Machine tool and method for compensating for thermal displacement of machine tool

Abstract

To perform more accurate thermal displacement compensation by taking into account the internal temperature of the aircraft's components. [Solution] A first temperature sensor MS is provided on the surface of the crossbeam 3, which is a Y-axis moving body, the base 4, which is an X-axis moving body, and the slider 6, which is a U-axis moving body, all of which are components of the machine. A second temperature sensor AS is provided on the frame 10F located between the cover 10 and the machine components. The control device calculates a first estimated temperature by correcting the temperature detected by the temperature sensors MS provided on each machine component with a predetermined first correction coefficient, and adds this to a second estimated temperature obtained by correcting the temperature detected by the temperature sensor AS with a predetermined second correction coefficient to obtain the combined temperature of each machine component. Based on the combined temperature, the control device calculates the amount of thermal displacement of the machine in a predetermined direction and performs thermal displacement correction in that predetermined direction.

Description

[Technical Field]

[0001] The present invention relates to a machine tool that performs thermal displacement compensation and a method for compensating for thermal displacement of a machine tool. [Background technology]

[0002] Generally, in machine tools, changes in the ambient temperature around the machine cause thermal displacement, resulting in an error between the controlled machining position and the actual machining position. Therefore, the controlled machining position is corrected to correspond to the amount of thermal displacement of the machine. The machine is formed by combining multiple machine components as a whole. Therefore, the total thermal displacement of the machine is simply the sum of the thermal displacements of each of the multiple machine components in a predetermined direction. The amount of thermal displacement of a machine component can be calculated from the internal temperature of the machine component, the expansion coefficient of the machine component, and the length of the machine component in the direction of displacement.

[0003] When an aircraft expands or contracts in response to changes in the ambient temperature, there is a time lag between the time the aircraft's temperature changes to track the ambient temperature and the time it takes for the aircraft's temperature to equalize with the ambient temperature, thus completing the expansion or contraction. The time required for the thermal displacement of each of the multiple aircraft components varies considerably depending on the material and volume of the components. In other words, each aircraft component has a different time constant for the change in thermal displacement in response to temperature changes. Therefore, if the thermal displacement of the entire aircraft is calculated based on the temperature of one representative aircraft, an unacceptable error may occur between the calculated thermal displacement and the actual thermal displacement.

[0004] For example, Patent Document 1 discloses a method for determining the amount of thermal displacement in the direction of the main axis by considering the time difference in thermal displacement time in each of several machine components, including a tool, and correcting for thermal displacement. Patent Document 2 also discloses a method for detecting temperature changes at at least two locations on a machine that undergoes temperature changes with different time constants, calculating a combined temperature, and calculating the amount of thermal displacement of the machine based on that combined temperature. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 6-22779 [Patent Document 2] Japanese Patent Publication No. 2004-42260 [Overview of the project] [Problems that the invention aims to solve]

[0006] To accurately calculate thermal displacement, it is necessary to know the internal temperature of the aircraft's components. However, physically placing a temperature sensor at the center of the aircraft's internal structure is difficult for many components. Even if it were possible to place a temperature sensor at an ideal location inside the aircraft's internal structure, the effort and cost involved, including aircraft maintenance, would not justify the practical benefits. Therefore, in most components, the temperature sensor is placed on the surface of the aircraft's internal structure, away from its internal center.

[0007] Because there is a time lag in temperature changes between the interior and surface of the aircraft components, the temperature detected by the temperature sensor on the surface of the aircraft component at a given point in time differs from the temperature at an ideal location inside the aircraft component. Furthermore, the temperature detected by the temperature sensor on the surface of the aircraft component is affected by the ambient temperature, and therefore does not accurately represent the surface temperature of the aircraft component. Consequently, depending on the required machining accuracy, there is still a risk of unacceptable errors between the calculated thermal displacement and the actual thermal displacement.

[0008] In view of the above problems, the main objective of the present invention is to provide an improved machine tool and a method for correcting thermal displacement in a machine tool that can perform thermal displacement correction considering the internal temperature of the machine tool components. Several advantages that can be obtained by the present invention will be described in detail as they arise in the description of the embodiments of the invention.

