Working machinery

Abstract

To provide a machine tool that can suppress variations in product length. [Solution] The machine tool 1 comprises a first spindle unit 10 for gripping a workpiece W, a second spindle unit 20 positioned opposite the first spindle unit 10 and gripping one end of the workpiece W gripped by the first spindle unit 10, a turret 31 to which a parting tool 35a for machining the workpiece W is attached, and a second spindle movement mechanism 23 that moves the second spindle unit 20 by the output of a motor 23a. With the second spindle unit 20 gripping one end of the workpiece W gripped by the first spindle unit 10, the second spindle movement mechanism 23 moves the second spindle unit 20 in a direction that reduces the absolute value of the load current of the motor 23a (for example, in the direction of arrow Y1), then the parting tool 35a cuts the workpiece W and hands it over to the second spindle unit 20.

Description

Technical Field

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

Background Art

[0002] In machine tools, those having a main spindle and a rear spindle that receives a workpiece from the main spindle are known. For example, Patent Document 1 discloses a machine tool that can grip a workpiece with a main spindle and a rear spindle and perform plunge cutting.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the machine tool of Patent Document 1, when the rear spindle grips the workpiece grasped by the main spindle, a load is applied to the workpiece, and the workpiece may be grasped in a deflected state. When the workpiece is cut in that state, there is a problem that the product length varies.

[0005] The present invention has been made paying attention to such problems, and an object thereof is to provide a machine tool capable of suppressing variations in product length.

Means for Solving the Problems

[0006] To achieve the above objective, the machine tool of the present invention comprises a first spindle unit for gripping a workpiece, a second spindle unit positioned opposite the first spindle unit and gripping one end of the workpiece gripped by the first spindle unit, a tool post to which a tool for machining the workpiece is attached, and a moving mechanism for moving the second spindle unit by the output of a motor. With the second spindle unit gripping one end of the workpiece gripped by the first spindle unit, the second spindle unit is moved by the moving mechanism in a direction that reduces the absolute value of the motor load current, after which the workpiece is cut by the tool and handed over to the second spindle unit. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a machine tool that can suppress variations in product length. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view of a machine tool according to an embodiment of the present invention. [Figure 2] This is a view from arrow II in Figure 1, and is a schematic front view of a machine tool according to an embodiment of the present invention. [Figure 3] This is a cross-sectional view taken along line III-III in Figure 1, and is a side view showing a turret device of a machine tool according to an embodiment of the present invention. [Figure 4] This is a schematic front view showing the machining process performed by a machine tool according to an embodiment of the present invention in the order of steps (a) to (c). [Figure 5] Continuing from Figure 4, this is a schematic front view showing the machining process performed by the machine tool in order from process (a) to (c). [Figure 6] This is a flowchart illustrating the machining process of a machine tool according to an embodiment of the present invention. [Figure 7] This is a flowchart illustrating the workpiece transfer process of a machine tool according to an embodiment of the present invention. [Figure 8]This is a timing chart showing the position adjustment of the second spindle unit of a machine tool according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, a machine tool according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the first spindle unit and the second spindle unit, which is the rear spindle unit, are arranged facing each other, and "forward" for the first spindle unit means the direction toward the second spindle unit, and "forward" for the second spindle unit means the direction toward the first spindle unit.

[0010] The machine tool 1 shown in Figures 1 and 2 comprises a bed S which is a base for supporting each component of the machine tool 1, a first spindle unit 10, a second spindle unit 20, a turret device 30, and a control unit 300.

[0011] The first spindle unit 10 holds the workpiece W and rotates the held workpiece W around the rotation axis. The first spindle unit 10 comprises a first spindle 11 that grips the workpiece W and a first headstock 12 that rotatably supports the first spindle 11. The first headstock 12 is fixedly installed on the upper surface of the bed S.

[0012] In the following explanation, we define a Cartesian coordinate system in which the Z-axis is the direction parallel to the rotation axis of the first principal spindle 11, the X-axis is the direction perpendicular and horizontal to the Z-axis, and the Y-axis is the vertical direction, and will refer to it as appropriate.

[0013] Furthermore, the first spindle unit 10 includes a built-in motor 101 and a collet chuck device 103 for gripping the workpiece W.

[0014] The built-in motor 101 is housed in the first headstock 12 and rotates the first spindle 11.

