In-machine measurement system temperature measuring device and measurement thermal error compensation method based on the device

Abstract

This invention proposes a temperature measurement device for an in-machine measurement system and a method for compensating for measurement thermal errors based on this device. Temperature sensors are used to acquire the temperatures of the spindle, feed axis, and ambient temperature. A standard device is used to calibrate the errors caused by temperature changes in the spindle and feed axis. A thermal error model and a compensation model for the in-machine measurement system are established. During the actual measurement of the part, the compensation amount is calculated based on the established compensation model and added to the in-machine measurement results to offset the errors introduced by temperature changes in the CNC machine tool spindle and feed axis. This method aims to reduce the thermal errors introduced by the spindle and feed axis during measurement and improve the accuracy of in-machine measurement. It compensates for the thermal errors of the spindle and feed axis in the in-machine measurement results of the part, overcoming the low accuracy of existing in-machine measurement technologies. This invention is simple, reliable, and can be extended to the in-machine measurement of other multi-axis machine tools to improve the accuracy of in-machine measurement results, thus possessing certain engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement technology, and specifically relates to an in-machine measurement system temperature measuring device and a measurement thermal error compensation method based on the device. Background Technology

[0002] In-machine measurement is a detection method that uses a CNC machine tool as a carrier, and identifies the shape and position dimensions of the workpiece's machining features through a probe mounted on the spindle, and adjusts subsequent machining based on the measurement results. In-machine measurement has the advantages of measuring in the in-situ on the machine tool after machining and avoiding errors introduced by secondary clamping of the workpiece, and has broad application prospects in the field of precision machining.

[0003] In-machine measurement systems consist of CNC machine tool bodies, CNC systems, servo systems, and measurement systems. The accuracy of their measurement results is affected by many factors, which has led to the limited use of in-machine measurement technology. In order to improve the accuracy of in-machine measurement results, it is necessary to analyze and compensate for the errors of in-machine measurement systems.

[0004] The CNC machine tool body is a hardware component of the in-machine measurement system. During actual machining, it is inevitably affected by factors such as cutting heat, frictional heat of moving pairs, power source heat generation, and ambient temperature, resulting in temperature changes. Studies have shown that thermal errors account for 40% to 70% of the error sources. As key components of CNC machine tools, the spindle and feed axis have complex structures, generate a large amount of heat, and have uneven heat source distribution. The deformation of the machine tool structure caused by temperature changes will change the relative positions between CNC machine tool parts, causing the probe to deviate from the theoretical position during actual measurement and reducing the accuracy of the in-machine measurement results. The error caused by the above-mentioned temperature changes during in-machine measurement is called the thermal error of in-machine measurement.

[0005] In conclusion, it is particularly necessary to design a method to compensate for thermal errors in machine measurements. Summary of the Invention

[0006] The technical problem solved by this invention is: in order to compensate for thermal errors in in-machine measurements, this invention proposes an in-machine measurement system temperature measuring device and a measurement thermal error compensation method based on the device.

[0007] The technical solution of the present invention is: an in-machine measurement system temperature measuring device, including several resistance temperature sensors, a microcontroller and a Bluetooth transmission module, a resistance transmitter, a power supply circuit and a receiving client;

[0008] The aforementioned resistance temperature sensors are arranged at the temperature measurement points to collect signals; the signals are conditioned by the resistance temperature transmitter to obtain temperature values; the temperature values ​​are transmitted to the receiving client via a microcontroller and a Bluetooth transmission module to realize the monitoring of the temperature of the monitored object.

[0009] The in-machine measurement thermal error compensation method based on temperature measuring devices includes the following steps:

[0010] Step 1: Construct a thermal error model for the in-machine measurement system, including the following sub-steps:

[0011] Step 1.1: Collect temperature data using the temperature sensor in the temperature measuring device. This includes collecting the CNC machine tool spindle temperature and its corresponding ambient temperature, including the initial temperature and the temperature data set. The initial temperature is:

[0012]

[0013] In the formula, The initial temperature of all temperature measuring points on the main spindle. The temperature value at the initial state of the q1th temperature measuring point on the main axis;

[0014] The temperature data set is as follows:

[0015]

[0016] In the formula, The m1th temperature at all temperature measurement points on the main spindle. The temperature value at the q1th temperature measurement point on the main axis for the m1st measurement is given.

[0017] Collect the temperature of the CNC machine tool feed axes and their corresponding ambient temperatures, including the initial temperature and a set of temperature data. The initial temperature is:

[0018]

[0019] In the formula, The initial temperature of all temperature measuring points on the feed axis. This represents the initial temperature value at the q2th temperature measurement point of the feed axis.

