JP6500602B2 - Machine tool, calculation method and computer program - Google Patents

Description

  The present invention relates to a machine tool, calculation method and computer program for calculating the thermal displacement of a column supporting a spindle head.

  The machine tool includes a spindle head supporting a spindle, a nut connected to the spindle head, and a screw shaft screwed to the nut via a rolling element. A column supports the nut and screw shaft, and a motor is connected to the screw shaft. When the screw shaft and the nut are driven, frictional heat is generated between them, so the screw shaft extends. The machine tool calculates the displacement amount of the screw shaft based on the frictional heat. The machine tool uses the displacement amount of the screw shaft for drive control of the motor to control the position of the spindle (see, for example, Patent Document 1).

JP, 2009-214283, A

  The column supports a controller that controls the drive of the motor and the spindle. The controller generates heat which thermally displaces the column and shifts the position of the main shaft.

  The present invention has been made in view of such circumstances, and provides a machine tool, a calculation method, and a computer program for calculating the thermal displacement of a column.

  The machine tool according to the present invention comprises a spindle head supporting the spindle, a column supporting the spindle head, extending vertically, and a column provided for moving the spindle head vertically. In a machine tool provided with a mechanism and a control device provided on the column and controlling the drive of the spindle and the moving mechanism, the column is vertically moved below the moving mechanism by heat conducted from the control device. And an arithmetic unit for calculating the amount of thermal displacement displaced.

  A machine tool according to the present invention includes a correction unit that corrects the target value by adding the calculation result of the calculation unit to the target value of the upper and lower position on the spindle set by the control device, the control device The driving of the moving mechanism is controlled based on the correction result of the correction unit.

  In the machine tool according to the present invention, at the upper and lower positions corresponding to the moving mechanism, the control device is located on the opposite side of the moving mechanism, and at the position where the moving mechanism is provided by heat conducted from the control device. A second operation unit that calculates a second thermal displacement amount in which the column is displaced in the vertical direction, and a thermal displacement amount calculated by the operation unit and a second thermal displacement amount calculated by the second operation unit And an adder.

  In the machine tool according to the present invention, the second arithmetic unit calculates the second thermal displacement amount in correspondence with the upper and lower positions of the column, and the addition result of the adding unit is set at each upper and lower position of the column It is characterized by storing in association.

  The machine tool according to the present invention includes a second correction unit that corrects the target value by adding the addition result of the addition unit to the target value of the vertical position of the spindle set by the control device. The control device controls the drive of the moving mechanism based on the correction result of the second correction unit.

  The calculation method according to the present invention calculates the amount of thermal displacement of a spindle head supporting a spindle, a moving mechanism for moving the spindle head up and down, and a control unit controlling a drive of the spindle and the moving mechanism. The thermal displacement amount in which the column is displaced in the vertical direction below the moving mechanism is calculated by the heat conducted from the control device.

  A computer program according to the present invention is a computer program that can be executed by a control device that calculates the amount of thermal displacement of a column supporting a moving mechanism for moving the spindle head up and down according to the control program. The control unit is provided on the column, and the control unit functions as a calculation unit that calculates a thermal displacement amount in which the column is vertically displaced below the moving mechanism by heat conducted from the control unit. I assume.

  If the column is thermally displaced below the moving mechanism, the moving mechanism is vertically displaced, so the spindle head is also displaced regardless of the vertical position of the spindle head in the moving mechanism. The upper and lower positions of the control device and the moving mechanism correspond, and the control device is located on the opposite side of the moving mechanism. In the column, the portion provided with the control device has a higher temperature than the portion provided with the moving mechanism, so the column bends due to the temperature difference between the two portions. The start position of bending starts from the lower side of the moving mechanism. The column displaces up and down by bending. Therefore, in the present invention, the thermal displacement amount in the vertical direction of the column is calculated on the lower side of the moving mechanism.

  In the present invention, the calculated thermal displacement amount is added to the target value to realize the position correction of the spindle.

  The upper and lower positions of the control device and the moving mechanism correspond, and the control device is located on the opposite side of the moving mechanism. In the column, the portion provided with the control device has a higher temperature than the portion provided with the moving mechanism, so the column bends due to the temperature difference between the two portions. The column displaces up and down by bending. The angle of bending changes with the vertical position of the column. That is, the bending angle differs between the upper side and the lower side of the moving mechanism, and the amount of displacement in the vertical direction also differs. Therefore, in the present invention, the second thermal displacement amount in the vertical direction of the column generated by bending is calculated, and the calculated second thermal displacement amount is added to the thermal displacement amount.

