Machine tools

Abstract

To provide a machine tool that does not require a special machining program for completing machining of a work-piece in the middle of machining and ending continuous machining both when using and not using a different system of a cutter holder for machining the work-piece in the middle of machining.SOLUTION: A control unit (70) of a machine tool (1) determines whether or not a first cutter holder 30 is to be used for machining a work-piece W2 which is being machined, based on a machining program PR2; when the control unit of the machine tool completes the machining of the work-piece W2 in the middle of machining and terminates continuous machining, the control unit of the machine tool simultaneously advances a first system and a second system according to the machining program PR2 while preventing a work-piece W1 gripped by a first spindle (11) from being machined in a case where the first cutter holder 30 is used to machine the work-piece W2 which is in the middle of machining; and the control unit of the machine tool stops the first system and advances the second system according to the machining program PR2 in a case where the first cutter holder 30 is not used for machining the work-piece W2 which is in the middle of machining.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a machine tool that is equipped with a plurality of headstocks and performs continuous machining of a workpiece by simultaneously advancing a plurality of systems. [Background technology]

[0002] A known machine tool is an NC (numerically controlled) lathe equipped with a front headstock and a back headstock. The NC lathe performs front machining of a workpiece held by the front spindle using a tool attached to a tool rest. After the front machining, the workpiece is held by the back spindle, and the back of the workpiece being machined and held by the back spindle is machined using a tool attached to the tool rest. During continuous machining of a workpiece, a first system that performs front machining of the workpiece and a second system that performs back machining of the workpiece after the front machining proceed simultaneously according to a machining program.

[0003] The NC lathe disclosed in Patent Document 1 is capable of simultaneously running a first spindle system that drives a first spindle etc. and a second spindle system that drives a second spindle etc., and performs simultaneous machining by shifting the cycle start timing between the first spindle system and the second spindle system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-118201 Summary of the Invention [Problem to be solved by the invention]

[0005] It is conceivable to simultaneously operate the first system, which drives the front spindle, etc., and the second system, which drives the back spindle, etc., during continuous workpiece machining, and complete the workpiece in the middle of machining at the end of continuous machining. When the tool post included in the first system is not used for back machining, by operating the second system and stopping the first system, it is possible to perform back machining of the workpiece held by the back spindle without performing front machining of the workpiece held by the front spindle. However, when the tool post included in the first system is used for back machining, stopping the first system prevents the workpiece in the middle of machining from being completed, and continuing the operation of the first system results in unintended front machining of the workpiece held by the front spindle. Therefore, when using the tool post included in the first system for back machining, the operator must create a special machining program to perform back machining of the workpiece held by the back spindle without performing front machining of the workpiece held by the front spindle at the end of continuous machining. Therefore, the operator must create separate machining programs for when the tool post included in the first system is used for back machining and when it is not.

[0006] The present invention discloses a machine tool that does not require a special machining program to complete the machining of a workpiece in the middle of machining and end continuous machining, whether or not a separate tool post is used for machining the workpiece in the middle of machining. [Means for solving the problem]

[0007] The machine tool of the present invention is a machine tool that performs continuous machining of a workpiece, a first headstock provided with a first spindle that grips the workpiece; a second headstock provided with a second spindle that grips the workpiece being processed and transferred from the first spindle; a first tool rest to which a first tool is attached that machines the workpiece held by at least one of the first spindle and the second spindle; a second tool rest to which a second tool is attached that machines the workpiece in the middle of machining held by the second spindle; a first system for driving the first headstock including the first spindle and the first tool rest, and a second system for driving the second headstock including the second spindle and the second tool rest, and a machining program created by an operator. and a control unit that simultaneously performs the steps according to the The control unit Whether or not the first tool rest is to be used for machining the workpiece in the middle of machining is determined by the machining program Description of Determine based on When the continuous machining is to be ended by completing the machining of the workpiece in the middle of machining, if the first tool rest is used for machining the workpiece in the middle of machining, While following the description of the first tool post in the first system and the description of the second system among the descriptions of (1), the first headstock is retracted to a position that prevents contact between the workpiece and the first tool, and the drive of the first headstock is stopped. , the first system and the second system while preventing the workpiece held by the first spindle from being machined. The same Progressing at a time, When the continuous machining is ended by completing the machining of the workpiece in the middle of machining, if the first tool rest is not used for machining the workpiece in the middle of machining, the machining program for performing the continuous machining is While following the description of the second system in the description of , stopping the first system By doing so, The second system Proceed It has a mode of causing the [Effects of the Invention]

[0008] According to the present invention, a machine tool can be provided that does not require a special machining program to complete the machining of a workpiece in the middle of machining and end continuous machining, whether or not a separate tool post is used to machine the workpiece in the middle of machining. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view schematically showing an example of the configuration of a machine tool. [Figure 2] FIG. 1 is a diagram illustrating an example of a system. [Figure 3] FIG. 2 is a block diagram schematically illustrating an example of the configuration of an electric circuit of a machine tool. [Figure 4]FIG. 10 is a diagram schematically showing an example of a machining program written so as not to use a first tool rest for machining a workpiece that is currently being machined. [Figure 5] FIG. 10 is a diagram schematically showing an example of a machining program written so that a first tool rest is used to machine a workpiece that is currently being machined. [Figure 6] 10 is a flowchart schematically illustrating an example of a final machining execution setting process. [Figure 7] 10 is a flowchart schematically showing a processing process. [Figure 8] 10 is a flowchart schematically showing a processing process. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the present invention. Of course, the following embodiments are merely examples of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution of the invention.

