Machine tool

Abstract

To provide a machine tool which can enhance accuracy of a thermal displacement correction amount.SOLUTION: A machine tool includes: a temperature detection part; a slide 44; a slide movement mechanism for moving the slide 44; a slide position detection part 47; a memory for storing a position of the slide 44 when contact of the slide 44 is detected by the slide position detection part 47 when thermal displacement in a reference state, as a reference position; a deviation amount acquisition part for acquiring a difference between a reference position and a detection position as a deviation amount in a state where the thermal displacement occurs; a position correction coefficient acquisition part for acquiring a position correction coefficient according to the position of the slide 44; a temperature correction coefficient acquisition part for acquiring a temperature correction coefficient according to the detected temperature; a thermal displacement acquisition part for acquiring a thermal displacement correction amount on the basis of the deviation amount, the position correction coefficient and the temperature correction coefficient; and a processing part for processing workpiece by moving the slide 44 with addition of the thermal displacement correction amount.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a machine tool. [Background technology]

[0002] For example, the machine tool described in Patent Document 1 is equipped with a touch switch that measures the position of a slide part that moves due to the rotation of a ball screw, and determines the amount of thermal displacement from the difference between the previously measured position of the slide part (reference position) and the position of the slide part measured before machining the workpiece, and calculates a correction amount based on this amount of thermal displacement. Furthermore, for example, the thermal displacement compensation method described in Patent Document 2 calculates the amount of thermal displacement of components constituting the machine tool using temperature changes detected by a temperature sensor, and compensates for the thermal displacement of the components constituting the machine tool based on the calculated amount of thermal displacement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5883264 [Patent Document 2] Japanese Patent Application Publication No. 3-79256 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration described in the above Patent Document 1, the amount of correction is determined according to the amount of thermal displacement of the ball screw, so the thermal displacement of the entire machine tool cannot be taken into account in the amount of correction. Furthermore, in the configuration described in Patent Document 2, the amount of thermal change is calculated indirectly in response to a temperature change, so the actual amount of thermal change cannot be directly taken into account in the amount of correction. Therefore, in the configurations of Patent Documents 1 and 2, there is room for improvement in the accuracy of the amount of correction of thermal displacement.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a machine tool that can improve the accuracy of the amount of thermal displacement compensation. [Means for solving the problem]

[0006] In order to achieve the above object, the machine tool according to the present invention comprises: A machine tool for machining a workpiece, a slide position detection unit that detects approach or contact of the slide; a memory that stores, as a reference position, a position of the slide when the slide position detection unit detects the approach or contact of the slide in a reference state of thermal displacement; a deviation amount acquisition unit that acquires, as a deviation amount, a difference between the reference position and a detection position at which the slide position detection unit detects the approach or contact of the slide in a state in which thermal displacement has occurred relative to the reference state; a position correction coefficient acquisition unit that acquires a position correction coefficient according to the position of the slide; a temperature correction coefficient acquisition unit that acquires a temperature correction coefficient according to the temperature detected by the temperature detection unit; a thermal displacement correction amount acquisition unit that acquires a thermal displacement correction amount based on the acquired deviation amount, the position correction coefficient, and the temperature correction coefficient; and a processing unit that processes the workpiece by moving the slide relative to the workpiece via the moving mechanism while taking into account the acquired thermal displacement correction amount. The temperature correction coefficient is set so that the higher the temperature detected by the temperature detection unit, the larger the amount of movement of the slide by the processing unit. do. Effect of the Invention

[0007] According to the present invention, the accuracy of the thermal displacement compensation amount can be improved in a machine tool. [Brief description of the drawings]

