Thermal displacement correction device and thermal displacement correction method for machine tool

Abstract

The present invention provides a thermal displacement correction device and a thermal displacement correction method for a machine tool. In the thermal displacement correction of the machine tool, the accuracy of the thermal displacement correction is improved by effectively learning the relationship between the temperature and the displacement. The thermal displacement correction device includes a temperature sensor that measures the temperature of each part; a thermal displacement estimation unit that estimates a thermal displacement correction amount based on a pre-set thermal displacement estimation formula; a position control device that corrects a shaft command value based on the thermal displacement correction amount; a displacement measurement device that measures the displacement after correction of the shaft command value; a thermal displacement correction learning data recording unit that records temperature information and displacement information at the time when the displacement is measured; a thermal displacement correction learning unit that determines the thermal displacement estimation formula based on the recorded temperature information and displacement information; and a displacement measurement timing diagnosis unit that compares the temperature information at the time of past displacement measurement recorded at a prescribed diagnosis timing with the current temperature information, and determines whether or not to perform the measurement of the displacement using the displacement measurement device.

Description

Technical Field

[0001] This invention relates to an apparatus and method for improving the accuracy of thermal displacement correction in machine tool thermal displacement correction that estimates thermal displacement based on temperature information by effectively learning the relationship between temperature and displacement. Background Technology

[0002] When machining is performed using a machine tool, thermal deformation occurs in various parts of the machine tool due to mechanical heat generated by the movement of the spindle and feed axis, as well as temperature changes in the machine tool's operating environment and coolant. This thermal displacement causes a change in the relative position between the tool and the workpiece. Therefore, when the machine tool experiences thermal displacement during machining, the machining accuracy of the workpiece deteriorates.

[0003] As a method to suppress thermal displacement of machine tools, the following thermal displacement correction is effective and widely used: based on the temperature measured by temperature sensors installed in various parts of the machine tool structure, or the operating conditions of the spindle, feed axes, etc., the displacement is estimated based on a pre-programmed thermal displacement estimation formula, and the axis movement is changed accordingly. However, in thermal displacement correction, the correction cannot be performed smoothly when the machining content or operating environment changes, and there are situations where parameter adjustments are required. However, it is difficult for the operator to determine how to make the best adjustments.

[0004] As a solution to this problem, Patent Document 1 discloses a method that involves obtaining a set of measurement data including the temperature of various parts of the machine tool and the measured values ​​of thermal displacement measured by probes, etc., and using this combination of data as teacher data for machine learning to derive a thermal displacement prediction formula. Since the machine learning method derives the thermal displacement prediction formula based on actual measurement data, it has the advantage of easily achieving thermal displacement correction that matches the environment in which the machine tool is used. However, in machine learning, high accuracy is generally achieved with learned data, but overlearning can easily lead to larger errors with unlearned data. To prevent this, Patent Document 1 employs a calculation method such as regularized multiple regression analysis. This method prevents the calculation of large coefficients that could lead to larger errors for unknown inputs by adding a constraint to the usual regression analysis that minimizes error.

[0005] Patent Document 2 describes a method as follows: For the thermal displacement estimation formula, it is represented by the sum of a pre-set basic thermal displacement estimation formula and an adjustment thermal displacement estimation formula set based on thermal displacement adjustment data. For the coefficients of the adjustment thermal displacement estimation formula, a regularization parameter is used to determine the magnitudes that reduce both the thermal displacement estimation error and the coefficients of the adjustment thermal displacement estimation formula. Furthermore, the regularization parameter is determined based on the magnitude of the temperature change during measurement and the magnitude of the temperature change anticipated during actual use. When the temperature change during measurement is small, the coefficients of the derived adjustment thermal displacement estimation formula are reduced to prevent overlearning.