  In the present invention, the addition result of the adding unit is stored in association with each of the upper and lower positions of the column, and the position correction of the spindle at each of the upper and lower positions is facilitated.

  In the present invention, the thermal displacement amount and the second thermal displacement amount are added to the target value to realize the spindle position correction with high accuracy.

  If the column is thermally displaced below the moving mechanism, the moving mechanism is vertically displaced, so the spindle head is also displaced regardless of the vertical position of the spindle head in the moving mechanism. In the present invention, since the thermal displacement amount in the vertical direction of the column is calculated on the lower side of the moving mechanism, the position of the main shaft can be corrected based on the calculation result.

It is a perspective view which briefly displays a machine tool. It is a left view which briefly displays the upper part of a machine tool. It is a block diagram showing composition of a control system of a machine tool. It is a graph which shows the thermal displacement amount of the Z-axis direction of a column with respect to elapsed time. It is a flowchart explaining the correction | amendment process of the target position by a control part. It is a flowchart explaining the database creation process by a control part.

  Hereinafter, the present invention will be described based on the drawings showing a machine tool according to an embodiment. FIG. 1 is a perspective view schematically showing a machine tool, and FIG. 2 is a left side view schematically showing an upper portion of the machine tool. In the following description, upper and lower, right and left and front and back indicated by arrows in the drawings are used.

  The machine tool includes a base 52, a machine main body 53, an XY stage mechanism 60, a tool changer 80, and the like. The base 52 is a substantially rectangular base made of iron. The machine main body 53 is provided at the upper rear of the base 52 and performs processing such as cutting on a work (not shown) held on the XY stage mechanism 60. The XY stage mechanism 60 is provided at the upper center of the base 52, and drives the X stage 61 in the X axis direction (left and right direction) and the Y axis direction (front and rear direction). The tool changer 80 is provided at the upper part of the machine main body 53, and exchanges the tool T mounted on the main shaft 57 of the machine main body 53.

  The machine main body 53 includes a column 55, a spindle head 56, a spindle 57, the control device 1, and the like. The column 55 has a columnar shape and stands upright on the upper rear of the base 52. As shown in FIG. 2, a Z-axis direction moving mechanism 430 is provided on the front surface of the upper portion 55 b of the column 55. The Z-axis direction moving mechanism 430 includes a Z-axis ball screw 431, a nut 432 and a Z-axis motor 43. The Z-axis ball screw 431 extends vertically. The Z-axis motor 43 is connected to the upper end of the Z-axis ball screw 431. The nut 432 is screwed into the Z-axis ball screw 431. The spindle head 56 is provided on the nut 432. The Z-axis motor 43 rotates the Z-axis ball screw 431 in the forward and reverse directions. Therefore, the spindle head 56 moves in the Z-axis direction (vertical direction) together with the nut 432.

  The spindle head 56 rotatably supports the spindle 57. A lower end portion of the main shaft 57 is mounted with a tool T. The spindle head 56 includes a spindle motor 44 (see FIG. 3) at the top. The spindle motor 44 rotates the spindle 57.

  The tool changer 80 includes a disk-shaped tool magazine 81. The tool magazine 81 pivots about an axis by the drive of a magazine motor 45 (see FIG. 3). The tool magazine 81 comprises a plurality of pots 82. The plurality of pots 82 are circumferentially juxtaposed on the outer periphery of the tool magazine 81. Each pot 82 detachably accommodates the tool T. The tool changer 80 pivots the tool magazine 81 and moves the pot 82 equipped with the tool T to be used next to the tool change position. The tool changer 80 removes the tool T mounted on the main shaft 57, and mounts the tool T mounted on the pot 82 at the tool change position on the main shaft 57.

  The XY stage mechanism 60 includes an X stage 61, a Y stage 62, an X axis motor 41, a Y axis motor 42 (see FIG. 3), and the like. The X stage 61 is a workbench which holds a work on the upper surface. The Y stage 62 supports the X stage 61 movably in the X-axis direction on the upper surface, and is movable in the Y-axis direction at the center of the upper surface of the base 52.

  The base 52 is provided with a Y-axis ball screw (not shown) and a Y-axis motor 42. The Y stage 62 has a nut (not shown) on its lower surface. The nut is screwed into the Y-axis ball screw. The Y-axis motor 42 rotates the Y-axis ball screw in forward and reverse directions. Thus, the Y stage 62 moves in the Y axis direction together with the nut.

