In-situ measurement method for form and location tolerance of large-size annular part

Abstract

The invention discloses an in-situ measurement method for form and location tolerance of a large-size annular part, which belongs to the technical field of detection, is used for in-situ measurement of large-size annular optical and mechanical parts, and comprises the following steps of: (1) calibrating the precision of a numerical control machining center by using a scale, a laser interferometer and a standard ball; (2) measuring and debugging the workpiece to be parallel and concentric with the rotary table by using a dial gauge; (3) measuring workpiece parameters by using a laser tracker to establish a workpiece coordinate system; (4) measuring part contour parameters by using a laser tracker in combination with a machine tool; and (5) analyzing geometric quantity form and position errors of the part. The method solves the problem of in-situ measurement in the machining process of the large-size annular workpiece, reduces the risk and cost of repeated transportation and inspection of the workpiece, and has the characteristics of convenience in operation, safety, high efficiency, high measurement precision and the like.

Description

Technical Field

[0001] The invention belongs to the field of detection technology, and in particular relates to an on-site measurement method for the shape and position tolerance of a large-size annular part. Background Art

[0002] Large-size optical and mechanical parts are the core components of large-scale optoelectronic equipment. They are large in size, high in mass, and high in precision. Since the core components have many shape and position parameter indicators and high precision, each parameter indicator needs to be processed and tested repeatedly during the development process to meet the technical requirements. At the same time, indicator detection requires the application of large-scale metrological three-coordinate measuring machines to complete related precision detection work. Therefore, the detection cost is too high. In addition, repeated lifting of parts for transportation and inspection has great risks, and the detection and debugging time is uncontrollable. Summary of the invention

[0003] In order to solve the problem that the shape tolerance needs to be measured in situ during the development of large-scale annular optical machine parts above 2m, an in-situ measurement method for the shape and position tolerance of large-scale annular parts is provided. The present invention uses a gantry machining center and a precision rotary table, combined with the spatial measurement technology of a laser tracker, to solve the in-situ detection of geometric parameters of large-scale optical machine parts, with good detection precision and accuracy. The invention effectively reduces the product development cycle and risk, and saves time costs.

[0004] The technical solution adopted by the present invention is: an in-situ measurement method for the shape and position tolerance of a large-sized annular part, the method comprising the following steps:

[0005] Step 1: Calibration and correction of X, Y, Z, and C axis precision of CNC machining center;

[0006] Step 2: Adjust the workpiece to be parallel and concentric with the rotary table;

[0007] Step 3: Measure the workpiece parameters and establish the workpiece coordinate system;

[0008] Step 4: Measure the outer contour space points of the workpiece ring plane, outer cylindrical surface, and inner cylindrical surface;

[0009] Step 5: Data processing, analysis of geometric tolerances, and determination of the deviation direction of the workpiece geometric error based on the coordinate system for rework and inspection until the requirements are met.

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

[0011] (1) Due to the limitations of the traditional three-dimensional coordinate measuring machine due to the measurement principle, measurement range and high requirements of the measurement environment, it is not suitable for the on-site detection of optical and mechanical parts. At the same time, the equipment purchase cost is high, and the purchase, installation, commissioning and application cycle is long. In addition, the risk of transporting parts back and forth for inspection is high, and the development cycle is uncontrollable. When measuring by using the laser tracker transfer method, there will be a loss of accuracy, and only the measurement of relevant external parameters of the workpiece can be completed. By combining the laser tracker with the gantry CNC machining center, the on-site detection of high-precision indicators of the geometric tolerances of precision optical and mechanical parts is solved, and on-site guided processing is realized; at the same time, the probe distance between the target center and the indicator is calibrated, which can complete the synchronous measurement of the workpiece's external dimensional tolerance. Therefore, the present invention reduces the huge risks caused by the lifting and round-trip transportation of precision optical and mechanical parts, shortens the development cycle of this stage, and has good detection accuracy and precision;

[0012] (2) The detection method of the present invention is easy to operate, safe and efficient, and has relatively low cost;