[0011] (1) Overview of the technology included in this invention: First, an overview of the technology included in the present invention will be described with reference to the examples shown in Figures 1 to 8. Note that the figures in this application are diagrams showing schematic examples, and the magnifications in the directions shown in these figures may differ, and the figures may not be consistent. Of course, each element of the present technology is not limited to the specific example indicated by the symbol.

[0012] [Aspect 1] As illustrated in FIGS. 1 to 3, a machine tool (e.g., lathe 1) according to one aspect of the present technology is a machine tool (1) that continuously machines a workpiece W1 and includes a first headstock (e.g., front headstock 10), a second headstock (e.g., back headstock 15), a first tool rest 30, a second tool rest 40, and a control unit (e.g., NC device 70). The first headstock (10) is provided with a first spindle (e.g., front spindle 11) that grips the workpiece W1. The second headstock (15) is provided with a second spindle (e.g., back spindle 16) that grips the workpiece W2 that has been transferred from the first spindle (11) and is currently being machined. A first tool TO1 that machines the workpiece W1 gripped by at least one of the first spindle (11) and the second spindle (16) is attached to the first tool rest 30. A second tool TO2 is attached to the second tool rest 40 to machine the in-process workpiece W2 gripped by the second spindle (16). The control unit (70) simultaneously controls a first system (e.g., system 1) that drives the first headstock (10) including the first spindle (11) and the first tool rest 30, and a second system (e.g., system 2) that drives the second headstock (15) including the second spindle (16) and the second tool rest 40, in accordance with a machining program PR2. The control unit (70) determines whether or not to use the first tool rest 30 to machine the in-process workpiece W2 based on the machining program PR2, and performs control for the following cases when completing machining of the in-process workpiece W2 and terminating the continuous machining: When the first tool rest 30 is used to machine the workpiece W2 that is currently being machined, the control unit (70) causes the first system and the second system to proceed simultaneously according to the machining program PR2 while preventing the workpiece W1 held by the first spindle (11) from being machined. When the first tool rest 30 is not used to machine the workpiece W2 in the middle of machining, the control unit (70) stops the first system and causes the second system to proceed according to the machining program PR2.

[0013] In the above-described embodiment 1, a first system that drives the first headstock (10) including the first spindle (11) and the first tool rest 30, and a second system that drives the second headstock (15) including the second spindle (16) and the second tool rest 40, simultaneously proceed according to the machining program PR2. Here, whether or not the first tool rest 30 will be used to machine the workpiece W2 that is being held by the second spindle (16) and is currently being machined is determined based on the machining program PR2.

[0014] When the first tool rest 30 is used to machine the workpiece W2 in the middle of machining, when it is time to complete machining of the workpiece W2 in the middle of machining and end the continuous machining, the workpiece W1 held by the first spindle (11) is not machined, and the first and second systems proceed simultaneously according to the machining program PR2. As a result, machining of the workpiece W2 in the middle of machining is completed without using a special machining program, and the continuous machining ends. On the other hand, when the first tool rest 30 is not used to machine the workpiece W2 in the middle of machining, when it is time to complete machining of the workpiece W2 in the middle of machining and end the continuous machining, the first system stops and the second system proceeds according to the machining program PR2. As a result, it is time to complete machining of the workpiece W2 in the middle of machining and end the continuous machining, and the continuous machining ends. As described above, the above-mentioned aspect 1 can provide a machine tool that does not require a special machining program to complete the machining of the workpiece in progress and end continuous machining, both in the case where a tool post of a different system is used for machining the workpiece in progress and in the case where it is not used.

[0015] Here, the second spindle only needs to be able to grip the workpiece being processed that has been handed over from the first spindle, and may be a spindle opposite to the first spindle, or a spindle that is not opposite to the first spindle. The number of systems that proceed simultaneously is not limited to two, the first system and the second system, but may be three or more systems including the first system and the second system. In this application, the terms "first", "second", etc. are terms for distinguishing between elements among a plurality of elements having similarities, and do not imply any order. The above remarks also apply to the following aspects.

[0016] [Aspect 2] As illustrated in Fig. 6, the control unit (70) may receive a setting indicating whether or not to complete the machining of the workpiece W2 in the middle of machining when the continuous machining is terminated. If the setting indicates that the machining of the workpiece W2 in the middle of machining will not be completed, the control unit (70) may stop the first system and the second system without completing the machining of the workpiece W2 in the middle of machining when the continuous machining is terminated. This aspect allows the user to select whether or not to complete the machining of the workpiece W2 in the middle of machining when the continuous machining is terminated, thereby improving convenience.

[0017] [Aspect 3] 8 , when completing the machining of the workpiece W2 in progress and ending the continuous machining, if the first tool rest 30 is to be used to machine the workpiece W2 in progress, the control unit (70) may, in the first system, retract the first headstock (10) including the first spindle (11) gripping the workpiece W1 to a position that prevents contact between the workpiece W1 and the first tool TO1, and then stop driving the first headstock (10) and drive the first tool rest 30; or, in the second system, may drive at least the second headstock (15) including the second spindle (16) gripping the workpiece W2 in progress. This aspect can prevent interference between the workpiece W1 gripped by the first spindle (11) and the first tool TO1 when the first tool rest 30 is used to machine the workpiece W2 in progress at the time of ending the continuous machining, and therefore provides a suitable example of completing the machining of the workpiece in progress and ending the continuous machining.