Means for Solving the Problem

[0009] In view of the above problems, the machine tool of the present invention includes, in one or more selected machine body components forming the machine body, a first temperature sensor provided on the surface of each machine body component, and at least one second temperature sensor provided non - contactingly with respect to each machine body component at a position facing the position of all the first temperature sensors to detect the temperature of the environment around the machine body component. A first arithmetic unit calculates a first estimated temperature obtained by correcting the detected temperature of the first temperature sensor for each one or more machine body components with a predetermined first correction coefficient and calculates a second estimated temperature obtained by correcting the detected temperature of the second temperature sensor with a predetermined second correction coefficient, and adds the second estimated temperature to the first estimated temperature to obtain a composite temperature of the machine body component. A second arithmetic unit calculates the thermal displacement amount in a predetermined direction of the machine body based on the composite temperature obtained by the first arithmetic unit, and includes a control device that performs thermal displacement correction in a predetermined direction of the machine body.

[0010] Preferably, the first temperature sensor is provided at a position as close to the center as possible along a predetermined direction in which thermal displacement correction is performed on the surface of the machine body component.

[0011] In particular, the first correction coefficient and the second correction coefficient are determined in advance based on the ratio between the detected temperature of the first temperature sensor and the detected temperature of the second temperature sensor when the correlation coefficient is the one determined to have the strongest correlation among a plurality of correlation coefficients obtained by obtaining the correlation coefficient between the displacement amount in a predetermined direction of the machine body component and the composite temperature actually measured a plurality of times during a predetermined period.

[0012] The correlation coefficient is obtained by the following formula. ρ = Cov / σH·σT Here, ρ is the correlation coefficient, Cov is the covariance between the displacement amount in a predetermined direction and the composite temperature, σH is the standard deviation of the displacement amount in a predetermined direction, and σT is the standard deviation of the composite temperature.

[0013] In particular, this includes cases where one or more machine components are made of cast iron. It also includes cases where the machine tool is a wire electrical discharge machining (EDM) machine. Furthermore, when the machine tool is a wire electrical discharge machining (EDM) machine, the predetermined direction is the Y-axis direction.

[0014] The thermal displacement correction method for a machine tool of the present invention includes the steps of: calculating a first estimated temperature by correcting the detected temperature of a first temperature sensor, which is provided on the surface of each of the one or more machine tool components constituting the machine tool body, by a predetermined first correction coefficient; calculating a second estimated temperature by correcting the detected temperature of at least one second temperature sensor, which is provided non-contact with each machine tool component at a position opposite to the positions of all the first temperature sensors and detects the temperature of the environment surrounding the machine tool component, by a predetermined second correction coefficient; obtaining a composite temperature of the machine tool components by adding the second estimated temperature to the first estimated temperature; calculating the amount of thermal displacement of the machine tool in a predetermined direction based on the composite temperature obtained by the first calculation device; and performing thermal displacement correction of the machine tool in a predetermined direction based on the calculated amount of thermal displacement in the predetermined direction.

[0015] The first and second correction coefficients are predetermined based on the ratio of the temperature detected by the first temperature sensor to the temperature detected by the second temperature sensor, which is determined from among multiple correlation coefficients that the correlation coefficient is judged to be the strongest correlation, obtained by calculating the correlation coefficient between the amount of displacement of the aircraft components in a predetermined direction and the combined temperature, measured multiple times during a predetermined period.

[0016] The correlation coefficient is calculated using the following formula. ρ = Cov / σH·σT However, ρ is the correlation coefficient, Cov is the covariance between the displacement in a given direction and the combined temperature, σH is the standard deviation of the displacement in a given direction, and σT is the standard deviation of the combined temperature.

[0017] In particular, the predetermined direction is the Y-axis direction. Furthermore, the predetermined directions for correction are the Y-axis direction and the V-axis direction. [Effects of the Invention]

[0018] A first temperature sensor can detect the surface temperature of the aircraft components. A second temperature sensor can detect the ambient temperature surrounding the aircraft components. The internal temperature of the aircraft components can be estimated by multiplying the change in surface temperature by a predetermined first correction coefficient. Furthermore, the temperature affecting the first temperature sensor can be estimated by multiplying the ambient temperature by a predetermined second correction coefficient. Therefore, by adding the second estimated temperature to the first estimated temperature, the internal temperature of the aircraft components can be obtained more accurately.

