JP6561788B2 - Thermal displacement correction device - Google Patents

Description

  The present invention relates to a thermal displacement correction apparatus.

  Patent Document 1 describes a thermal displacement correction device that performs thermal displacement correction with high accuracy in real time. This apparatus performs high-speed structural analysis by a finite element method based on temperature information detected by a temperature sensor. In structural analysis, the machine tool structure is divided into multiple blocks, and the temperature at each node contained in each block is set to a constant value, greatly reducing the amount of heat displacement calculated at each node. ing.

  Patent Document 2 describes a method of calculating a thermal displacement correction value for a command value of NC data. The entire range of the machining area is divided into grids, the thermal displacement correction value is stored in association with each grid point, and the command is based on the correction value at each grid point constituting the unit grid where the current machining point exists. A correction value for the value is calculated.

International Publication No. 2012/157687 JP 2012-234424 A

  In Patent Document 2, the correction value of the thermal displacement amount associated with each lattice point is a value having a specific position as an origin. Here, when the machine tool performs thermal displacement correction during machining, a correction value for the thermal displacement amount is calculated for each command value. The number of bits of the data type (integer type) of the thermal displacement correction value is a number corresponding to the maximum value of the thermal displacement correction value. Therefore, the larger the maximum value of the thermal displacement correction value, the larger the number of bits of the data type, and a longer time is required for the thermal displacement correction calculation. As a result, the positioning accuracy of the moving body may be lowered, and the processing time may be increased.

  Therefore, in order to reduce the number of bits of the data type, it can be considered not to include the maximum value of the thermal displacement amount. However, in this case, the effect of the thermal displacement correction cannot be obtained near the maximum value of the thermal displacement amount.

  An object of this invention is to provide the thermal displacement correction apparatus which can acquire the effect of thermal displacement correction reliably, reducing a data type.

  The thermal displacement correction device is configured to set a first thermal displacement amount setting the first thermal displacement amount in the predetermined axis direction corresponding to each machining point for the entire machining area with respect to the first position in the predetermined axis direction of the machine tool. And a second position located between the set maximum value and the minimum value of the first thermal displacement amount as a reference, the second thermal displacement relative to the predetermined axis corresponding to each processing point for the entire processing region range A second thermal displacement amount setting unit for setting an amount; an origin shift amount storage unit for storing an origin shift amount from the first position to the second position; and during the machining of the workpiece by the machine tool, the predetermined amount Based on the command machining point acquisition unit that acquires the command machining point in the axial direction, the command machining point, and the second thermal displacement amount set by the second thermal displacement amount setting unit, the command machining point The corresponding second thermal displacement amount is taken as a correction value. Comprising a correction value acquisition unit that, based on the obtained the correction value and the origin shift amount, and a correction unit that corrects the command value of the predetermined axis direction.

  During machining, the correction value for the command value corresponds to the command machining point in the second thermal displacement amount. The second thermal displacement amount is based on a second position located between the maximum value and the minimum value of the first thermal displacement amount. That is, the maximum value of the second thermal displacement amount is equal to or less than the difference between the maximum value and the minimum value of the first thermal displacement amount. Accordingly, the number of bits of the data type of the correction value is sufficient according to the maximum value of the second thermal displacement amount. As described above, the number of bits of the data type of the correction value can be reduced, and the time required for acquiring the correction value can be shortened. Therefore, the thermal displacement correction can be reliably performed for the entire range. That is, the effect of thermal displacement correction can be obtained with certainty.

It is a figure which shows the machine structure of the machine tool of this embodiment. It is a figure which shows the thermal displacement state of a machine tool. When the machine tool is in the thermal displacement state shown in FIG. 2, the first thermal displacement amount corresponding to the machining point is shown. It is a functional block diagram regarding the thermal displacement correction apparatus of a machine tool. A diagram in which the entire range of the machining area is divided into a lattice shape is indicated by a broken line, and one unit lattice including a command value machining point is indicated by a solid line. (First example) A second thermal displacement amount based on the second position O2a when the origin shift amount is ΔZa is shown. (Second example) The second thermal displacement amount with reference to the second position O2b when the origin shift amount is ΔZb is shown. (Third example) A second thermal displacement amount based on the second position O2c when the origin shift amount is ΔZc is shown. (Fourth example) A second thermal displacement amount based on the second position O2d when the origin shift amount is ΔZd is shown.