[0020] The temperature data set is as follows:

[0021]

[0022] In the formula, This represents the m2th temperature measured at all temperature measurement points on the feed shaft. This is the temperature value at the q2th temperature measurement point on the feed axis during the m2nd measurement.

[0023] Step 1.2: Calibrate the spindle error and feed axis error of the CNC machine tool.

[0024] Spindle error includes initial error and error data set. The initial error is:

[0025]

[0026] In the formula, The initial error of all calibration points on the main spindle. This is the initial error value for the n1th calibration point;

[0027] The error dataset is as follows:

[0028]

[0029] In the formula, This is the m1th error of all calibration points on the main spindle. This is the m1-th error value of the n1-th calibration point;

[0030] Calibrate the feed axis error, including the initial error and the error data set. The initial error is...

[0031]

[0032] In the formula, The initial error for all calibration points of the feed axis. This is the initial error value for the n2th calibration point;

[0033] The feed axis error data set is as follows:

[0034]

[0035] In the formula, For the m2th error of all calibration points on the feed axis, This represents the m2th error value of the n2th calibration point.

[0036] Step 1.3: For the temperature data set T from Step 1.1 s T f Classify and analyze the correlation between the error data and each temperature measurement point in step 1.2. Based on the clustering results, select the key temperature measurement points for the main spindle and the feed axis respectively. The number of key temperature measurement points for the main spindle is 1, and the number of key temperature measurement points for the feed axis is k (k≥1).

[0037] Step 1.4: Establish a thermal error model based on the temperature data and error data of key temperature measurement points;

[0038] The spindle thermal error model is as follows:

[0039]

[0040] In the formula, For the m1th thermal error of all points to be calibrated, This represents the thermal error value of the n1th calibration point in the m1st iteration.

[0041] The feed axis thermal error model is as follows:

[0042]

[0043] In the formula, For the m2th thermal error of all points to be calibrated, Let be the thermal error value of the n2th calibration point at the m2th calibration. Wherein, the temperature rise at the m2th calibration in equation (11) is... The thermal error corresponding to the m2th time in equation (12);

[0044] Step 1.5: Establish the feed axis positioning error model, as follows:

[0045] Geometric error

[0046]

[0047] In the formula, For the initial positioning error of the feed axis p x The position of the point to be calibrated on the step gauge, a0 is a constant term, a1, a2, ..., a r r is the coefficient, and r is the degree of the polynomial.

[0048] Thermal error

[0049]

[0050] In the formula, Thermal error α is the first-order fitting slope of the feed axis positioning error, b0 is a constant term, and b1, b2, ..., b k Here, k is the coefficient, and k is the number of critical temperature measurement points on the feed axis. This represents the m2-th temperature rise value at the k-th critical temperature measurement point;

[0051] Step 2: Construct error compensation models, including spindle error compensation models and feed axis error compensation models. The spindle error compensation model includes the initial spindle error compensation amount. and spindle thermal error compensation amount The feed axis error compensation model includes the feed axis geometric error compensation amount. Thermal error compensation amount

[0052] Step 3: In-machine measurement results with compensation within the CNC system:

[0053] The final error compensation amount is:

[0054] The compensation for in-machine measurement results is as follows:

[0055] m Last=m Meas +Δ

[0056] In the formula, m Meas The coordinates of the measurement point obtained in the CNC system, m Last These are the final coordinates of the measured points after error compensation.

[0057] Furthermore, in step 1.1, collecting the spindle temperature of the CNC machine tool and its corresponding ambient temperature includes the following steps:

[0058] (1) A number of temperature sensors are used to perform contact measurement on the CNC machine tool. The temperature sensors are evenly arranged at a distance of w1 meters from the CNC machine tool, and the total number of temperature sensors arranged at the two locations is q1, where q1 > 0.

[0059] (2) In the initial state, collect temperature data from q1 temperature sensors;

[0060] (3) The spindle moves within the set speed range and collects temperature data from the temperature sensors m1 times at fixed intervals until thermal equilibrium is reached. The collection ends and a set of temperature data is obtained.

[0061] Furthermore, the temperature sensors are respectively arranged on both sides of the main axis of the CNC machine tool, at the end of the spindle, and on the spindle box wall.

[0062] Furthermore, in step 1.1, collecting the temperature of the CNC machine tool feed axis and its corresponding ambient temperature includes the following steps:

[0063] (1) The feed axis of the CNC machine tool is measured by contact using temperature sensors. Several temperature sensors are evenly arranged at a distance of w2 meters from the CNC machine tool, and the total number of temperature sensors arranged at the two locations is q2, where q2 > 0.

