Machine tool and method for setting pressurizing force

Abstract

The machine tool (10) comprises: a pair of center members (20, 21) that support both end portions of the workpiece (W); a pressing device (36) for applying a pressurizing force to the workpiece (W) by making the pair of center members (20, 21) approach each other in the axial direction (CD); a data acquisition device (32) that acquires basic shape data (DA) about the basic shape of the workpiece (W) or buckling flexure shape data (DB) about the buckling flexure shape of the workpiece (W) in a state in which buckling flexure has occurred as a result of the workpiece W being supported by the center members (20, 21); a calculation device (33) for calculating an optimum pressurizing force (FE) on the basis of the basic shape data (DA) or buckling flexure shape data (DB) and a program (37) for calculating the optimum pressurizing force (FE); and a control device (35) that by controlling the pressing device (36), adjusts the pressurizing force applied to the workpiece W on the basis of the optimum value (FE) for the pressurizing force calculated by the calculation device (33).

Description

Machine tool and pressure setting method

[0001] The present invention relates to a machine tool and a pressing force setting method.

[0002] BACKGROUND ART Machine tools have been known in the past that support a workpiece by clamping both ends of the workpiece between a pair of center members, rotate the workpiece around a rotation axis that passes through the center members, and press a processing means against the rotated workpiece to process it.

[0003] For example, Patent Document 1 proposes a pressure-controlling tailstock that has a drive means for adjusting the pressure force of the center member, calculates the grinding resistance from the grinding wheel spindle load, and is equipped with a control means for controlling the drive means so as to change the pressure force of the center member in accordance with the calculated grinding resistance and the pre-stored rigidity of the workpiece.

[0004] Japanese Patent Application Publication No. 10-277932

[0005] However, according to the above technology, the center pressure is controlled based on the "predetermined value (which varies depending on the weight and rigidity of the workpiece to be ground)" described in paragraph

[0023] of Patent Document 1. The pressure to be controlled is set in consideration of the grinding resistance calculated based on the processing conditions, the machine configuration, and the like. Therefore, setting an appropriate pressure requires the experience and skill of a skilled worker, and therefore labor savings are desired.

[0006] Furthermore, for a new workpiece that is different from the workpiece for which the "specified value" was measured, the "specified value" will naturally be different. For this reason, it is conceivable to perform machining on a different workpiece, measure the grinding resistance, and then set a new "specified value." However, re-measuring the grinding resistance anew is cumbersome. For this reason, it is desirable to shorten the time required to set the pressure.

[0007] Furthermore, for a new workpiece whose "prescribed value" is different from that of the workpiece for which it was measured, it is conceivable to select a workpiece whose material, shape, etc. are similar to that of the new workpiece from among workpieces whose "prescribed values" are already known, and control the pressure force based on the "prescribed value" of the selected workpiece. However, when based on the "prescribed value" of a similar workpiece, it is difficult to accurately control the pressure force, and therefore, it is desirable to improve the accuracy of setting the pressure force.

[0008] An object of the present disclosure is to provide a machine tool and a method for setting a pressurizing force on a workpiece that reduce labor, shorten time, and improve setting accuracy when setting the pressurizing force on the workpiece.

[0009] The present disclosure relates to a machine tool (10) including: a pair of center members (20, 21) that sandwich and support both ends of a workpiece (W) in an axial direction (CD) of the workpiece; a pressing device (36) that applies a pressing force to the workpiece by bringing at least one of the pair of center members closer to the other center member in the axial direction; a data acquisition device (32) that acquires basic shape data (DA) related to the basic shape of the workpiece, or buckling deflection shape data (DB) related to the buckling deflection shape of the workpiece in a state in which buckling deflection occurs as a result of the workpiece being supported by the center members; a calculation device (33) that calculates an optimal value of the pressing force based on the basic shape data or the buckling deflection shape data and a program (37) for calculating an optimal value of the pressing force; and a control device (35) that controls the pressing device to adjust the pressing force to be applied to the workpiece based on the optimal value of the pressing force calculated by the calculation device.

[0010] Another aspect of the present disclosure is a pressing force setting method including: a step of supporting both ends of a workpiece (W) by sandwiching them in an axial direction (CD) of the workpiece with a pair of center members (20, 21); a step of applying a pressing force to the workpiece by using a pressing device (36) to move at least one of the pair of center members closer to the other center member in the axial direction; a data acquisition step of acquiring basic shape data (DA) relating to the basic shape of the workpiece, or buckling deflection shape data (DB) relating to the buckling deflection shape of the workpiece in a state in which buckling deflection occurs as a result of the workpiece being supported by the center members; a step of calculating an optimal value of the pressing force based on the basic shape data or the buckling deflection shape data and a program (37) for calculating an optimal value of the pressing force; and a step of adjusting the pressing force to be applied to the workpiece based on the optimal value of the pressing force calculated by a control device (35) controlling the pressing device.

[0011] According to the present disclosure, an appropriate pressure can be calculated based on basic shape data or buckling deflection shape data. This allows the pressure to be set without relying on an expert, thereby saving labor. Furthermore, there is no need to machine a workpiece in advance to determine the conditions for setting the pressure, which reduces the time required to set the pressure. Furthermore, since the pressure is calculated based on basic shape data or buckling deflection shape data related to the workpiece to be machined, the accuracy of setting the pressure can be improved.

[0012] As described above, according to the present disclosure, when setting the pressure force to be applied to a workpiece, it is possible to reduce labor, shorten time, and improve setting accuracy.

[0013] In addition, the symbols in parentheses in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention.