[0013] (3) The detection method of the present invention is not limited to the on-site detection of the form and position tolerances of large-diameter optical components and precision machinery, but can also be applied to the on-site detection of the size and form and position tolerances of large-scale precision special material product parts in various industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The figure is a flow chart of an on-site measurement method for the shape and position tolerance of a large-sized annular part;

[0015] Figure 2 This is the structural diagram of the CNC machining center;

[0016] Figure 3 A schematic diagram of workbench accuracy calibration for an in-situ measurement method of the form and position tolerances of a large-sized annular part;

[0017] Figure 4 It is a schematic diagram of the implementation of an on-site measurement method for the shape and position tolerance of a large-sized annular part;

[0018] Figure 5 Schematic diagram of the measurement point distribution of an on-site measurement method for the form and position tolerance of large-sized annular parts. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned purpose, the present invention adopts the following technical scheme.

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. Implementation process: The in-situ detection process of the shape and position tolerance of a ring-shaped part with an outer shape of 2200mm×500mm is described in detail by using the method of the present invention.

[0021] The present invention proposes an on-site measurement method for the shape and position tolerance of large-sized annular parts. Figure 1 As shown, follow these steps to implement it:

[0022] Step 1: Calibration and correction of X, Y, Z, and C axis precision of CNC machining center;

[0023] Before the workpiece is processed, Figure 2 , Figure 3 As shown in the figure, firstly, the straightness of the X, Y, and Z linear motion axes of the CNC machining center and the verticality of the machine tool worktable are detected and corrected using a standard ruler and angle ruler. Secondly, the positioning and repeatability accuracy of the X, Y, and Z linear motion axes are detected and corrected using a laser interferometer. The positioning and repeatability accuracy of the C axis of the rotary table of the CNC machining center are calibrated and corrected using an autocollimator. Finally, as shown in the figure, Figure 3 As shown, a standard ball is fixed to the center of the rotary table, and radial measurement indicators and axial measurement indicators are used to measure the axial and radial runout errors of the rotary table;

[0024] The three-dimensional adjustment mechanism is installed to the center of the rotary table, and is detected and aligned to be parallel to the rotary table through the axial measurement indicator. The standard ball is then fixed to the upper end face of a cylindrical tooling with a fulcrum height of >200mm and a diameter of 50mm, and the lower end face is fixed to the upper surface of the three-dimensional adjustment mechanism. Finally, the radial measurement indicator is used to measure and debug the concentricity of the standard ball and the rotary table.

[0025] Step 2: Adjust the workpiece to be parallel and concentric with the rotary table;

[0026] like Figure 4 As shown, the indicator is fixed on the spindle of the CNC machining center, the probe of the indicator is firstly contacted with the plane of the ring mouth of the workpiece, the rotary table is controlled to rotate to 0°, 120°, and 240° respectively to record the runout difference of the indicator, and the parallelism of the workpiece and the rotary table is adjusted to ≤0.01mm through the three-dimensional adjustment mechanism at the bottom of the workpiece; then the probe of the indicator is contacted with the outer cylindrical surface of the workpiece, and the rotary table is controlled to rotate to 0°, 180°, 90°, and 270° respectively. According to the record runout difference of the indicator, the workpiece and the rotary table are adjusted to be concentric ≤0.01mm through the three-dimensional adjustment mechanism at the bottom of the workpiece;

[0027] Step 3: Measure the workpiece parameters and establish the workpiece coordinate system;

[0028] The ring surface and outer cylindrical surface of the workpiece are evenly distributed with 16 measurement points in the circumferential direction. The laser tracker is combined with the target to directly measure and fit the flatness and the center of the circle. Then the straight line between the +X target point and the center of the circle is measured to establish the Cartesian coordinate system of the workpiece.