[0006] Existing technical documents

[0007] Patent Document 1: Japanese Patent No. 6564412

[0008] Patent Document 2: Japanese Patent Application Publication No. 2020-99982 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, the regularization methods used in Patent Documents 1 and 2 function by reducing the coefficients of the derived predictive formula for thermal displacement. Therefore, in unlearned temperature environments, this prevents the thermal displacement correction error from becoming extremely large due to overlearning. On the other hand, for actual thermal displacement, the thermal displacement correction amount may become smaller. Therefore, a sufficient correction effect cannot be obtained, and a relatively large residual thermal displacement correction error may remain. In the learning process for thermal displacement correction, it is desirable to minimize unlearned temperature environments for the applicable machine tool.

[0011] Therefore, the present invention addresses the above-mentioned problems and aims to provide a thermal displacement correction device and a thermal displacement correction method for machine tools. In the thermal displacement correction of machine tools that estimate thermal displacement based on temperature information, the accuracy of thermal displacement correction can be improved by effectively learning the relationship between temperature and displacement.

[0012] Methods for solving problems

[0013] To achieve the above objectives, the first invention of the present invention provides a thermal displacement correction device for a machine tool, comprising:

[0014] Temperature measurement unit, which measures the temperature of various parts of the machine tool;

[0015] A thermal displacement estimation unit estimates the thermal displacement of the machine tool based on the temperature and a pre-set thermal displacement estimation formula.

[0016] The thermal displacement correction unit corrects the shaft command value based on the estimated thermal displacement.

[0017] A displacement measurement unit measures the displacement of the machine tool after the correction of the axis command value;

[0018] A data recording unit records temperature information and displacement when the displacement is measured using the displacement measuring unit; and

[0019] The thermal displacement correction learning unit determines the thermal displacement estimation formula based on the temperature information and displacement recorded in the data recording unit.

[0020] Its features are,

[0021] The thermal displacement correction device of the machine tool includes a displacement measurement timing diagnosis unit. At a specified diagnosis time, the displacement measurement timing diagnosis unit compares the temperature information recorded in the data recording unit during past displacement measurements with the current temperature information obtained from the temperature measurement unit, and decides whether to use the displacement measurement unit to measure the displacement.

[0022] Another aspect of the first invention is characterized in that, in the above structure, the displacement measurement timing diagnosis unit compares the temperature information at the time of the previous displacement measurement with the current temperature information to determine whether to use the displacement measurement unit to measure the displacement.

[0023] Another aspect of the first invention is characterized in that, in the above structure, the displacement measurement timing diagnosis unit compares the temperature information from two or more past displacement measurements with the current temperature information to determine whether to use the displacement measurement unit to measure the displacement.

[0024] Another aspect of the first invention is characterized in that, in the above structure, the temperature information includes the rate of temperature change during displacement measured using the displacement measuring unit.

[0025] Another aspect of the first invention is characterized in that, in the above structure, the temperature information includes the temperature difference measured at multiple locations when the displacement is measured using the displacement measuring unit.

[0026] Another aspect of the first invention is characterized in that, in the above structure, a diagnostic timing setting unit is further provided, which sets the instruction time of a specific action or a specified time interval as the specified diagnostic timing.

[0027] Another aspect of the first invention is characterized in that, in the above structure, the diagnostic timing setting unit sets the time when at least one of the following instructions is executed: tool change, program end, or movement to the upper end of the Z position, as the prescribed diagnostic timing.

[0028] To achieve the above objectives, the second invention of this invention provides a method for thermal displacement correction of a machine tool, which includes the following steps:

[0029] Temperature measurement steps: Measure the temperature of various parts of the machine tool;

[0030] The thermal displacement estimation step estimates the thermal displacement of the machine tool based on the temperature and a pre-set thermal displacement estimation formula.

[0031] The thermal displacement correction step corrects the shaft command value based on the estimated thermal displacement.

[0032] The displacement measurement step involves measuring the displacement of the machine tool after the correction of the axis command value;

[0033] The data recording step records the temperature information and the displacement when the displacement was measured in the displacement measurement step; and

[0034] The thermal displacement correction learning step determines the thermal displacement estimation formula based on the temperature information and displacement recorded in the data recording step.

[0035] Its features are,

[0036] Before the displacement measurement step, a displacement measurement timing diagnosis step is performed. In this displacement measurement timing diagnosis step, at a predetermined diagnosis timing, the temperature information recorded in the data recording step during past displacement measurements is compared with the current temperature information obtained in the temperature measurement step to determine whether to perform displacement measurement in the displacement measurement step.