[0015] The collet chuck device 103 is arranged at the tip of the first spindle 11. The collet chuck device 103 is provided with a collet chuck (not shown) having three equally divided serrations when viewed in the axial direction. By the reduction and expansion of the serrated portion of the collet chuck, the collet chuck device 103 clamps or unclamps the workpiece W.

[0016] The second spindle unit 20 is arranged opposite to the first spindle unit 10 in the Z-axis direction. The second spindle unit 20 receives the workpiece W from the first spindle unit 10 and rotates the workpiece W about a rotation axis extending in the Z-axis direction. Similar to the first spindle unit 10 described above, the second spindle unit 20 includes a second spindle 21 for gripping the workpiece W and a second spindle base 22 for rotatably supporting the second spindle 21. In addition, as shown in FIG. 2, the second spindle unit 20 includes a second spindle moving mechanism 23 for moving the second spindle base in the Z-axis direction.

[0017] The second spindle moving mechanism 23 shown in FIG. 2 has a motor 23a, a ball screw 23b, and a nut 23c. The motor 23a drives the ball screw 23b. The ball screw 23b extends in the Z-axis direction and rotates about a rotation axis parallel to the Z-axis. The rotational force of the motor 23a is converted into linear motion in the Z-axis direction by the ball screw 23b and the nut 23c. Thereby, the second spindle base 22 connected to the nut 23c moves in the Z-axis direction.

[0018] The motor 23a is, for example, a servo motor. The motor 23a is controlled by the control unit 300 and performs position control so as not to shift at the stopped position even during stoppage.

[0019] Furthermore, the second spindle unit 20 includes a built-in motor 201 and a collet chuck device 203.

[0020] The built-in motor 201 is housed in the second spindle base 22 and rotates the second spindle 21.

[0021] The collet chuck device 203 is located at the tip of the second spindle 21. The collet chuck device 203 is equipped with a collet chuck (not shown) having three equally divided slots when viewed from the axial direction. The collet chuck device 203 clamps or unclams the workpiece W by reducing or expanding the diameter of the slots of the collet chuck.

[0022] As shown in Figures 1 to 3, the turret device 30 comprises a turret 31 as a tool post, a support section 32, a turret Z-axis movement mechanism 33 and a turret Xt-axis movement mechanism 34, a tool 35, a Z-axis slide 36, an Xt-axis slide base 37, and an Xt-axis slide 38.

[0023] A Z-axis slide 36, which is movable in the Z-axis direction, is positioned on the bed S. An Xt-axis slide base 37 is positioned on the upper surface of the Z-axis slide 36, parallel to the Xt-axis in Figure 3. An Xt-axis slide 38, which is movable in the Xt-axis direction, is positioned on the Xt-axis slide base 37. Here, the Xt-axis in this specification is perpendicular to the Z-axis (horizontal direction), similar to the X-axis (horizontal direction), but is an axis parallel to the direction of movement of the turret 31, which is angled upward from the workpiece W side with respect to the X-axis.

[0024] The turret 31 is formed to hold multiple types of tools 35, such as cutting tools, drills, and parting tools 35a, arranged radially around its outer circumference.

[0025] The support section 32 is positioned on the Xt-axis slide 38 and supports the turret 31 so that it can rotate around a rotation axis 31c extending in the Z-axis direction. A turret rotation motor (not shown) is located on the support section 32 to rotate the turret 31. The turret rotation motor rotates the turret 31 to index one of several types of tools 35 mounted on the outer circumference of the turret 31. In this specification, indexing a tool 35 means positioning the tool 35 in the circumferential direction of the turret 31 to a position where it will machine the workpiece W.

[0026] The turret Z-axis movement mechanism 33 moves the Z-axis slide 36 in the Z-axis direction. The turret Xt-axis movement mechanism 34 moves the Xt-axis slide 38 in the Xt-axis direction as shown in Figure 3. As the turret device 30 moves in the Z-axis and Xt-axis directions, the indexed tool 35 cuts into the workpiece W. The turret Z-axis movement mechanism 33 and the turret Xt-axis movement mechanism 34 are each equipped with a motor, a ball screw, and a nut, and move the support part 32 by converting the rotational force of the motor into linear motion using the ball screw and nut.