[0019] According to the machine tool of the present invention, the amount of thermal displacement of each machine component can be calculated based on the internal temperature of each machine component with greater precision. Therefore, even when it is difficult to install temperature sensors inside the machine components, the amount of thermal displacement of each machine component can be calculated based on the internal temperature of each machine component, and thermal displacement correction can be performed more accurately for the entire machine. As a result, machining can be performed more easily, effectively, and with higher precision. [Brief explanation of the drawing]

[0020] [Figure 1] This is a left side view of a wire electrical discharge machine according to an embodiment of the present invention. [Figure 2] Figure 1 is a perspective view of the wire electrical discharge machining machine. [Figure 3] This is a diagram illustrating an example of test results showing the relationship between the thermal displacement of aircraft components and the composite temperature using a correlation coefficient. [Figure 4] This graph shows an example of the results obtained by correcting thermal displacement using the thermal displacement correction method of the present invention. [Modes for carrying out the invention]

[0021] Figures 1 and 2 show an overview of a machine tool representing a typical embodiment of the present invention. The machine tool shown in Figures 1 and 2 is a wire electrical discharge machining (EDM) machine. Figures 1 and 2 show the state in which the chamber wall of the machining chamber of the wire EDM machine has been lowered to its lower limit. In the wire EDM machine shown in Figures 1 and 2, the direction in which the machining chamber is installed from the center of the machine body is the front side of the machine body, the right side when viewed from the front is the right side of the machine body, the left side when viewed from the front is the left side of the machine body, and the direction opposite to the front is the rear side. The wire electrode, which is the tool, and the conductive workpiece are not shown in the figures.

[0022] The wire electrical discharge machining machine of the embodiment shown in Figure 1 comprises a bed 1, a column 2, a cross beam 3, a base 4, a top beam 5, a slider 6, a head 7, and a table 8 as main machine components that greatly affect the thermal displacement of the entire machine. The wire electrical discharge machining machine of the embodiment also comprises a machining tank 9 and a cover 10 as main auxiliary machine components. The wire electrical discharge machining machine of the embodiment also comprises a work stand 11, an upper arm 12, and a lower arm 13 as main auxiliary machine components.

[0023] In the wire electrical discharge machining machine of this embodiment, more precisely, the bed 1 is molded as the base portion and the column 2 is molded integrally with the bed 1 as the upright portion of the bed 1 to form a single machine component, and the column 2 is a part of the bed 1 and is included in the bed 1. However, since there are machine tools with a structure similar to the wire electrical discharge machining machine of this embodiment in which the base portion and the upright portion of the bed 1 are molded separately, for convenience in describing this embodiment, the column 2 will be shown separately. However, when explaining how to calculate the amount of thermal displacement in the main machine component, the column 2 may be included in the bed 1 and referred to as the bed 1.

[0024] Bed 1 is the base. Bed 1 is placed on the floor. Column 2 is the upright portion of Bed 1, molded integrally with Bed 1. Crossbeam 3, base 4, top beam 5, and slider 6 are all moving parts that reciprocate horizontally. Crossbeam 3, base 4, and top beam 5 are stacked in order on the upper surface of Bed 1, including column 2. Slider 6 is located in front of Top Beam 5. Head 7 is a moving part that reciprocates vertically. Head 7 is located on the front side of Slider 6. Table 8 is a workbench. Table 8 is fixed to the front upper surface of Bed 1.

[0025] In the wire electrical discharge machining machine of this embodiment, the main components of the machine body, including the bed 1 (including column 2), cross beam 3, base 4, top beam 5, slider 6, bed 7, and table 8, are all made of cast iron. Even in the case of a machine tool in which some or all of the main components of the machine body are made of a material with low thermal displacement, such as carbon fiber reinforced plastic (CFRP) or ceramics, it is still beneficial to obtain the amount of thermal displacement of the machine body using the thermal displacement correction method of the present invention.

[0026] The crossbeam 3 is a Y-axis moving body that reciprocates in the Y-axis direction, which is a single horizontal linear axis direction. The base 4 is an X-axis moving body that reciprocates in the X-axis direction, which is a single horizontal linear axis direction perpendicular to the Y-axis direction. The top beam 5 is a tapered V-axis moving body that reciprocates in the V-axis direction, which is a single horizontal linear axis direction parallel to the Y-axis direction. The slider 6 is a tapered U-axis moving body that reciprocates in the U-axis direction, which is a single horizontal linear axis direction parallel to the X-axis direction. The head 7 is a spindle moving body that reciprocates in the Z-axis direction, which is a single vertical linear axis direction. The table 8 is fixed on the bed 1 and substantially forms the bottom plate of the machining chamber 9.

[0027] The machining tank 9 is a tank for storing electrical discharge machining fluid when the workpiece is immersed in the electrical discharge machining fluid during machining. When the workpiece is exposed to the air during machining, the machining tank 9 is a splash guard that covers the workpiece to prevent the electrical discharge machining fluid supplied to the machining gap from splashing around the machine. The machining tank 9 is mounted on the front upper surface of the bed 1.