[0064] (2) In the initial state, temperature data from q2 temperature sensors are collected;

[0065] (3) The feed axis moves within the set speed range and collects temperature data from the temperature sensors m2 times at fixed intervals until thermal equilibrium is reached. The collection ends and a set of temperature data is obtained.

[0066] Furthermore, the temperature sensor is arranged at the nut of the feed axis of the CNC machine tool, the front and rear bearings of the feed axis lead screw, and the left and right guide rails.

[0067] Furthermore, in step 1.2, obtaining the spindle error data includes the following steps:

[0068] (1) In the initial state, measure the North Pole of the standard sphere and n1 points to be calibrated evenly distributed along the equator of the standard sphere, and n1≥5;

[0069] (2) The initial error data of the spindle is obtained by the difference between the measured value of each point and the theoretical position of that point on the standard sphere;

[0070] (3) The spindle rotates at the set speed, and the calibration point of the standard ball is measured every w3 time interval until thermal equilibrium is reached; a total of m1 measurements are taken to obtain spindle error data, where m1>5.

[0071] Furthermore, in step 1.2, obtaining the error data of the feed axis includes the following steps:

[0072] (1) In the initial state, measure the center position of the step gauge block, and measure a total of n2 points to be calibrated, where n2>10;

[0073] (2) The initial positioning error data of the feed axis is obtained by the difference between the measured value of each point and the theoretical position of that point on the step gauge;

[0074] (3) The feed axis rotates at the set speed, and the calibration point of the standard ball is measured every w4 time interval until thermal equilibrium is reached; a total of m2 measurements are taken to obtain spindle error data, where m2>5.

[0075] Furthermore, in step 2, the spindle error compensation model includes:

[0076] The initial spindle error is calculated as follows: An initial spindle error compensation table is established, which includes the position of the standard ball to be calibrated and its corresponding error. The measurement point position is obtained through the CNC system, and the measurement point position is substituted into the compensation table. Linear interpolation is then used to calculate the compensation amount for the initial spindle error.

[0077] The spindle thermal error is calculated as follows: A spindle thermal error compensation table is established, which includes the standard ball calibration point position, temperature rise value, and the corresponding error between the two. The measurement point position is obtained through the CNC system, and the temperature of the key measurement point is obtained by the temperature measuring device. The temperature rise value is obtained by calculating the difference between the temperature of the key measurement point and the ambient temperature. Measurement point location, temperature rise value Substituting the values ​​into the compensation table, the spindle thermal error compensation amount is calculated using bilinear interpolation.

[0078] Furthermore, in step 2, the feed axis error compensation model includes:

[0079] The feed axis geometric error is calculated as follows: The position p of the calibration point on the step gauge is obtained through the CNC system. x Substitute it into the geometric error The geometric error of the feed axis was calculated. That is, compensation amount

[0080] The feed axis thermal error is calculated as follows: Obtain the position p of the point to be calibrated on the step gauge. x The temperature at key measuring points is obtained by a temperature measuring device, and the temperature rise is calculated by the difference between the temperature at the key measuring points and the ambient temperature. Position p x Temperature rise Substitute into the thermal error formula The thermal error of the feed axis was calculated. That is, compensation amount Invention Effects

[0081] The technical advantages of this invention are as follows: This invention addresses the thermal errors present in in-machine measurement by proposing a temperature measurement device for an in-machine measurement system and a method for compensating for measurement thermal errors based on this device. This invention uses temperature sensors to acquire the spindle, feed axis, and ambient temperature. It calibrates the errors caused by temperature changes in the spindle and feed axis using a standard device, establishing a thermal error model and a compensation model for the in-machine measurement system. During the actual measurement of the part, the compensation amount is calculated based on the established compensation model and added to the in-machine measurement results to offset the errors introduced by temperature changes in the CNC machine tool spindle and feed axis. This method aims to reduce the introduction of thermal errors from the spindle and feed axis during measurement and improve the accuracy of in-machine measurement. Step 3 performs thermal error compensation for the spindle and feed axis in the in-machine measurement results of the part, overcoming the low accuracy of existing in-machine measurement technologies. The error compensation method of this invention is simple and reliable, and can be widely applied to the in-machine measurement of other multi-axis machine tools to improve the accuracy of in-machine measurement results, thus possessing certain engineering application value. Attached Figure Description