(1. Machine configuration of machine tool)
A horizontal machining center as an example of the machine tool 10 will be described with reference to FIG. The machine tool 10 is a machine tool having three linear shaft members (X, Y, Z axes) orthogonal to each other and a rotary shaft member (B axis) in the vertical direction as moving shaft members. The machine tool 10 to which the present invention is applied is not limited to the machine tool 10 described below.

  As shown in FIG. 1, the machine body of the machine tool 10 includes a bed 11, a column 12, a saddle 13, a main shaft 14, a slide table 15, and a turntable 16 as structures. The bed 11 has a substantially rectangular shape and is arranged on the floor. A column 12 is provided on the bed 11 so as to be movable in the X-axis direction (the front-rear direction in FIG. 1). A saddle 13 is provided on the side surface of the column 12 so as to be movable in the Y-axis direction (up and down direction in FIG. 1). The saddle 13 is provided with a main shaft 14 so as to be rotatable about an axis parallel to the Z-axis direction. A rotary tool 19 is attached to the tip of the main shaft 14. A slide table 15 is provided on the bed 11 so as to be movable in the Z-axis direction. A turntable 16 is provided on the slide table 15 so as to be rotatable around the Y axis (B axis). A workpiece W is fixed to the turntable 16 via a jig.

(2. Explanation of thermal displacement state of machine tools)
Next, the thermal displacement state of the machine tool 10 will be described with reference to FIGS. However, FIG. 2 exaggerates the thermal displacement. However, the thermal displacement state shown in FIG. 2 is an example, and the deformed shape varies depending on the structure of the machine tool 10. Here, in the present embodiment, the thermal displacement correction at the Z-axis position will be described, but the same applies to the thermal displacement correction at the X-axis position or the Y-axis position, and further to the thermal displacement correction at other axial positions. .

  FIG. 2 shows a first position O1, which is a reference for performing thermal displacement correction. The first position O1 is a reference position selected at the time of initial setting of machine control or machine design. As shown in FIG. 2, the upper surface of the bed 11 is deformed so as to extend to the left side. That is, the position of the workpiece W is displaced in the positive direction of the Z-axis as the Z-axis position of the slide table 15 increases. Further, the sliding surface of the saddle 13 of the column 12 is deformed so as to incline to the left side toward the tip end side. That is, the position of the rotary tool 19 is displaced in the positive direction of the Z axis as the Y1 position of the saddle 13 increases.

  In the above-described thermal displacement state, the first thermal displacement amount Z1 in the Z-axis direction corresponding to each machining point for the entire machining area is as shown in FIG. Here, the first thermal displacement amount Z1 is a thermal displacement amount at each machining point when the first position O1 is used as a reference. Similarly, the amount of thermal displacement in the X-axis direction and the Y-axis direction can be similarly expressed. However, since the first thermal displacement amount Z1 in the Z-axis direction has the most influence on the machining accuracy, only the Z-axis direction will be described.

  FIG. 3 shows the first thermal displacement amount Z1 corresponding to the Y-axis position of the saddle 13 when the Z-axis position of the slide table 15 is Z = 0, 100, 200, 300, and 400, respectively.

  Regardless of the Z-axis coordinate value of the slide table 15, the greater the Y-axis coordinate value of the saddle 13, the greater the first thermal displacement amount Z1. Regardless of the Y-axis position of the saddle 13, the first thermal displacement amount Z1 increases as the Z-axis coordinate value of the slide table 15 increases. Therefore, when the Y-axis coordinate value of the saddle 13 is small, the difference between the minimum value and the maximum value of the first thermal displacement amount Z1 is small. On the other hand, when the Y-axis coordinate value of the saddle 13 is large, the difference between the minimum value and the maximum value of the first thermal displacement amount Z1 is large.