[0008] [Figure 1] 1 is a front view of a machine tool according to an embodiment of the present invention; [Diagram 2] 1 is a plan view of a machine tool in a state where a tool unit according to an embodiment of the present invention is omitted; [Diagram 3]1 is a side view of a machine tool according to an embodiment of the present invention; [Figure 4] 1 is a partial side view of a machine tool according to an embodiment of the present invention; [Diagram 5] 1 is a schematic diagram illustrating a state in which a detected portion of a slide according to an embodiment of the present invention is located at the origin of a machine coordinate system. FIG. [Figure 6] 4 is a flowchart showing a procedure of a processing process according to an embodiment of the present invention. [Figure 7] 10 is a flowchart showing a procedure for a deviation amount acquisition process according to an embodiment of the present invention. [Figure 8] FIG. 11 is a diagram showing a temperature range for a reference temperature and an upper limit set temperature according to an embodiment of the present invention. [Figure 9] 5 is a diagram showing the positional relationship in the X-axis direction of the origin of the machine coordinate system, a detection position, a reference position, and a stroke end according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a machine tool according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the machine tool 1, which is a lathe, includes a bed S which is a base for the entire machine tool 1, a spindle unit 10 having a spindle 11, a slide movement mechanism 40, a tool unit 50, a temperature detection unit 80, and a control unit 300. In the following, the axial direction along the rotation axis of spindle 11 is defined as the Z-axis direction, and as shown in FIG. 3, the direction extending obliquely with respect to the height direction (the up and down direction in FIG. 3) perpendicular to the Z-axis direction is defined as the X-axis direction.

[0010] 1, the spindle unit 10 includes a spindle 11 that rotates while gripping a workpiece W, and a headstock 12 that rotatably supports the spindle 11. A workpiece rotating motor (not shown) that rotates the spindle 11 is built into the headstock 12. The spindle unit 10 is configured to be immovable relative to the bed S.

[0011] As shown in FIG. 1, the tool unit 50 machines a workpiece W held by a spindle 11. The tool unit 50 includes a tool holding portion 51 that holds a tool 70, and a support portion 52 that rotatably supports the tool holding portion 51. The tool holding portion 51 is a turret, and is formed so as to be capable of holding various tools including a tool 70 which is a cutting tool, arranged on the outer periphery. The support portion 52 supports the tool holding portion 51 rotatably about a rotation axis 51C extending along the Z-axis direction. A work rotation motor (not shown) that rotates the tool holding portion 51 is built into the support portion 52.

[0012] The slide movement mechanism 40 includes an X movement mechanism 40X that moves the tool unit 50 in the X-axis direction, and a Z movement mechanism 40Z that moves the tool unit 50 in the Z-axis direction. As shown in FIG. 4, the X-movement mechanism 40X includes a drive unit 41, a ball screw 42, a nut 43, a slide 44, a slide base 45, rotation support units 46a and 46b, a coupling unit 46c, a slide position detection unit 47, an air blower 48, and a holding member 49.

[0013] The driving unit 41 is a motor, and rotates the ball screw 42 to move the slide 44 in the X-axis direction. The output shaft 41a of the driving unit 41 is connected to a first end E1 of the ball screw 42, which is the end farthest from the main shaft 11 (see FIG. 3), via a coupling unit 46c. The coupling unit 46c is a joint that transmits the rotation of the output shaft 41a to the ball screw 42 and absorbs the elongation of the ball screw 42. The coupling unit 46c has an elastic member that elastically deforms in response to the elongation of the ball screw 42, such as a leaf spring (not shown). The ball screw 42 extends along the X-axis direction, and is supported by the slide base 45 via rotation support portions 46a and 46b so as to be rotatable about its axis. The nut 43 is fitted onto the outer periphery of the ball screw 42 so as to be movable along the ball screw 42 as the ball screw 42 rotates about its axis. The slide 44 is fixed to the nut 43 and is formed to be movable along the X-axis direction together with the nut 43. A support portion 52 of the tool unit 50 is fixed to the slide 44. The slide 44 includes a detection target portion 44a formed in a columnar shape on a side surface facing the slide position detection portion 47 and capable of coming into contact with the slide position detection portion 47. The slide 44 and the tool unit 50 move in the X-axis direction in response to thermal displacement of the ball screw 42.

[0014] The rotation support parts 46a and 46b are housed in the slide base 45 and rotatably support both ends of the ball screw 42. The rotation support part 46a has a bearing provided around the second end E2, which is one of the ends of the ball screw 42 and is closer to the main shaft 11 (see FIG. 3). The rotation support part 46b has a bearing provided around the first end E1 of the ball screw 42, which is farther from the main shaft 11. The rotation support part 46b is fixed to the slide base 45 so as not to be displaced even if the first end E1 of the ball screw 42 extends. The first end E1 of the ball screw 42 is provided at a position farther from the bed S (see FIG. 3) than the second end E2 of the ball screw 42. The rotation support portion 46a restricts the expansion of the ball screw 42 in the X-axis direction. The coupling portion 46c absorbs the expansion of the ball screw 42 in the X-axis direction. As a result, the ball screw 42 expands toward the drive portion 41 due to a temperature rise, as shown by the arrow J1 in Fig. 4. Therefore, the displacement of the first end E1 of the ball screw 42 in the X-axis direction due to a temperature rise is larger than the displacement of the second end E2 in the X-axis direction.