[0014] 1 is a partially cutaway front view showing a machine tool of embodiment 1 and embodiment 2. FIG. 2 is a partially cutaway plan view showing a machine tool of embodiment 1. FIG. 3 is a partially enlarged side view showing a loader arm of embodiment 1. FIG. 4 is a block diagram showing the system configuration of the machine tool of embodiment 1. FIG. 5 is a partially enlarged front view showing a state in which a workpiece is placed on a temporary rest in the machine tool of embodiment 1. FIG. 6 is a partially enlarged front view showing a state in which a headstock side center member and a tailstock side center member are in contact with the workpiece in the machine tool of embodiment 1. FIG. 7 is a partially enlarged front view showing a state in which a workpiece is supported by being clamped between the headstock side center member and the tailstock side center member, and the axis of the workpiece is aligned with the headstock side center member and the tailstock side center member in the machine tool of embodiment 1. FIG. 8 is a partially enlarged front view showing a state in which the workpiece has buckled and deformed downward in the vertical direction due to excessive pressure applied to the workpiece in the machine tool of embodiment 1. 14. A graph showing changes in the distance between the sensor and the workpiece with respect to the pressure force applied to the workpiece. A flowchart showing the operation of the machine tool of embodiment 1. A graph showing changes in the distance between the sensor and the workpiece with respect to the pressure force applied to the workpiece in the machine tool of embodiment 1. A block diagram showing the system configuration of a machine tool of a modified embodiment of embodiment 1. A flowchart showing the operation of the machine tool of a modified embodiment of embodiment 1. A partially enlarged front view showing the operation of the machine tool of a modified embodiment of embodiment 1. A partially enlarged front view showing the operation of the machine tool of a modified embodiment of embodiment 1, which is different from that in FIG. 14. A graph showing changes in the distance between the sensor and the workpiece with respect to the pressure force applied to the workpiece in the machine tool of embodiment 1. A block diagram showing the system configuration of a machine tool of embodiment 2. A flowchart showing a main routine of the operation of the machine tool of embodiment 2. A flowchart showing a pressure force setting process of the machine tool of embodiment 2. A graph showing changes in the distance between the sensor and the workpiece with respect to the pressure force applied to the workpiece in the machine tool of embodiment 2. A block diagram showing the system configuration of a machine tool of embodiment 3. A flowchart showing a main routine of the operation of the machine tool of embodiment 3. Fig. 10 is a flowchart showing an optimum value setting process for the machine tool of embodiment 3. Fig. 11 is a partially enlarged front view showing a state in which a workpiece is held between a headstock side center member and a tailstock side center member by a loader in the machine tool of embodiment 3.10 is a graph showing changes in the distance between the sensor and the workpiece relative to the pressure force applied to the workpiece in the machine tool of the third embodiment.

[0015] (Embodiment 1) 1. Overview of Machine Tool 10 An overview of a machine tool 10 according to embodiment 1 of the present invention will be described with reference to Figures 1 and 5. In this embodiment, a grinding machine will be described as an example of the machine tool 10. However, the machine tool 10 is not limited to a grinding machine, and any machine tool 10 having a configuration in which a workpiece W is supported by a pair of center members (20, 21) described below, such as a lathe or machining center, can be appropriately selected.

[0016] The machine tool 10 rotates the workpiece W, which is the object to be machined, around the axis C of the workpiece W, rotates a grinding wheel 16, which is a tool that is a rotating body, and moves the grinding wheel 16 relatively close to the workpiece W in a direction intersecting the axis C of the workpiece W, thereby grinding the outer or inner surface of the workpiece W. The machine tool 10 can be a table traverse type grinding machine, a wheelhead traverse type grinding machine, or the like. The machine tool 10 can also be a cylindrical grinding machine, a cam grinding machine, or the like.

[0017] In this embodiment, the workpiece W is, for example, a member formed in a shaft shape, and the outer circumferential surface of the workpiece W is taken as an example to be processed. However, the shape of the workpiece W is not limited to a shaft shape, and it can be any shape, such as a cylindrical shape having an inner circumferential surface. When the workpiece W is cylindrical, the inner circumferential surface of the workpiece W can be the processed part.

[0018] As shown in Fig. 5, the workpiece W in this embodiment includes a cylindrical main body W1, a receiving portion W2 protruding outward in the axial direction CD from both ends of the main body W1, and a center receiving portion W3 protruding outward in the axial direction CD from both ends of the receiving portion W2. The receiving portion W2 is formed with a smaller diameter than the main body W1. The receiving portion W2 is a portion supported by a temporary support pedestal 17 (an example of a support member) described below. The center receiving portion W3 is formed with a smaller diameter than the receiving portion W2. The center receiving portion W3 is a portion sandwiched between a headstock-side center member 20 (an example of a center member, an example of a support member) and a tailstock-side center member 21 (an example of a center member, an example of a support member) described below. Center holes W4 are formed on both end surfaces of the center receiving portion W3, into which the tips of the headstock-side center member 20 and the tailstock-side center member 21 fit. The inner surface of the center hole W4 is formed into a conical concave surface, while the outer surfaces of the headstock side center member 20 and the tailstock side center member 21 are formed into conical convex surfaces.

[0019] 2. Detailed Configuration of Machine Tool 10 The detailed configuration of the machine tool 10 will be described with reference to FIGS. 1 to 3. In this embodiment, the machine tool 10 is a table traverse type cylindrical grinding machine. However, a wheelhead traverse type machine tool 10 may also be used. As shown in FIGS. 1 and 2, the machine tool 10 mainly includes a bed 11, a headstock 12, a tailstock 13, a table 14, a grinding wheel 15, a grinding wheel 16, a temporary rest 17, a sensor 18 (an example of a first sensor), a loader 19, a headstock-side center member 20, a tailstock-side center member 21, and a cover 22. However, in the first embodiment, the sensor 18 is used for illustrative purposes and is not an essential component.

[0020] The cover 22 includes a cover main body 22a that covers the grinding machine main body, a standby table cover 22b that covers the standby table 30, and a loader cover 22c that covers the loader 19. The cover main body 22a covers the bed 11, headstock 12, tailstock 13, table 14, grinding wheel head 15, grinding wheel 16, temporary rest 17, headstock side center member 20, and tailstock side center member 21 that constitute the grinding machine main body from the front-rear direction, the left-right direction, and above. However, opening / closing doors (not shown) for loading and unloading the workpiece W are provided on the front and ceiling surfaces of the cover main body 22a. Furthermore, the standby table cover 22b covers the standby table 30 from the front-rear direction, the left-right direction, and above. The standby table cover 22b also has opening / closing doors (not shown) on the front and ceiling surfaces for loading and unloading the workpiece W. The loader cover 22c covers the loader 19 installed above the cover body 22a and the standby table cover 22b from the front-rear and left-right directions.

[0021] The bed 11 is fixed on an installation surface. When viewed from above, the bed 11 is formed in a roughly T-shape, with a portion extending in the Z-axis direction and a portion extending in the X-axis direction connected together. A table 14 is disposed on the upper surface of the portion of the bed 11 extending in the Z-axis direction. The table 14 is formed in a rectangular shape that is elongated in the Z-axis direction. The table 14 moves in the Z-axis direction by rotational driving of a Z-axis servo motor 23a.

[0022] The headstock 12 is provided on the upper surface of the table 14, on the front side in the X-axis direction (the lower side in FIG. 2) and on one end side in the Z-axis direction (the left side in FIG. 2). The headstock 12 includes a headstock-side center member 20.

[0023] The tailstock 13 is provided on the upper surface of the table 14, on the front side in the X-axis direction (the lower side in FIG. 2) and on the other end side in the Z-axis direction (the right side in FIG. 2). The tailstock 13 includes a tailstock-side center member 21.