[0018] (2) Specific examples of machine tool configurations: 1 is a front view showing a schematic configuration of a lathe 1 as an example of a machine tool, and FIG. 2 shows a schematic system of the lathe 1. In Fig. 1, symbol D81 indicates the upward direction, symbol D82 indicates the downward direction, symbol D83 indicates the leftward direction, and symbol D84 indicates the rightward direction, all of which are based on the direction in which the lathe 1 shown in Fig. 1 is viewed.

[0019] The lathe 1 is an NC lathe equipped with a front headstock 10, a front headstock drive unit 13, a back headstock 15, a back headstock drive unit 18, a support stand 25, a first tool rest 30, a first tool rest drive unit 31, a second tool rest 40, a second tool rest drive unit 41, an NC (numerical control) unit 70, etc. Here, the front headstock 10 is an example of a first headstock provided with a front spindle 11 as a first spindle. The back headstock 15 is an example of a second headstock provided with a back spindle 16 as a second spindle. The NC unit 70 is an example of a control unit. The lathe 1 may be provided with a tool rest, such as a third tool rest, which is different from the first tool rest 30 and the second tool rest 40. Of course, the lathe 1 may be provided with a spindle, such as a third main spindle, which is different from the first main spindle and the second main spindle.

[0020] The front headstock 10 is fitted with a front spindle 11 that releasably grips a rod-shaped workpiece W1 inserted from the rear by a material feeder 20, as shown in FIG. 3. The front end 11a of the front spindle 11 faces the back spindle 16, and the rear end 11b of the front spindle 11 faces the material feeder 20. The front spindle 11 has a through-hole 11h that runs along the spindle center line AX1. The workpiece W1 is inserted into the through-hole 11h from the rear. The back headstock 15 is fitted with a back spindle 16, an example of an opposing spindle, that releasably grips a workpiece W2 that is being machined and protruding forward from the front end 11a of the front spindle 11. The front end 16a of the back spindle 16 faces the front end 11a of the front spindle 11. In other words, the front spindle 11 and the back spindle 16 face each other. The forward direction of the front spindle 11 refers to the direction in which the workpiece W1 is pushed out from the front spindle 11, which is the right direction D84 in the example shown in FIG. 1. The rearward direction of the front spindle 11 refers to the direction from the front spindle 11 toward the material feeder 20, which is the left direction D83 in the example shown in FIG. 1. The forward direction of the back spindle 16 refers to the direction in which the back spindle 16 moves toward the front spindle 11, which is the left direction D83 in the example shown in FIG. 1. A guide bush 14 can be attached to the mounting hole 26 of the support base 25, and although not shown, the front part of the front spindle 11 can also be inserted into it. Therefore, the lathe 1 is a moving spindle type lathe that can be switched between the presence and absence of a guide bush 14.

[0021] The front spindle 11 is equipped with a gripper 12 that releasably grips the workpiece W1, and is rotatable about the spindle center line AX1 together with the workpiece W1 gripped by the gripper 12. The NC device 70 controls the gripping state of the gripper 12 by driving a gripping actuator 12a, as shown in FIG. 3. The gripper 12 may be configured, for example, by a collet. The front headstock drive unit 13 moves the front headstock 10, to which the front spindle 11 is attached, in the +Z1 direction and the -Z1 direction (see FIG. 2) in accordance with commands from the NC device 70. The +Z1 direction and the -Z1 direction are directions along the Z1 axis, which serves as a control axis; the +Z1 direction is the rightward direction D84 shown in FIG. 1, and the -Z1 direction is the leftward direction D83 shown in FIG. 1.

[0022] The back spindle 16 includes a gripper 17 that releasably grips a workpiece W2 included in the workpiece W1 and is rotatable about the spindle center line AX2. The workpiece W2 is a part of the rod-shaped workpiece W1 supplied from the material feeder 20, including its tip, and is separated from the rod-shaped workpiece W1 by a cut-off tool (not shown) after front machining. The NC unit 70 controls the gripping state of the gripper 17 by driving a gripping actuator 17a, as shown in FIG. 3. The gripper 17 may be, for example, a collet. The back headstock drive unit 18 moves the back headstock 15, to which the back spindle 16 is attached, in the +Z2 and -Z2 directions and the +X2 and -X2 directions (see FIG. 2) in accordance with commands from the NC unit 70. The +Z2 direction and the -Z2 direction are directions along the Z2 axis as a control axis, with the +Z2 direction being the left direction D83 shown in Figure 1 and the -Z2 direction being the right direction D84 shown in Figure 1. The +X2 direction and the -X2 direction are directions along the X2 axis as a control axis and are opposite directions to each other. The Z2 axis and the X2 axis are orthogonal to each other, but they do not have to be orthogonal as long as they intersect. The workpiece W2, which is in the middle of being processed and separated from the rod-shaped workpiece W1, is turned into a finished product by machining its back surface.