[0015] As shown in Fig. 4, the holding member 49 is fixed to the upper part of the rotation support part 46b, and holds the slide position detection part 47 and the air blower 48. The holding member 49 does not displace regardless of thermal displacement of the ball screw 42 due to a rise in temperature. As shown in Fig. 5, the holding member 49 has a recess 49a formed in a portion corresponding to the slide position detection part 47 in order to facilitate the installation work of the slide position detection part 47. The recess 49a is formed so as to face the detection part 44a of the slide 44.

[0016] The slide position detection unit 47 is a touch switch in this example. The slide position detection unit 47 outputs a detection signal that detects the contact of the slide 44 to the control unit 300 (see FIG. 1). As shown in FIG. 4, the slide position detection unit 47 is located radially outward of the first end E1 of the ball screw 42, in the upward direction in this example. As shown in FIG. 5, the slide position detection unit 47 includes a rod-shaped contact detection member 47a, and detects the contact of the slide 44 when the detected portion 44a comes into contact with the tip of the contact detection member 47a. The air blower 48 supplies air to blow away foreign matter such as chips between the slide position detection unit 47 and the detection target unit 44a of the slide 44. As shown in Fig. 4, the air blower 48 is located radially outward of the slide position detection unit 47 from the first end E1 of the ball screw 42, or upward in this example.

[0017] 1 and 2, the Z movement mechanism 40Z includes a drive unit 40Z1, a ball screw 40Z2, a nut 40Z3, a rotation support unit 40Z5, and a slide 40Z4, similar to the X movement mechanism 40X. The Z movement mechanism 40Z further includes a pair of rails 40Z6 into which the slide 40Z4 is fitted so as to be slidable in the Z-axis direction. The pair of rails 40Z6 extend along the Z-axis direction and are arranged in parallel. Note that in FIG. 2, the tool unit 50 is omitted, and only the portion of the slide 40Z4 that fits into the rails 40Z6 is shown. The ball screw 40Z2 extends along the Z-axis direction. The X-movement mechanism 40X is mounted on the slide 40Z4. When the driving unit 40Z1 rotates the ball screw 40Z2 about its axis, the nut 40Z3 moves in the Z-axis direction together with the slide 40Z4 and the X-movement mechanism 40X.

[0018] 2, the temperature detection unit 80 detects the temperature of the machine tool 1 and outputs the detection result to the control unit 300. In this example, the temperature detection unit 80 is fixed to the bed S. More specifically, the temperature detection unit 80 is provided on the upper surface of the bed S at a position facing the tool unit 50 in the height direction.

[0019] As shown in FIG. 1, a control unit 300 controls the spindle unit 10, the slide movement mechanism 40, and the tool unit 50. The control unit 300 includes, for example, a CPU (Central Processing Unit) (not shown) and a memory 301 such as a ROM (Read Only Memory) that stores a program (for example, processing described later) that defines the procedure of processing by the CPU. In addition to the program, the memory 301 stores data relating to the reference position P1, position correction coefficients A1 to A8, and equation (1) for calculating the temperature correction coefficient B, which will be described later, and the like.

[0020] 5, reference position P1 indicates the position of slide 44 at which contact of slide 44 is detected by slide position detection unit 47 in a reference state in which there is no thermal displacement in machine tool 1, in mechanical coordinates in the X-axis direction. This reference state refers to, for example, a state in which machine tool 1 reaches a thermal equilibrium state after the operation of machine tool 1 has stopped.