[0027] The control unit 300 shown in Figure 1 controls the operation of each part of the machine tool 1. The control unit 300 consists of a CPU (Central Processing Unit), a memory unit 303, etc. The control unit 300 executes machining processes according to the NC program stored in the memory unit 303. The control unit 300 also has a load current value acquisition unit 301 and a position adjustment processing unit 302. The load current value acquisition unit 301 acquires the current value (amperes) of the motor 23a when the workpiece W is held by the first spindle unit 10 and the second spindle unit 20, and calculates the load current value (%) as the ratio of the acquired current value to the rated current value of the motor 23a. The position adjustment processing unit 302 adjusts the position of the second spindle unit 20 in the Z-axis direction based on the load current value (%) calculated by the load current value acquisition unit 301. Note that the closer the calculated load current value (%) is to 0 (the smaller the absolute value), the smaller the motor load. Furthermore, the sign (±) of the load current value simply indicates the direction of the load and is not related to the magnitude of the load.

[0028] The memory unit 303 includes ROM (Read Only Memory), RAM (Random Access Memory), etc., and stores the program executed by the control unit 300, as well as necessary data. For example, the memory unit 303 stores the load current value acquired and calculated by the load current value acquisition unit 301, the first threshold (%) and second threshold (%) which are compared with the load current value calculated by the load current value acquisition unit 301, and the amount of movement (mm) to be moved at one time when adjusting the position of the second spindle unit 20. The control unit 300 may be pre-installed in the machine tool 1, or it may be installed in a computer that is retrofitted to the machine tool 1.

[0029] Next, the machining process in the machine tool 1 according to this embodiment will be described with reference to Figures 4 to 7. In the following operations, unless otherwise specified, the operation of each part of the machine tool 1 is performed under the control of the control unit 300, which has a load current value acquisition unit 301 and a position adjustment processing unit 302. The operator determines the first threshold (%), the second threshold (%), and the amount of movement (mm) of the second spindle unit 20, and inputs these values ​​in advance via the input unit 305 (Figures 1 and 2) before machining.

[0030] First, as shown in Figure 6, the workpiece W is supplied to the first spindle unit 10 (step S101). The collet chuck device 103 shown in Figures 1 and 2 is unclamped, and the workpiece W (bar stock) is supplied from a material feeder (not shown) installed behind the first spindle unit 10. Then, the workpiece W is set by clamping it with the collet chuck device 103.

[0031] Next, the control unit 300 rotates the turret 31 via a turret rotation motor (not shown) to change the tool 35 and process the workpiece W held by the first spindle unit 10 (step S102).

[0032] Once the machining of the workpiece W is complete, the control unit 300 then instructs the turret Xt-axis movement mechanism 34 to move the turret 31 in the Xt-axis direction and retract it (step S103). This prevents interference between the tool 35 and the workpiece W when the turret 31 is rotated. Subsequently, the control unit 300 rotates the turret 31 via a turret rotation motor (not shown) to index the parting tool 35a as shown in Figure 3 or Figure 4(a) (step S104). This allows the parting tool 35a to be advanced (moved toward the workpiece W in the Xt-axis direction), as shown in Figure 5(b), thereby enabling parting of the workpiece W.

[0033] Next, a workpiece transfer process is performed in which the workpiece W held by the first spindle unit 10 is transferred to the second spindle unit 20 (step S105 in Figure 6). The flow of this workpiece transfer process is shown in Figure 7.

[0034] In order to execute the workpiece transfer process (step S105), first, as shown in Figure 4(b), the control unit 300 instructs the motor 23a to move the second spindle unit 20 in the Z-axis direction to the gripping position of the workpiece W, as indicated by arrow Y1 (step S201 in Figure 7). At this time, the second spindle unit 20 is in an unclamped state, not gripping the workpiece W.

[0035] Next, the control unit 300 causes the second spindle unit 20 to grip one end of the workpiece W held by the first spindle unit 10 via the collet chuck device 203 (step S202). At this time, a load is inevitably applied to the workpiece W due to the clamping operation. For example, as shown in the enlarged view of Figure 4(c), a downward deflection occurs in the workpiece W, and the second spindle unit 20 receives a force F2 from the workpiece W towards the rear. In Figure 4(c), the deflection of the workpiece W is exaggerated. Note that when the workpiece W is gripped by the second spindle unit 20, the direction in which the workpiece W deflects, and the direction and magnitude of the force acting on the second spindle unit 20 vary and are not always the same.