[0082] Figure 1 Flowchart of the implementation of the present invention

[0083] Figure 2 In-machine measurement system temperature measuring device

[0084] Figure 3 Hardware composition diagram of temperature measuring device

[0085] Figure 4 Temperature measuring device lower-level computer software architecture diagram

[0086] Figure 5 Temperature measuring device host computer software architecture diagram

[0087] Figure 6 Constructing a thermal error model for an in-machine measurement system

[0088] Figure 7 The point to be calibrated on the standard ball

[0089] Figure 8 The calibration point on the step gauge

[0090] Figure 9 Constructing an error compensation model for an on-machine measurement system

[0091] Figure 10 In-machine measurement results compensation within the CNC system Detailed Implementation

[0092] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0093] See Figures 1-10 Taking a three-axis CNC machine tool as an example, the technical solution of the present invention will be further explained and illustrated with reference to the accompanying drawings.

[0094] First, an in-machine measurement system with a temperature measurement device needs to be built. (See also...) Figure 2 The temperature measuring device integrates multiple resistance temperature sensors, which can be installed close to the spindle and feed axis of the CNC machine tool for signal acquisition. Through the data processing and wireless communication functions of the temperature measuring device, the signal is conditioned to obtain the temperature value and sent to the computer to achieve continuous temperature monitoring. The communication function between the computer and the CNC machine tool is realized through the machine tool communication gateway, and the temperature data received by the computer is written into the machine tool variables.

[0095] The temperature measuring device includes both hardware and software design. The hardware design consists of four parts: a PT100 resistance temperature sensor, a resistance temperature transmitter, a microcontroller and Bluetooth module, and a power supply circuit. The PT100 temperature sensor is placed at the temperature measurement point to collect the signal. The resistance temperature transmitter performs signal conditioning to obtain the temperature value. The microcontroller and Bluetooth module acquire the temperature value and transmit it to the computer. The power supply module provides the power voltage to the resistance temperature transmitter, microcontroller, and Bluetooth module. The functions and descriptions of each part are as follows: Figure 3 As shown. The software design is divided into lower-level software and upper-level software. The microcontroller lower-level software is developed using C language, utilizing official library functions and adopting modular programming. The lower-level software architecture of the temperature measuring device is as follows. Figure 4 As shown, the functions include handshake connection, 485 communication, data processing, wireless settings, wireless data transmission, and watchdog program design; the host computer software runs on the Windows platform and adopts the Winform development platform based on C#. The host computer software architecture of the temperature measuring device is as follows. Figure 5As shown, the functions include wireless initialization, wireless data reception, data visualization, data saving, report generation, and variable writing.

[0096] After the temperature measuring device is set up, based on this temperature measuring device, combined with Figure 6 The thermal error of the on-machine measurement system of a three-axis CNC machine tool is measured and compensated. The specific steps are as follows:

[0097] Step 1: Construct a thermal error model for the in-machine measurement system, including the following sub-steps:

[0098] Step 1.1: Collect the temperature near the CNC machine tool spindle and feed axis, as well as the ambient temperature, including the following two parts:

[0099] ① Collect CNC machine tool spindle temperature and ambient temperature

[0100] First, temperature sensors are placed on the left side, right side, end of the spindle, and spindle box wall of the CNC machine tool for contact measurement. Temperature sensors are also placed at a distance of 0.5 to 2m from the CNC machine tool to measure the ambient temperature. A total of q1 (q1>0) temperature sensors are placed, i.e., q1 temperature measurement points.

[0101] Then, in the initial state, the temperatures of q1 temperature measurement points are collected.

[0102]

[0103] In the formula, The initial temperature of all temperature measuring points on the main spindle. The temperature value at the initial state of the q1th temperature measuring point on the main axis.

[0104] Finally, the spindle undergoes thermodynamic motion at a speed of 2000–8000 r / min, and the temperature of q1 temperature measurement points is collected every 10–40 minutes, for a total of m1 (m1 > 5) temperature data acquisitions, until thermal equilibrium is reached, and the spindle temperature T is obtained. S :

[0105]

[0106] In the formula, The m1th temperature at all temperature measurement points on the main spindle. It is the temperature value of the q1th temperature measuring point on the main axis at the m1st time.

[0107] ② Collect the feed axis temperature of the CNC machine tool and the ambient temperature.

[0108] First, temperature sensors are placed at the nut of the feed axis of the CNC machine tool, the front and rear bearings of the feed axis lead screw, and the left and right guide rails for contact measurement. Temperature sensors are also placed at a distance of 0.5 to 2m from the CNC machine tool to measure the ambient temperature. A total of q2 (q2>0) temperature sensors are placed, i.e., q2 temperature measurement points.