  The Y stage 62 includes an X-axis ball screw (not shown) and an X-axis motor 41. The X stage 61 has a nut (not shown) on its lower surface. The nut is screwed into the X-axis ball screw. The X-axis motor 41 rotates the X-axis ball screw in forward and reverse directions. Thus, the X stage 61 moves in the X axis direction together with the nut. Further, the X stage 61 moves in the Y axis direction via the Y stage 62. Therefore, the X-stage 61 can move in both the X-axis direction and the Y-axis direction.

  The control device 1 is provided on the rear surface of the upper portion 55b of the column 55, and controls the driving of the X-axis motor 41, the Y-axis motor 42, the Z-axis motor 43, the spindle motor 44 and the magazine motor 45. Each of the above motors is a servomotor.

  FIG. 3 is a block diagram showing a configuration of a control system of a machine tool. The control device 1 includes a control unit 10, an input unit 17, a display unit 18, an X-axis drive control unit 21, a Y-axis drive control unit 22, a Z-axis drive control unit 23, a spindle drive control unit 24, a magazine drive control unit 25, etc. Equipped with Hereinafter, the X-axis drive control unit 21 to the magazine drive control unit 25 will be collectively referred to as drive control units 21 to 25. The control unit 10 includes a CPU, a ROM, a RAM, a non-volatile memory, an input / output interface, a timer, etc., reads a control program stored in the ROM or the non-volatile memory, The drive control units 21 to 25 are controlled based on the information. The non-volatile memory or RAM stores the target position and various information.

  The machine tool 2 includes the above-described X-axis motor 41, Y-axis motor 42, Z-axis motor 43, spindle motor 44, magazine motor 45, and the like. Hereinafter, the X-axis motor 41 to the magazine motor 45 are collectively referred to as the motors 41 to 45. The motors 41-45 include encoders 41A-45A, respectively. The encoders 41A to 45A detect the positions of the motors 41 to 45, and output feedback signals to the drive control units 21 to 25.

  Each of the drive control units 21 to 25 outputs a pulse signal for driving each of the motors 41 to 45 based on a control signal supplied from the control unit 10. The drive control units 21 to 25 receive feedback signals from the encoders 41A to 45A, and perform feedback control of position and speed. Each of the drive control units 21 to 25 transmits position information based on feedback signals from the respective encoders 41A to 45A to the control unit 10 in response to a request from the control unit 10. The control unit 10 displays the position information received from each of the drive control units 21 to 25 on the display unit 18. The input unit 17 receives an operation of the worker.

FIG. 4 is a graph showing the amount of thermal displacement of the column 55 in the Z-axis direction with respect to the elapsed time. In FIG. 4, the horizontal axis indicates the elapsed time (minute) after the power of the control device 1 is turned on, and the vertical axis indicates the displacement amount (μm) of the column 55 in the Z-axis direction. The P indicates the position of the spindle head 56 in the Z-axis direction, Z ₀ represents the lowest position of the spindle head 56, Z _MAX represents the uppermost position of the spindle head 56. K1 is a graph showing the thermal displacement amount in the Z-axis direction of the column 55 in the P = Z _0, K2 is a graph showing the thermal displacement amount in the Z-axis direction of the column 55 in the P = Z _MAX.

  A probe for detection is provided on the spindle head 56, and a detection base is provided on the front side of the column 55. The spindle head 56 is disposed at a predetermined position P, and the probe is in contact with the detection base. The time change of was measured. That is, after the power supply of the control device 1 is turned on, the displacement amount of the spindle head 56 in the Z-axis direction is measured at position P, and this measured value is used as the thermal displacement amount of the column 55 in the Z-axis direction. The thermal displacement amount is positive when the spindle head 56 is displaced downward due to thermal deformation.

  The heat generated by the controller 1 is conducted to the column 55, and the column 55 extends in the Z-axis direction. Further, the column 55 is contracted in the Z axis direction by cooling. It also bends due to the temperature difference before and after the column. When the column bends, the spindle head 56 is displaced to the lower side of the Z axis. The thermal displacement of the column 55 can be roughly classified into a first thermal displacement at the lower portion 55 a of the column 55 and a second thermal displacement at the upper portion 55 b of the column 55. The lower portion 55 a is located below the Z-axis direction moving mechanism 430.