(3. Functional block configuration related to thermal displacement correction device for machine tool)
Next, a functional block configuration related to the thermal displacement correction device 20 of the machine tool 10 will be described with reference to FIGS. The thermal displacement correction device 20 corrects the command value based on the NC data in order to eliminate the positional shift due to the thermal displacement of the structure of the machine tool 10.

  The thermal displacement correction apparatus 20 includes the units 21 to 29 shown in FIG. The temperature sensor 21 is provided on an object to be structurally analyzed by the analysis unit 22 in the structure of the machine tool 10. For example, the temperature sensor 21 is provided in the bed 11 and the column 12. The temperature sensor 21 measures in real time during processing. For example, the temperature sensor 21 acquires the temperature every several seconds.

  The analysis unit 22 calculates the amount of thermal displacement of the structure by performing a structural analysis by a finite element method or the like based on the temperature information of the temperature sensor 21. The analysis unit 22 can calculate, for example, the thermal displacement amount of the sliding surface of the slide table 15 in the bed 11 and the thermal displacement amount of the sliding surface of the saddle 13 in the column 12.

  The analysis unit 22 applies, for example, a method described in International Publication No. 2012/157687. The analysis unit 22 can be executed in real time during processing by applying the method. The analysis unit 22 executes, for example, every few seconds, similarly to the acquisition timing of the temperature information by the temperature sensor 21.

  The analysis unit 22 forms a structure model that is an object by a plurality of elements in the structure analysis. Each element is a tetrahedral primary element, a tetrahedral secondary element, a hexahedral primary element, a hexahedral secondary element, or the like. Then, the analysis unit 22 sets a boundary condition for each node (element vertex) of the structure model. The boundary condition is a constraint condition regarding a position, a temperature condition, or the like. The analysis unit 22 divides the structure model into a plurality of blocks as the temperature condition of each node, and sets the temperature of the plurality of nodes included in the plurality of blocks to a uniform value. One block has a size including a plurality of elements. Thus, by setting the temperature of the nodes in each block to a uniform value, the calculation amount of the structural analysis by the analysis unit 22 is greatly reduced, and real-time high-speed calculation is possible.

  Based on the thermal displacement amount of the structure obtained by the analysis unit 22, the first thermal displacement amount setting unit 23 uses the first position O1 as a reference, and the first thermal displacement amount setting unit 23 in the Z-axis direction according to each machining point for the entire machining region range. One thermal displacement amount Z1 is set. The processing by the first thermal displacement amount setting unit 23 is executed in real time during processing.

  The first thermal displacement amount Z1 will be described with reference to FIG. As shown in FIG. 5, the entire machining area of the machine tool 10 is divided into a lattice shape, and the first thermal displacement amount Z1 is associated with each lattice point P. That is, a different first thermal displacement amount Z1 is set for each lattice point P. The first thermal displacement amount Z1 is a value with the first position O1 as a reference (origin). As shown in FIG. 2, the first thermal displacement amount Z1 at each lattice point P becomes larger as the Y-axis coordinate value becomes larger, and becomes larger as the Z-axis coordinate value becomes larger. Although not shown in FIG. 2, the first thermal displacement amount Z1 changes according to the X-axis coordinate value.

  Based on the first thermal displacement amount Z1 set by the first thermal displacement amount setting unit 23, the second thermal displacement amount setting unit 24 is the second in the Z-axis direction corresponding to each lattice point P for the entire processing region range. A thermal displacement amount Z2 is set. The processing by the second thermal displacement amount setting unit 24 is executed in real time during processing.

  The second thermal displacement amount Z2 is a value with the second position O2 different from the first position O1 as a reference (origin). In the present embodiment, the second position O2 is a position shifted in the Z-axis direction with respect to the first position O1. The second position O2 is located between the maximum value and the minimum value of the first thermal displacement amount Z1. Here, the second position O2 is a position shifted from the first position O1 as the origin of the correction value used in the calculation for the purpose of reducing the number of bits of the data type of the correction value of thermal displacement described later. is there. For example, one of the following four examples is adopted as the second position O2.