[0028] Cover 10 is a protective plate that prevents, for example, something from getting under the machine or colliding with it. Cover 10 is provided on both the left and right sides of the machine, a short distance from the machine itself. Figures 1 and 2 show the machine with cover 10 removed. In particular, the position of cover 10 is indicated by a dotted line in Figure 1. In the wire electrical discharge machining machine of this embodiment, a panel-type cover that covers the head is provided on the front side of the machine, but its illustration and explanation are omitted. Covers can also be provided on the top or rear side of the machine as needed, but a detailed explanation is omitted.

[0029] The work stand 11 is erected on the table 8 so that the workpiece is positioned straddling the lower arm 13. The work stand 11 is a support base that can fix the workpiece and supply power to it. The upper arm 12 supports an upper guide assembly including an upper wire guide (not shown). The lower arm 13 supports a lower guide assembly including a lower wire guide (not shown).

[0030] The three side walls of the machining tank 9—the front wall and both left and right walls—reciprocate as a single unit in the W-axis direction, which is a vertical line parallel to the Z-axis direction. In other words, the machining tank 9 moves up and down. A workpiece (not shown) is attached to the work stand 11 in an appropriate manner. The workpiece is completely contained within the machining tank 9 when it is raised to its highest position.

[0031] A first temperature sensor MS is provided in one or more selected main components forming the aircraft body to detect the surface temperature of the component. In particular, the temperature sensor MS is positioned as centrally as possible along a predetermined direction for performing thermal displacement compensation on the surface of the component. Preferably, the temperature sensor MS is installed at a position sufficiently far from heat-generating components such as motor coils or from positions that are likely to be exposed to direct sunlight locally for extended periods.

[0032] In the wire electrical discharge machining machine of the embodiment shown in Figures 1 and 2, when the predetermined direction for performing thermal displacement compensation is the Y-axis direction, a first temperature sensor MS is provided on the bed 1, the cross beam 3, the base 4, and the slider 6, respectively. The temperature sensor MS is, for example, a thermistor. Each temperature sensor MS provided on the bed 1, the cross beam 3, the base 4, and the slider 6 is mounted in an appropriate manner so that its detection portion accurately contacts the surface of the machine component.

[0033] At least one second temperature sensor AS is provided at a position opposite to the position of the first temperature sensor MS on each of the machine components, detecting the temperature of the machine component or the surrounding environment of the first temperature sensor MS in a non-contact manner. Generally, the temperature of the surrounding environment of the machine components is the ambient temperature of the room in which the wire electrical discharge machining machine is installed.

[0034] The second temperature sensor AS is positioned to better detect the ambient temperature and to face all of the first temperature sensors MS. For example, in a wire electrical discharge machine as shown in the embodiments of Figures 1 and 2, where all of the multiple temperature sensors MS are oriented in the same direction and mounted on the surface of each machine component, the temperature sensor AS is positioned to face all of the temperature sensors MS at a short distance away.

[0035] The second temperature sensor AS is a thermistor, just like the first temperature sensor MS. The temperature sensor AS is non-contact with all major components of the machine. To better detect the ambient temperature, it is desirable that the temperature sensor AS be installed at a sufficient distance from heat-generating components, such as motor coils. It is also desirable that the temperature sensor AS be positioned as close as possible to all the temperature sensors MS.

[0036] If the distance between one of the multiple first temperature sensors MS and the second temperature sensor AS is large enough to cause an unacceptable error in the thermal displacement correction amount of the aircraft calculated between the actual ambient temperature detected by the temperature sensor MS and the ambient temperature detected by the second temperature sensor AS, then another second temperature sensor AS can be provided at a position that keeps the temperature difference within an acceptable range.

[0037] As shown in Figures 1 and 2, in the wire electrical discharge machining machine of this embodiment, a first temperature sensor MS is provided on the left-facing side of each of the bed 1, cross beam 3, base 4, and slider 6. A single second temperature sensor AS is located a short distance from the multiple temperature sensors MS on a frame 10F between each machine component and the cover 10. However, in the bed 1 including column 2, the temperature of the electrical discharge machining fluid stored in the machining tank 9 provided on the front upper surface of the bed 1 also affects its thermal displacement, so it is excluded from the thermal displacement correction in this embodiment.

