A spindle rotation error measurement method based on dual probes

Abstract

The present invention discloses a method for measuring the spindle rotation error based on dual probes. The method is as follows: First, a cylindrical sample is coaxially installed on the spindle to be measured. The probe device is arranged radially along the cylindrical sample; after the two probe devices simultaneously perform data acquisition in the tapping mode, they simultaneously perform data acquisition in the contact mode. In the data acquisition in the tapping mode, the spindle to be measured rotates for multiple circles to obtain multiple sets of displacement data. In the contact mode, the spindle to be measured rotates for one circle, leaving scratch marks on the spindle to be measured. Second, the inclination error of the spindle is calculated based on the displacement data; third, the axial error of the spindle to be measured is obtained based on the scratch marks. The present invention obtains radial displacement data and scratch marks through the probe scratching function, and with the corresponding calculations, it can simultaneously measure the inclination error, radial error and axial error of the spindle to be measured, thereby accurately evaluating the rotation accuracy of the spindle to be measured.

Description

Technical Field

[0001] The present invention belongs to the field of spindle rotation error measurement in precision measurement technology, and relates to a method and device for measuring spindle rotation error using two probes, mainly using the micro-nano scratching function of the probes. Background Art

[0002] The accuracy of machine tools largely determines the precision of machined parts. To ensure the machining quality of mechanical products, the development of high-precision machine tools is an inevitable trend. The spindle is the core component of CNC machine tools, and its rotational error is a significant factor affecting machine tool machining accuracy. Experimental studies have shown that during precision machining, spindle rotational error accounts for 30% to 70% of the total error, and the higher the machine tool's accuracy level, the greater the proportion of spindle rotational error in the total error. Measuring rotational error is of great practical significance for evaluating machine tool spindle accuracy, monitoring spindle operating status, and promptly detecting and diagnosing spindle faults.

[0003] At present, there are many methods for measuring the spindle rotation error. The commonly used measurement method is the error separation method using a standard rod, which uses one-dimensional displacement sensors such as capacitive and eddy current to measure the error motion of the spindle. However, a standard rod is required in the measurement, which increases the processing and manufacturing cost and difficulty, and requires error separation. Some scholars have proposed a light target tracking method to measure the spindle rotation error, but this method is easily affected by the external environment and the experimental conditions are relatively harsh. The present invention designs a measurement method and device for measuring the spindle rotation error using a principle similar to that of an atomic force microscope (AFM) probe. This method can measure high-precision spindle rotation errors using only dual probes and evaluate the spindle. Summary of the Invention

[0004] The purpose of the present invention is to provide a measurement method and device for detecting spindle rotation errors using dual probes.

[0005] The dual-probe-based spindle rotation error measurement method comprises the following steps:

[0006] Step 1: Install a cylindrical sample coaxially on the spindle to be measured; arrange two probe devices radially along the two data acquisition positions on the cylindrical sample; the probe device has two working modes, namely tapping mode and contact mode; in tapping mode, the probe in the probe device presses against the cylindrical sample and vibrates, and the displacement information is read through the contact signal; in contact mode, the probe in the probe device presses against the cylindrical sample, applies pressure to scratch the cylindrical sample, and reads the displacement data. After the two probe devices simultaneously perform data acquisition in tapping mode, they then simultaneously perform data acquisition in contact mode. In the data acquisition in tapping mode, the spindle to be measured rotates multiple times to obtain multiple sets of displacement data. In contact mode, the spindle to be measured rotates one cycle.

[0007] The probe device in tapping mode acquires radial displacement data, ΔZ(θ), where θ is the phase of the measured spindle. The probe device in contact mode leaves a scratch mark on the cylindrical sample. Two sets of radial displacement data, ΔZ(θ), are obtained, denoted as ΔZ1(θ) and ΔZ2(θ), along with two scratch marks.

[0008] Step 2: Calculate the spindle inclination error as follows:

[0009]

[0010] Where ε1(θ) and ε2(θ) are the installation eccentricity and roundness errors of the cylindrical sample at the two data collection positions, respectively. ΔL is the axial distance between the two data collection positions.

[0011] Step 3: Scan the sample's scratched surface and read the scratch marks to obtain a scratch image; the displacement of the track on the scratch image along the spindle's axial direction is used as the axial error of the spindle being measured.

[0012] Preferably, in the tapping mode, the vibration frequency of the probe is 0.5 MHz to 1 MHz. In the contact mode, the pressure of the probe on the columnar sample is 1 to 10 μN.