  The thermal displacement of the lower portion 55a displaces the Z-axis direction moving mechanism 430 in the Z-axis direction. Therefore, regardless of the vertical position of the spindle head 56 in the Z-axis direction moving mechanism 430, the spindle head 56 is similarly displaced in the Z-axis direction. The thermal displacement amount in this case corresponds to the first thermal displacement amount (see FIG. 4).

  When the control device 1 generates heat, the column 55, particularly the upper portion 55b, has a higher temperature than the portion on the control device 1 side in the Z-axis direction moving mechanism 430 side, so as shown by the one-dot chain line in FIG. 55 bends to the front side. The thermal displacement amount generated by the bending of the column 55 corresponds to the second thermal displacement amount, and the second thermal displacement amount depends on the position in the Z-axis direction (see FIG. 4).

The amount of thermal displacement of the column 55 is calculated based on the following equation (first order lag model).
(DT / dt) · c = −T (t) h + q (t) (1)

Z (t) = αT (t) (3)
Here, T represents a temperature raised from the reference temperature, h represents a heat radiation coefficient, c represents a heat capacity, q represents the amount of heat conducted from the control device 1 to the column 55, and Z represents a thermal displacement amount in the Z axis direction. Indicates a thermal expansion coefficient.

When the power supply of the control device 1 is off (when the column 55 is cooled), the first thermal displacement amount is discretized and expressed based on the equations (1) to (3) as follows: become.
ΔZ _c (t + dtc) = ΔZ _c (t) · exp (−h _z dtc) (4)
Note h _z represents the time constant of the first thermal displacement amount, dtc represents the elapsed time, [Delta] Z _c denotes a first thermal displacement amount. The time constant h _z is predetermined based on the measurement result.

On the other hand, when the power supply of the control device 1 is turned off, the second thermal displacement amount is discretely expressed as follows.
ΔZ _p (t + dtc) = ΔZ _p (t) · exp (−h _p dtc) (5)
Here, h _p represents a time constant of the second thermal displacement amount, and ΔZ _p represents a first thermal displacement amount. The time constant h _p is predetermined based on the measurement result.

When the power of the control device 1 is on (when heat is conducted from the control device 1 to the column 55), the first thermal displacement amount is discretized based on the equations (1) to (3). If it represents, it will become as follows.
ΔZ _c (t + dt) = ΔZ _c (t) · exp (−h _z dt) + (1−exp (−h _z dt)) · q _z (6)
Note that q _z represents the maximum value of the first thermal displacement amount generated by the heat conducted from the control device 1 and is determined in advance by measurement. Moreover, dt shows elapsed time.

On the other hand, when the power supply of the control device 1 is turned on, the second thermal displacement amount is discretely expressed as follows.
ΔZ _p (t + dt) = ΔZ _p (t) · exp (−h _p dt) + (1−exp (−h _p dt)) · q _p (7)
Note that q _p indicates the maximum value of the second thermal displacement amount generated by the heat conducted from the control device 1 and is determined in advance by measurement.

Therefore, when the power supply of the control device 1 is turned on, the thermal displacement amount ΔZ (t + dt, P) of the column 55 at the position P in the Z-axis direction is as follows from the equations (6) and (7) .
ΔZ (t + dt, P) = ΔZ _c (t + dt) + ΔZ _p (t + dt) · (P−Z ₀ ) (8)
Incidentally, as described above, Z ₀ represents the lowest position of the spindle head 56.

FIG. 5 is a flow chart for explaining the correction processing of the target position by the control unit 10. The control control unit 10 records the time in the non-volatile memory when the power is off, and stores the first displacement amount ΔZ _c and the second displacement amount ΔZ _p in the non-volatile memory when the power is off. In addition, it shall start timing at the time of power on.

  When the power is turned on (step S1), the control unit 10 stores the time when the power is turned on in the non-volatile memory (step S2), and starts clocking (step S3). The control unit 10 reads the control program and determines whether or not the read control program includes a positioning command for positioning the spindle 57 (spindle head 56) at the target position (target value) (step S4). If the positioning command is not included (step S4: NO), the control unit 10 returns the process to step S4.

When the positioning command is included (step S4: YES), the control unit 10 refers to the non-volatile memory, calculates the difference between the time when the power is off and the time when the power is on, and proceeds from power off to on The time is acquired (step S5). The control unit 10 calculates a first displacement amount from power off to on (step S6). That is, the control unit 10, based on the equation (4), the elapsed time acquired in step S5 is applied to dtc of formula (4), calculates the first displacement amount [Delta] Z _c at the target position. The column 55 is cooled during the period from the power off to the on.