[0037] Invention Effects

[0038] According to the present invention, temperature information and displacement are recorded when displacement is measured. At a predetermined diagnostic time, the recorded temperature information from past displacement measurements is compared with the current temperature information to determine whether to perform displacement measurement. Thus, displacement can be measured even when the current temperature is not yet learned. Therefore, the relationship between temperature and displacement can be effectively learned, improving the accuracy of thermal displacement correction.

[0039] According to another aspect of the present invention, by comparing the temperature information at the time of the previous displacement measurement with the current temperature information, it is determined whether to perform a displacement measurement, thereby enabling a simple process to determine whether to perform a measurement.

[0040] According to another aspect of the present invention, by comparing the temperature information from two or more past displacement measurements with the current temperature information, displacement can be measured only when no learning has been performed, thereby minimizing the time loss caused by displacement measurement.

[0041] According to another aspect of the present invention, by using the rate of temperature change as temperature information, it is possible to more reliably determine whether the current temperature condition has not been learned.

[0042] According to another aspect of the present invention, by using the temperature difference measured at multiple locations as temperature information, it is possible to more reliably determine whether the current temperature condition has not been learned.

[0043] According to another aspect of the invention, by determining the displacement by comparing the temperature at the time of a specific action instruction or at a certain time interval, the displacement can be measured at a time when it does not interfere with the machine tool's original machining operation as much as possible.

[0044] According to another aspect of the invention, by comparing the temperature when at least one of the commands for tool change, program end, or movement to the upper end of the Z position is executed, displacement measurement can be performed at a time that does not interfere with the machine tool's original machining operation as much as possible. Attached Figure Description

[0045] Figure 1 This is a structural diagram of the thermal displacement correction device for machine tools using the present invention.

[0046] Figure 2 This is a flowchart of the thermal displacement correction method.

[0047] Figure 3 This is a flowchart of the process for diagnosing the timing of displacement measurement.

[0048] Figure 4 This is an example of a screen that sets the timing for diagnostic conditions.

[0049] Label Explanation

[0050] 1: Thermal displacement correction device; 2: Temperature sensor; 3: Thermal displacement estimation unit; 4: Thermal displacement estimation formula; 5: Thermal displacement correction amount; 6: Position control device; 7: Thermal displacement correction result simulation unit; 8: Display device; 9: Displacement measurement device; 10: Displacement data; 11: Thermal displacement correction learning data recording unit; 12: Displacement information; 13: Temperature information; 14: Thermal displacement correction learning unit; 15: Input device; 16: Timing diagnosis conditions; 17: Displacement measurement timing diagnosis unit; 18: Displacement measurement command. Detailed Implementation

[0051] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0052] Figure 1 This is a structural diagram of the thermal displacement correction device 1 for a machine tool using the present invention.

[0053] In the thermal displacement correction device 1, based on information from temperature sensors 2 installed at multiple locations on the machine tool, the thermal displacement estimation unit 3 estimates the thermal displacement using thermal displacement estimation formula 4. Based on the estimated thermal displacement, a thermal displacement correction amount 5 is output to the position control device 6, which then performs axis movement corresponding to the thermal displacement correction amount 5, thereby executing the correction. Typically, the thermal displacement estimation formula is set per axis; for a 3-axis machining center, separate thermal displacement estimation formulas are set for the X, Y, and Z axes. This can be considered the minimum structure required for successful thermal displacement correction.

[0054] In actual structures, to visualize the thermal displacement correction results, the thermal displacement is sometimes simulated in the thermal displacement correction result simulation unit 7 to show how the thermal displacement is reduced through thermal displacement correction, and the result is output to the display device 8. Furthermore, a displacement measuring device 9 is installed to acquire displacement data 10, which is stored as displacement information 12 in the thermal displacement correction learning data recording unit 11. Regarding the displacement measuring device 9, for example, a position measuring sensor such as a contact probe can be installed on the spindle of the machine tool to measure a specific point on the worktable. Alternatively, a displacement sensor can be installed on the side of the worktable, and the spindle can be brought close to the displacement sensor for measurement. Based on the displacement information 12, the temperature measured by the temperature sensor 2 is stored as temperature information 13 in the thermal displacement correction learning data recording unit 11. Based on the data stored in the thermal displacement correction learning data recording unit 11, a new thermal displacement estimation formula 4 is learned and determined in the thermal displacement correction learning unit 14.