[0013] As a preference, step 4 is performed after step 3 is performed; the specific process of step 4 is: extracting the radial error σ of the measured spindle θ =ΔZ(θ)-ε(θ); where ε(θ) is the installation eccentricity and roundness error of the cylindrical sample when collecting radial displacement data ΔZ(θ).

[0014] Preferably, the material of the columnar sample is injection-molded polycarbonate.

[0015] Preferably, the spindle to be measured rotates at a plurality of different speeds, and the inclination error, axial error and radial error of the spindle to be measured are collected according to the methods described in steps 2 to 5.

[0016] Preferably, the dual-probe-based spindle tilt error measurement method uses a measuring device comprising a first probe device (1), a second probe device (2), a cylindrical sample (3), and a clamping device (4). The clamping device (4) is coaxially fixed to the end of the spindle (5); the cylindrical sample (3) is coaxially fixed to the clamping device (4). The first probe device (1) and the second probe device (2) are mounted on a machine frame and are pressed against different positions on the spindle (5) aligned along the axial direction.

[0017] As a preference, obtain the tilt error The expression process is as follows:

[0018] Establish radial displacement ΔZ i The expression of (θ) is as follows:

[0019]

[0020]

[0021] Among them, σ θ is the radial error. Error introduced by the spindle inclination; i = 1, 2.

[0022] By subtracting and transforming the two radial displacement expressions, we can obtain the following relationship:

[0023]

[0024] Calculate the inclination error of the measured spindle The relationship is as follows:

[0025]

[0026] Due to the inclination error The value of is small, Approximately Obtain the inclination error The expression:

[0027]

[0028] The present invention has the beneficial effects:

[0029] The present invention draws on the two-mode switching function of the AFM; however, the differences from the AFM are as follows: 1. The AFM has only one probe, which makes it difficult to measure the three spindle errors. The present invention utilizes a dual-probe structure to achieve this. 2. The AFM has a complex structure and limited measurement space, making it difficult to directly measure spindle errors. The present invention can design a dual-probe integral mounting structure and miniaturize it to meet the actual spindle measurement requirements. 3. The AFM range is not suitable for spindle error measurement, and there are problems with measuring spindle errors of lower precision. The present invention can increase the actual measurement range and adapt to the measurement and evaluation of various types of spindle rotation errors.

[0030] Compared with the existing technology, the present invention has the following advantages: 1. The present invention adopts contact measurement with higher stability and reliability, and only requires the accuracy of the side shape of the sample. 2. Current detection mostly adopts capacitance or eddy current one-dimensional displacement sensors for measurement, which has requirements on the material of the object to be measured. The present invention only requires non-soft materials, and the material requirements are reduced. 3. The present invention only uses two identical probes for measurement, without the need for multiple sensors, and the complexity of installation and operation is reduced. 4. Through the reverse installation method, the inversion method can be used for error separation, which improves the measurement accuracy of the spindle rotation error, which is of great significance to improving the manufacturing of precision parts.

[0031] The present invention obtains radial displacement data and scratch marks through the probe scratching function. Combined with corresponding calculations, it can simultaneously measure the inclination error, radial error and axial error of the measured spindle, thereby accurately evaluating the rotation accuracy of the measured spindle. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 1 is a schematic diagram of the overall structure of the measuring device used in the present invention;

[0033] Figure 2 This is a schematic diagram of the principle for solving the spindle inclination error in the present invention.

[0034] Figure 3 This is a schematic diagram of the principle of solving the spindle axial error in the present invention.

[0035] Figure 4 This is a schematic diagram of the principle of solving the spindle radial error in the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings.

[0037] like Figure 1 、 2 , 3 and 4 show a method for measuring the spindle inclination error based on dual probes, and the measuring device used includes a first probe device 1, a second probe device 2, a columnar sample 3 and a clamping device 4. The clamping device 4 is coaxially fixed to the end of the spindle 5 by a screw; the columnar sample 3 is coaxially fixed to the end of the spindle 5 by the clamping device 4 and the screw. During operation, the clamping device 4 coaxially installed with the spindle 5 can drive the columnar sample 3 to rotate under the drive of the spindle. The material of the columnar sample is injection-molded polycarbonate, which has high stability and the surface roughness can be controlled to tens of nanometers or even a few nanometers, and is simple to process. Therefore, the influence of surface roughness can be ignored during data processing.