[0023] The rod-shaped workpiece W1 is not limited to a solid material such as a long columnar material, but may be a hollow material such as a long cylindrical material.

[0024] The support base 25 is located between the front headstock 10 and the back headstock 15 in the direction along the Z1 axis, and has a mounting hole 26 that penetrates in the direction along the Z1 axis. When a guide bush is used as shown in FIG. 1, the guide bush 14 is inserted into the mounting hole 26 and is removably attached to the support base 25. The guide bush 14 supports the workpiece W1 that protrudes forward from the through hole 11h of the front spindle 11 so that it can slide in the Z axis direction. The portion of the workpiece W1 that protrudes from the guide bush 14 toward the back spindle 16 (rightward D84) is machined by the first tool TO1. When a guide bush is not used, the front part of the front spindle 11 is inserted into the mounting hole 26. The portion of the workpiece W1 that protrudes forward (rightward D84) from the front spindle 11 is machined by the first tool TO1.

[0025] A plurality of first tools TO1 for machining a workpiece W1 held by at least one of the front spindle 11 and the back spindle 16 are attached to the first tool rest 30. The first tool rest drive unit 31 moves the first tool rest 30, to which the plurality of first tools TO1 are attached, in the +X1 direction, the -X1 direction, and the +Y1 direction, and the -Y1 direction (see FIG. 2) in accordance with commands from the NC device 70. The +X1 direction and the -X1 direction are directions along the X1 axis, which serves as a control axis. The +X1 direction is the upward direction D81 shown in FIG. 1, and the -X1 direction is the downward direction D82 shown in FIG. 1. The +Y1 direction and the -Y1 direction are directions along the Y1 axis, which serves as a control axis, and are opposite directions to each other. The X1 axis and the Y1 axis are orthogonal to each other, but they do not have to be orthogonal as long as they intersect. In FIG. 2, the +Y1 direction is aligned with the -X2 direction and the -Y1 direction is aligned with the +X2 direction, but the -X1 direction may be aligned with the -X2 direction and the +X1 direction may be aligned with the +X2 direction. The first tool rest 30 may be a comb tool rest, a turret tool rest, or the like.

[0026] The plurality of first tools TO1 include cutting tools including cut-off tools, rotary tools such as rotary drills and end mills, etc. The plurality of first tools TO1 shown in Figures 1 and 2 include a front side tool TO1a that machines a workpiece W1 held by the front spindle 11, and a back side tool TO1b that machines a workpiece W2 that is held by the back spindle 16 and is in the middle of being machined. A cut-off tool is included in the front side tool TO1a, but may also be included in the back side tool TO1b.

[0027] A plurality of second tools TO2 are attached to the second tool rest 40 for machining a workpiece W2 that is gripped by the back spindle 16 and is currently being machined. The second tool rest drive unit 41 moves the second tool rest 40, to which the plurality of second tools TO1 are attached, in the +Y2 direction and the -Y2 direction (see FIG. 2) in accordance with commands from the NC device 70. The +Y2 direction and the -Y2 direction are directions along the Y2 axis, which serves as a control axis, and the +Y2 direction is the upward direction D81 shown in FIG. 1, and the -Y2 direction is the downward direction D82 shown in FIG. 1. The plurality of second tools TO2 include drills, taps, and the like.

[0028] It should be noted that the drawings referred to in this specification merely show examples for explaining the present technology and do not limit the present technology. The explanation of the positional relationship of each part is merely an example. Therefore, reversing the left and right sides, reversing the direction of rotation, etc. are also included in the present technology. The identity of direction, position, etc. is not limited to strict agreement, and includes deviations from strict agreement due to error.

[0029] As shown in FIG. 2, the NC device 70 simultaneously operates two systems according to a machining program: system 1, which drives the front headstock 10 including the front spindle 11 and the first tool rest 30; and system 2, which drives the back headstock 15 including the back spindle 16 and the second tool rest 40. Here, system 1 is an example of the first system, and system 2 is an example of the second system. Although the back tool TO1b attached to the first tool rest 30 is included in system 1, it is used for back machining of the workpiece W2 that is currently being machined. In this case, systems 1 and 2 must be operated simultaneously to perform back machining of the workpiece W2 that is currently being machined.

[0030] FIG. 3 shows a schematic diagram of the electrical circuit configuration of a lathe 1 equipped with an NC device 70. The NC device 70 is connected to an operation unit 80, a material feeder 20, a headstock drive unit 13, a headstock rotation drive unit 11c, a gripping actuator 12a, a backhead drive unit 18, a backhead rotation drive unit 16c, a gripping actuator 17a, a first tool rest drive unit 31, a second tool rest drive unit 41, and the like. The headstock rotation drive unit 11c is equipped with a servo motor (not shown, for example, a built-in motor) and rotates the headstock spindle 11 about the spindle center line AX1. The gripping actuator 12a drives the gripper 12 of the headstock spindle 11. The backhead rotation drive unit 16c is equipped with a servo motor (not shown, for example, a built-in motor) and rotates the backhead spindle 16 about the spindle center line AX2. The gripping actuator 17a drives the gripping portion 17 of the back spindle 16. The NC device 70 includes a CPU 71 (a processor), a ROM 72 (a semiconductor memory), a RAM 73 (a semiconductor memory), a clock circuit 74, an I / F (interface) 75, and other components. In FIG. 3, the I / Fs for the operation unit 80, material feeder 20, headstock drive unit 13, headstock rotation drive unit 11c, gripping actuator 12a, backstock drive unit 18, backstock rotation drive unit 16c, gripping actuator 17a, first tool rest drive unit 31, and second tool rest drive unit 41 are collectively referred to as I / F 75. The ROM 72 contains a control program PR1 for interpreting and executing the machining program PR2. The ROM 72 may be a rewritable semiconductor memory. The RAM 73 stores the machining program PR2 created by the operator in a rewritable manner. The machining program is also called an NC program. The CPU 71 uses the RAM 73 as a work area and executes the control program PR1 recorded in the ROM 72 to realize the functions of the NC device 70.