[0055] As described above, a technique exists that optimizes the thermal displacement estimation formula through learning, thereby achieving more effective thermal displacement correction. However, in this prior art, the timing of measuring displacement data 10 using the displacement measuring device 9 is not specifically considered. As a general practice, a method is envisioned that measurements are taken at regular time intervals, and displacement information is accumulated. Machine tool manufacturers conduct experiments by subjecting the machine tool's operating conditions and the ambient temperature of the environment where the machine tool is placed to various changes. During these experiments, displacement is measured at regular time intervals, and learning data for thermal displacement correction is collected when the machine tool undergoes various temperature changes. If machine tool manufacturers collect this learning data for thermal displacement correction, they can obtain sufficiently high-quality learning data using this prior art.

[0056] However, when users want to collect learning data for thermal displacement correction during machine tool operation, they may not be able to collect effective data. For example, if the user executes an instruction to measure displacement at the same time every day, it is assumed that only data under the same temperature environment is collected. When learning the thermal displacement estimation formula based on such biased data, overlearning problems and other issues arise, making effective thermal displacement correction difficult.

[0057] Therefore, the present invention is characterized by the following structure being added in order to learn an effective and highly stable thermal displacement estimation formula.

[0058] The timing diagnosis condition 16 can be set in the input device 15. At a time that matches the setting of the timing diagnosis condition 16, the displacement measurement timing diagnosis unit 17 compares the current temperature obtained from the temperature sensor 2 with the past temperature recorded as temperature information 13 to diagnose whether displacement measurement should be performed. If the diagnosis indicates that measurement is required, a displacement measurement command 18 is output. As a result, the displacement measurement device 9 can acquire displacement data 10 at a more appropriate time.

[0059] In this invention, according to Figure 2 The flowchart is used to execute the thermal displacement correction method based on thermal displacement correction device 1.

[0060] First, in S1, the temperature of each part of the machine tool is measured by temperature sensor 2 (temperature measurement step).

[0061] Next, in S2, the thermal displacement estimation unit 3 estimates the thermal displacement based on the information obtained from the temperature sensor 2 and the thermal displacement estimation formula 4 (thermal displacement estimation step).

[0062] Next, in S3, the position control device 6 corrects the command value of each axis based on the thermal displacement correction amount 5 output from the thermal displacement estimation unit 3 (thermal displacement correction step).

[0063] Then, in S4, the displacement measurement timing diagnosis unit 17 determines whether the timing diagnosis conditions are met (whether it is the right time to perform displacement measurement) (displacement measurement timing diagnosis step).

[0064] If the timing diagnosis conditions are met in S4, then in S5 it is determined whether displacement measurement is required. If displacement measurement is not required, return to S4.

[0065] If it is determined in S5 that displacement measurement is required, in S6, displacement measurement is performed using displacement measuring device 9 to obtain displacement data 10, which is recorded as displacement information 12 in thermal displacement correction learning data recording unit 11 (displacement measurement step). Furthermore, temperature data obtained from temperature sensor 2 is recorded as temperature information 13 in thermal displacement correction learning data recording unit 11 (data recording step).

[0066] Then, in S7, the thermal displacement correction learning unit 14 learns and determines a new thermal displacement estimation formula 4 based on the displacement information 12 and temperature information 13 stored in the thermal displacement correction learning data recording unit 11, and updates the thermal displacement estimation formula 4 in the thermal displacement estimation unit 3 (thermal displacement correction learning step).

[0067] Next, use Figure 3 The flowchart for Figure 2 The process from displacement measurement timing diagnosis to the recording of displacement and temperature information (processing S4 to S6) is described in detail.