[0038] There is a time lag between the internal temperature of the aircraft components and the surface temperature of those components. Therefore, there is a temperature difference between the temperature detected by the temperature sensor MS and the internal temperature of the aircraft components at the time of detection by the temperature sensor MS. Consequently, the thermal displacement of the aircraft components can be accurately determined by calculating it using a predetermined formula based on the internal temperature of the aircraft components.

[0039] Therefore, by multiplying the temperature detected by the first temperature sensor MS by a first predetermined correction coefficient that takes into account a time delay, the internal temperature of the aircraft component is estimated from the surface temperature of the aircraft component at the time the temperature sensor MS detected the temperature. The estimated internal temperature of the aircraft component is defined as the first estimated temperature.

[0040] Here, the temperature detected by the first temperature sensor MS is the surface temperature of the aircraft component, but strictly speaking, it includes the influence of the ambient temperature surrounding the aircraft component. Therefore, simply put, the temperature obtained by subtracting the temperature component that affects the temperature sensor MS from the temperature detected by the second temperature sensor AS, which detects the ambient temperature, can be considered to be the surface temperature of the aircraft component.

[0041] The temperature detected by the second temperature sensor AS may be slightly affected by the temperature of the component to which the temperature sensor AS is attached. Also, since the temperature sensor AS is located a short distance from the first temperature sensor MS, there may be a small temperature difference between the ambient temperature around the temperature sensor MS and the temperature detected by the temperature sensor AS.

[0042] Therefore, the temperature component of the ambient temperature affecting the temperature sensor MS is defined as the second estimated temperature by multiplying the temperature detected by the second temperature sensor AS by a predetermined second correction coefficient, so as to comprehensively correspond to the extent to which the ambient temperature affects the temperature detected by the first temperature sensor MS.

[0043] The detection signals from the first temperature sensor MS and the second temperature sensor AS are input to a control device (not shown). The control device determines the combined temperature of the selected main body components that are subject to thermal displacement correction in a predetermined direction from among a plurality of main body components forming the body as T, and the detected temperature from the first temperature sensor MS as Q. M Q is the temperature detected by the second temperature sensor AS. A , the first correction coefficient is K M , the second correction coefficient is K AWhen doing so, calculate the combined temperature T of the aircraft structural members according to the following arithmetic expression. The unit of temperature is degrees Celsius. T [°C] = K M ·Q M + K A ·Q A (1)

[0044] The first correction coefficient K M and the second correction coefficient K A in Equation 1 can be obtained by experiments for each model. Specifically, the first correction coefficient K M and the second correction coefficient K A For example, for all aircraft structural members that cause thermal displacement affecting the position error in a predetermined direction, measure the thermal displacement in the predetermined direction of each aircraft structural member at each predetermined time, and measure the surface temperature of each aircraft structural member and the temperature of the environment around each aircraft structural member, and obtain them from the correlation coefficient between the thermal displacement amount in the predetermined direction of each aircraft structural member and the combined temperature.

[0045] Obtain the correlation coefficient of the combined temperature with respect to the displacement amount in the predetermined direction of the aircraft structural member actually measured at each predetermined time, and based on the ratio of the detected temperature of the first temperature sensor MS and the detected temperature of the second temperature sensor AS when it is determined to be the correlation coefficient with the strongest correlation, determine the correction coefficients K M and K A [[ID=�0]]At this time, the sum of the correction coefficients K M and K A is set to 1. The correlation coefficient ρ can be obtained by the following formula. Cov in the following formula is the covariance of the displacement amount in the predetermined direction and the combined temperature, σH is the standard deviation of the displacement amount in the predetermined direction, and σT is the standard deviation of the combined temperature. ρ = Cov / σH·σT (2)

[0046] Figure 3 shows the correlation coefficient values ​​between the amount of thermal displacement in the Y-axis direction and the combined temperature for the crossbeam 3, base 4, and slider 6, which are selected main machine components arranged vertically and affect the position error in the Y-axis direction in a wire electrical discharge machining machine according to the embodiment. For example, according to Figure 3, for all machine components, the correction coefficient K is calculated from the ratio of the surface temperature of the machine to the ambient temperature when the correlation coefficient is closest to 1.000 and the correlation between the amount of thermal displacement and the combined temperature is judged to be the strongest. M Set this to 1.2, and the correction coefficient K A It is found that setting this to -0.2 is appropriate.

[0047] In the embodiment shown in Figure 3, the correlation coefficients of the crossbeam 3, base 4, and slider 6 with respect to each of the aircraft components are calculated using a first correction coefficient K from the combined temperature of the aircraft. M It is calculated at the same time. Therefore, when calculating the combined temperature of each aircraft component, the first correction coefficient K M and the second correction coefficient K A When determining the combined temperature of each aircraft component, the same value is obtained when determining the thermal displacement of each aircraft component, but this does not cause any calculation problems. Furthermore, the method for determining the correction coefficient is not limited to that using the correlation coefficient.