[0031] The operation unit 80 includes an input unit 81 and a display unit 82, and functions as a user interface for the NC device 70. The input unit 81 is configured, for example, by buttons or a touch panel for receiving operation inputs from an operator. The display unit 82 is configured, for example, by a display for displaying the contents of various settings received as operation inputs from the operator and various information related to the lathe 1. The operator can store the machining program PR2 in the RAM 73 using the operation unit 80 or an external computer (not shown).

[0032] The headstock drive unit 13 includes a servo amplifier connected to the NC device 70, a servo motor connected to the servo amplifier, a feed mechanism, and a guide in order to move the headstock 10 including the head spindle 11 along the Z1 axis. The headstock drive unit 13 controls the position of the headstock 10 on the Z1 axis in accordance with commands from the NC device 70. The head spindle rotation drive unit 11c controls the rotational position of the head spindle 11 in accordance with commands from the NC device 70. The back headstock drive unit 18 includes a servo amplifier connected to the NC device 70, a servo motor connected to the servo amplifier, a feed mechanism, and a guide in order to move the back headstock 15 including the back spindle 16 along the Z2 axis. The back headstock drive unit 18 controls the position of the back headstock 15 on the Z2 axis in accordance with commands from the NC device 70. The back spindle rotation drive unit 16c controls the rotational position of the back spindle 16 in accordance with commands from the NC device 70.

[0033] The first tool post driver 31 includes a servo amplifier connected to the NC device 70, a servo motor connected to the servo amplifier, a feed mechanism, and a guide, in order to move the first tool post 30 along the X1-axis and Y1-axis. The first tool post driver 31 controls the position of the first tool post 30 on the X1-axis and Y1-axis in accordance with commands from the NC device 70. The second tool post driving unit 41 includes a servo amplifier connected to the NC device 70, a servo motor connected to the servo amplifier, a feed mechanism, and a guide, in order to move the second tool post 40 along the Y2 axis. The second tool post driving unit 41 controls the position of the second tool post 40 on the Y2 axis in accordance with commands from the NC device 70.

[0034] The NC device 70 mainly performs front machining of the workpiece W1 in the system 1 shown in Fig. 2, and mainly performs back machining of the workpiece W2 that is being processed and has been handed over from the front spindle 11 in the system 2 shown in Fig. 2. The lathe 1 performs cut-off processing by cutting off the workpiece W1 held by both the front spindle 11 and the back spindle 16 using a cut-off bit, so the NC device 70 synchronizes both systems 1 and 2 during the cut-off processing. Furthermore, when the back side tool TO1b shown in Fig. 2 is used for back machining, the NC device 70 also synchronizes both systems 1 and 2. The NC device 70 controls the machining of the workpiece W1 in the following manner.

[0035] In system 1, the NC device 70 first causes the front spindle 11 to grip the rod-shaped workpiece W1 in a state where the tip of the workpiece W1 is positioned with its tip protruding forward from the guide bush 14. In this state, the NC device 70 controls the drive of the front headstock 10 including the front spindle 11 and the first tool rest 30 so that the front side of the workpiece W1 is machined with the front side tool TO1a. After the front machining, the NC device 70 controls the drive of the back spindle stock 15 including the back spindle 16 in the system 2 so that the back spindle 16 grips the workpiece W2 that is being machined and is held by the front spindle 11. Since this control is performed at the beginning of the cut-off process, the NC device 70 synchronizes both systems 1 and 2.

[0036] Next, the NC device 70 rotates the front spindle 11 and the back spindle 16 in synchronization in both systems 1 and 2, and controls the drive of the first tool post 30 in system 1 so that the cut-off bit separates the workpiece W2 being machined from the next workpiece W1. When the above cut-off processing is completed, the NC device 70 controls the back surface machining of the workpiece W2 that is being held by the back surface spindle 16 and is in the middle of being machined.

[0037] When the first tool rest 30 is not used for back surface machining, in system 2, the NC device 70 controls the driving of the back headstock 15 including the back spindle 16 and the second tool rest 40 so that the second tool TO2 performs back surface machining of the workpiece W2 that is currently being machined. After back surface machining, the NC device 70 controls the driving of the back headstock 15 including the back spindle 16 so that the product is discharged. While back surface machining and product discharge are being performed in system 2, front surface machining of the next workpiece W1 can be performed in system 1. In the cut-off process, the tip of the rod-shaped workpiece W1 protrudes forward from the guide bush 14 and is positioned, so in system 1, the NC device 70 controls the drive of the front headstock 10 including the front spindle 11 and the first tool rest 30 so that front surface machining of the next workpiece W1 is performed with the front side tool TO1a.