[0036] Thus, when the second spindle unit 20 receives a force F2 from the workpiece W to the rear, the motor 23a outputs a rotational torque that applies a force F1 to move the second spindle unit 20 forward in order to maintain its stopping position. In this way, the output of the motor 23a to maintain the stopping position of the second spindle unit 20 corresponds to the force that the second spindle unit 20 receives from the workpiece W. The greater the deflection of the workpiece W, the greater the force from the workpiece W, and the greater the current flowing to the motor 23a (the greater the load current value (%)).

[0037] Next, the load current value acquisition unit 301 acquires the current value (amperes) in the state shown in Figure 4(c) where the second spindle unit 20 is clamped to the workpiece W (step S203 in Figure 7). At this time, if the second spindle unit 20 receives a force from the workpiece W to the rear and outputs in a direction that moves the second spindle unit 20 forward to counteract that force, the current value of the motor 23a will be a negative value. On the other hand, if the second spindle unit 20 receives a force from the workpiece W to the front and outputs in a direction that moves the second spindle unit 20 backward to counteract that force, the current value of the motor 23a will be a positive value.

[0038] Next, the load current value acquisition unit 301 calculates the load current value (%) by determining the ratio of the acquired current value to the rated current value of the motor 23a (step S204). For example, if the rated current value of the motor 23a is 40A (amperes) and the acquired current value is 2A (amperes), the load current value acquisition unit 301 calculates a load current value of 5%.

[0039] Next, the position adjustment processing unit 302 compares the load current value (%) calculated by the load current value acquisition unit 301 with the second threshold value (%) entered by the operator, and determines whether the load current value (%) is greater than the second threshold value (%) (step S205). Here, the second threshold value (%) is a limit value for determining whether an excessive load is acting on the workpiece W. Step S205 shows the case where a positive value is entered by the operator for the second threshold value (%). That is, the second threshold value (%) is the upper limit of the current value of the motor 23a when a load is applied in the rotational direction that retracts the second spindle unit 20. On the other hand, if a negative value is entered by the operator for the second threshold value (%), step S205 becomes a step to determine whether the load current value (%) is less than the second threshold value (%). If the position adjustment processing unit 302 determines that the load current value (%) is greater than (exceeds) the second threshold (%) (step S205: Yes), it displays a warning message on the display unit 304 (Figure 1) indicating that an excessive load is being placed on the workpiece W, decides to terminate the machining process (step S206), and ends the workpiece transfer process.

[0040] On the other hand, if in step S205 it is determined that the load current value (%) is less than or equal to the second threshold (%) (step S205: No), the position adjustment processing unit 302 determines whether the load current value (%) is greater than or equal to the input first threshold (%) (step S207). Here, the first threshold (%) is a threshold used to determine whether the load acting on the workpiece W is sufficiently small. Step S207 shows the case where the operator inputs a negative value for the first threshold (%). That is, the first threshold (%) is a threshold used to determine whether the output of the motor 23a in the rotational direction that advances the second spindle unit 20 has become sufficiently small (whether the load on the workpiece W has become small). When the load on the workpiece W becomes small, the deflection of the workpiece W also becomes small. On the other hand, if the operator inputs a positive value for the first threshold (%), step S207 becomes a step to determine whether the load current value (%) is less than or equal to the first threshold (%).

[0041] In step S207, if it is determined that the load current value (%) is less than or equal to the first threshold (%) (step S207: No), the position adjustment processing unit 302 assumes that a large load is acting on the workpiece W and moves the second spindle unit 20 in a direction that reduces the load current value (step S208). Specifically, as shown in Figure 5(a), the position adjustment processing unit 302 moves (retracts) the second spindle unit 20 to the +Z side (right side in the figure) as indicated by arrow Y2, in order to reduce the force pushing the second spindle unit backward (to reduce the load acting on the workpiece W). At this time, the position adjustment processing unit 302 moves the second spindle unit 20 in the Z-axis direction by the amount of movement (mm) input via the input unit 305 (Figure 1). This amount of movement (mm) is set to the amount by which the second spindle unit 20 must be moved multiple times to raise the current value of the motor 23a, which has been obtained as a negative value, to the first threshold (%).

[0042] Then, after moving the second spindle unit 20 in step S208, the control unit 300 returns to step S203 and acquires the current value of the motor 23a with the workpiece W clamped again (step S203). Then, the position adjustment processing unit 302 calculates the load current value based on the newly acquired current value and the rated current value of the motor 23a (step S204), and if necessary, moves the second spindle unit 20 again in the direction of reducing the load current value. In this way, the second spindle unit 20 is moved in the direction of reducing the load current value until the calculated load current value (%) is equal to or greater than the first threshold (%).