[0024] Between the headstock-side center member 20 of the headstock and the tailstock-side center member 21 of the tailstock 13, a workpiece W (an example of the workpiece W) to be machined is supported rotatably around the Z axis with the axis C as its center. The workpiece W is rotated by driving a headstock-side motor 24 provided on the headstock and a tailstock-side motor 25 provided on the tailstock 13. In other words, the headstock 12 and the tailstock 13 rotatably support both ends of the workpiece W.

[0025] The tailstock 13 is equipped with a pressing device 36 for applying a pressing force to the workpiece W. The pressing device 36 includes a tailstock drive device 26 that moves the tailstock 13 in the Z-axis direction, an elastic member 27 such as a spring, and a connecting member 28 that connects the elastic member 27 to the tailstock 13. The tailstock drive device 26 can be appropriately selected from known servo motors, hydraulic devices, etc. A pressing force is applied to the workpiece W by a resilient force resulting from elastic deformation of the elastic member 27.

[0026] A temporary support table 17 on which the workpiece W is placed before being clamped between the headstock side center member 20 and the tailstock side center member 21 is provided on the upper surface of the table 14, protruding upward from the upper surface of the table 14.

[0027] The grinding wheel head 15 is provided on the upper surface of a portion of the bed 11 extending in the X-axis direction so as to be movable in the X-direction. The grinding wheel head 15 is moved by driving a motor 15a provided on the bed 11. The grinding wheel 16 is rotatably supported on the grinding wheel head 15. The grinding wheel 16 is rotated by driving a motor 16a provided on the grinding wheel head 15. The grinding wheel 16 is configured by fixing a plurality of abrasive grains with a bond material.

[0028] The sensor 18 is disposed on the upper surface of the wheel head 15, in the vicinity of the grinding wheel 16. The sensor 18 is attached to the underside of the tip of an arm 29 that extends in an L-shape from the upper surface of the wheel head 15. The arm 29 is configured to be rotatable around the Y-axis direction as its axis of rotation, thereby enabling it to avoid the loader 19, which will be described later. The sensor 18 detects the shape of the workpiece W held between the headstock-side center member 20 and the tailstock-side center member 21. The sensor 18 also measures the distance between the workpiece W and the sensor 18. Examples of the sensor 18 include a CCD element, an optical camera, and a laser sensor.

[0029] The sensor 18 is disposed above or vertically above the vertical direction of the workpiece W in a state in which the workpiece W is supported by the headstock-side center member 20 and the tailstock-side center member 21 so that the axial direction CD of the workpiece W is horizontal. The sensor 18 in this embodiment is disposed vertically above the workpiece W.

[0030] A standby table 30 on which the workpiece W is placed is disposed to the side of the bed 11. A receiving table 17a (an example of a support member) on which the workpiece W is placed is provided on the upper surface of the standby table 30 so as to protrude from the upper surface of the standby table 30.

[0031] 1, a loader 19 is disposed above the bed 11 and the standby table 30. The loader 19 transports the workpiece W placed on the standby table 30 to a position between the headstock 12 and the tailstock 13, and also transports the workpiece W after machining to the next process. The loader 19 includes a loader beam 61 and a loading unit 62.

[0032] The loader beam 61 is installed horizontally in the Z-axis direction. A loading unit 62 is attached to the loader beam 61 so as to be movable in the Z direction.

[0033] As shown in FIG. 3 , the loading unit 62 includes a loader arm 63, a loader hand 64, gripping claws 65 a, 65 b, 66 a, and 66 b, and an actuator 67. The loading unit 62 is NC-controlled to move and position along the loader beam 61. The loader arm 63 is provided so as to be movable and positioned in the vertical direction (Y-axis direction) from a carrier portion of the loading unit 62 suspended from the loader beam 61. The loader hand 64 is connected to the lower end of the loader arm 63 so as to be tiltable about the Z-axis. The loader hand 64 is also provided with gripping claws 65 a, 65 b and gripping claws 66 a, 66 b. The gripping claws 65 a and 65 b are each formed in an inverted V-shape and are arranged side by side so that their gripping centers coincide with the Z-axis direction, as shown in FIG. 3 . The gripping claws 66a and 66b have the same configuration as the gripping claws 65a and 65b, and as shown in Figure 3, are arranged at 90 degrees offset from each other around the tilting axis of the loader hand 64. The gripping claws 65a, 65b, 66a, and 66b are controlled to open and close by an actuator (not shown) to grip and release the workpiece W. The actuator 67 is provided at the lower end of the loader arm 63, and tilts the loader hand 64 in response to a control command to position it at a predetermined angle.

[0034] 3. System Configuration of Machine Tool 10 Next, the system configuration of the machine tool 10 will be described with reference to Fig. 4. The machine tool 10 includes an input device 31, a data acquisition device 32, a calculation device 33, a storage device 34, a control device 35, and a pressing device 36.

[0035] Basic shape data DA relating to the basic shape of the workpiece W is input to the input device 31. Examples of the input device 31 include a keyboard and a Universal Serial Bus (USB) port to which an external storage device such as a USB memory is connected. The basic shape data DA includes design shape data DA1 of the workpiece W. The design shape data DA1 includes two-dimensional or three-dimensional CAD data of the workpiece W. The basic shape data DA also includes actual measurement data obtained by actually measuring the workpiece W outside the machine tool 10.

[0036] The data acquisition device 32 acquires design shape data DA1 as basic shape data DA input from the input device 31. The calculation device 33 acquires the basic shape data DA (design shape data DA1) from the data acquisition device 32. The calculation device 33 calculates an optimal value of the pressing force to be applied to the workpiece W (hereinafter referred to as optimal pressing force FE) based on the basic shape data DA (design shape data DA1) and a program 37 stored in the storage device 34.

[0037] The storage device 34 stores a program 37 for calculating an optimal press force FE to be applied to the workpiece W. The storage device 34 may store one program 37 or multiple programs 37. The program 37 may be a rule-based program based on classical mechanics, or may be a program that applies a trained model based on machine learning. When the storage device 34 stores multiple programs 37, the program 37 used to calculate the press force is appropriately selected from the multiple programs 37.

[0038] The control device 35 adjusts the pressure applied to the workpiece W by controlling the pressing device 36 based on the optimum pressing force FE calculated by the arithmetic device 33. In detail, the control device 35 applies a pressing force to the workpiece W by the elastic force of the elastic member 27 via the connecting member 28 by moving the tailstock 13 in the Z-axis direction using the tailstock driving device 26.

[0039] 4. Supporting State of Workpiece W and Pressing Force The supporting state of the workpiece W by the headstock side center member 20 and the tailstock side center member 21 and the pressing force applied to the workpiece W will be described with reference to FIGS. 5 to 9.