[0038] When the backside tool TO1b attached to the first tool rest 30 included in the system 1 is used for backside machining, the NC device 70 advances both systems 1 and 2 so that at least the backside tool TO1b performs backside machining of the workpiece W2 that is currently being machined. Here, the NC device 70 controls the drive of at least the first tool rest 30 in the system 1, and controls the drive of at least the back headstock 15 including the back spindle 16 in the system 2. When the second tool TO2 attached to the second tool rest 40 included in the system 2 is also used for backside machining, the NC device 70 controls the drive of the back headstock 15 including the back spindle 16 and the second tool rest 40 in the system 2 so that the second tool TO2 performs backside machining of the workpiece W2 that is currently being machined. After backside machining, the NC device 70 controls the drive of the back headstock 15 including the back spindle 16 to eject the product. While the back side tool TO1b is not being used for back side machining, it is possible to perform front side machining of the next workpiece W1 in system 1. During this time, in system 1, the NC device 70 controls the drive of the front headstock 10 including the front spindle 11 and the first tool rest 30 so that the front side tool TO1a performs front side machining of the next workpiece W1.

[0039] In this manner, the NC device 70 simultaneously executes the processes for the paths 1 and 2. The operator prepares a machining program PR2 for each of the paths 1 and 2 to machine the workpiece W1. In a lathe in which path 1 on the front spindle and path 2 on the back spindle perform overlapping machining simultaneously according to machining program PR2, if both paths 1 and 2 stop during continuous machining at the beginning of machining program PR2, the machine stops with the back spindle 16 picking up the incomplete, or partially machined, workpiece W2. As time passes in this state, thermal displacement occurs, with the metal parts shrinking as the machine cools. This causes dimensional displacement, resulting in a deviation when continuous machining is resumed, in which the dimensions of the machined workpiece differ from those of the workpiece being continuously operated, resulting in the product being discarded. Therefore, it is conceivable to skip the front machining of workpiece W1 held by the front spindle 11 during the cycle stop and only perform back machining of the partially machined workpiece W2 held by the back spindle 16.

[0040] For example, if a special machining program is prepared that only processes the back surface when the cycle stops, it will be possible to complete the machining of workpiece W2 that is currently being machined. However, creating a special machining program that only processes the back surface when the cycle stops will be time-consuming.

[0041] If the system 1 on the front spindle side is not used for back surface machining, the NC device 70 may proceed with the system 2 on the back spindle side while stopping the system 1 on the front spindle side. This allows back surface machining of the workpiece W2 that is being machined and held by the back spindle 16 without performing front surface machining of the workpiece W1 held by the front spindle 11. However, when the backside tool TO1b included in the system 1 on the front spindle side is used for backside machining, stopping the system 1 on the front spindle side makes it impossible to complete machining of the workpiece W2 that is currently being machined. Also, if the operation of the system 1 on the front spindle side is continued, unintended front side machining will be performed on the workpiece W1 held by the front spindle 11. It is time-consuming to create separate machining programs PR2 for when the backside tool TO1b included in the system 1 on the front spindle side is used for backside machining and when it is not.

[0042] In this specific example, whether or not to use the first tool post 30 to machine the workpiece W2 currently being machined is automatically determined based on the machining program PR2, thereby eliminating the need for a special machining program in both cases where the first tool post 30 is used and where it is not used to machine the workpiece W2 currently being machined.

[0043] First, an example of the machining program PR2 will be described with reference to Figures 4 and 5. In Figures 4 and 5, "x" represents a number from 0 to 9. FIG. 4 shows a schematic example of a machining program PR2 written so that the first tool rest 30 is not used for machining the back surface of the workpiece W2 currently being machined. At the beginning of the machining programs for paths 1 and 2, a command to stop the machining cycle is written. For stopping The command is a command for stopping the machining program when the condition for stopping the machining cycle is met.

[0044] In the machining program for path 2 shown in Figure 4, a cycle stop command is followed by a group of commands for back machining of the workpiece W2 currently being machined using the second tool TO2 attached to the second tool rest 40. Here, the T2000 series indicates one of the second tools TO2, and "T2xx1" is a command for identifying the corresponding second tool TO2. "Ux" indicates the machining depth, and "Sxxxx" indicates the number of rotations per unit time (e.g., in rpm) of the back spindle 16. " / " indicates a skip function that does not execute subsequent commands in block units when the back spindle 16 is not gripping a workpiece. "G0 Zxx.x" is a command for moving the back spindle 16 to position Zxx.x on the Z2 axis. "G1 Wx.x Fx.xx" is a command for moving the back spindle 16 a distance xx immediately after W at a speed of x.xx immediately after F. The reason why "G0 Zxx.x" is written again after "G1 Wx.x Fx.xx" is to return the back spindle 16 to its original position on the Z2 axis after machining. After the command group for performing back machining, a pick-up command is written to grip the next workpiece W2 being machined by the back spindle.

[0045] While the second tool TO2 is being used to perform back machining of the currently-machined workpiece W2, a group of commands for front machining of the next workpiece W1 can be written in the machining program for path 1. Here, numbers in the T100 to T900 series indicate the front-side tool TO1a, for example, one of the cutting tools, and "T1xx" is a command to identify the corresponding front-side tool TO1a. After the group of commands for front machining, and immediately after the command for gripping the workpiece W2 being machined in system 2 with the back spindle, a cut-off command for cutting through the workpiece W1 with a cut-off bit is written.