[0068] First, in S101 ( Figure 2 The timing of diagnostic conditions in S4) can be determined, for example, by being able to Figure 4 In that kind of screen, settings are made via input device 15. Figure 4 In the example, during operation, specific action instructions can be selected as conditions, such as "when changing tools," "when the main program ends," or "when at the top of the Z position." On the other hand, during standby, settings can be configured at certain time intervals. Figure 4 In this example, the setting is configured to occur every 15 minutes. When this timing condition is met, a diagnostic process to determine whether to perform displacement measurement begins. This allows displacement measurement to be performed at a time that minimizes disruption to the machine tool's normal machining operations.

[0069] Next, in S102, the current temperature data θ is obtained. n =(θ 1，n θ 2，n ,···,θ k，n The following will represent the k temperature data as θ = (θ1, θ2, ..., θ...). k The temperature data obtained n times from the start of the process will be represented as θ. n =(θ 1，n θ 2，n ,···,θ k，n ).

[0070] Next, in S103, the current temperature index Θ is calculated as temperature information. n =(Θ 1，n Θ 2，n ,···Θ l，n Temperature indices are obtained by processing acquired temperature data. Relative to the original temperature data θ (lowercase Theta), the temperature index is represented by Θ (uppercase Theta). Calculations include, for example, averaging multiple temperatures or calculating the difference between two temperatures. Furthermore, the rate of change can be calculated using differentiation, or delay processing can be performed using filters. Multiple temperature indices can also be calculated. For example, with l temperature indices, it is represented as Θn = (Θ... 1，n Θ 2，n ,···Θ l，n )

[0071] Next, in S104, from the database ( Figure 1Thermal displacement correction learning data recording unit 11) calls up past temperature index Θ n-m Then in S105, Θ n and Θ n-m The components are compared, and the existence of a threshold A is determined as shown in Formula 1 below. l The above ingredients. Θ n-m This indicates the temperature index at a time point m prior to the current nth processing iteration. It can compare only the time point m=1 (the previous processing iteration), or it can compare all past temperature indices for m=1, 2, ..., n-1. Alternatively, it can compare all values ​​for a single temperature index.

[0072] [Number 1]

[0073] |Θ 1.n -Θ 1.n-1 |≥A1or|Θ 1.n -Θ 1.n-2 |≥A1 or...or|Θ 1.n -Θ 1.n-m |≥A1

[0074] or|Θ 2.n -Θ 2.n-1 |≥A2or|e 2.n -Θ 2.n-2 |≥A2or...or|Θ 1.n -Θ 2.n-m |≥A2

[0075] …

[0076] or |Θ l.n -Θ l.n-1 |≥A l or|Θ l.n -e l.n-2 |≥A l or...or|Θ l.n -Θ l.n-m |≥A l (Formula 1)

[0077] A1: Temperature index relative to the threshold of component 1

[0078] Satisfying the condition in Formula 1 means that the current temperature obtained is different from the recorded past temperature, i.e., it is an unlearned temperature for the machine tool's thermal displacement correction device 1. In Formula 1, even if only one difference is greater than the threshold A1, the process proceeds to S107, indicating that displacement measurement will be performed. If there are no differences greater than the threshold A1, the process proceeds to S106, indicating that displacement measurement will not be performed. S102 to S107 are equivalent to... Figure 2 S5.

[0079] The threshold A1 used for judgment in Formula 1 is as follows: Figure 4 As shown, settings can also be configured through the screen.

[0080] Formula 1 is an example of a method for comparing current temperature information with past temperature information; other formulas can also be used for comparison. For example, instead of judging by taking the differences of each component of the temperature index separately, the total of the differences can be used for judgment.

[0081] If it is determined in S107 that a displacement measurement is required, the process proceeds to S108, where the displacement is measured and recorded in the database. Furthermore, in S109, the current temperature data θ is... n =(θ 1，n θ 2，n ,···,θ k，n The current temperature index Θ is recorded in the database, specifically in S110. n =(Θ 1，n Θ 2，n ,···Θ 1，n S108~S110 are equivalent to Figure 2 S6.