  (First Example) The second position O2a of the first example will be described with reference to FIG. The second position O2a in the first example is an intermediate value between the maximum value and the minimum value of the first thermal displacement amount Z1. Therefore, the data type of the second thermal displacement amount Z2 at each grid point P is a signed integer type that can represent both positive and negative integers. In this case, the Y axis is Y2a. The origin shift amount from the first position O1 to the second position O2a is ΔZa.

  (Second Example) The second position O2b of the second example will be described with reference to FIG. The second position O2b in the second example is a predetermined representative position Pb between the maximum value and the minimum value of the first thermal displacement amount Z1. In this example, the representative position Pb corresponds to a processing point in a state in which the saddle 13 is located at the lowest position and the slide table 15 is located closest to the column 12 side. That is, the representative position Pb is a position where the first thermal displacement amount Z1 is the smallest. However, the representative position Pb is not limited to the viewpoint that the first thermal displacement amount Z1 is small, and may be a point selected from another viewpoint. For example, the representative position Pb may be a point in the vicinity of the workpiece W that is a part that easily affects the machining accuracy.

  In this case, the data type of the second thermal displacement amount Z2 at each lattice point P is an unsigned integer type (an integer type with only positive values). In this case, the Y axis is Y2b. The origin shift amount from the first position O1 to the second position O2b is ΔZb.

  (Third Example) The second position O2c of the third example will be described with reference to FIG. The second position O2c of the third example is located between the maximum value and the minimum value of the first thermal displacement amount Z1 in the machining range of the workpiece W in the Z-axis direction. FIG. 8 shows a case where the machining range of the workpiece W in the Z-axis direction is a range from Z = 100 to Z = 300, for example.

  Since the second position O2a in the first example covers the entire range in the Z-axis direction, the range from Z = 0 to Z = 400 is targeted. On the other hand, the second position O2c in the third example targets a partial range (Z = 100 to Z = 300) in the Z-axis direction. In particular, the second position O2c is an intermediate value between the maximum value and the minimum value of the first thermal displacement amount Z1 in the machining range of the workpiece W in the Z-axis direction. Therefore, the data type of the second thermal displacement amount Z2 at each grid point P is a signed integer type that can represent both positive and negative integers. In this case, the Y axis is Y2c. The origin shift amount from the first position O1 to the second position O2c is ΔZc.

  (Fourth Example) The second position O2d of the fourth example will be described with reference to FIG. The second position O2d of the fourth example is located between the maximum value and the minimum value of the first thermal displacement amount Z1 in the machining range of the workpiece W in the Z-axis direction. Furthermore, the second position O2d of the fourth example is a predetermined representative position Pd between the maximum value and the minimum value of the first thermal displacement amount Z1. In this example, the representative position Pd is a position corresponding to the origin Pd of the workpiece coordinate system.

  In this case, the data type of the second thermal displacement amount Z2 at each lattice point P is an unsigned integer type (an integer type with only positive values). In this case, the Y axis is Y2d. The origin shift amount from the first position O1 to the second position O2d is ΔZd.

  Here, the data type (integer type) will be described. The unsigned integer type interprets the bit sequence as it is as a numerical value. The signed integer type differs depending on the negative value representation method. Examples of the signed integer type include a sign-mantissa part, a 1's complement, a 2's complement, and an excess N. As the second thermal displacement amount Z2 in the first example and the third example, any one of four types of signed integer types is employed.

The “sign-mantissa part” expression is a method of adding a sign bit to express positive / negative. For example, “−127” in the expression “sign-significant part” is represented by an 8-bit bit pattern “11111111”.
The “1's complement” representation applies a bitwise NOT of the absolute value to the representation of the negative number. For example, “−127” in the “1's complement” expression is represented by an 8-bit bit pattern “10000000”.