[0046] FIG. 5 shows a schematic example of a machining program PR2 written so that the first tool rest 30 is used for machining the back surface of the workpiece W2 that is currently being machined. In the machining program for path 1 shown in FIG. 5, a command to stop the cycle is followed by a group of commands (not shown) for machining the front side of the workpiece W1. These commands are followed by a group of commands for using the back side tool TO1b attached to the first tool post 30. Here, the T3000 series indicates one of the back side tools TO1b, and "T3xx1" is a command for indexing the corresponding back side tool TO1b. "Ux" indicates the machining depth. "G0 Yx.x" is a command for moving the first tool post 30 to the Yx.x position on the Y1 axis. "Mxx0" is a sync command for synchronizing the processing of path 2 with the processing of path 1. When "Mxx0" for path 1 is read, processing of path 2 is performed according to the command following "Mxx0" for path 2.

[0047] In the machining program for path 2 shown in Figure 5, after the cycle stop command, a group of commands are written to perform back machining of the workpiece W2 in cooperation with path 1. Here, "T3xx1" is a command to align the corresponding back tool TO1b with the coordinate system of the back spindle 16. Since "T3xx1" written in path 2 is not a command to index the corresponding back tool TO1b, "T3xx1" must be written in path 1. "G0 Zxxx.x Uxx Sxxx" is a command to move the back spindle 16 to position Zxxx.x on the Z2 axis, set the machining depth to Uxx, and set the number of rotations per unit time of the back spindle 16 to Sxxx. "G1 Wx.x Fx.xx" is a command to move the back spindle 16 a distance of xx immediately after W at a speed of x.xx immediately after F. The reason why "G0 Zxxx.x" is written after "G1 Wx.x Fx.xx" is to return the back spindle 16 to its original position on the Z2 axis after machining. "Mxx1" is a waiting command that synchronizes the processing of path 1 with the processing of path 2. When "Mxx1" for path 2 is read, the processing of path 1 is carried out according to the command that follows "Mxx1" for path 1. After the command group for performing back machining, a pick-up command is written to grip the next workpiece W2 being machined by the back spindle.

[0048] In the machining program for system 1, after "Mxx1" and immediately after the command for system 2 to grip the workpiece W2 being machined with the back spindle, a cut-off command for cutting through the workpiece W1 with the cut-off bit is written.

[0049] Some users may wish to leave the workpiece W2 in the middle of machining as it is when the continuous machining is ended. Therefore, the lathe 1 allows the operator to select whether or not to complete the machining of the workpiece W2 in the middle of machining when the continuous machining is ended.

[0050] (3) Example of final processing setup process: FIG. 6 illustrates a schematic example of a final machining execution setting process that accepts a setting indicating whether to complete machining of the workpiece W2 in the middle of machining when the continuous machining is terminated. When the NC device 70 shown in FIG. 3 accepts an instruction to display the final machining execution setting screen 200 via the input unit 81, it executes a process of displaying the final machining execution setting screen 200 on the display unit 82 (step S102). Hereinafter, the term "step" will be omitted. The final machining execution setting screen 200 has a display area asking "Do you want to perform final part machining?", a "Yes" button 201 for accepting an instruction to complete machining of the workpiece W2 in the middle of machining when the continuous machining is terminated, and a "No" button 202 for accepting an instruction not to complete machining of the workpiece W2 in the middle of machining when the continuous machining is terminated. The final machining indicated as "final part machining" on the final machining execution setting screen 200 refers to back surface machining of the workpiece W2 in the middle of machining when the continuous machining is terminated.

[0051] When the NC device 70 receives an operation of the "Yes" button 201 or the "No" button 202 at the input unit 81, the process proceeds to S104, and branches the process depending on whether or not final machining is to be performed.

[0052] When the NC device 70 receives the operation of the "Yes" button 201 at the input unit 81, it sets final machining to be performed (S106) and ends the final machining execution setting process. The process of S106 can be a process of storing information indicating the execution of final machining in the RAM 73 or ROM 72. For example, when the NC device 70 prepares a setting flag in the RAM 73 or ROM 72, it can set the flag to a value indicating the execution of final machining. A flag having a value indicating the execution of final machining indicates that the setting will complete the machining of the workpiece W2 that is currently being machined. Furthermore, the information indicating the execution of final machining may be input to a latching relay in the programmable logic controller.

[0053] On the other hand, when the NC device 70 receives operation of the "No" button 202 at the input unit 81, it sets final machining not to be performed (S108) and ends the final machining execution setting process. The process of S108 can be a process of storing information indicating that final machining will not be performed in the RAM 73 or ROM 72. For example, the NC device 70 can set a value indicating that final machining will not be performed in a flag. A flag having a value indicating that final machining will not be performed indicates that the setting will not complete machining of the workpiece W2 that is currently being machined. Furthermore, the information indicating that final machining will not be performed may be input to a latching relay in a programmable logic controller. Whether or not to complete the machining of the workpiece W2 in the middle of machining when the continuous machining is ended may be set by accepting the operation of a mechanical switch, for example.