[0038] During operation, both the first and second probe assemblies 1 and 2 are positioned radially relative to the cylindrical sample 3, pressing against the side of the sample to accurately measure spindle rotational error without introducing other errors. The first and second probe assemblies 1 and 2 are aligned along the axial direction of the cylindrical sample 3. The first and second probe assemblies 1 and 2 share the same structure, each equipped with a probe that can vibrate at a specified frequency under the action of a power element and compress the sample with a constant pressure.

[0039] The specific steps of the dual-probe spindle inclination error measurement method are as follows:

[0040] Step 1: Install the clamping device 4 coaxially on the end face of the spindle 5. This can be done using a shaft alignment device, or by slowly rotating the spindle after initially installing the measurement target and repeatedly adjusting the position of the clamping device by tapping with a dial indicator and a rubber rod, ensuring that the eccentricity error between the clamping device and the spindle axis is less than 3 μm. The cylindrical sample 3 is secured to the end face of the spindle 5 by the clamping device 4. The two probe devices are positioned radially with respect to the cylindrical sample 3.

[0041] Step 2: Turn on the probe measurement device and set it to tapping mode; start the motor to drive the main shaft to drive the clamping device to rotate together; while the columnar sample 3 rotates, the two probe devices measure the rotation of the columnar sample 3 in tapping mode, and the displacement sensor records the radial displacement of the sample 3. The obtained data is recorded as ΔZ1(θ) and ΔZ2(θ). After obtaining multiple sets of data, increase the probe normal load to change the two probe devices 1 and 2 from tapping mode to contact mode, so that the probe device tips are pressed into the surface of the columnar sample 3; the measured main shaft drives the columnar sample 3 to rotate 360°, and the probe device tips will leave a circle of scratch marks on the columnar sample 3. After moving 360°, reduce the normal load to separate the probe device from the columnar sample 3, and end the scratching.

[0042] Step 3: The installation eccentricity error and roundness error of the two experiments are recorded as ε1(θ) and ε2(θ) respectively; the eccentricity error and roundness error can be separated by existing separation technology, such as the reversal method, which rotates the dual probes 180° for installation, rotates the main shaft 180°, and measures again, which can effectively separate the shape error. Let the radial error be σ θ ; θ is the phase of the main axis (relative to the initial position, the main axis drives the cylindrical sample to rotate the angle); ΔL is the axial distance between the two experiments. The process of calculating the inclination error using the above data is as follows:

[0043] 3-1. Radial displacement ΔZ recorded by the displacement sensor i (θ) is determined by the installation eccentricity error and roundness error ε i (θ), radial error σ θ And the error introduced by the tilt error Composition; i is the number of data collection, the value is 1, 2, radial displacement ΔZ i The expression of (θ) is as follows:

[0044]

[0045]

[0046] 3-2. Subtracting the above two radial displacement expressions yields:

[0047]

[0048] Where ΔZ i (θ)(i=1,2) is a known quantity, ε i (θ) can be separated and obtained using existing methods. Therefore, the error introduced by the inclination angle can be expressed as:

[0049]

[0050] 3-3. If Figure 2 As shown; the inclination angle of the main axis Can be solved:

[0051]

[0052] Because of the inclination error is very small, so it can be approximated So the inclination error You can write:

[0053]

[0054] Therefore, we can use the above operation to measure the spindle inclination error, and can measure the spindle inclination error at different phases. This is of great significance to improving the accuracy of machine tools.

[0055] Step 4: Determine the spindle axial error. The method for measuring the axial direction of the two scratch marks is the same. By scanning and reading the scratch marks, an image of the scratch marks can be obtained. Figure 3 As shown, by reading the displacement δ of the image scratch mark along the axial direction Z (θ), the displacement δ Z (θ) is the axial error of the test spindle at phase θ. Take the displacement δ Z The maximum value of (θ) is taken as the maximum axial error.

[0056] Step 5: Solve the spindle radial error. The two sets of radial displacement data are processed in the same way. In the above experiment, one set of radial displacement data ΔZ(θ) detected by the probe device; the radial displacement ΔZ(θ) recorded by the displacement sensor is composed of the installation eccentricity error and roundness error ε(θ), radial error σ θ and radial offset introduced by inclination error The radial error is insensitive to the spindle inclination error, so the radial offset introduced by the inclination error is ignored. The radial displacement data ΔZ(θ) is distributed on a base circle with R0 as the radius through the phase, where R0 is the radius of the cylindrical sample. The installation error and roundness error ε(θ), radial error σ θ are all represented on this base circle, such as Figure 4 shown.