[0048] The thermal displacement of each aircraft component can be determined from the following known formula, where H is the thermal displacement (μm) of the aircraft component in a predetermined direction, and T n n is the combined temperature at a certain time (n is an integer), α is the coefficient of linear expansion of the aircraft's structural members ( / °C·m), and L is the length of the aircraft's structural members (m). H=(T n -T n+1 )α·L (3)

[0049] The thermal displacement of the machine in a predetermined direction is the sum of the displacements of multiple machine components arranged in that predetermined direction. For example, in the wire electrical discharge machine of this embodiment, the thermal displacement in the Y-axis direction along the horizontal straight line 1 axis is the sum of the thermal displacements in the Y-axis direction of the cross beam 3, the base 4, and the slider 6. In this case, instead of determining the thermal displacement of the machine in a predetermined direction from the sum of the thermal displacements of multiple machine components, a method can be used to determine the thermal displacement of the machine in a predetermined direction from the combined temperature of multiple known machine components.

[0050] Figure 4 shows the wire electrical discharge machining machine according to the embodiments of Figures 1 and 2, and the correction coefficient K in Equation 2 is derived from the correlation coefficient shown in Figure 3. M and correction coefficient K A The results of comparing the thermal displacement H calculated by determining the combined temperature T in the Y-axis direction for each of the multiple aircraft components with the thermal displacement measured in reality are shown.

[0051] The control device (not shown) includes a first calculation device that determines the combined temperature T of multiple aircraft components, and a second calculation device that calculates the amount of thermal displacement H in a predetermined direction of the aircraft based on the combined temperature T determined by the first calculation device, and performs thermal displacement correction in a predetermined direction of the aircraft based on the amount of thermal displacement H calculated by the second calculation device.

[0052] The first computing unit calculates the temperature detected by the first temperature sensor MS for each component of the aircraft body using a predetermined first correction coefficient K M The first estimated temperature corrected by the second temperature sensor AS is calculated, and the temperature detected by the second temperature sensor AS is corrected by a predetermined second correction coefficient K. A The second estimated temperature, corrected by the first estimated temperature, is calculated and added to the first estimated temperature to determine the combined temperature of the aircraft's components. The second calculation unit calculates the amount of thermal displacement H in a predetermined direction of the aircraft based on the combined temperature T obtained by the first calculation unit. Note that the first and second calculation units can be combined into a single calculation unit.

[0053] The control device receives temperature readings from the first temperature sensor MS and the second temperature sensor AS at predetermined intervals to determine the amount of thermal displacement of each component of the aircraft in a predetermined direction. Then, it corrects the positional error caused by the total amount of thermal displacement of the aircraft in a predetermined direction from the sum of the amounts of thermal displacement of each component in a predetermined direction.

[0054] In the wire electrical discharge machining machine of this embodiment, the machining position error due to the amount of thermal displacement occurring in a horizontal straight line 1 axial direction passing through the front and rear of the machine body is distributed and appears as a position error in the Y axial direction determined by the position of the lower wire guide on a predetermined machining surface, and a position error in the V axial direction determined by the position of the upper wire guide on a tapered surface. Therefore, the control device corrects the position error in the Y axial direction based on the amount of thermal displacement of the cross beam 3, and corrects the position error in the V axial direction based on the amount of thermal displacement of the base 4 and slider 6.

[0055] Next, embodiments of the thermal displacement compensation method for machine tools according to the present invention will be described. The embodiments described below are suitable thermal displacement compensation methods for wire electrical discharge machining machines shown in Figures 1 and 2.

[0056] In the wire electrical discharge machining machine shown in Figures 1 and 2, the first temperature sensor MS is provided on the crossbeam 3, the base 4, and the left side of the slider 6, respectively. The second temperature sensor AS is provided on an auxiliary piece of equipment such as a frame 10F located between the cover 10 and the main machine components, which are installed on the left side of the machine.

[0057] The predetermined direction for performing thermal displacement correction is the Y-axis direction. A first correction coefficient K is set in advance. M and the second correction coefficient K A We will obtain this. As already explained, the first correction coefficient K M and the second correction coefficient K A The first temperature sensor MA's detected temperature Q is determined by calculating the correlation coefficient between the displacement amounts in the Y-axis direction of the aircraft components crossbeam 3, base 4, and slider 6, which are actually measured multiple times during a predetermined period, and the combined temperature, and then determining the correlation coefficient that shows the strongest correlation among multiple correlation coefficients.M and the temperature Q detected by the second temperature sensor AS A It is determined based on the ratio.