The “2's complement” representation is represented by a bit pattern that is one greater than the “1's complement” representation. For example, “−127” in the “2's complement” expression is represented by an 8-bit bit pattern “10000001”.
The “Excess N” expression is also called an offset binary, and uses a predetermined number N as a bias value. 0 is represented by N, and -N is represented by a bit pattern in which zeros are arranged. For example, “−127” in the expression “Excess 127” is represented by an 8-bit bit pattern “00000000”.

  For example, in the case of 8 bits, the above-described expressions of the unsigned integer type and the signed integer type can represent the numerical ranges shown in the following table.

  Therefore, the second thermal displacement amount Z2 based on the second position O2a of the first example and the second thermal displacement amount Z2 based on the second position O2b of the second example are represented by the same number of bits. be able to. Further, the second thermal displacement amount Z2 based on the second position O2c of the third example and the second thermal displacement amount Z2 based on the second position O2d of the fourth example are in the Z-axis direction of the workpiece W. The processing range is targeted. Therefore, the second thermal displacement amount Z2 can be limited to the number of bits representing only the processing range. In this case, it can be expressed by a smaller number of bits than in the first and second examples. The third example and the fourth example can be expressed by the same number of bits.

  In addition, the second position O2 is shifted between the maximum value and the minimum value of the first thermal displacement amount Z1 in addition to the case of the first to fourth examples described above, and the number of bits of the data type of the correction value described later. Any other position may be used as long as the effect of reducing the size can be obtained.

Returning to FIG. The origin shift amount storage unit 25 stores an origin shift amount (any one of ΔZa to ΔZd) from the first position O1 to the second position (any one of O2a to O2d).
The command machining point acquisition unit 26 acquires command machining points in the Z-axis direction based on NC data during machining of the workpiece W by the machine tool 10.

  The correction value acquisition unit 27 corrects the second thermal displacement amount Z2 corresponding to the command processing point based on the command processing point and the second thermal displacement amount Z2 set in the second thermal displacement amount setting unit 24. Get as. The correction value calculation method will be described with reference to FIG.

  Assume that the command machining point is located in the unit cell indicated by the solid line in FIG. In this case, the second thermal displacement amount Z2 of the eight lattice points P of the unit lattice including the command machining point is acquired. The correction value acquisition unit 27 calculates a correction value corresponding to the command machining point based on the second thermal displacement amounts Z2 of the eight grid points P according to the position of the command machining point in the unit grid.

  At this time, the second thermal displacement amount Z2 of each lattice point P is expressed by a predetermined number of bits. Accordingly, since the second thermal displacement amount Z2 of the eight lattice points P is used in calculating the correction value, the correction value calculation process requires time corresponding to the number of bits of the second thermal displacement amount Z2 of the lattice point P. . However, since the second thermal displacement amount Z2 can be expressed by a smaller number of bits than the first thermal displacement amount Z1, the correction value calculation process does not use the first thermal displacement amount Z1 but the second thermal displacement amount Z1. Since the amount Z2 is used, processing can be performed in a short time.

  Based on the correction value acquired by the correction value acquisition unit 27 and the origin shift amount (any of ΔZa to ΔZd) stored in the origin shift amount storage unit 25, the correction unit 28 sets the command value in the Z-axis direction. to correct. Here, the correction value acquired by the correction value acquisition unit 27 is based on the second position (any one of O2a to O2d). Therefore, by adding the origin shift amount (any one of ΔZa to ΔZd) to the correction value, the correction value based on the first position O1 can be calculated, and the slide table is based on the value obtained by adding the correction value to the command value. 15 is driven.

  The display unit 29 sequentially displays the amount of thermal displacement corresponding to the command machining point during machining. However, the thermal displacement amount displayed on the display unit 29 is not the second thermal displacement amount Z2 but a value corresponding to the first thermal displacement amount Z1. The second position (any one of O2a to O2d) serving as a reference for the second thermal displacement amount Z2 changes each time the processing of the analysis unit 22 is performed. However, the first position O1, which serves as a reference for the first thermal displacement amount Z1, is unchanged. Therefore, the display unit 29 displays the amount of thermal displacement corresponding to the command machining point when the first position O1, which is an invariant specific position, is used as a reference.