[0040] 5 shows a state in which the workpiece W is placed on the temporary rest 17. The rest portion W2 of the workpiece W is placed on the temporary rest 17. The center receiving portion W3 is spaced apart from the headstock-side center member 20 and the tailstock-side center member 21. The axis C of the workpiece W is located below the tip end of the headstock-side center member 20 and the tip end of the tailstock-side center member 21. In this state, no pressure is being applied to the workpiece W.

[0041] Fig. 6 shows a state in which the tailstock 13 approaches the headstock 12, causing the tip ends of the headstock side center member 20 and the tailstock side center member 21 to come into contact with the center receiving portion W3 of the workpiece W. The headstock side center member 20 and the tailstock side center member 21 are in contact with the center receiving portion W3 of the workpiece W, but no pressing force is being applied to the workpiece W. Fig. 9 shows a graph showing changes in the distance between the sensor 18 and the workpiece W relative to the pressing force applied to the workpiece W. In the graph of Fig. 9, the point where the pressing force is 0 corresponds to the state shown in Fig. 6.

[0042] As the tailstock 13 approaches the headstock 12, the tips of the headstock center member 20 and tailstock center member 21 fit into the center hole W4 formed in the center receiving portion W3 of the workpiece W. The conical convex surfaces formed at the tips of the headstock center member 20 and tailstock center member 21 then slide against the conical concave surfaces formed in the center hole W4, causing the workpiece W to be clamped between the headstock center member 20 and tailstock center member 21 and lifted off the temporary rest 17. As a result, as shown in the graph in Figure 9, the distance between the sensor 18 and the workpiece W decreases as the pressure applied to the workpiece W increases. However, in this state, the pressure applied to the workpiece W is insufficient.

[0043] Figure 7 shows a state in which the tailstock 13 has come even closer to the headstock 12. The axis C of the workpiece W is aligned with the tip of the headstock center member 20 and the tip of the tailstock center member 21. This positions the workpiece W relative to the headstock center member 20 and the tailstock center member 21. In the graph of Figure 9, this corresponds to the point where the pressure is F1 and the distance between the sensor 18 and the workpiece W is D1. Because the workpiece W is positioned relative to the headstock center member 20 and the tailstock center member 21, the slope of the graph is 0. In other words, the differential coefficient of the graph is 0.

[0044] As the tailstock 13 approaches the headstock 12 further, the pressure applied to the workpiece W increases. As described above, the workpiece W is positioned relative to the headstock side center member 20 and the tailstock side center member 21, and no buckling deflection occurs in the workpiece W, so there is almost no change in the distance between the sensor 18 and the workpiece W. In this state, the pressure applied to the workpiece W is appropriate.

[0045] As shown in Figure 8, when the pressure applied to the workpiece W reaches F2, the workpiece W begins to deform significantly due to buckling. As a result, as shown in Figure 9, the distance between the sensor 18 and the workpiece W begins to increase again. In this state, the pressure applied to the workpiece W is excessive. The increase in the distance between the sensor 18 and the workpiece W means that the workpiece W will buckle downward in the direction of gravity. Since the workpiece W deforms slightly downward in the direction of gravity due to its own weight, application of excessive pressure makes it more likely to buckle downward in the direction of gravity. When the workpiece W is in a state of buckling deformation, the workpiece W cannot be machined accurately.

[0046] 9, the optimum pressure force FE is set at any point within the range of pressure forces F1 to F2. The optimum pressure force FE can vary depending on which physical property of the workpiece W is emphasized. For example, if emphasis is placed on the machining accuracy of the workpiece W, it would be preferable to increase the pressure force applied to the workpiece W as much as possible. From this perspective, F2 appears to be the optimum pressure force.

[0047] On the other hand, when the wear of the headstock-side center member 20 and the tailstock-side center member 21 is taken into consideration, it seems preferable to make the pressure applied to the workpiece W as small as possible. From this point of view, F1 seems to be the optimum pressure force.

[0048] Furthermore, examples of the physical properties of the workpiece W include runout, roundness, surface roughness, etc. The optimum pressure force FE can be set from the viewpoint of each of these physical properties.

[0049] 5. Operation of Machine Tool 10 The operation of machine tool 10 will be described with reference to FIGS. 10 and 11. FIG. 10 shows a flowchart relating to the operation of machine tool 10 according to this embodiment. As shown in FIG. 10, when machine tool 10 is started, data acquisition device 32 acquires design shape data DA1 as basic shape data DA (S1). An operator may input basic shape data DA (design shape data DA1) to machine tool 10 from input device 31 such as a keyboard, or may connect a USB memory to a USB port and input basic shape data DA (design shape data DA1) stored in the USB memory to machine tool 10. At this time, the operator may also input which of the physical properties of workpiece W is to be emphasized.

[0050] In S2, the arithmetic unit 33 calculates the optimum pressure force FE to be applied to the workpiece W. The arithmetic unit 33 may set the optimum pressure force FE for the workpiece W based on the physical properties prioritized by the operator. Furthermore, the arithmetic unit 33 may set the optimum pressure force FE to a value obtained by multiplying, by a predetermined magnification, the pressure force F1 at the point where the differential coefficient becomes 0 in a graph showing the change in the distance between the sensor 18 and the workpiece W relative to the pressure force.

[0051] Next, in a placing step (S3), the workpiece W is placed on the temporary rest 17 by the loader 19. In detail, the workpiece W placed on the temporary rest 17 of the waiting table 30 is gripped by the gripping claws 66a, 66b of the loading unit 62, and the loader hand 64 gripping the workpiece W is moved above the temporary rest 17 provided on the table 14 by the loader arm 63 and the loader beam 61. The loader arm 63 descends, the gripping claws 66a, 66b of the loading unit 62 open, and the workpiece W is placed on the temporary rest 17.

[0052] The control device 35 applies the optimum pressure force FE calculated by the calculation device 33 to the workpiece W by bringing the tailstock 13 closer to the headstock 12 (S4). As shown in Fig. 11, the control device 35 applies the optimum pressure force FE to the workpiece W within the appropriate pressure force range of F1 to F2.

[0053] Next, in the grinding step (S5), the workpiece W is ground. In detail, the control device 35 rotates the headstock-side motor 24 and the tailstock-side motor 25 to rotate the workpiece W. The control device 35 rotates the X-axis servo motor 23b to bring the grinding wheel 15 closer to the workpiece W. This brings the grinding wheel 16 into contact with the surface of the workpiece W. The control device 35 rotates the Z-axis servo motor 23a to move the table 14 in the Z-axis direction. This grinds the surface of the workpiece W.

[0054] When grinding of the workpiece W is completed, it is determined whether the operation of the machine tool 10 is completed (S6). If it is determined that the operation of the machine tool 10 is not completed (S6: N), the process returns to S1 and the operations of S1 to S5 are repeated. On the other hand, if it is determined that the operation of the machine tool 10 is completed (S6: Y), the operation of the machine tool 10 is completed.