[0058] In the following explanation, the first estimated temperature is the temperature Q detected by the first temperature sensor MS. M A first predetermined correction coefficient K that takes into account the time delay. M The second estimated temperature is the internal temperature of the aircraft's components, which is estimated by multiplying by [a certain factor]. The second estimated temperature is the temperature Q detected by the second temperature sensor AS. A A predetermined second correction coefficient K A This is the temperature component of the ambient temperature that affects the temperature sensor MS, which is estimated by multiplying by [a certain factor].

[0059] First, the temperature Q detected by the first temperature sensor MS is provided on the surface of the crossbeam 3, the base 4, and the slider 6, which are selected machine components closely related to the thermal displacement compensation in the Y-axis direction in the wire electrical discharge machine of the embodiment. M a predetermined first correction coefficient K M The first estimated temperature, corrected by [the formula], is calculated. Also, the detected temperature Q of the second temperature sensor AS is calculated. A a predetermined second correction coefficient K A The second estimated temperature, corrected by the formula, is calculated. Then, the second estimated temperature is added to the first estimated temperature to determine the combined temperature T of each component of the aircraft: the crossbeam 3, the base 4, and the slider 6.

[0060] Next, the thermal displacement H in the Y-axis direction of the aircraft is calculated based on the combined temperature T. When the thermal displacements of the crossbeam 3, base 4, and slider 6 are calculated separately, the sum of the thermal displacements of each aircraft component is taken as the thermal displacement of the aircraft. Then, a thermal displacement correction in the Y-axis direction of the aircraft is performed based on the calculated thermal displacement H in the Y-axis direction.

[0061] In the wire electrical discharge machining machine of this embodiment, the machining position error due to the amount of thermal displacement occurring in a horizontal straight line 1 axial direction passing through the front and rear of the machine body is distributed and appears as a position error in the Y axial direction determined by the position of the lower wire guide on a predetermined machining surface, and a position error in the V axial direction determined by the position of the upper wire guide on a tapered surface. Therefore, the position error in the Y axial direction is corrected based on the amount of thermal displacement of the cross beam 3, and the position error in the V axial direction is corrected based on the amount of thermal displacement of the base 4 and slider 6.

[0062] When correcting positional errors in the X-axis direction, which is the direction of another horizontal straight line perpendicular to the Y-axis direction, or when correcting positional errors in the Z-axis direction, which is the direction of a vertical straight line perpendicular to the Y-axis direction, thermal displacement correction can be performed in the same manner as when correcting positional errors in the Y-axis direction. However, as in the wire electrical discharge machine of the embodiment, due to the structure of the machine body in which the lower arm 13 extending in the Y-axis direction supports the wire guide, the effect of thermal displacement on the required positioning accuracy is relatively small in the X-axis direction and the Z-axis direction, so it is not essential to perform thermal displacement correction using the thermal displacement correction method of the present invention.

[0063] The third temperature sensor RS, provided in the machining chamber 9, is used to continuously detect the temperature of the electrical discharge machining fluid in order to maintain a constant fluid temperature in the electrical discharge machining machine within the machining chamber 9. In the wire electrical discharge machining machine of this embodiment, the third temperature sensor RS can be used, for example, as a temperature sensor to detect the ambient temperature when performing thermal displacement compensation of the bed 1. It can also be used, for example, to estimate the temperature of the lower arm 13.

[0064] When correcting the bed 1 using the third temperature sensor RS with the thermal displacement correction method of the present invention, for example, the temperature of the environment around the bed 1 can be determined by the combined temperature of the first temperature sensor MS and the third temperature sensor RS, which are provided on the surface of the bed 1.

[0065] The machine tool and thermal displacement compensation method for the machine tool described above are not limited to the wire electrical discharge machine and thermal displacement compensation method of the embodiment, but several examples have already been shown and can be substituted, modified, or combined without departing from the technical concept of the present invention.