[0029] Step 4: Measure the outer contour space points of the workpiece ring plane, outer cylindrical surface, and inner cylindrical surface;

[0030] Among them Figure 4 As shown, the rotary table is controlled to drive the workpiece to move to the initial position. The target and indicator of the laser tracker are fixed on the spindle of the CNC machining center, so that the indicator probe contacts the ring surface. The rotary table is synchronously controlled to rotate at 16 positions at equal intervals. The laser tracker is used in combination with the target to measure and record the 16 coordinate points distributed on the circumference of the ring surface, as shown in FIG. Figure 5 As shown, the collection of contour measurement points of the ring plane, outer cylindrical surface, and inner cylindrical surface is completed.

[0031] The C axis of the rotary table rotates at intervals of 22.5°, with a delay of 6 seconds for each rotation. The CNC machine tool spindle is synchronously controlled to make the indicator probe contact the measured point and keep the contact force change less than 2 microns each time. The laser tracker adopts the IFM interference stable point measurement mode to synchronously collect position information. The measurement sequence is to take the +X target point as the starting point, first measure the ring mouth plane to divide 16 coordinate points equally in the circumferential direction, then measure the outer cylindrical surface to evenly distribute 16 coordinate points along the circumference, evenly distribute five cut circles in the axial direction, a total of 80 coordinate points, and finally measure the five cut circles of the inner cylindrical surface to a total of 80 coordinate points;

[0032] The rotary table needs to rotate 2 circles before measurement to eliminate the return error. The indicator table uses a high-precision digital inductive probe to keep the measuring force consistent. The measuring points can be increased or decreased according to the size and accuracy of the parts. The measurement form of the inner and outer cylindrical surfaces is measured according to the cylindrical line or spiral line distribution.

[0033] Step 5: Data processing, analysis of geometric tolerances, and determination of the deviation direction of the geometric error of the parts according to the coordinate system for rework and inspection until the requirements are met.

[0034] In the coordinate system described in step three, the coordinate values ​​of the measuring point (X, Y, Z) at the ring plane 16 are first derived, and the cylindrical coordinate values ​​(ρ, Ф, z) are generated by taking the center radius of the outer cylinder of the ring plane as the polar diameter ρ, the rotation angle of the rotary table every 22.5 degrees as the polar angle Ф, and the axial error as the height value Z.

[0035] Next, in step 4, Figure 5The coordinate values ​​of 80 measuring points (X, Y, Z) on the inner and outer cylindrical surfaces are derived, with the inner and outer cylindrical surface contour measuring points to the workpiece center radius as the polar diameter ρ, the rotary table rotation angle of 22.5 degrees as the polar angle Ф, and the height difference between the first and fifth circle section measuring points corresponding to the upper and lower circles as the height value Z, generating the inner and outer cylindrical coordinate values ​​(ρ, Ф, z) respectively.

[0036] Finally Figure 5 As shown in the figure, under the unified reference coordinates, the cylindrical coordinate values ​​(ρ, Ф, z) generated by the ring plane, inner cylindrical surface and outer cylindrical surface are imported into the SA measurement and analysis software to fit and evaluate the various form and position tolerances of the workpiece, such as cylindricity, verticality, coaxiality, flatness, etc. If there is an excess tolerance, the deviation direction is determined in the coordinate system, and rework and inspection are performed until the requirements are met.

[0037] The known technologies in the art involved in the present invention are not described in detail.

Claims

1. An in-situ measurement method for the shape and position tolerance of large-sized annular parts, characterized in that: The method comprises the following steps: Step 1: Calibration and correction of X, Y, Z, and C axis precision of CNC machining center; Step 2: Adjust the workpiece to be parallel and concentric with the rotary table; Step 3: Measure the workpiece parameters and establish the workpiece coordinate system; Step 4: Measure the outer contour space points of the workpiece ring plane, outer cylindrical surface, and inner cylindrical surface; Step 5: Data processing, analysis of geometric tolerances, and determination of the deviation direction of the workpiece geometric error based on the coordinate system for rework and inspection until the requirements are met.