[0055] 6. Effects of the Present Embodiment According to the present embodiment, an appropriate pressing force can be calculated based on the basic shape data DA (design shape data DA1). This allows the pressing force to be set without relying on an experienced operator, thereby saving labor. Furthermore, there is no need to machine the workpiece W in advance to determine the conditions for setting the pressing force, so the time required to set the pressing force can be shortened. Furthermore, since the pressing force is calculated based on the basic shape data DA (design shape data DA1) related to the workpiece W to be machined, the accuracy of setting the pressing force can be improved.

[0056] (Modification 1 of Embodiment 1) Next, Modification 1 of Embodiment 1 will be described with reference to Figures 12 to 16. Note that, of the symbols used hereinafter, those that are the same as those used in the previously described embodiments represent the same components, etc. as those in the previously described embodiments, unless otherwise specified.

[0057] Figure 12 shows the system configuration of the machine tool 10a of this embodiment. In this embodiment, the sensor 18 is used as an essential component. The sensor 18 of this embodiment acquires support state shape data DA2 as basic shape data DA. The support state shape data DA2 is data relating to the shape of the workpiece W in a state in which the workpiece W is supported by the headstock side center member 20 and tailstock side center member 21 as support members and in which no buckling deflection occurs. The other components are the same as in embodiment 1, so repeated explanations will be omitted.

[0058] Next, the operation of the machine tool 10a of this modified example will be described with reference to Figures 13 to 16. A flowchart relating to the operation of the machine tool 10a of this modified example is shown in Figure 13. When the machine tool 10a is started, the workpiece W is placed on the temporary rest 17 of the table 14 (S3).

[0059] The control device 35 brings the tailstock 13 closer to the headstock 12, thereby supporting the workpiece W by sandwiching it between the headstock side center member 20 and the tailstock side center member 21 (S11). At this time, the control device 35 applies a pressure F1 to the workpiece W that is sufficient to prevent the workpiece W from falling off the headstock side center member 20 and the tailstock side center member 21. For example, the control device 35 may determine the pressure F1 by detecting the load acting on the headstock side center member 20 or the tailstock side center member 21. The graph in Figure 16 shows points where the pressure F1 is being applied to the workpiece W.

[0060] Next, the control device 35 moves the table 14 in the Z-axis direction, thereby causing the sensor 18 to scan the workpiece W along the axial direction CD of the workpiece W. Fig. 14 shows a state in which the sensor 18 is located at one end (the left end in Fig. 14) of the main body portion W1 in the axial direction CD of the workpiece W, and Fig. 15 shows a state in which the sensor 18 is located at the other end (the right end in Fig. 15) of the main body portion W1 in the axial direction CD of the workpiece W. In this way, the sensor 18 acquires supported state shape data DA2, which is data on the shape of the workpiece W in a state in which the workpiece W is supported by the headstock side center member 20 and the tailstock side center member 21 and in a state in which buckling deflection does not occur (S12).

[0061] 13, the data acquisition device 32 acquires the support state shape data DA2 from the sensor 18 and transmits it to the calculation device 33. The calculation device 33 calculates the optimum pressure force FE to be applied to the workpiece W based on the acquired support state shape data DA2 and the program 37 stored in the storage device 34 (S13).

[0062] The control device 35 further moves the tailstock 13 closer to the headstock 12, thereby applying the optimum pressure FE calculated by the calculation device 33 to the workpiece W (S4).

[0063] Next, the grinding process is carried out (S5). When grinding of the workpiece W is completed, it is determined whether or not the operation of the machine tool 10 has finished (S6). If it is determined that the operation of the machine tool 10 has not finished (S6: N), the process returns to S3 and the operations of S3 to S5 are repeated. On the other hand, if it is determined that the operation of the machine tool 10 has finished (S6: Y), the operation of the machine tool 10 finishes.

[0064] According to this embodiment, the pressing force is calculated based on the basic shape data DA (support state shape data DA2) relating to the workpiece W to be machined, so that the accuracy of setting the pressing force can be improved.

[0065] (Variation 2 of Embodiment 1) In Variation 1 of Embodiment 1, the support state shape data DA2 as the basic shape data DA acquired by the sensor 18 is data relating to the shape of the workpiece W in a state in which the workpiece W is supported by the headstock side center member 20 and the tailstock side center member 21 as support members. In Variation 2 of Embodiment 1, the support state shape data DA2 may be data relating to the shape of the workpiece W in a state in which the workpiece W is supported by the temporary support table 17 as a support member.

[0066] 13, the processing is performed in the order of S3 "Placement step" → S12 "Basic shape data acquisition" → S13 "Pressure force calculation step" → S4 "Pressure step" → S5 and subsequent steps. In the pressure step (S4), the control device 35 applies the optimum pressure force FE calculated by the calculation device 33 to the workpiece W by bringing the tailstock 13 closer to the headstock 12. As shown in FIG. 16, the control device 35 applies the optimum pressure force FE to the workpiece W within an appropriate pressure force range between F1 and F2.

[0067] (Embodiment 2) Next, a machine tool 10b according to embodiment 2 will be described with reference to Fig. 1 and Figs. 17 to 20. Fig. 17 is a block diagram showing the system configuration of the machine tool 10b according to this embodiment. The sensor 18 detects buckling deflection shape data DB relating to the buckling deflection shape of the workpiece W in a state in which buckling deflection occurs due to the workpiece W being supported by the headstock-side center member 20 and the tailstock-side center member 21. The sensor 18 according to this embodiment is an example of a second sensor.

[0068] The sensor 18 is disposed above or below the workpiece W in the vertical direction, with the workpiece W supported by the headstock side center member 20 and the tailstock side center member 21 so that the axial direction CD of the workpiece W is horizontal. In this embodiment, the sensor 18 is disposed above the workpiece W in the vertical direction. When both ends of the workpiece W are supported by the headstock side center member 20 and the tailstock side center member 21, the workpiece W may bend downward in the vertical direction due to its own weight. Therefore, when a pressure force is applied to the workpiece W from both ends by the headstock side center member 20 and the tailstock side center member 21, the workpiece W may bend downward in the vertical direction. Therefore, by disposing the sensor 18 above or below the workpiece W in the vertical direction, it is possible to accurately detect the displacement of the workpiece W when a pressure force is applied to the workpiece W.

[0069] Furthermore, the sensor 18 is disposed at a position where the amount of buckling deflection of the workpiece W is maximized by applying a pressure to the workpiece W while the workpiece W is supported by the headstock-side center member 20 and the tailstock-side center member 21. In this embodiment, as shown in FIG. 1 , the sensor 18 is disposed near the center position in the axial direction CD of the workpiece W, which is the position where the amount of buckling deflection of the workpiece W is maximized. "Near the center position" includes the center position in the axial direction CD and, even if the position is not the center position, includes a range in which the center position can be substantially recognized. However, the position where the amount of buckling deflection of the workpiece W is maximized is not limited to near the center position in the axial direction CD of the workpiece W. By disposing the sensor 18 at the position where the amount of buckling deflection of the workpiece W is maximized, the accuracy of the buckling deflection shape data DB can be improved, and therefore the accuracy of calculating the optimum pressing force FE can be improved.