[0021] A method for setting the reference position P1 will be described. This setting operation may be performed by an operator and an operation by the operator, or may be performed automatically by the control unit 300, for example. First, in a reference state in which there is no thermal displacement in the machine tool 1, particularly the ball screw 42, the control unit 300 moves the slide 44 (more precisely, the detected portion 44a, the same applies below) to the origin P0 of the machine coordinate system in the X-axis direction, as shown in Fig. 5, via the slide moving mechanism 40. The origin P0 of the machine coordinate system is a position that does not reach the stroke end Pz of the slide 44. Then, the slide position detection unit 47 is placed near the detection target portion 44a. For example, the slide position detection unit 47 is placed at a distance of about 1 mm in the X-axis direction from the detection target portion 44a. Next, the control unit 300 supplies air to the gap between the slide position detection unit 47 and the detection target unit 44a via the air blower 48, and then moves the slide 44 toward the slide position detection unit 47 via the slide movement mechanism 40. At this time, the movement speed of the slide 44 is slower than that during processing (for example, during the processing of step S107 described later), and the maximum movement distance of the slide 44 is, for example, 2 mm. Then, when the control unit 300 receives a detection signal from the slide position detection unit 47 detecting that the slide 44 has come into contact, it stops the supply of air from the air blower 48 and the movement of the slide 44, and stores the mechanical coordinates of the slide 44 at this time in the memory 301 as a reference position P1. As shown in FIG. 9, the reference position P1 is located between the mechanical coordinate origin P0 and the stroke end Pz in the X-axis direction. Note that, when the control unit 300 does not receive a detection signal from the slide position detection unit 47, it notifies the operator that an error has occurred. Finally, the control unit 300 returns the slide 44 to the mechanical coordinate origin P0. This completes the setting of the reference position P1.

[0022] As shown in FIG. 1, the control unit 300 includes, as functional blocks, a deviation amount acquisition unit 302, a position correction coefficient acquisition unit 303, a temperature correction coefficient acquisition unit 304, a thermal displacement correction amount acquisition unit 305, and a processing unit 306. The operation of each functional block will be described below, along with the processing executed by the control unit 300, with reference to the flowchart in Fig. 6. The control unit 300 executes this processing in accordance with an NC (Numerical Control) program registered in the memory 301.

[0023] First, the control unit 300 moves the slide 44 to the mechanical coordinate origin P0 via the slide moving mechanism 40 (S101). Note that the process of step S101 may be executed at the beginning of the deviation amount acquisition process described later. Furthermore, the control unit 300 selects one of the tools 70 held by the tool holding unit 51, and performs offset correction to correct the offset amount according to the selected tool 70 (S102). This offset correction is a position correction of the slide 44 according to the shape of the tool 70, the attachment position of the tool 70, or the like. The above steps S101 and S102 may be executed in the reverse order, or may be executed simultaneously.

[0024] Next, the deviation amount acquiring unit 302 acquires the deviation amount ΔF from the difference between the reference position P1 stored in advance in the memory 301 and the detection position P2 at which the slide position detecting unit 47 detects the contact of the slide 44 (S103).

[0025] The deviation amount acquisition process in step S103 will be described with reference to the sub-flowchart of FIG. First, with the slide 44 positioned at the origin P0 of the machine coordinate system, the control unit 300 supplies air to the gap between the slide position detection unit 47 and the detection target unit 44a via the air blower 48 (S103a). This air blows away foreign matter such as cutting chips, thereby improving the detection accuracy of the slide position detection unit 47.

[0026] Then, the deviation amount acquisition unit 302 moves the slide 44 from the mechanical coordinate origin P0 toward the slide position detection unit 47 via the slide moving mechanism 40 (S103b). At this time, the moving speed of the slide 44 is slower than that during processing (e.g., during the processing of step S107 described later), and the maximum moving distance of the slide 44 is, for example, 2 mm. When the deviation amount acquisition unit 302 receives a detection signal from the slide position detection unit 47 that detects the contact of the slide 44, it stops the movement of the slide 44 and acquires the mechanical coordinates of the slide 44 at this time as the detection position P2 (S103c). Then, the deviation amount acquisition unit 302 acquires the deviation amount ΔF from the difference (P1-P2) in the distance in the X-axis direction between the reference position P1 and the detection position P2, and stores the acquired deviation amount ΔF in the memory 301 (S103d). Next, the control unit 300 stops the supply of air via the air blower 48 (S103e) and returns the slide 44 to the mechanical coordinate origin P0 via the slide movement mechanism 40 (S103f). With the above, the deviation amount acquisition process ends, and the process proceeds to step S104 in FIG. 6. Note that, when the deviation amount acquisition unit 302 does not receive a detection signal from the slide position detection unit 47 in the above step S103c, it notifies the operator that an error has occurred. Here, the reference position P1 is a position where the slide 44 contacts the slide position detection unit 47 in a reference state where there is no thermal displacement, and in this reference state, the reference position P1 and the detection position P2 coincide with each other. On the other hand, when thermal displacement occurs with respect to this reference state, the ball screw 42 extends in the X-axis direction as shown by the arrow J1 in FIG. 4. In this way, when thermal displacement occurs in the ball screw 42, the slide 44 approaches the slide position detection unit 47, and as a result, the detection position P2 deviates from the reference position P1 to approach the origin P0 of the machine coordinates as shown in FIG. 9. Also, as the amount of thermal displacement of the ball screw 42 increases, the detection position P2 moves away from the reference position P1, and the deviation amount ΔF increases.