Next, the control unit 10 calculates a second displacement amount from power off to on (step S7). That is, the control unit 10, based on the equation (5), the elapsed time acquired in step S5 is applied to dtc of formula (5), calculates a second displacement amount [Delta] Z _p at the target position.

Next, the control unit 10 refers to a timer, acquires an elapsed time after power on (step S8), and calculates a first displacement amount after power on (step S9). That is, based on the equation (6), the elapsed time acquired in step S8 is applied to dt in equation (6), and the first thermal displacement amount calculated in step S6 is ΔZ _c (t in equation (6) To calculate the first displacement amount ΔZ _c (t + dt) at the target position.

The control unit 10 calculates a second displacement amount after power on (step S10). That is, based on the equation (7), the elapsed time acquired in step S8 is applied to dt in equation (7), and the second thermal displacement amount calculated in step S7 is ΔZ _p (t in equation (7) To calculate the second displacement amount ΔZ _p (t + dt) at the target position.

Next, the control unit 10 calculates the displacement amount based on the equation (8) (step S11). That is, the first displacement amount ΔZ _c (t + dt) and the second displacement amount ΔZ _p (t + dt) calculated in steps S7 and S8 are applied to equation (8), and the target position is applied to the Z-axis direction position P. Calculate the displacement amount. When the target position is Z ₀ (lowermost position), the second displacement amount ΔZ _p (t + dt) is zero, and only the first displacement amount may be considered as the displacement amount.

The control unit 10 corrects the target position (step S12). That is, the displacement amount calculated in step S11 is added to the target position to correct the target position.
The correction is performed based on the following equation.
Z _op = P−ΔZ (t, P) (9)
Note Z _op indicates a target position after correction, ΔZ (t, P) represents a displacement amount calculated in step S11.

  When the column lower portion 55a is thermally displaced, the Z-axis direction moving mechanism 430 is displaced in the vertical direction, so the spindle head 56 is also displaced regardless of the vertical position of the spindle head 56 in the Z-axis direction moving mechanism 430. The machine tool according to the embodiment calculates the amount of thermal displacement in the vertical direction of the lower portion 55a of the column, so the position of the main shaft 57 can be corrected based on the calculation result.

  The column 55 bends due to the temperature difference between the portion provided with the control device 1 and the portion provided with the Z-axis direction moving mechanism 430. The column 55 is vertically displaced by bending. The angle of bending varies with the vertical position of the column 55. The machine tool according to the embodiment calculates the second thermal displacement amount of the vertical direction of the column 55 which changes depending on the vertical position of the column 55 caused by bending, and calculates the second thermal displacement amount as the first thermal displacement amount. The position of the main shaft 57 can be corrected more accurately.

  The control unit 10 configures an arithmetic unit, a correction unit, a second arithmetic unit, a second correction unit, and an addition unit.

(Modification example)
The control unit 10 may store the displacement amount of the column 55 in correspondence with each position in the Z-axis direction, and create a database. FIG. 6 is a flowchart for explaining the database creation process by the control unit 10. It is assumed that Z _n (n = 0, 1, 2,..., MAX) is preset in the non-volatile memory as a parameter indicating each position in the Z-axis direction. Z ₀ represents the lowest position of the spindle head 56, according to the value of n increases, Z _n represents a more upper position, Z _MAX represents the highest position.

Steps S21 to S23 are the same as steps S1 to S3, and thus detailed description will be omitted. The control unit 10, which has started clocking in step S23, sets Z _n at the position P in the Z-axis direction, and sets 0 to n (step S24). Control unit 10 executes steps S25 to S27. Steps S25 to S27 are the same as steps S5 to S7, and thus detailed description will be omitted.

The control unit 10 stands by until a predetermined time elapses after the power is turned on (step S28: NO). If the predetermined time has elapsed (step S28: YES), the first displacement amount after the predetermined time has elapsed is calculated (step S29). That is, based on the equation (6), the predetermined time is applied to dt of the equation (6), and the first thermal displacement calculated in step S26 is applied to ΔZ _c (t) of the equation (6) The first displacement amount ΔZ _c (t + dt) at the Z-axis direction position P is calculated.

The control unit 10 calculates a second displacement amount after a predetermined time has elapsed (step S30). That is, based on the equation (7), the predetermined time is applied to dt of the equation (7), and the second thermal displacement amount calculated in step S27 is applied to ΔZ _p (t) of the equation (7). The second displacement amount ΔZ _p (t + dt) at the position P in the Z-axis direction is calculated.