(4. Effects of the embodiment)
The thermal displacement correction device 20 sets a first thermal displacement amount Z1 in the Z-axis direction corresponding to each machining point for the entire machining area with the first position O1 in the Z-axis direction of the machine tool 10 as a reference. The Z axis corresponding to each machining point for the entire machining area range with reference to the displacement amount setting unit 23 and the second positions O2a to O2d located between the maximum value and the minimum value of the set first thermal displacement amount Z1. A second thermal displacement amount setting unit 24 for setting a second thermal displacement amount Z2 with respect to, an origin shift amount storage unit 25 for storing origin shift amounts ΔZa to ΔZd from the first position O1 to the second positions O2a to O2d, During machining of the workpiece W by the machine tool 10, the command machining point acquisition unit 26 that acquires the command machining point in the Z-axis direction, the command machining point, and the second set by the second thermal displacement amount setting unit 24. Based on thermal displacement Z2, command machining point A correction value acquisition unit 27 that acquires the second thermal displacement amount Z2 corresponding to the correction value as a correction value, and a correction unit 28 that corrects the command value in the Z-axis direction based on the acquired correction value and origin shift amounts ΔZa to ΔZd, Is provided.

  During machining, the correction value for the command value corresponds to the command machining point in the second thermal displacement amount Z2. The second thermal displacement amount Z2 is based on the second positions O2a to O2d located between the maximum value and the minimum value of the first thermal displacement amount Z1. That is, the maximum value of the second thermal displacement amount Z2 is equal to or less than the difference between the maximum value and the minimum value of the first thermal displacement amount Z1. Therefore, the number of bits of the data type (integer type) of the correction value is sufficient according to the maximum value of the second thermal displacement amount Z2. As described above, the number of bits of the data type of the correction value can be reduced, and the time required for acquiring the correction value can be shortened. Therefore, the thermal displacement correction can be reliably performed for the entire range. That is, the effect of thermal displacement correction can be obtained with certainty.

  The thermal displacement correction device 20 calculates the amount of thermal displacement of the structure by performing a structural analysis based on the temperature sensor 21 arranged at a predetermined part of the structure of the machine tool 10 and the temperature information of the temperature sensor 21. And an analyzing unit 22 for performing the processing. Then, the first thermal displacement amount setting unit 23 sets the first thermal displacement amount Z1 based on the thermal displacement amount of the structure obtained by the analysis unit 22.

  That is, each time the structural analysis is performed by the analysis unit 22, the first thermal displacement amount Z1 is calculated. Accordingly, the maximum value and the minimum value of the first thermal displacement amount Z1 change. Here, the second thermal displacement amount setting unit 24 calculates the second thermal displacement amount Z2 based on the first thermal displacement amount Z1. Therefore, the second thermal displacement amount Z2 and the origin shift amounts ΔZa to ΔZd change according to the change in the maximum value and the minimum value of the first thermal displacement amount Z1. That is, the number of bits of the data type of the correction value can be reduced by appropriately changing the second positions O2a to O2d according to the analysis result.

  Further, the analysis unit 22, the first thermal displacement amount setting unit 23, and the second thermal displacement amount setting unit 24 are executed during machining by the machine tool 10. By sequentially changing the second positions O2a to O2d during processing according to the obtained first thermal displacement amount Z1, the number of bits of the data type of the correction value can always be made small. Therefore, the correction value calculation process can be performed in a short time.

  Further, as shown in the first example, the second position O2a is an intermediate value between the maximum value and the minimum value of the first thermal displacement amount Z1. In this case, the number of bits of the data type of the correction value can be surely reduced. As shown in the second example, the second position O2b is a predetermined representative position Pb among the maximum value and the minimum value of the first thermal displacement amount Z1. Also in this case, the number of bits of the data type of the correction value can be surely reduced.

