, any changes or replacements within the technical scope disclosed by the application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the application.

Claims

1. A method for measuring the position of large-span screw holes and the flatness of scraping on components, characterized in that: The following steps are involved: Step 1: Construct a composite target base. The composite target base consists of a base, a magnetic positioning ball, a threaded rod, a locking mechanism, and a spherical corner mirror. The upper surface of the base is machined with an internal cone, and three magnetic positioning balls are installed in the internal cone. The magnetic positioning balls are used to place and center the spherical corner mirror and provide a suitable magnetic force to adsorb the spherical corner mirror. 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 serves as a standard threaded rod and cooperates with the measured screw hole to realize the measurement of the center coordinate of the screw hole. Step 2: Use a composite target as the measurement target for the laser tracker. A spherical corner frustum is fixed on the upper end of the target. The spherical corner frustum is centered using a magnetic positioning ball. The center of the spherical corner frustum is concentric and perpendicular to the threaded rod at the lower end of the composite target. The threaded rod serves as a standard rod and cooperates with the threaded hole to reproduce the coordinates of the center point of the measured screw hole. The laser tracker is used to collect the coordinates of the center point of the measured threaded hole from the spherical corner frustum, and the positional relationship between the measured threaded holes is analyzed. Step 3: Use a composite target as the target for measuring the spherical conic mirror of the laser tracker. Remove the threaded rod to make the bottom of the composite target contact the scraping plane. Use the laser tracker SA software scanning measurement mode with a scanning interval of 5 mm and a scanning speed of 100 mm / 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 to 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 components according to claim 1 is characterized by: In step 1, the centers of the pitch 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 flatness of scraping of components 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 to match the measurement of different threaded holes. When used, they are installed and locked 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 repeated 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 flatness of scraping of components according to claim 1 is characterized by: The locking mechanism is fixed to the bottom of the base as a threaded sleeve, realizing the connection between the threaded rod and the bottom of the base.

5. The in-situ measurement method for the position of large-span screw holes and the flatness of scraping of components according to claim 1 is characterized by: The base is made of tetrafluoroethylene, and its outer shape 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 flatness of scraping of components 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 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.

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