[0057] 5-1. Therefore, the radial displacement ΔZ(θ) obtained by the displacement sensor can be expressed as:

[0058] ΔZ(θ)=ε(θ)+σ θ

[0059] 5-2. In related research, the method of separating the installation eccentricity error and the roundness error ε(θ) has been very mature, such as the reversal method; then the spindle radial error σ θ It can be expressed as:

[0060] σ θ =ΔZ(θ)-ε(θ)

[0061] Take the radial error σ θ The maximum value is taken as the maximum radial error.

[0062] Therefore, this embodiment obtains the inclination error, axial error, and radial error during the spindle rotation process, can comprehensively evaluate the spindle rotation error, and helps to improve the spindle accuracy.

Claims

1. A spindle rotation error measurement method based on dual probes, characterized by: The following steps are involved: Step 1: Install the cylindrical sample coaxially on the main shaft to be tested; Two probe devices are radially arranged along two data collection locations on the cylindrical sample. The probe devices have two operating modes: tapping mode and contact mode. In tapping mode, the probes in the probe devices vibrate against the cylindrical sample, and displacement information is read through contact signals. In contact mode, the probes in the probe device are pressed against the cylindrical sample and apply pressure to scratch the cylindrical sample, and the displacement data is read. After the two probe devices simultaneously collect data in tapping mode, they simultaneously collect data in contact mode. During the tapping mode data collection, the spindle under test rotates multiple times to obtain multiple sets of displacement data. In contact mode, the spindle under test rotates one cycle. The data obtained by the probe device in tapping mode is radial displacement data , is the phase of the measured spindle; the tip of the probe device in contact mode will leave a scratch mark on the cylindrical sample; two sets of radial displacement data are obtained , respectively 、 , and two carved marks; Step 2: Calculate the spindle inclination error as follows: ； in, 、 They are the installation eccentricity and roundness errors of the cylindrical sample at the two data collection positions; is the axial distance between the two data collection positions; Step 3: Scan the sample's scratched surface and read the scratch marks to obtain a scratch image; the displacement of the track on the scratch image along the spindle's axial direction is used as the axial error of the spindle being measured.

2. The method for measuring spindle rotation error based on dual probes according to claim 1, characterized in that: In tapping mode, the vibration frequency of the probe is 0.5MHz to 1MHz.

3. The method for measuring spindle rotation error based on dual probes according to claim 1, characterized in that: In contact mode, the pressure of the probe on the cylindrical sample is 1μN to 10μN.

4. The method for measuring spindle rotation error based on dual probes according to claim 1, characterized in that: After executing step 3, execute step 4. The specific process of step 4 is: extract the radial error of the spindle being measured ;in, To collect radial displacement data When the cylindrical sample is installed, the eccentricity and roundness error are detected.

5. The method for measuring spindle rotation error based on dual probes according to claim 1, characterized in that: The material of the columnar sample is injection-molded polycarbonate.

6. The method for measuring spindle rotation error based on dual probes according to claim 4, characterized in that: The spindle under test rotates at a plurality of different speeds, and the inclination error, axial error, and radial error of the spindle under test are collected according to the methods described in steps 2 to 4.

7. The method for measuring spindle rotation error based on dual probes according to claim 1, characterized in that: The measuring device used includes a first probe device (1), a second probe device (2), a cylindrical sample (3) and a clamping device (4); the clamping device (4) is coaxially fixed to the end of a main shaft (5); the cylindrical sample (3) is coaxially fixed to the clamping device (4); the first probe device (1) and the second probe device (2) are mounted on a frame and abut against different positions on the main shaft (5) aligned along the axial direction.

8. The method for measuring spindle rotation error based on dual probes according to claim 1, characterized in that: Obtaining tilt error The expression process is as follows: Establish radial displacement The expression is as follows: = + + ( ) = + + ( ) in, is the radial error; ( ) is the error introduced by the spindle inclination; i=1,2; By subtracting and transforming the two radial displacement expressions, we can obtain the following relationship: ； Calculate the inclination error of the measured spindle The relationship is as follows: ； Due to the inclination error The value of is small, Approximately sin ; Get the inclination error The expression: 。

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