  Moreover, as shown in the third example, the second position O2c is located between the maximum value and the minimum value of the first thermal displacement amount Z1 in the machining range of the workpiece W in the Z-axis direction. Compared to the first and second examples, the number of bits of the data type of the correction value actually used can be reduced. Further, as shown in the fourth example, the second position O2d is an intermediate value between the maximum value and the minimum value of the first thermal displacement amount Z1 in the machining range of the workpiece W in the Z-axis direction. In this case, as in the third example, the number of bits of the data type of the correction value actually used can be reduced.

  Further, the thermal displacement correction device 20 displays the thermal displacement amount corresponding to the command machining point when the invariant specific position (for example, the first position O1) is used as a reference. Here, in the correction value calculation process, the second thermal displacement amount Z2 based on the changing second positions O2a to O2d is used. On the other hand, the amount of thermal displacement displayed on the display unit 29 is a value based on an invariable specific position. By setting the thermal displacement amount displayed on the display unit 29 as a value based on the specific position where the thermal displacement is unchanged, the operator can surely understand how the thermal displacement amount is changed during processing.

10: Machine tool, 20: Thermal displacement correction device, 21: Temperature sensor, 22: Analysis unit, 23: First thermal displacement amount setting unit, 24: Second thermal displacement amount setting unit, 25: Origin shift amount storage unit, 26: command machining point acquisition unit, 27: correction value acquisition unit, 28: correction unit, 29: display unit, O1: first position, O2, O2a-O2d: second position, P: lattice point, Pb, Pd: Representative position, W: Workpiece, Z1: First thermal displacement, Z2: Second thermal displacement, ΔZa-ΔZd: Origin shift

Claims (8)

A first thermal displacement amount setting unit configured to set the first thermal displacement amount in the predetermined axis direction according to each machining point with respect to the entire machining region with respect to the first position in the predetermined axis direction of the machine tool;
Based on the second position located between the set maximum value and minimum value of the first thermal displacement amount, the second thermal displacement amount with respect to the predetermined axis corresponding to each processing point is set for the entire processing region range. A second thermal displacement amount setting unit to perform,
An origin shift amount storage unit for storing an origin shift amount from the first position to the second position;
A command machining point acquisition unit that acquires a command machining point in the predetermined axis direction during machining of a workpiece by the machine tool;
A correction value for acquiring the second thermal displacement amount corresponding to the command processing point as a correction value based on the command processing point and the second thermal displacement amount set by the second thermal displacement amount setting unit. An acquisition unit;
A correction unit that corrects the command value in the predetermined axis direction based on the acquired correction value and the origin shift amount;
A thermal displacement correction device comprising: The thermal displacement correction device is
A temperature sensor disposed at a predetermined part of the structure of the machine tool;
An analysis unit that calculates a thermal displacement amount of the structure by performing a structure analysis based on temperature information of the temperature sensor;
With
The thermal displacement correction device according to claim 1, wherein the first thermal displacement amount setting unit sets the first thermal displacement amount based on a thermal displacement amount of the structure obtained by the analysis unit.   The thermal displacement correction device according to claim 2, wherein the analysis unit, the first thermal displacement amount setting unit, and the second thermal displacement amount setting unit are executed during processing by the machine tool.   The thermal displacement correction device according to any one of claims 1 to 3, wherein the second position is an intermediate value between a maximum value and a minimum value of the first thermal displacement amount.   4. The thermal displacement correction device according to claim 1, wherein the second position is a predetermined representative position between a maximum value and a minimum value of the first thermal displacement amount.   The second position according to any one of claims 1 to 3, wherein the second position is located between a maximum value and a minimum value of the first thermal displacement amount in a machining range of the workpiece in the predetermined axial direction. Thermal displacement correction device.   The thermal displacement correction device according to claim 6, wherein the second position is an intermediate value between the maximum value and the minimum value of the first thermal displacement amount in the machining range of the workpiece in the predetermined axis direction.   The said thermal displacement correction | amendment apparatus is a thermal displacement correction | amendment apparatus of Claim 3 which displays the thermal displacement amount corresponding to the said instruction | indication process point, when an invariable specific position is made into a reference | standard.

Images