[0070] The buckling deflection shape data DB is data on the amount of deflection of the workpiece W detected by the sensor 18 when the workpiece W has buckled and is also data on the amount of deflection of the workpiece W that changes when the pressure applied to the workpiece W is changed. Note that the above-mentioned amount of deflection includes the amount of buckling deflection when the workpiece W has buckled and the amount of deflection when the workpiece W has been deformed downward in the vertical direction due to its own weight. Note that the amount of deflection indicates the value of the deflection.

[0071] The data acquisition device 32 acquires the buckling deflection shape data DB detected by the sensor 18. The data acquisition device 32 transmits the buckling deflection shape data DB to the control device 35. The control device 35 controls the pressing device 36 based on the buckling deflection shape data DB. The control device 35 determines whether the slope of a graph of the gap between the sensor 18 and the workpiece W versus the applied pressure is zero. When the slope of the graph of the gap between the sensor 18 and the workpiece W versus the applied pressure is zero, the control device 35 transmits the buckling deflection shape data DB to the calculation device 33. The control device 35 also determines whether the applied pressure to the workpiece W is greater than a predetermined applied pressure F2. When the applied pressure to the workpiece W is greater than the predetermined applied pressure F2, the control device 35 stops the machine tool 10.

[0072] The calculation device 33 acquires the buckling deflection shape data DB from the data acquisition device 32. The calculation device 33 calculates an optimum pressure force FE to be applied to the workpiece W based on the buckling deflection shape data DB and a program 37 stored in the storage device 34.

[0073] The calculation device 33 transmits the optimum pressure force FE to the control device 35. The control device 35 controls the pressing device 36 based on the optimum pressure force FE calculated by the calculation device 33, thereby applying the optimum pressure force FE to the workpiece W.

[0074] The configuration other than that described above is substantially the same as that of the first embodiment, so the same components are given the same reference numerals and redundant explanations will be omitted.

[0075] Next, the operation of the machine tool 10b of this embodiment will be described with reference to Figures 18 to 20. Figure 18 shows a main routine of the machine tool 10b of this embodiment. When the machine tool 10b is started, the loader 19 places the workpiece W on the temporary rest 17 of the table 14 (S3).

[0076] Next, a pressure force setting step is executed (S21), and an optimum pressure force FE is applied to the workpiece W.

[0077] Next, in the grinding step (S5), the workpiece W is ground. When grinding of the workpiece W is completed, it is determined whether or not the operation of the machine tool 10b has finished (S6). If it is determined that the operation of the machine tool 10b has not finished (S6: N), the process returns to S3 and the operations of S3 to S5 are repeated. On the other hand, if it is determined that the operation of the machine tool 10b has finished (S6: Y), the operation of the machine tool 10b finishes.

[0078] Next, a flowchart of the pressure force setting step is shown in Fig. 19. When the pressure force setting step (S21) is executed, the control device 35 applies a pressure force to the workpiece W by bringing the tailstock 13 closer to the headstock 12 (S22).

[0079] The sensor 18 detects the buckling deflection shape data DB of the workpiece W and transmits it to the data acquisition device 32 (S23). The data acquisition device 32 transmits the received buckling deflection shape data DB to the calculation device 33.

[0080] Fig. 20 shows a graph of the distance between the sensor 18 and the workpiece W versus the pressure applied to the workpiece W in the machine tool 10b of this embodiment. Fig. 20 shows the graph from a point where the pressure is 0 and the distance between the sensor 18 and the workpiece W is D0. D0 is the distance between the sensor 18 and the workpiece W in a state where the workpiece W is placed on the temporary support table 17.

[0081] The calculation device 33 determines whether the slope of the graph of the distance between the sensor 18 and the workpiece W versus the pressure applied to the object is 0 based on the buckling deflection shape and the buckling deflection shape data DB (S24). When the calculation device 33 determines that the slope of the graph of the distance between the sensor 18 and the workpiece W versus the pressure applied is not 0 (S24: N), the process returns to S22.

[0082] When the calculation device 33 determines that the slope of the graph of the gap between the sensor 18 and the workpiece W versus the pressure force is 0, the calculation device 33 calculates the optimum pressure force FE based on the buckling deflection shape data DB and the program 37 stored in the storage device 34 (S25). The calculation device sets the optimum pressure force FE, for example, by multiplying the pressure force F1 when the slope of the graph of the gap between the sensor 18 and the workpiece W versus the pressure force is 0 by a predetermined magnification. However, the method of calculating the optimum pressure force FE is not limited to the above method.

[0083] The control device 35 applies the optimum pressure FE to the workpiece W (S26). This completes the pressure setting process.

[0084] According to this embodiment, an appropriate pressure can be calculated based on the buckling deflection shape data DB. This allows the pressure to be set without relying on an expert, thereby saving labor. Furthermore, there is no need to machine the workpiece W in advance to determine the conditions for setting the pressure, so the time required to set the pressure can be shortened. Furthermore, since the pressure is calculated based on the buckling deflection shape data DB for the workpiece W to be machined, the accuracy of setting the pressure can be improved.

[0085] (Third Embodiment) Next, a machine tool 10c according to a third embodiment will be described. Fig. 21 shows a block diagram illustrating the system configuration of the machine tool 10c according to this embodiment. The machine tool 10c according to this embodiment includes an input device 31, a sensor 18, a data acquisition device 32, a calculation device 33, a storage device 34, a control device 35, and a pressing device 36. The calculation device 33 includes a first calculation unit 33a and a second calculation unit 33b. The control device 35 includes a first control unit 35a and a second control unit 35b.

[0086] The first calculation unit 33a calculates an initial pressure force FS based on the basic shape data DA (design shape data DA1 or support state shape data DA2) acquired from the input device 31 or the sensor 18 via the data acquisition device 32 and an initial value calculation program 37a for calculating the initial value of the pressure force (hereinafter referred to as the initial pressure force FS). The basic shape data DA in this embodiment is the design shape data DA1 described in the first embodiment. The initial value calculation program 37a is stored in the storage device 34.