[0027] Next, the position correction coefficient acquisition unit 303 acquires a position correction coefficient Ax corresponding to the position of the slide 44 in the X-axis direction, which is the tool cutting direction, during machining from among the multiple position correction coefficients A1 to A8 stored in the memory 301 (S104). The position correction coefficient Ax is any one position correction coefficient selected from the multiple position correction coefficients A1 to A8 stored in advance in the memory 301. In addition, in this step S104, the position correction coefficient acquisition unit 303 recognizes the position of the slide 44 during machining based on a command related to the machining diameter of the workpiece W included in the NC program.

[0028] 4, the position correction coefficients A1 to A8 are set to different values ​​depending on the position of the slide 44 on the ball screw 42. Since the elongation of the first end E1 of the ball screw 42 is absorbed, the closer the position of the slide 44 is to the first end E1 of the ball screw 42, the greater the effect of thermal displacement on the position of the slide 44. For this reason, the position correction coefficients A1 to A8 are set to values ​​less than or equal to 1, and larger as the position of the slide 44 approaches the first end E1 of the ball screw 42.

[0029] In this example, the eight position correction coefficients A1 to A8 are assigned to eight regions C1 to C8 divided in the axial direction of the ball screw 42. The position correction coefficients A1 to A8 are set for the regions C1 to C8 such that the position correction coefficients increase by 0.1 as they approach the first end E1 of the ball screw 42. Of the regions C1 to C8, the region C8 closest to the first end E1 of the ball screw 42 is assigned a position correction coefficient A8 of 0.8. Of the regions C1 to C8, the region C1 closest to the second end E2 of the ball screw 42 is assigned a position correction coefficient A1 of 0.1. In step S104, the position correction coefficient acquisition unit 303 acquires one of the position correction coefficients A1 to A8 as the position correction coefficient Ax according to the region C1 to C8 in which the slide 44 is located.

[0030] Next, the temperature correction coefficient acquisition unit 304 acquires the temperature correction coefficient B based on the temperature detected by the temperature detection unit 80 (S105). Temperature correction coefficient B is a value that is set to keep the cutting edge position of tool 70 constant regardless of temperature changes based on the correlation between temperature changes in machine tool 1 and the cutting edge position of tool 70, and is set so that its value increases as the temperature detected by temperature detection unit 80 increases. For example, temperature correction coefficient B can be calculated from the following formula (1). B={Δx-Δz(n-0.125)} / 0.125*Δz···(1) B: Temperature correction coefficient Δx: Difference between reference temperature K and current temperature G Δz: Difference between reference temperature K and upper limit temperature H n: Temperature range (n=0.125, 0.25, . . . , 0.875, 1) The reference temperature K is set in advance based on the temperature around the machine tool 1. Upper limit set temperature H is set based on the upper limit of the temperature at which the temperature saturates (becomes constant after rising) in the environment in which machine tool 1 is operated. The current temperature G is the temperature detected by the temperature detection unit 80. 8, temperature section n is set to a value between 0.125 and 1 according to the temperature range I1 to I8 to which the current temperature G belongs, with the value being set smaller as the temperature range I1 approaches the higher temperature side. Temperature range I1 is set to temperatures equal to or lower than a reference temperature K, and temperature ranges I2 to I8 are set at equal temperature intervals between the reference temperature K and an upper limit set temperature H.

[0031] In the above step S105, the temperature correction coefficient acquisition unit 304 acquires the temperature section n corresponding to the temperature range I1 to I8 to which the current temperature G detected by the temperature detection unit 80 belongs, and acquires the temperature correction coefficient B from the above formula (1) using this current temperature G and the temperature section n. The temperature ranges I1 to I8 and the number of temperature divisions n can be changed as appropriate.