[0043] On the other hand, if the load current value (%) is less than or equal to the second threshold (%) (step S205: No), and in step S207 the load current value (%) is greater than or equal to the first threshold (%) (step S207: Yes), the control unit 300 performs a parting-off process on the workpiece W (step S209). The control unit 300 synchronizes the built-in motor 101 of the first spindle unit 10 and the built-in motor 201 of the second spindle unit 20, as shown in Figure 1, to rotate the workpiece W. Then, the control unit 300 advances the turret 31 via the turret Xt axis movement mechanism 34, so that the parting-off tool 35a can be applied to the workpiece W and processed, as shown in Figure 5(b). As a result the workpiece W is separated, and one of the separated parts of the workpiece W is transferred to the second spindle unit 20, completing the workpiece transfer process.

[0044] When the workpiece transfer process in step S105 shown in Figure 6 is completed, the control unit 300 determines whether or not to terminate the machining process (step S106). If the workpiece transfer process shown in Figure 7 has gone through step S206, the control unit 300 determines that the machining process should be terminated (step S106: Yes), and terminates the machining process.

[0045] On the other hand, in the workpiece transfer process shown in Figure 7, if step S206 has not been taken (step S106: No), the control unit 300 performs machining on the workpiece W held by the second spindle unit 20 (step S107). Specifically, as shown in Figure 5(c), the control unit 300 moves the second spindle unit 20, which is holding the workpiece W, backward to the machining position indicated by arrow Y3. Then, the control unit 300 machines the workpiece W with the tool 35 provided on the turret 31.

[0046] Finally, the workpiece W held by the second spindle unit 20 is discharged by a workpiece conveyor (not shown) (step S108). This completes the machining process of the workpiece W.

[0047] Next, an example of position adjustment of the second spindle unit 20 will be explained with reference to Figure 8. In the machining process of the workpiece W shown in Figure 8, it is assumed that the operator has entered the following into the memory unit 303: first threshold = -2 (%), second threshold = 10%, and the amount of movement S1 of the second spindle unit 20 in one cycle = 0.003 (mm). For simplicity, it is assumed that the initial position of the second spindle unit 20 that grasps the workpiece W is 0 (mm).

[0048] First, let's assume that at time t1, the second spindle unit 20 grasped the workpiece W, and the load current value of motor 23a was calculated to be -6 (%). Since the load current value is negative, the second spindle unit 20 receives a force backward, and motor 23a outputs a force in the rotational direction that moves the second spindle unit 20 forward.

[0049] Here, the load current value of -6(%) is less than or equal to the second threshold (10(%)) (Step S205: No) and less than or equal to the first threshold (-2(%)) (Step S207: No). Therefore, in its determination at time t2, the control unit 300 decides to move the second spindle unit 20 in a direction that reduces the load current value.

[0050] Then, at time t3, the control unit 300 moves the second spindle unit 20 to the +Z side by a movement amount S1: 0.003 mm. This movement of the second spindle unit 20 reduces the deflection of the workpiece W and the force acting on the second spindle unit 20, which causes a change in the load current value of the motor 23a.

[0051] Next, the control unit 300 calculates the load current value of motor 23a as -4(%) at time t4. The load current value of -4(%) is less than or equal to the second threshold (10(%)) (step S205: No) and less than or equal to the first threshold (-2(%)) (step S207: No). Therefore, in the determination at time t4, the control unit 300 makes a second decision to move the second spindle unit 20 in the direction that reduces the load current value.

[0052] Then, at time t5, the control unit 300 moves the second spindle unit 20 to the +Z side by a movement amount S1: 0.003 mm. This movement of the second spindle unit 20 reduces the deflection of the workpiece W and the force acting on the second spindle unit 20, which causes a change in the load current value of the motor 23a.

[0053] Next, the control unit 300 calculates the load current value of motor 23a as -2(%) at time t6. The load current value of -2(%) is less than or equal to the second threshold (10(%)) (Step S205: No) and greater than or equal to the first threshold (-2(%)) (Step S207: Yes). Therefore, the control unit 300 does not move the second spindle unit 20 any further. After that, as shown in Figure 5(b), the control unit 300 advances the parting tool 35a (moves it toward the workpiece W in the Xt axis direction) to perform parting on the workpiece W. This completes the workpiece W transfer process.