[0109] Then, in the initial state, the temperatures of q2 temperature measurement points are collected.

[0110]

[0111] In the formula, The initial temperature of all temperature measuring points on the feed axis. This is the initial temperature value at the q2th temperature measurement point of the feed axis.

[0112] Finally, the feed axis undergoes thermodynamic motion at a feed rate of 1000–8000 mm / min, and the temperature is collected at q2 measurement points every 10–40 minutes, for a total of m2 (m2 > 5) temperature data acquisitions, until thermal equilibrium is reached, and the feed axis temperature T is obtained. F :

[0113]

[0114] In the formula, This represents the m2th temperature measured at all temperature measurement points on the feed shaft. This is the temperature value at the q2th temperature measurement point on the feed axis during the m2nd measurement.

[0115] Step 1.2: Calibrate the errors of the CNC machine tool spindle and feed axes, including the following:

[0116] ① Calibrate the error of CNC machine tool spindle

[0117] To calibrate the error of a CNC machine tool spindle, a standard ball and a probe are used. The standard ball is placed on the worktable, and the probe is used to collect points on the surface of the ball.

[0118] First, in the initial state, the probe is used to measure the North Pole of the standard sphere and points distributed at intervals of 15° to 90° along the equator of the standard sphere, for a total of n1 (n1≥5) calibration points are measured, such as... Figure 7 As shown.

[0119] Then, the initial error of the spindle is obtained by the difference between the measured value and the theoretical value at each calibration point.

[0120]

[0121] In the formula, The initial error of all calibration points on the main spindle. This is the initial error value for the n1th calibration point.

[0122] Finally, the spindle undergoes thermal motion at a speed of 2000–8000 r / min, and the calibration point on the standard sphere is measured every 10–40 minutes until thermal equilibrium is reached. A total of m1 (m1 > 5) error data acquisitions are performed to obtain the spindle error data E. S :

[0123]

[0124] In the formula, This is the m1th error of all calibration points on the main spindle. This is the m1-th error value of the n1-th calibration point.

[0125] ② Calibrate the error of the feed axes of CNC machine tools

[0126] The positioning error of the feed axis of a CNC machine tool is calibrated using a step gauge and a probe. The step gauge is placed on the worktable, parallel to the direction of the feed axis movement, and the probe is used to collect points on the gauge block.

[0127] First, in the initial state, the probe is used to measure the points on the step gauge block, measuring a total of n² (n² > 10) points to be calibrated, such as... Figure 8 As shown;

[0128] Then, the initial positioning error E0 of the feed axis is obtained by the difference between the measured value and the theoretical value at each calibration point. f :

[0129]

[0130] In the formula, The initial error for all calibration points of the feed axis. This is the initial error value for the n2th calibration point.

[0131] Finally, the feed axis undergoes warm-up motion at a feed rate of 1000–8000 mm / min, and the calibration point on the step gauge block is measured every 10–40 minutes until thermal equilibrium is reached. Error data is collected m² (m² > 5) times to obtain the positioning error E of the feed axis. F :

[0132]

[0133] In the formula, For the m2th error of all calibration points on the feed axis, This is the m2th error value of the n2th calibration point.

[0134] Step 1.3: Selecting key temperature measurement points

[0135] Cluster analysis was used to analyze the temperature data T S T F Classification, and analysis of T using correlation analysis. S 、and E S T F With E F Based on the correlation and clustering results, key temperature measurement points are selected. The number of key temperature measurement points on the main axis is 1, and the number of key temperature measurement points on the feed axis is k (k≥1).

[0136] Step 1.4: Establish a thermal error model based on the temperature data and error data of key temperature measurement points.

[0137] ① Establish a spindle thermal error model

[0138] Calculate the temperature difference between the key temperature measurement points on the spindle and the ambient temperature to obtain the temperature rise ΔT. S :

[0139]

[0140] In the formula, This refers to the m1th temperature rise at a key temperature measurement point on the main shaft. This is the temperature rise value at the m1th time of one key temperature measurement point on the main shaft.

[0141] The thermal error E of the spindle is obtained by calculating the difference between the error of the spindle each time and the initial error of the spindle. ST :

[0142]

[0143] In the formula, For the m1th thermal error of all points to be calibrated, This is the thermal error value of the n1th calibration point in the m1st iteration.