[0032] The following describes an example of how to obtain the temperature correction coefficient B. Each value is set, for example, as follows. Standard temperature K: 20℃ Current temperature G:25℃ Upper limit setting temperature H: 30℃ Δx(=GK):25℃-20℃=5℃ Δz(=HK): 30℃-20℃=10℃ For each temperature range I2 to I8 [Δz / (total number of divisions - 1)]: [10℃ / (8-1)] = 1.43℃ Temperature classification n:0.5 In the above example, when the temperature correction coefficient B is calculated using the above formula (1), the temperature correction coefficient B becomes 1.

[0033] Next, as shown in FIG. 6, the thermal displacement correction amount acquisition unit 305 multiplies the acquired deviation amount ΔF by a temperature correction coefficient B and a position correction coefficient Ax to acquire a thermal displacement correction amount (S106). Then, the processing unit 306 processes the workpiece W while moving the slide 44 via the slide moving mechanism 40, taking into account the acquired thermal displacement compensation amount (S107), and ends this processing. For example, in step S107, while the workpiece W gripped by the spindle 11 is rotated together with the spindle 11, the processing unit 306 moves the tool 70 together with the slide 44 in the X-axis direction via the X-movement mechanism 40X while taking into account the thermal displacement compensation amount to set the cutting amount into the workpiece W, and then sends the tool 70 together with the slide 44 in the Z-axis direction relative to the workpiece W via the Z-movement mechanism 40Z. Thereby, the outer diameter of the workpiece W is cut. The thermal change amount acquisition process in the above-mentioned steps S103 to S106 may be performed every time one workpiece W is machined, every time multiple workpieces W are machined, or every time a preset set time elapses. In addition, this thermal change amount acquisition process may be executed independently as a program separate from the processing of the workpiece W in step S107.

[0034] (effect) According to the embodiment described above, the following effects are achieved. (1) Machine tool 1 includes a temperature detection unit 80 that detects the temperature of machine tool 1, a slide 44 that is formed to be movable relative to workpiece W, a slide movement mechanism 40 that is an example of a movement mechanism that moves slide 44 together with tool 70 relative to workpiece W, a slide position detection unit 47 that detects contact of slide 44, a memory 301 that stores, as a reference position P1, the position of slide 44 when contact of slide 44 is detected by slide position detection unit 47 in a reference state, and a memory 302 that stores, as a reference position P1, the position of slide 44 when contact of slide 44 is detected by slide position detection unit 47 in a reference state. the position correction coefficient acquisition unit 303 acquiring a position correction coefficient Ax according to the position of the slide 44; a temperature correction coefficient acquisition unit 304 acquiring a temperature correction coefficient B according to the temperature detected by the temperature detection unit 80; a thermal displacement correction amount acquisition unit 305 acquiring a thermal displacement correction amount based on the acquired deviation amount ΔF, position correction coefficient Ax, and temperature correction coefficient B; and a processing unit 306 processing the workpiece W by moving the slide 44 via the slide moving mechanism 40 while taking into account the acquired thermal displacement correction amount. According to this configuration, the thermal displacement correction amount is more accurate because it is acquired based on the deviation amount ΔF, the position correction coefficient Ax, and the temperature correction coefficient B. Therefore, the workpiece W can be machined with high accuracy.

[0035] (2) The slide moving mechanism 40 includes a ball screw 42 extending along the moving direction (for example, the X-axis direction) of the slide 44, a coupling portion 46c which is an example of an absorbing portion that absorbs the elongation of a first end E1 of the ball screw 42, a rotation support portion 46a which is an example of a restricting portion that restricts the elongation of a second end E2 of the ball screw, a nut 43 fitted onto the outer periphery of the ball screw 42, and a drive portion 41 which moves the slide 44 together with the nut 43 by rotating the ball screw 42. The position correction coefficient acquisition portion 303 applies stronger position correction by increasing the value of the acquired position correction coefficient Ax as the position of the slide 44 when machining the workpiece W becomes closer to the first end E1. According to this configuration, the extension direction of the ball screw 42 is defined, so that the degree of the effect of thermal displacement according to the position of the slide 44 relative to the ball screw 42 becomes clear, and it is possible to realize a position correction coefficient Ax suitable for the effect of thermal displacement. Therefore, it is possible to improve the amount of thermal displacement correction, and therefore the machining accuracy.