[0054] The present invention is not limited to the embodiments and drawings described above. Modifications (including the deletion of components) can be made as appropriate without altering the essence of the invention.

[0055] In the above embodiment, the first spindle unit 10 was configured not to move in the Z-axis direction, but it may be configured to include a Z-axis movement mechanism. The first spindle unit 10 may then be moved using the Z-axis movement mechanism of the first spindle unit 10 to reduce the load acting on the workpiece W held by the second spindle unit 20. The second spindle unit 20 may also be equipped with a Y-axis movement mechanism.

[0056] Furthermore, although the description has focused on the case where the tool post to which the tool 35 is attached is of the turret type, it may also be of the comb-blade type.

[0057] Additionally, a rear tool post may be separately provided for machining the workpiece W grasped by the second spindle unit 20.

[0058] Furthermore, the chuck devices provided on the first spindle unit 10 and the second spindle unit 20 are not limited to collet chuck devices 103 and 203, but may also be three-jaw chuck devices.

[0059] Furthermore, the values ​​of the first and second thresholds are arbitrary and can be set to appropriate values ​​depending on the workpiece being processed and the machine tool.

[0060] Furthermore, the relationship between the ± value of the load current and the rotation direction of motor 23a is just one example; the opposite setting may also be used.

[0061] Furthermore, the ratio of the acquired current value to the rated current value of the motor 23a was calculated as the load current value (%), and the position of the second spindle unit 20 in the Z-axis direction was adjusted based on this calculated load current value (%). However, the position of the second spindle unit 20 in the Z-axis direction may also be adjusted based on the current value (amperes) acquired from the motor 23a and the first threshold value (amperes) and second threshold value (amperes) entered by the operator. In this case, step S204, which calculates the load current value shown in Figure 7, can be omitted.

[0062] Furthermore, in the above, the current value of motor 23a, the first threshold, and the second threshold were treated as having positive and negative values ​​depending on the rotation direction output by motor 23a. However, the operation of the machine tool 1 may also be controlled using the absolute values ​​of these values. For example, the absolute value of the first threshold may be set to 2 (%) and the absolute value of the second threshold to 10 (%), and the second spindle unit 20 may be moved so that the absolute value of the calculated load current value (%) approaches 0. In this case, if the absolute value (%) of the load current value exceeds the second threshold (if it is large), a warning should be issued and the machining should be terminated. Alternatively, the second spindle unit 20 may be moved until the absolute value (%) of the load current value becomes less than or equal to the first threshold (until the first threshold is reached).

[0063] Furthermore, although it was explained that the first threshold (%), the second threshold (%), and the amount of movement of the second spindle unit 20 (mm) are determined by the operator and input via the input unit 305 before machining, these values ​​may be stored in advance in the storage unit 303, and the control unit 300 may read these values ​​according to the workpiece to be machined.

[0064] Furthermore, while the example of displaying a warning message on the display unit 304 (Figure 1) and terminating the machining process midway as a warning of high load on the workpiece W was explained, the form of the warning is arbitrary. For example, a warning sound may be emitted from the speaker, or a notification that the load current value has exceeded the limit may be given. Alternatively, the user may be notified by a display on the display unit 304 and an audio notification from the speaker.

[0065] (effect) The embodiments described above provide the following effects. (1) The machine tool 1 according to the above embodiment includes a first spindle unit 10 for gripping a workpiece W, a second spindle unit 20 positioned opposite the first spindle unit 10 and gripping one end of the workpiece W gripped by the first spindle unit 10, a tool post (turret 31) to which a tool 35 for machining the workpiece W is attached, and a moving mechanism (second spindle moving mechanism 23) that moves the second spindle unit 20 by the output of the motor 23a. With one end of the workpiece W gripped by the first spindle unit 10 gripped by the second spindle unit 20, the second spindle unit is moved by the moving mechanism (second spindle moving mechanism 23) in a direction that reduces the absolute value of the load current of the motor 23a, and then the workpiece W is cut by the tool 35 and handed over to the second spindle unit 20. This configuration produces the effects of (a) to (c). (a) By reducing the absolute value of the load current of motor 23a, the load acting on the workpiece gripped by the second spindle unit 20 is reduced, and the deflection of the workpiece W as shown in Figure 4(c) is reduced. As a result, the workpiece W can be gripped in the correct gripping position. (b) Furthermore, since parting-off can be performed while the workpiece W is held in the correct gripping position, variations in product length can be suppressed. (c) Reducing variations in product length can improve product quality.