[0144] Among them, the temperature rise of the m1th time in equation (9) The thermal error of the m1th time in equation (10)

[0145] ②Establish a thermal error model for the feed shaft

[0146] First, calculate the temperature difference between the key temperature measurement points on the feed axis and the ambient temperature to obtain the temperature rise value ΔT. F :

[0147]

[0148] In the formula, For the m2th temperature rise at all critical temperature measurement points of the feed shaft, This represents the temperature rise value at the k-th critical temperature measurement point on the feed axis during the m2-th measurement.

[0149] Then, the difference between the positioning error of the feed axis each time and the initial positioning error is calculated to obtain the thermal error E of the feed axis. FT :

[0150]

[0151] In the formula, For the m2th thermal error of all points to be calibrated, Let be the thermal error value of the n2th calibration point at the m2th calibration. Wherein, the temperature rise at the m2th calibration in equation (11) is... The thermal error of the m2th time in equation (12)

[0152] Step 1.5: Establish the feed axis positioning error model: Divide the feed axis positioning error into geometric errors. and thermal error

[0153] Geometric error It only depends on the position coordinates of the point to be calibrated on the step gauge in the machine tool. Polynomial fitting modeling is used, and the expression is:

[0154]

[0155] In the formula, For the initial positioning error of the feed axis p x The position of the point to be calibrated on the step gauge, a0 is a constant term, a1, a2, ..., a r Let r be the coefficient and r be the degree of the polynomial.

[0156] thermal error of feed axis The temperature rise at the key temperature measurement point of the feed axis and the position coordinates of the calibration point on the step gauge in the machine tool are related. A model is established by modeling the relationship between the thermal error and the slope of the first-order fitting of the positioning error, and the position of the calibration point on the step gauge. The expression is:

[0157]

[0158] In the formula, Thermal error α is the first-order fitting slope of the feed axis positioning error, b0 is a constant term, and b1, b2, ..., b k Here, k is the coefficient, and k is the number of critical temperature measurement points on the feed axis. This represents the m2th temperature rise value at the kth critical temperature measurement point.

[0159] Step 2: Construct an error compensation model for the on-machine measurement system, combined with Figure 9This includes the following sub-steps:

[0160] Step 2.1: Spindle Error Compensation Model

[0161] Spindle initial error: Establish a spindle initial error compensation table, which includes the position of the standard ball to be calibrated and its corresponding error. Obtain the measurement point position through the CNC system, substitute the measurement point position into the compensation table, and use linear interpolation to calculate the compensation amount for the spindle initial error.

[0162] Spindle thermal error: A spindle thermal error compensation table is established, which includes the standard ball calibration point position, temperature rise value, and the corresponding error between the two. The measurement point position is obtained through the CNC system, and the temperature of the key measurement point is obtained by a temperature measuring device. The temperature rise value is calculated by the difference between the temperature of the key measurement point and the ambient temperature. Measurement point location, temperature rise value Substituting the values ​​into the compensation table, the spindle thermal error compensation amount is calculated using bilinear interpolation.

[0163] Step 2.2: Feed axis error compensation model

[0164] Feed axis geometric error: The position p of the point to be calibrated on the step gauge is obtained through the CNC system. x Substituting it into equation (13) yields the geometric error of the feed axis. That is, compensation amount

[0165] Feed axis thermal error: The position p of the calibration point on the step gauge is obtained through the CNC system. x The temperature at key measuring points is obtained by a temperature measuring device, and the temperature rise is calculated by the difference between the temperature at the key measuring points and the ambient temperature. Position p x Temperature rise Substituting into equation (14), the feed axis thermal error is calculated. That is, compensation amount

[0166] Step 3: Compensate for on-machine measurement results within the CNC system, and combine them with... Figure 10 The final error compensation amount Δ includes the initial error compensation amount of the spindle. Spindle thermal error compensation Feed axis geometric error compensation and feed axis thermal error compensation amount Four parts:

[0167]

[0168] The compensation for in-machine measurement results is as follows:

[0169] m Last =m Meas +Δ (16)

[0170] In the formula, m Meas The coordinates of the measurement point obtained in the CNC system, m Last These are the final coordinates of the measured points after error compensation.