[0036] (3) The machine tool 1 includes a spindle 11 that rotates while gripping a workpiece W, and a tool unit 50 that has a tool 70 and moves together with a slide 44. The slide movement mechanism 40 moves the slide 44 in an X-axis direction that intersects with the rotation axis of the workpiece W gripped by the spindle 11. The reference position P1 is located at a first end E1 of a ball screw 42 that extends along the X-axis direction and is far from the spindle 11, i.e., corresponds to the stroke end of the slide 44. According to this configuration, the reference position P1 is the position that is most affected by the thermal displacement in the ball screw 42. Therefore, it is possible to reliably obtain the deviation amount ΔF associated with even slight thermal displacement, and it is possible to improve the thermal displacement correction amount and, ultimately, the machining accuracy.

[0037] The present disclosure is not limited to the above-described embodiments and drawings. Modifications (including deletion of components) can be made as appropriate within the scope of the present disclosure. An example of a modification will be described below.

[0038] (Modification) Although the slide position detection unit 47 in the above embodiment is a touch switch, it may be a non-contact sensor of various types that detects the approach of the slide 44. For example, if this non-contact sensor can measure the distance to the slide 44, the control unit 300 can obtain the deviation amount ΔF without actually moving the slide 44 from the mechanical coordinate origin P0 to the detection position P2. The air blower 48 in the above embodiment can be omitted.

[0039] In the above embodiment, the temperature detection unit 80 is provided on the bed S, but the installation position of the temperature detection unit 80 is not limited thereto. For example, as shown by the dashed line in Fig. 4, the temperature detection unit 180 may be provided, for example, in the vicinity of the ball screw 42, for example, in the slide base 45 or the rotation support unit 46a in the vicinity of the second end E2 of the ball screw 42. Also, for example, as shown by the dashed line in Fig. 4, the temperature detection unit 280 may be provided in the tool unit 50. Furthermore, for example, as shown by the dashed line in Fig. 2, the temperature detection unit 380 may be provided in a portion supporting the end of the Z movement mechanism 40Z, for example, the ball screw 40Z2.

[0040] In the above embodiment, the control unit 300 performs thermal displacement correction for the movement of the slide 44 in the X-axis direction, but this is not limiting, and thermal displacement correction may be performed for the movement of the slide 44 in the Z-axis direction. This is particularly useful when the tool 70 is a drill or the like that cuts in the Z-axis direction. In this case, the control unit 300 may obtain the temperature correction coefficient B based on the temperature detected by the temperature detection unit 380. Furthermore, the control unit 300 may obtain the temperature correction coefficient B based on a plurality of temperatures detected by the temperature detection units 80, 180, 280, and 380.

[0041] In the above embodiment, the X-axis direction is set obliquely with respect to the height direction (the up-down direction in FIG. 3), but the present invention is not limited thereto, and the X-axis direction may be set in a direction perpendicular to the height direction, and the Y-axis direction may be set in the height direction. In this case, machine tool 1 may include a Y-moving mechanism that moves slide 44 in the Y-axis direction, in addition to X-moving mechanism 40X and Z-moving mechanism 40Z. The Y-moving mechanism may be composed of a drive unit, a ball screw, a nut, and the like, similar to X-moving mechanism 40X and Z-moving mechanism 40Z. In this case, control unit 300 may perform thermal displacement correction for the movement of slide 44 in the Y-axis direction.

[0042] The control unit 300 may also perform thermal displacement correction on the headstock 12 of the spindle unit 10 that is configured to be immovable relative to the bed S. Furthermore, the spindle unit 10 may be configured to be movable relative to the bed S. In this case, for example, the machine tool 1 includes a spindle movement mechanism that moves the spindle unit 10. This spindle movement mechanism may be composed of a drive unit, a ball screw, a nut, a slide, and the like, similar to the X-movement mechanism 40X and the Z-movement mechanism 40Z. The control unit 300 may also perform thermal displacement correction for the movement of the headstock 12 of the spindle unit 10.

[0043] In the above embodiment, the number of position correction coefficients A1 to A8 stored in the memory 301 is eight, but it may be a number other than eight. In addition, the position correction coefficient Ax may be calculated by a formula in which the position of the slide 44 is multiplied by a proportionality coefficient.

[0044] In the above embodiment, the temperature correction coefficient B was calculated from the above formula (1), but this is not limited to this and can be modified as appropriate as long as the formula is such that the value of the temperature correction coefficient B increases as the temperature detected by the temperature detection unit 80 increases. Furthermore, the temperature correction coefficient B may be acquired from the temperature detected by the temperature detection unit 80 by referring to a pre-stored data table.