[0066] (2) In the machine tool according to the above embodiment, a first threshold value is set for the load current value of the motor 23a, and the moving mechanism (second spindle moving mechanism 23) moves the second spindle unit 20 until the load current value of the motor 23a reaches the set first threshold value. This configuration produces the effects of (d) to (e). (d) Since the workpiece W is disconnected when the load current value reaches a constant value (first threshold), the recognition state is highly reproducible, and the workpiece W can be disconnected under the same recognition conditions each time. (e) By setting the first threshold value lower, the load current value of the motor 23a can be further reduced, and the workpiece W can be grasped while the deflection is small.

[0067] (3) In the machine tool according to the above embodiment, the amount of movement S1 that the second spindle unit 20 can move at one time is determined in order to reduce the absolute value of the load current, and the second spindle unit 20 repeats movement of the determined amount S1 until the absolute value of the load current reaches the first threshold. This configuration produces the effect of (f). (f) By moving the second spindle unit 20 in multiple steps, the position of the second spindle unit can be adjusted until the load current value reaches the first threshold.

[0068] (4) In the machine tool according to the above embodiment, a second threshold value is set for the load current value of the motor 23a, and a warning is issued if the absolute value of the load current value of the motor 23a is equal to or greater than the absolute value of the second threshold value. This configuration produces the effect of (g). (g) If an excessive load is applied to the workpiece W, the workpiece W is being handled abnormally, and the user can be notified of this as a warning, and the machining process can be stopped.

[0069] (5) In the machine tool according to the above embodiment, the first threshold can be set for each workpiece W. This configuration produces the effects of (h) to (i). (h) A value suitable for the shape of the workpiece W to be processed can be set, thereby improving the quality of the product. (i) When changing the workpiece W to be processed, it is only necessary to recall the value set for each workpiece, making it easy to process different workpieces. [Explanation of Symbols]

[0070] 1...Machine tool, 10...First spindle unit, 11...First spindle, 12...First headstock, 20...Second spindle unit, 21...Second spindle, 22...Second headstock, 23...Second spindle movement mechanism, 23a...Motor, 23b...Ball screw, 23c...Nut, 30...Turret device, 31...Turret, 31c...Rotating shaft, 32...Support, 33...Turret Z-axis movement mechanism, 34...Turret Xt-axis movement mechanism, 35...Tool, 35a...Protrusion Cutting tool, 36...Z-axis slide, 37...Xt-axis slide base, 38...Xt-axis slide, 101, 201...Built-in motor, 103, 203...Collet chuck device, 300...Control unit, 301...Load current value acquisition unit, 302...Position adjustment processing unit, 303...Storage unit, 304...Display unit, 305...Input unit, F...Force, S...Bed, S1...Amount of movement, W...Workpiece, t1, t2, t3, t4, t5, t6...Time.

Claims

1. The first spindle unit that grasps the workpiece, A second spindle unit is positioned opposite the first spindle unit and grasps one end of the workpiece that the first spindle unit grasps, A tool post to which a tool for machining the aforementioned workpiece is attached, The system includes a moving mechanism that moves the second spindle unit by the output of a motor, With the second spindle unit gripping one end of the workpiece held by the first spindle unit, the second spindle unit is moved by the moving mechanism in a direction that reduces the absolute value of the motor load current, and then the workpiece is cut by the tool and handed over to the second spindle unit. Machine tools.

2. A first threshold value is set for the load current value of the motor. The moving mechanism moves the second spindle unit until the load current value of the motor reaches the set first threshold. The machine tool according to claim 1.

3. In order to reduce the absolute value of the load current, the amount of movement that the second spindle unit can move at one time is determined. The second spindle unit repeats the movement of a predetermined amount until the absolute value of the load current reaches the first threshold. The machine tool according to claim 2.

4. A second threshold value is set for the load current value of the motor. If the absolute value of the load current of the motor is greater than or equal to the absolute value of the second threshold, a warning is issued. The machine tool according to claim 1.

5. The first threshold can be set for each workpiece. The machine tool according to claim 2 or 3.

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