Claims

1. A method for compensating for thermal errors in an on-machine measurement system temperature measuring device, wherein the on-machine measurement system temperature measuring device includes several resistance temperature sensors, a microcontroller and a Bluetooth transmission module, a resistance temperature transmitter, a power supply circuit, and a receiving client; the several resistance temperature sensors are arranged at the temperature measuring point for signal acquisition; the signal is conditioned by the resistance temperature transmitter to obtain a temperature value; the temperature value is transmitted to the receiving client through the microcontroller and the Bluetooth transmission module to realize the monitoring of the temperature of the monitored object; Its features are, The method includes the following steps: Step 1: Construct a thermal error model for the in-machine measurement system, including the following sub-steps: Step 1.1: Collect temperature data using the temperature sensor in the temperature measuring device, whereby... Collect the spindle temperature of the CNC machine tool and its corresponding ambient temperature, including the initial temperature and the temperature data set. The initial temperature is: In the formula, The initial temperature of all temperature measuring points on the main spindle. Main axis Temperature values ​​at each temperature measurement point under initial conditions; The temperature data set is as follows: In the formula, The first of all temperature measurement points on the main spindle Secondary temperature, Main axis The first temperature measurement point The temperature value of the next step; Collect the temperature of the CNC machine tool feed axes and their corresponding ambient temperatures, including the initial temperature and a set of temperature data. The initial temperature is: In the formula, The initial temperature of all temperature measuring points on the feed axis. For the feed axis Temperature values ​​at each temperature measurement point under initial conditions; The temperature data set is as follows: In the formula, For all temperature measurement points of the feed axis Secondary temperature, For the feed axis The first temperature measurement point The temperature value of the next step; Step 1.2: Calibrate the spindle error and feed axis error of the CNC machine tool. Spindle error includes initial error and error data set. The initial error is: In the formula, The initial error of all calibration points on the main spindle. For the first Initial of the points to be calibrated Initial error value; The error dataset is as follows: In the formula, The first of all calibration points on the main axis Error For the first The first point to be calibrated Error value; Calibrate the feed axis error, including the initial error and the error data set. The initial error is... In the formula, The initial error for all calibration points of the feed axis. For the first Initial error values ​​for each calibration point; The feed axis error data set is as follows: In the formula, For all calibration points of the feed axis Error For the first The first point to be calibrated Error value; Step 1.3: Process the temperature data set from Step 1.1 , The data was categorized, and the correlation between the error data and each temperature measurement point in step 1.2 was analyzed. Based on the clustering results, key temperature measurement points for the main spindle and feed axis were selected. The number of key temperature measurement points for the main spindle was 1, and the number of key temperature measurement points for the feed axis was [missing information]. ,and Step 1.4: Establish a thermal error model based on the temperature data and error data of key temperature measurement points; First, calculate the temperature difference between the key temperature measurement points on the feed axis and the ambient temperature to obtain the temperature rise value. : In the formula, For all critical temperature measurement points of the feed axis Secondary temperature rise, For the feed axis The first key temperature measurement point The temperature rise value of the next step; Then, the difference between the positioning error of the feed axis in each step and the initial positioning error is calculated to obtain the thermal error of the feed axis. : In the formula, For all points to be calibrated Secondary heat error For the first The first point to be calibrated The thermal error value of the second time; The feed axis thermal error model is as follows: In the formula, For all points to be calibrated Secondary heat error For the first The first point to be calibrated The thermal error value; temperature rise value The first in the formula The next temperature rise Thermal error of the corresponding feed axis In the formula, the first The thermal error of the second time; Step 1.5: Establish the feed axis positioning error model, as follows: Geometric error : In the formula, For the initial positioning error of the feed axis , The location of the point to be calibrated on the step gauge. For constant terms, , … For coefficients, The degree of the polynomial Thermal error : In the formula, Thermal error , The slope of the first-order fitted error of the feed axis positioning error. For constant terms, , … For coefficients, The number of critical temperature measurement points on the feed axis. For the first The first key temperature measurement point Secondary temperature rise; Step 2: Construct error compensation models, including spindle error compensation models and feed axis error compensation models. The spindle error compensation model includes the initial spindle error compensation amount. and spindle thermal error compensation amount The feed axis error compensation model includes the feed axis geometric error compensation amount. Thermal error compensation amount ; Step 3: In-machine measurement results with compensation within the CNC system: The final error compensation amount is: The compensation for in-machine measurement results is as follows: In the formula, The coordinates of the measurement points obtained in the CNC system. These are the final coordinates of the measured points after error compensation.

2. The on-machine measurement thermal error compensation method for the on-machine measurement system temperature measuring device as described in claim 1, characterized in that, In step 1.1, collecting the spindle temperature of the CNC machine tool and its corresponding ambient temperature includes the following steps: (1) Contact measurement is performed on the CNC machine tool using several temperature sensors. The temperature sensors are evenly arranged at a distance of w1 meters from the CNC machine tool, and the total number of temperature sensors arranged at both locations is [missing information]. , ; (2) In the initial state, data collection Temperature data from one temperature sensor; (3) The spindle moves within a set speed range and collects data at fixed intervals. Second-rate The temperature data from each temperature sensor is collected until thermal equilibrium is reached, at which point the data acquisition ends, resulting in a set of temperature data.