[0066] For example, instead of a wire electrical discharge machining machine having a structure in which a crossbeam that reciprocates in the Y-axis direction on the upper surface of a column that is molded integrally with the bed and is part of the bed, and a base that moves in the X-axis direction is mounted on the crossbeam, it can be applied to a cutting machine having a structure in which a saddle that reciprocates in the Y-axis direction on the bed, and a table that reciprocates in the X-axis direction is mounted on the saddle. [Explanation of Symbols]

[0067] 1 bed 2 Columns 3 Crossbeam 4 bases 5 Top beam 6 Sliders 7 heads 8 tables 9 Processing tank 10 Covers 10F Frame 11 Workstand 12 Upper Arm 13 Lower Arm MS First Temperature Sensor AS Second temperature sensor RS third temperature sensor

Claims

1. In one or more selected aircraft components that form the aircraft, A first temperature sensor is provided on the surface of each of the aforementioned aircraft components, At least one second temperature sensor is provided non-contact with each of the aircraft components at a position opposite to all of the positions of the first temperature sensors, and detects the temperature of the environment surrounding the aircraft component. A control device comprising: a first calculation device that calculates a first estimated temperature for each of the one or more aircraft components by correcting the temperature detected by the first temperature sensor with a predetermined first correction coefficient, and a second estimated temperature by correcting the temperature detected by the second temperature sensor with a predetermined second correction coefficient, and adds the second estimated temperature to the first estimated temperature to obtain the combined temperature of the aircraft components; and a second calculation device that calculates the amount of thermal displacement of the aircraft in a predetermined direction based on the combined temperature obtained by the first calculation device, wherein the control device performs thermal displacement correction of the aircraft in a predetermined direction. A machine tool equipped with [a specific feature / feature].

2. The machine tool according to claim 1, wherein the first temperature sensor is provided as centrally as possible along the predetermined direction for performing thermal displacement correction on the surface of the machine body component.

3. The machine tool according to claim 1, characterized in that the first correction coefficient and the second correction coefficient are predetermined based on the ratio of the detected temperature of the first temperature sensor to the detected temperature of the second temperature sensor when the correlation coefficient between the amount of displacement of the machine body components in the predetermined direction and the combined temperature, which is determined from a plurality of correlation coefficients, is judged to be the correlation coefficient with the strongest correlation.

4. The machine tool according to claim 2, characterized in that the correlation coefficient is obtained by the following formula. ρ=Cov / σH・σT However, ρ is the correlation coefficient, Cov is the covariance between the displacement in a given direction and the synthesis temperature, σH is the standard deviation of the displacement in a given direction, and σT is the standard deviation of the synthesis temperature.

5. The machine tool according to claim 1, characterized in that the one or more machine body components are made of cast iron.

6. The machine tool according to claim 1, wherein the machine tool is a wire electrical discharge machine.

7. The machine tool according to claim 6, wherein the predetermined direction is the Y-axis direction.

8. A step of calculating a first estimated temperature by correcting the temperature detected by a first temperature sensor provided on the surface of each of the one or more aircraft components that make up the aircraft body with a predetermined first correction coefficient, A step of calculating a second estimated temperature by correcting the detected temperature of at least one second temperature sensor, which is provided non-contact with each of the aircraft components at positions opposite to all of the first temperature sensors and detects the temperature of the environment surrounding the aircraft components, by a predetermined second correction coefficient, A step of determining the composite temperature of the aircraft components by adding the second estimated temperature to the first estimated temperature, A step of calculating the amount of thermal displacement of the machine in a predetermined direction based on the composite temperature obtained by the first computing device, A step of correcting the thermal displacement of the machine in the predetermined direction based on the calculated amount of thermal displacement in the predetermined direction, A method for compensating for the thermal displacement of a machine tool, comprising the above.

9. The thermal displacement correction method for a machine tool according to claim 8, characterized in that the first correction coefficient and the second correction coefficient are predetermined based on the ratio of the temperature detected by the first temperature sensor to the temperature detected by the second temperature sensor when the correlation coefficient between the amount of displacement of the machine body components in the predetermined direction and the combined temperature, which is determined from a plurality of correlation coefficients, is judged to be the correlation coefficient with the strongest correlation.

10. The thermal displacement correction method for a machine tool according to claim 9, characterized in that the correlation coefficient is obtained by the following formula. ρ=Cov / σH・σT However, ρ is the correlation coefficient, Cov is the covariance between the displacement in a given direction and the synthesis temperature, σH is the standard deviation of the displacement in a given direction, and σT is the standard deviation of the synthesis temperature.

11. The method for compensating for thermal displacement of a machine tool according to claim 10, wherein the predetermined direction is the Y-axis direction.

12. The thermal displacement correction method according to claim 11, wherein the predetermined directions for correction are the Y-axis direction and the V-axis direction.

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