[0082] The thermal displacement correction device 1 and thermal displacement correction method described above include: a temperature sensor 2 (temperature measurement unit) that measures the temperature of various parts of the machine tool; a thermal displacement estimation unit 3 (thermal displacement estimation unit) that estimates the thermal displacement correction amount 5 (thermal displacement) of the machine tool based on the temperature and a pre-set thermal displacement estimation formula 4; a position control device 6 (thermal displacement correction unit) that corrects the axis command value based on the estimated thermal displacement correction amount 5; a displacement measuring device 9 (displacement measuring unit) that measures the displacement of the machine tool after the axis command value has been corrected; a thermal displacement correction learning data recording unit 11 (data recording unit) that records temperature information 13 and displacement information 12 (displacement) when the displacement is measured using the displacement measuring device 9; and a thermal displacement correction learning unit 14 (thermal displacement correction learning unit) that determines the thermal displacement estimation formula 4 based on the temperature information 13 and displacement information 12 recorded in the thermal displacement correction learning data recording unit 11 and performs processing steps S1 to S7.

[0083] Furthermore, it is equipped with a displacement measurement timing diagnosis unit 17 (displacement measurement timing diagnosis unit), which determines the prescribed diagnostic timing in S4 by comparing the temperature information 13 of past displacement measurements recorded in the thermal displacement correction learning data recording unit 11 with the current temperature information 13 obtained from the temperature sensor 2, and decides whether to use the displacement measurement device 9 to measure the displacement.

[0084] Thus, according to the present invention, temperature information 13 and displacement information 12 at the time of displacement measurement can be recorded. At a predetermined diagnostic time, the recorded temperature information 13 from past displacement measurements is compared with the current temperature information 13 to determine whether to perform displacement measurement. Therefore, displacement can be measured even when the current temperature is not yet learned. As a result, the relationship between temperature and displacement can be effectively learned, improving the accuracy of thermal displacement correction.

[0085] In particular, when deciding whether to perform a displacement measurement, if the temperature information from the previous displacement measurement is compared with the current temperature information (S104), it is possible to determine whether to perform the measurement through simple processing.

[0086] Furthermore, if the temperature information from two or more previous displacement measurements is compared with the current temperature information (S104), displacement can be measured only without prior learning, thus minimizing the time loss caused by displacement measurement.

[0087] Furthermore, if the rate of temperature change is used as temperature information (S103), it is possible to more reliably determine whether the current temperature condition has not been learned.

[0088] Furthermore, if the temperature difference measured at multiple locations is used as temperature information (S103), it is possible to more reliably determine whether the current temperature condition has not been learned.

[0089] On the other hand, an input device 15 (diagnostic timing setting unit) is provided to set a predetermined diagnostic timing when a specific action instruction or a certain time interval is executed. This allows for displacement measurement at a timing that minimizes interference with the machine tool's normal machining operations. Specifically, a determination is made by comparing temperature at least once an instruction for tool change, program termination, or movement towards the upper Z position is executed. Figure 4 This allows for displacement measurement at a time when it does not interfere with the machine tool's original machining operations as much as possible.

Claims

1. A thermal displacement correction device for a machine tool, comprising: Temperature measurement unit, which measures the temperature of various parts of the machine tool; A thermal displacement estimation unit estimates the thermal displacement of the machine tool based on the temperature and a pre-set thermal displacement estimation formula. The thermal displacement correction unit corrects the shaft command value based on the estimated thermal displacement. A displacement measuring unit measures the displacement of the machine tool after the correction of the axis command value; A data recording unit records the temperature information and the displacement when the displacement is measured using the displacement measuring unit. as well as The thermal displacement correction learning unit determines the thermal displacement estimation formula based on the temperature information and displacement recorded in the data recording unit. Its features are, The machine tool's thermal displacement correction device includes a displacement measurement timing diagnosis unit. At a predetermined diagnosis timing, this unit compares the temperature information from past displacement measurements recorded in the data recording unit with the current temperature information obtained from the temperature measurement unit, and determines whether to use the displacement measurement unit to measure the displacement. The displacement measurement timing diagnosis unit compares the temperature information from two or more past displacement measurements with the current temperature information to determine whether to use the displacement measurement unit to measure the displacement.