3. The on-machine measurement thermal error compensation method for the on-machine measurement system temperature measuring device as described in claim 2, characterized in that, The temperature sensors are respectively arranged on both sides of the main axis of the CNC machine tool, at the end of the spindle, and on the wall of the spindle box.

4. The on-machine measurement thermal error compensation method for the on-machine measurement system temperature measuring device as described in claim 1, characterized in that, In step 1.1, collecting the temperature of the CNC machine tool feed axis and its corresponding ambient temperature includes the following steps: (1) Contact temperature sensors are used to measure the feed axes of the CNC machine tool. Several temperature sensors are evenly arranged at a distance of w2 meters from the CNC machine tool, and the total number of temperature sensors arranged at both locations is [missing information]. , ; (2) In the initial state, data collection Temperature data from one temperature sensor; (3) The feed axis moves within a set speed range and data is collected at fixed intervals. Second-rate The temperature data from each temperature sensor is collected until thermal equilibrium is reached, at which point the data acquisition ends, resulting in a set of temperature data.

5. The on-machine measurement thermal error compensation method for the on-machine measurement system temperature measuring device as described in claim 4, characterized in that, The temperature sensor is located at the nut of the feed axis of the CNC machine tool, the front and rear bearings of the feed axis lead screw, and the left and right guide rails.

6. The on-machine measurement thermal error compensation method for the on-machine measurement system temperature measuring device as described in claim 1, characterized in that, In step 1.2, obtaining the spindle error data includes the following steps: (1) In the initial state, the north pole and the equator of the standard sphere are evenly distributed. One point to be calibrated, and ; (2) The initial error data of the principal axis is obtained by the difference between the measured value of each point and the theoretical position of that point on the standard sphere; (3) The spindle rotates at a set speed, and the calibration point of the standard ball is measured every w3 time intervals until thermal equilibrium is reached; a total of m1 measurements are taken to obtain spindle error data, of which .

7. The on-machine measurement thermal error compensation method for the on-machine measurement system temperature measuring device as described in claim 1, characterized in that, In step 1.2, obtaining the error data of the feed axis includes the following steps: (1) In the initial state, the center position of the step gauge block is measured, and a total of 100 points are measured. One point to be calibrated, and ; (2) The initial positioning error data of the feed axis is obtained by the difference between the measured value of each point and the theoretical position of that point on the step gauge; (3) The feed axis rotates at the set speed, and the calibration point of the standard ball is measured every w4 time interval until thermal equilibrium is reached; a total of m2 measurements are taken to obtain the spindle error data, of which .

8. The method for compensating for thermal errors in on-machine measurement of the temperature measuring device in the on-machine measurement system as described in claim 1, characterized in that, In step 2, the spindle error compensation model includes: The initial spindle error is calculated as follows: An initial spindle error compensation table is established, which includes the standard ball's calibration point position and its corresponding error; the measurement point position is obtained through the CNC system, and the measurement point position is substituted into the compensation table using linear interpolation to calculate the compensation amount for the initial spindle error. ; The spindle thermal error is calculated as follows: A spindle thermal error compensation table is established, including the standard ball calibration point location, temperature rise value, and the corresponding error between the two. The measurement point location is obtained through the CNC system, and the temperature of the key measurement point is obtained by a temperature measuring device. The temperature rise value is obtained by calculating the difference between the temperature of the key measurement point and the ambient temperature. The measurement point location and temperature rise value will be recorded. Substituting the values ​​into the compensation table, the spindle thermal error compensation amount is calculated using bilinear interpolation. .

9. The on-machine measurement thermal error compensation method for the on-machine measurement system temperature measuring device as described in claim 1, characterized in that, In step 2, the feed axis error compensation model includes: The feed axis geometric error is calculated as follows: The position of the calibration point on the step gauge is obtained through the CNC system. Substitute it into the geometric error The geometric error of the feed axis was calculated. That is, compensation amount ; The feed axis thermal error is calculated as follows: Obtain the position of the calibration point on the step gauge. The temperature at key measuring points is obtained by a temperature measuring device, and the temperature rise is calculated by the difference between the temperature at the key measuring points and the ambient temperature. , position Temperature rise Substitute into the thermal error formula The thermal error of the feed axis was calculated. That is, compensation amount .

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