2. The in-situ measurement method of the shape and position tolerance of a large-sized annular part according to claim 1 is characterized in that: In step one, before processing the workpiece, first use a standard ruler and a protractor to detect and correct the straightness of the X, Y, and Z linear motion axes of the CNC machining center and the verticality of the machine tool worktable. Secondly, use a laser interferometer to detect and correct the positioning and repeat positioning accuracy of the X, Y, and Z linear motion axes. Use an autocollimator to calibrate and correct the C-axis positioning and repeat positioning accuracy of the rotary table of the CNC machining center. Finally, use a standard ball to calibrate the axis shake error of the rotary table; wherein the standard ball is fixed to the center of the rotary table, the standard ball fulcrum is located on the upper end face of a cylindrical tooling with a height of >200mm and a diameter of 50mm, the lower end face of the cylindrical tooling is fixed to the three-dimensional adjustment mechanism and synchronously installed to the center of the rotary table, and an indicator gauge is used to measure and debug the concentricity of the standard ball and the rotary table.

3. The in-situ measurement method of the shape and position tolerance of a large-sized annular part according to claim 2 is characterized in that: In step 2, the spindle of the CNC machining center is fixed by using an indicator, so that the probe of the indicator contacts the plane of the ring of the workpiece, the rotary table is controlled to rotate to 0°, 120°, and 240° respectively to record the runout difference of the indicator, the workpiece is adjusted to be parallel to the rotary table, and then the probe of the indicator is contacted with the outer cylindrical surface of the workpiece, and the rotary table is controlled to rotate to 0°, 180°, 90°, and 270° respectively to record the runout difference of the indicator in sequence, and the workpiece is adjusted to be concentric with the rotary table; The bottom of the workpiece is supported by a three-dimensional adjustment mechanism, and the workpiece is accurately aligned through translation and tilt functions.

4. The in-situ measurement method of the shape and position tolerance of a large-sized annular part according to claim 3 is characterized in that: In step three, the ring mouth plane and the outer circle are equally divided into 16 points in the circumferential direction, and the flatness and the center of the circle are measured and fitted using a laser tracker. Then, the straight line between the +X target point and the center of the circle is measured to establish the Cartesian coordinate system of the workpiece.

5. The in-situ measurement method for the shape and position tolerance of a large-sized annular part according to claim 4 is characterized in that: In step 4, the rotary table is controlled to drive the workpiece to move to the initial position, the laser tracker target and the indicator are fixed on the spindle of the CNC machining center, the rotary table is controlled to rotate at an equal interval of 22.5 degrees, the spindle of the CNC machining center is synchronously controlled to drive the indicator to contact the ring plane, the laser tracker is used to measure and record the displacement information, and the collection of the ring plane, the outer cylindrical surface, and the inner cylindrical surface measurement points are completed in sequence; the laser tracker adopts the IFM interference stable point measurement mode, and the rotary table rotates 2 circles before measurement to eliminate the return error; the measurement sequence takes the +X target point as the starting point, first measures the ring plane and divides it into 16 coordinate points in the circumferential direction, then measures the outer cylindrical surface, and evenly distributes 5 cut circles, each cut circle is divided into 16 coordinate points in the circumference, a total of 80 measurement points, the Z-direction measurement sequence is from the first cut circle measurement point to the fifth cut circle measurement point, and finally measures the five cut circle measurement points of the inner cylindrical surface, a total of 80 measurement points; The contact measuring force of the indicator remains the same, the measuring points increase or decrease according to the size and accuracy of the workpiece, and the inner and outer cylindrical surfaces are measured according to the cylindrical line or spiral line distribution.

6. The in-situ measurement method for the shape and position tolerance of a large-sized annular part according to claim 5 is characterized in that: In step five, 16 coordinate points (x, y, z) of the ring plane are exported and converted into cylindrical coordinate values ​​through data processing; 16 lines of the inner and outer cylindrical surfaces and 80 contour coordinate points (x, y, z) are exported respectively, and converted into inner and outer cylindrical coordinate values ​​through data processing, and input into the laser tracker SA software, and the cylindricity, verticality, coaxiality, flatness and other form and position errors are fitted and analyzed under the unified reference coordinate system. If there are out-of-tolerance items, the deviation direction is determined under the coordinates, and rework and inspection are performed until the requirements are met.

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