[0045] In the above embodiment, the control unit 300 acquires both the temperature correction coefficient B and the position correction coefficient Ax in the processing, but it may acquire either the temperature correction coefficient B or the position correction coefficient Ax and multiply only this one by the deviation amount ΔF. In addition, in the above embodiment, the elongation of the first end E1 of the ball screw 42 is absorbed and the elongation of the second end E2 of the ball screw 42 is restricted, but conversely, the elongation of the second end E2 of the ball screw 42 may be absorbed and the elongation of the first end E1 of the ball screw 42 may be restricted. In this case, the position correction coefficient acquisition unit 303 decreases the value of the acquired position correction coefficient Ax as the position of the slide 44 when machining the workpiece W becomes closer to the first end E1.

[0046] In the above embodiment, the tool unit 50 has a configuration including a turret, but is not limited to this and may be a tool spindle or a tool rest. Moreover, the tool 70 is not limited to a cutting tool, but may be a drill, an end mill, or the like. In the above embodiment, the machine tool 1 is a lathe, but the machine tool may be various other machine tools such as a machining center and a rolling machine other than a lathe. [Explanation of symbols]

[0047] 1...machine tool, 10...spindle unit, 11...spindle, 12...spindle stock, 40...slide movement mechanism, 40X...X movement mechanism, 40Z...Z movement mechanism, 41, 40Z1...drive unit, 42, 40Z2...ball screw, 44, 40Z4...slide, 40Z6...rail, 41a...output shaft, 43, 40Z3...nut, 44a...detectable part, 45...slide base, 46a, 46b, 40Z5...rotation support part, 46c...coupling part, 47...slide position detection part, 47a...contact detection member, 48...air blow, 49...holding member, 49a...recess, 50... Tool unit, 51...tool holding section, 51C...rotating axis, 52...support section, 70...tool, 80,180,280,380...temperature detection section, 300...control section, 301...memory, 302...deviation amount acquisition section, 303...position correction coefficient acquisition section, 304...temperature correction coefficient acquisition section, 305...thermal displacement correction amount acquisition section, 306...processing section, B...temperature correction coefficient, C1 to C8...area, E1...first end section, E2...second end section, A1 to A8, Ax...position correction coefficient, I1 to I8...temperature range, P1...reference position, P2...detection position, S...bed, W...workpiece, n...temperature category

Claims

1. A machine tool for machining a workpiece, comprising: A temperature detection unit that detects a temperature of the machine tool; A slide formed to be movable relative to the workpiece; a moving mechanism that moves the slide together with the tool relative to the workpiece; a slide position detection unit that detects the approach or contact of the slide; a memory that stores, as a reference position, a position of the slide when the approach or contact of the slide is detected by the slide position detection unit when thermal displacement is in a reference state; a deviation amount acquiring unit that acquires, as a deviation amount, a difference between the reference position and a detection position at which the slide position detecting unit detects the approach or contact of the slide in a state where a thermal displacement occurs with respect to the reference state; a position correction coefficient acquisition unit that acquires a position correction coefficient according to a position of the slide; a temperature correction coefficient acquisition unit that acquires a temperature correction coefficient according to the temperature detected by the temperature detection unit; a thermal displacement correction amount acquisition unit that acquires a thermal displacement correction amount based on the acquired deviation amount, the position correction coefficient, and the temperature correction coefficient; a processing unit that processes the workpiece by moving the slide relative to the workpiece via the moving mechanism while taking into account the acquired thermal displacement correction amount, The temperature correction coefficient is set so that the higher the temperature detected by the temperature detection unit, the larger the amount of movement of the slide by the processing unit. Machine tools.

2. The moving mechanism includes: A ball screw extending along the moving direction of the slide; an absorbing portion that absorbs elongation of a first end portion of the ball screw; a restricting portion that restricts the extension of a second end portion of the ball screw; a nut fitted onto an outer periphery of the ball screw; a drive unit that moves the slide together with the nut by rotating the ball screw, The position correction coefficient acquired by the position correction coefficient acquisition unit is set so that the closer the position of the slide when machining the workpiece is to the first end, the larger the amount by which the machining unit moves the slide. The machine tool according to claim 1.

3. A spindle that rotates while gripping the workpiece; a tool unit having the tool and moving together with the slide, The moving mechanism moves the slide in a direction intersecting a rotation axis of the workpiece gripped by the spindle, The reference position is located corresponding to the first end of the ball screw that is far from the main shaft extending along the intersecting direction.

3. The machine tool according to claim 2.

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