[0087] The second calculation unit 33b calculates the optimum pressurizing force FE based on the buckling deflection shape data DB acquired from the sensor 18 via the data acquisition device 32 and an optimum value calculation program 37b for calculating the optimum pressurizing force FE. The buckling deflection shape data DB in this embodiment is data on the amount of deflection of the workpiece W detected by the sensor 18 in the process in which the amount of buckling deflection caused in the workpiece W increases as the pressurizing force is increased from a state in which an initial pressurizing force FS is applied to the workpiece W by the headstock-side center member 20 and the tailstock-side center member 21. The optimum value calculation program 37b is stored in the storage device 34.

[0088] The first control unit 35a controls the pressing device 36 to apply a pressing force to the workpiece W so that the pressing force becomes the initial pressing force FS calculated by the first calculation unit 33a.

[0089] The second control unit controls the pressing device 36 to adjust the pressing force applied to the workpiece W based on the optimum pressing force FE calculated by the second calculation unit 33b.

[0090] The configuration other than that described above is substantially the same as that of the first embodiment, so the same components are given the same reference numerals and redundant explanations will be omitted.

[0091] Next, a main routine for the operation of the machine tool 10c of this embodiment is shown in Figure 22. When the machine tool 10 of this embodiment is started, in S31, the design shape data DA1 is acquired from the basic shape data DA.

[0092] The first calculation unit 33a calculates the initial pressure force FS to be applied to the workpiece W based on the basic shape data DA (S32).

[0093] Next, an optimum value setting step (S33) is executed. By executing the optimum value setting step, the workpiece W is supported by the headstock side center member 20 and the tailstock side center member 21 at the optimum pressing force FE.

[0094] Next, the grinding process is carried out to grind the workpiece W. When grinding of the workpiece W is completed, it is determined whether or not the operation of the machine tool 10c is completed (S5). If it is determined that the operation of the machine tool 10c has not completed (S6: N), the process returns to S32 and the operations of S32 to S5 are repeated. On the other hand, if it is determined that the operation of the machine tool 10c has completed (S6: Y), the operation of the machine tool 10c is completed.

[0095] Next, a flowchart of the optimum value setting step is shown in Figure 23. When the optimum value setting step is executed (S33), the loader 19 transports the workpiece W between the headstock side center member 20 and the tailstock side center member 21 (S34). When the workpiece W is positioned between the headstock side center member 20 and the tailstock side center member 21, an initial value pressurizing step is executed (S35). In the initial value pressurizing step, the first control unit moves the tailstock 13 closer to the headstock 12, thereby supporting the workpiece W by the headstock side center member 20 and the tailstock side center member 21. At this time, an initial pressurizing force FS is applied to the workpiece W.

[0096] 24 shows a state in which an initial pressure force FS is being applied to the workpiece W. The workpiece W is supported by the headstock side center member 20 and the tailstock side center member 21, while being held between them by the loader 19. After the initial pressure force FS is applied, the gripping jaws 65a, 65b, 66a, and 66b of the loader 19 open, and the workpiece W separates from the loader 19.

[0097] 25 shows a graph of the distance between the sensor 18 and the workpiece W versus the applied pressure. When an initial applied pressure FS is applied to the workpiece W, the distance between the sensor 18 and the workpiece W is D1.

[0098] 23 , in a pressure application step (S36), the control device 35 applies a pressure force to the workpiece W by further moving the tailstock 13 closer to the headstock 12. The application of the pressure force to the workpiece W causes the workpiece W to buckle.

[0099] Next, the sensor 18 detects the amount of buckling deflection that has occurred in the workpiece W (S37). As a result, the sensor 18 detects the buckling deflection shape data DB and transmits it to the second calculation unit 33b via the data acquisition device 32. In S38, the second calculation unit 33b calculates the optimum pressure force FE to be applied to the workpiece W based on the buckling deflection shape data DB and the optimum value calculation program 37b.

[0100] Next, the second control unit 35b acquires the optimum pressure force FE from the second calculation unit 33b, and applies the optimum pressure force FE to the workpiece W by bringing the tailstock 13 closer to the headstock 12 (S39). This completes the optimum value setting process.

[0101] As shown in FIG. 25, an optimum pressure force FE is applied to the workpiece W in a graph of the pressure force versus the distance between the sensor 18 and the workpiece W.

[0102] According to this embodiment, when the optimum pressure force FE is calculated using buckling deflection data, the time required to set the optimum pressure force FE can be reduced.

[0103] (Modification of Embodiment 3) In Embodiment 3, the basic shape data DA is the design shape data DA1 described in Embodiment 1. Alternatively, the basic shape data DA can be support state shape data DA2 as follows.

[0104] For example, machine tool 10 may be provided with a sensor (not shown) having a configuration similar to sensor 18 on standby table 30. This sensor is disposed above the vertical direction of workpiece W or vertically thereto, with workpiece W supported by receiving table 17a of standby table 30 as a support member so that the axial direction CD of workpiece W is horizontal. This sensor detects the shape of workpiece W supported by receiving table 17a. The sensor also measures the distance between workpiece W and the sensor. Examples of sensors include a CCD element, an optical camera, and a laser sensor.

[0105] In this case, the basic shape data DA is the support state shape data DA2 detected by the sensor provided on the standby table 30. In other words, the basic shape data DA is data relating to the basic shape of each part of the workpiece W in the axial direction CD detected by the sensor when the workpiece W as a support member is supported on the receiving table 17a of the standby table 30 and the sensor scans along the axial direction CD of the workpiece W.

[0106] (Other) In this embodiment, the loader 19 is configured to hold the workpiece W between the headstock side center member 20 and the tailstock side center member 21, but this is not limited to this. The worker may hold the workpiece W by hand, and the optimum value setting process (S33) may be performed in a state where the worker holds the workpiece W between the headstock side center member 20 and the tailstock side center member 21.

[0107] As another example, the sensor 18 may be configured to detect the basic shape of the workpiece W while the workpiece W is supported by the headstock side center member 20 and the tailstock side center member 21, and to detect the amount of deflection of the workpiece W while the workpiece W is supported by the headstock side center member 20 and the tailstock side center member 21. In this case, the basic shape data DA is data relating to the basic shape of each portion of the workpiece W in the axial direction CD detected by the sensor 18 by scanning the sensor 18 along the axial direction CD of the workpiece W.

[0108] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention.

[0109] After the workpiece W is supported by the center member, one end of the workpiece W can be held by a chuck provided on the headstock 12, or a locking member (e.g., a retainer) can be attached to one end of the workpiece W, and the workpiece W can be rotated by a pin provided on the headstock 12.

[0110] The storage unit may be configured to store a plurality of programs 37, and an appropriate program 37 may be selected from the plurality of programs 37 depending on the shape of the workpiece W, the shape of the center member, etc. The program 37 may be a rule-based program or a program 37 based on machine learning.

[0111] The basic shape data DA may be data regarding the basic shape of each part of the workpiece W in the axial direction CD detected by the sensor 18 by scanning the sensor 18 along the axial direction CD of the workpiece W when the workpiece W is supported on the temporary support table 17.