2. A thermal displacement correction device for a machine tool, comprising: Temperature measurement unit, which measures the temperature of various parts of the machine tool; A thermal displacement estimation unit estimates the thermal displacement of the machine tool based on the temperature and a pre-set thermal displacement estimation formula. The thermal displacement correction unit corrects the shaft command value based on the estimated thermal displacement. A displacement measuring unit measures the displacement of the machine tool after the correction of the axis command value; A data recording unit records the temperature information and the displacement when the displacement is measured using the displacement measuring unit. as well as The thermal displacement correction learning unit determines the thermal displacement estimation formula based on the temperature information and displacement recorded in the data recording unit. Its features are, The thermal displacement correction device for the machine tool includes: A diagnostic timing setting unit, wherein the diagnostic timing setting unit sets the instruction time of a specific action or a specified time interval as a specified diagnostic timing; as well as The displacement measurement timing diagnosis unit compares the temperature information from past displacement measurements recorded in the data recording unit with the current temperature information obtained from the temperature measurement unit at the predetermined diagnosis timing set by the diagnosis timing setting unit, and determines whether to use the displacement measurement unit to measure the displacement. The diagnostic timing setting unit sets the specified diagnostic timing when at least one of the following commands is executed: tool change, program end, or move to the upper end of the Z position.

3. The thermal displacement correction device for machine tools according to claim 1 or 2, characterized in that, The temperature information includes the rate of temperature change during displacement, measured using the displacement measuring unit.

4. The thermal displacement correction device for a machine tool according to claim 1 or 2, characterized in that, The temperature information includes the temperature difference measured at multiple locations when the displacement was measured using the displacement measuring unit.

5. A method for thermal displacement correction of a machine tool, comprising the following steps: Temperature measurement steps: Measure the temperature of various parts of the machine tool; The thermal displacement estimation step estimates the thermal displacement of the machine tool based on the temperature and a pre-set thermal displacement estimation formula. The thermal displacement correction step corrects the shaft command value based on the estimated thermal displacement. The displacement measurement step involves measuring the displacement of the machine tool after the correction of the axis command value; The data recording step records the temperature information and the displacement when the displacement was measured in the displacement measurement step. as well as The thermal displacement correction learning step determines the thermal displacement estimation formula based on the temperature information and displacement recorded in the data recording step. Its features are, Prior to the displacement measurement step, a displacement measurement timing diagnosis step is performed. In this step, at a predetermined diagnostic timing, the temperature information recorded in the data recording step for past displacement measurements is compared with the current temperature information obtained in the temperature measurement step to determine whether to perform displacement measurement in the next step. In the displacement measurement timing diagnosis step, the temperature information from two or more past displacement measurements is compared with the current temperature information to determine whether to perform displacement measurement in the displacement measurement step.

6. A method for thermal displacement correction of a machine tool, comprising the following steps: Temperature measurement steps: Measure the temperature of various parts of the machine tool; The thermal displacement estimation step estimates the thermal displacement of the machine tool based on the temperature and a pre-set thermal displacement estimation formula. The thermal displacement correction step corrects the shaft command value based on the estimated thermal displacement. The displacement measurement step involves measuring the displacement of the machine tool after the correction of the axis command value; The data recording step records the temperature information and the displacement when the displacement was measured in the displacement measurement step. as well as The thermal displacement correction learning step determines the thermal displacement estimation formula based on the temperature information and displacement recorded in the data recording step. Its features are, Prior to the displacement measurement step, the following steps are performed: The diagnostic timing setting step sets the command time of a specific action or a specified time interval as the specified diagnostic timing. as well as The displacement measurement timing diagnosis step involves comparing the temperature information from past displacement measurements recorded in the data recording step with the current temperature information obtained in the temperature measurement step at the predetermined diagnostic timing set in the diagnostic timing setting step, to determine whether to perform displacement measurement in the displacement measurement step. In the diagnostic timing setting step, at least one of the following commands—tool change, program end, and move to the upper end of the Z position—is set as the specified diagnostic timing.

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