Next, the control unit 10 calculates the amount of displacement based on the equation (8), associates it with the Z-axis direction position P, and stores it in the non-volatile memory (step S31). That is, the first displacement amount ΔZ _c (t + dt) and the second displacement amount ΔZ _p (t + dt) calculated in steps S27 and S28 are applied to equation (8), and the target position is applied to the Z-axis direction position P. Calculate and store the displacement amount. Then, the time at which the displacement amount is calculated is stored in the non-volatile memory (step S32).

  Next, the control unit 10 increments n (step S33), and determines whether n is larger than MAX (step S34). If n is not larger than MAX (step S34: NO), the control unit 10 returns the process to step S29.

  If n is larger than MAX (step S34: YES), the control unit 10 sets n to 0 (step S35), and returns the process to step S28. Then, the process stands by until a predetermined time has elapsed from the time stored in step S32 (step S28: NO), and the processes after step S29 are executed.

The control unit 10 stores the displacement amount of the column 55 in correspondence with each position (Z _n , n = 0, 1, 2,..., MAX) at a predetermined time, and creates a database. Do. Also, the control unit 10 updates the database each time a predetermined time elapses.

  When the read control program includes a positioning command, the control unit 10 refers to the database, acquires the displacement amount in the corresponding Z-axis direction, and corrects the target position based on Expression (9). By creating a thermal displacement database, correction of the target position is facilitated, and the processing speed of the correction is improved.

The displacement amount of the column 55 at the specific position Z _n in the Z-axis direction is calculated and stored, and the displacement amount of the column 55 at n = 0 to n-1, n + 1 to MAX corresponds to that of the column 55 at the specific position Z _n. It may be determined based on the displacement amount and the distance from the specific position Z _n . For example, the amount of displacement at each position may be determined so as to gradually decrease as the distance from the specific position Z _n increases. Alternatively, the average of the amounts of displacement at the two positions Z _n-1 and Z _n may be calculated, and the average may be the displacement in the sections Z _{n-1 to} Z _n .

1 control device 10 control unit (calculation unit, correction unit, second calculation unit, second correction unit, addition unit)
55 Column 56 Spindle head 57 Spindle 430 Z axis direction moving mechanism (moving mechanism)

Claims (7)

A spindle head supporting the spindle, a column supporting the spindle head and extending up and down, a moving mechanism provided on the column, the spindle head moving up and down, and the column A machine tool comprising a control device for controlling driving of the spindle and the moving mechanism,
A machine tool comprising: a calculation unit for calculating a thermal displacement amount in which the column is vertically displaced below the moving mechanism by heat conducted from the control device. The target value of the upper and lower position on the spindle set by the control device is added with the calculation result of the calculation part to correct the target value.
The machine tool according to claim 1, wherein the control device controls driving of the moving mechanism based on the correction result of the correction unit. In the upper and lower positions corresponding to the movement mechanism, the control device is located on the opposite side of the movement mechanism,
A second operation unit that calculates a second thermal displacement amount in which the column is vertically displaced at a position where the movement mechanism is provided by heat conducted from the control device;
The machine tool according to claim 1, further comprising: an addition unit that adds the thermal displacement amount calculated by the calculation unit and the second thermal displacement amount calculated by the second calculation unit. The second thermal processing unit calculates the second thermal displacement amount in association with the upper and lower positions of the column, and stores the addition result of the adding unit in association with the upper and lower positions of the column. The machine tool according to claim 3. The target value of the upper and lower position of the main spindle set by the control device is added with the addition result of the adding unit to correct the target value by a second correction unit.
The machine tool according to claim 3, wherein the control device controls driving of the moving mechanism based on the correction result of the second correction unit. A calculation method for calculating a thermal displacement of a column supporting a spindle head supporting a spindle, a moving mechanism for moving the spindle head up and down, and a control device controlling a drive of the spindle and the moving mechanism,
A thermal displacement amount in which the column is vertically displaced below the moving mechanism is calculated by the heat conducted from the control device. A computer program that can be executed by a control device that calculates a thermal displacement amount of a column supporting a moving mechanism for moving the spindle head up and down according to the control program,
The control device is provided in the column,
A computer program characterized by causing the control device to calculate a thermal displacement amount in which the column is displaced in the vertical direction below the moving mechanism by heat conducted from the control device.

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