[0112] It may also be configured to include two or more sensors 18. Of the multiple sensors 18, at least one may be a first sensor and at least one other may be a second sensor.

Claims

1. A pair of center members (20, 21) that sandwich and support both ends of a workpiece (W) from the axial direction (CD) of the workpiece; A pressing device (36) that applies a pressing force to the workpiece by approaching at least one of the pair of center members to the other center member in the axial direction; A data acquisition device (32) that acquires buckling deflection shape data (DB) regarding the buckling deflection shape of the workpiece in a state where the workpiece generates buckling deflection by being supported by the center member; An arithmetic device (33) that calculates an optimum value of the pressing force based on the buckling deflection shape data and a program (37) for calculating the optimum value of the pressing force; A control device (35) that adjusts the pressing force applied to the workpiece based on the optimum value of the pressing force calculated by the arithmetic device by controlling the pressing device; A second sensor (18) that detects the amount of deflection of the workpiece in a state where the workpiece is supported by the center member, the machine tool (10). The buckling deflection shape data is data on the amount of deflection of the workpiece detected by the second sensor in a state where the workpiece generates buckling deflection, and is data on the amount of deflection of the workpiece that changes when the pressing force is changed.

2. The machine tool according to claim 1, wherein the second sensor detects the amount of deflection of the workpiece at a position where the buckling deflection amount of the workpiece becomes maximum when the pressing force is applied to the workpiece in the axial direction of the workpiece.

3. The machine tool according to claim 2, wherein the second sensor detects the amount of deflection of the workpiece near the center position of the workpiece as a position where the buckling deflection amount of the workpiece becomes maximum in the axial direction of the workpiece.

4. The machine tool according to claim 1, wherein the second sensor is disposed above or below the workpiece in the vertical direction in a state where the workpiece is supported by the pair of center members such that the axial direction of the workpiece is horizontal, and detects the amount of downward deflection of the workpiece in the vertical direction.

5. Furthermore, a temporary support (17) that supports the workpiece from below is provided in a state before the workpiece is supported by the pair of center members. The buckling deflection shape data is data of the amount of deflection of the workpiece detected by the second sensor in a process in which the amount of buckling deflection generated in the workpiece increases when the workpiece is supported by the center member from a state of being supported by the temporary support and further a pressing force is applied by the center member. The machine tool according to claim 1.

6. The data acquisition device acquires basic shape data (DA) regarding the basic shape of the workpiece and the buckling deflection shape data. The buckling deflection shape data is data of the amount of deflection of the workpiece detected by the second sensor in a process in which the amount of buckling deflection generated in the workpiece increases when the pressing force is increased from a state where the pressing force of an initial value is applied to the workpiece by the center member. The arithmetic unit A first arithmetic unit (33a) that calculates the initial value of the pressing force based on the basic shape data and an initial value calculation program for calculating the initial value of the pressing force. A second arithmetic unit (33b) that calculates the optimum value of the pressing force based on the buckling deflection shape data and an optimum value calculation program for calculating the optimum value of the pressing force. The machine tool according to claim 1 includes the second arithmetic unit. The control device A first control unit (35a) that applies the pressing force to the workpiece so that the pressing force becomes the initial value calculated by the first arithmetic unit by controlling the pressing device. A second control unit (35b) that adjusts the pressing force applied to the workpiece based on the optimum value of the pressing force calculated by the second arithmetic unit by controlling the pressing device. The machine tool according to claim 1 includes the second control unit.

7. The second sensor detects the basic shape of the workpiece in a state where the workpiece is supported by the center member and also detects the amount of deflection of the workpiece in a state where the workpiece is supported by the center member. The basic shape data is data regarding the basic shape of each part in the axial direction of the workpiece detected by the second sensor by scanning the second sensor along the axial direction of the workpiece. The machine tool according to claim 6.

8. Furthermore, Before the workpiece is supported by the pair of center members, a temporary support (17) that supports the workpiece from below is provided. The machine tool according to claim 7, wherein the basic shape data is data regarding the basic shape of each part in the axial direction of the workpiece detected by the second sensor by scanning the second sensor along the axial direction of the workpiece in a state where the workpiece is supported by the temporary support base.

9. The basic shape data is pre-acquired design shape data (DA1) of the workpiece, The machine tool according to claim 6, wherein when the workpiece is loaded, the first control unit controls the pressing device to apply the pressing force to the workpiece so that the pressing force becomes the initial value calculated by the first calculation unit.

10. A step of sandwiching and supporting both ends of a workpiece (W) from the axial direction (CD) of the workpiece by a pair of center members (20, 21); A step of applying a pressing force to the workpiece by causing at least one of the pair of center members of the pressing device (36) to approach the other center member in the axial direction; A data acquisition step of acquiring buckling deflection shape data (DB) regarding the buckling deflection shape of the workpiece in a state where the workpiece has buckling deflection due to being supported by the center member; A step of calculating an optimum value of the pressing force based on the buckling deflection shape data and a program (37) for calculating the optimum value of the pressing force; A step of adjusting the pressing force applied to the workpiece based on the optimum value of the pressing force calculated by calculation by controlling the pressing device by a control device (35), In the data acquisition step, the buckling deflection shape data is data of the amount of deflection of the workpiece in a state where the workpiece has buckling deflection, detected by a second sensor (18) that detects the amount of deflection of the workpiece in a state where the workpiece is supported by the center member, and data of the amount of deflection of the workpiece that changes when the pressing force is changed. A pressing force setting method for acquiring the data.

11. The data acquisition step is The data acquisition device acquires basic shape data (DA) regarding the basic shape of the workpiece and the buckling deflection shape data, The buckling deflection shape data is data of the amount of deflection of the workpiece detected by the second sensor in the process in which the amount of buckling deflection generated in the workpiece increases as the pressing force is increased from the state where the initial value of the pressing force is applied to the workpiece by the center member. The step of calculating the optimum value of the pressing force includes: a step of calculating the initial value of the pressing force by a first calculation unit (33a) based on the basic shape data and an initial value calculation program for calculating the initial value of the pressing force; a step of calculating the optimum value of the pressing force by a second calculation unit (33b) based on the buckling deflection shape data and an optimum value calculation program for calculating the optimum value of the pressing force. The step of adjusting the pressing force applied to the workpiece includes: a step of applying the pressing force to the workpiece by a first control unit (35a) controlling the pressing device so that the pressing force becomes the initial value calculated by the first calculation unit; a step of adjusting the pressing force applied to the workpiece by a second control unit (35b) controlling the pressing device based on the optimum value of the pressing force calculated by the second calculation unit. The pressing force setting method according to claim 10.

12. (Deleted)

13. (Deleted)