[0054] (4) Examples of processing: 7 and 8 show a schematic example of machining processing performed when the machining program PR2 shown in Fig. 3 is executed. The machining processing is performed by the NC device 70 that executes the control program PR1.

[0055] When machining processing starts, the NC device 70 first determines whether or not a command to use the backside tool TO1b of the first system to machine the workpiece W2 that is currently being machined exists in the machining program of the second system (S202). For example, as shown in Fig. 5, if a command in the T3000 series exists in the machining program of the second system, it can be determined that a command to use the backside tool TO1b of the first system to machine the workpiece W2 that is currently being machined exists in the machining program of the second system. As shown in Fig. 4, if a command in the T3000 series does not exist in the machining program of the second system, it can be determined that a command to use the backside tool TO1b of the first system to machine the workpiece W2 that is currently being machined does not exist in the machining program of the second system. In this manner, the NC device 70 determines whether or not to use the first tool rest 30 for machining the workpiece W2 currently being machined, based on the machining program PR2.

[0056] The NC device 70 stores the determination result obtained by the process of S202 in the RAM 73 or the ROM 72 (S204). Thereafter, the NC device 70 controls the front surface machining of the workpiece W1 in path 1 according to the machining program PR2, controls the back surface machining of the workpiece W2 in path 2 and, if necessary, path 1 when the back spindle 16 is gripping the workpiece W2 in the middle of machining, and controls the discharge of the product in path 2 after the back surface machining (S206). As shown in Figures 4 and 5, each command in the machining program for path 2, except for the waiting command, has a " / " added to it, which indicates a skip function that does not execute the subsequent command group in block units when the back spindle 16 is not gripping a workpiece. As a result, when the back spindle 16 is gripping the workpiece W2 in the middle of machining, each command for path 2 is executed to perform back surface machining and discharge the product, and when the back spindle 16 is not gripping the workpiece W2 in the middle of machining, each command for path 2 is not executed.

[0057] After front surface machining, the NC device 70 synchronizes both paths 1 and 2, and in path 2, in accordance with a pick-up command, controls the drive of the back spindle stock 15, including the back spindle 16, so that the back spindle 16 grips the in-process workpiece W2 held by the front spindle 11 (S208). Here, as shown in FIGS. 4 and 5, the pick-up command for path 2 includes a " / " character, which indicates a skip function that does not execute subsequent commands in block units when the back spindle 16 is not gripping a workpiece. This causes the pick-up command to be executed when the back spindle 16 is gripping the in-process workpiece W2, and not when the back spindle 16 is not gripping the in-process workpiece W2. Therefore, when there is no in-process workpiece W2 to be back surface machined, unnecessary operations are eliminated in path 2, and back surface machining and product discharge are performed efficiently. Next, the NC device 70 rotates the front spindle 11 and back spindle 16 in both paths 1 and 2 in synchronization with each other, and controls the drive of the first tool rest 30 in path 1 so that the cut-off bit cuts through the workpiece W1 (S210). As a result, the front spindle 11 grips the next workpiece W1, and the back spindle 16 grips the workpiece W2 that is currently being machined.

[0058] After the cut-off process of S208 to S210, the NC device 70 proceeds to S214 in Fig. 8 if it has decided to terminate continuous machining of the workpiece W1, and repeats the processes of S206 to S212 if it has not decided to terminate continuous machining of the workpiece W1 (S212). For example, the NC device 70 can determine to terminate continuous machining and proceed to S214 in at least one of the following cases: when it receives a stock-out signal from the material feeder 20 indicating that the rod-shaped workpiece W1 has run out; when the number of times the front surface of the workpiece W1 has been machined reaches a set number of products; or when continuous machining is stopped by manual operation. If the above cases are not met, the NC device 70 determines not to terminate continuous machining and returns to S206.

[0059] In S214 shown in FIG. 8 , the NC device 70 proceeds to S216 if final machining is to be performed, and terminates the machining process if final machining is not to be performed. If information indicating final machining is to be performed is stored in the RAM 73 or ROM 72, such as when a setting flag has a value indicating final machining is to be performed, the final machining is set to be performed, and the NC device 70 proceeds to S216. If information indicating final machining is not to be performed is stored in the RAM 73 or ROM 72, such as when a setting flag has a value indicating final machining is not to be performed, the final machining is set to not be performed, and the NC device 70 terminates the machining process. In this way, when the setting indicating whether to complete machining of the workpiece W2 in the middle of machining when terminating continuous machining indicates that machining of the workpiece W2 in the middle of machining will not be completed, the NC device 70 stops both systems 1 and 2 without completing machining of the workpiece W2 in the middle of machining when terminating continuous machining.

[0060] In S216, the NC device 70 branches the process depending on whether the determination result stored in the RAM 73 or ROM 72 in S204 indicates that the first tool post 30 will be used to machine the workpiece W2 that is currently being machined. If the determination result indicates that path 1 will be used, the NC device 70 proceeds to S218, and if the determination result does not indicate that path 1 will be used, the NC device 70 proceeds to S222.

[0061] When the first tool rest 30 is used to machine the workpiece W2 currently being machined, the NC device 70 causes the headstock 11 to grip the workpiece W1 in the path 1, retracts the headstock 10 including the headstock 11 gripping the workpiece W1 to a position along the Z1 axis that prevents contact between the workpiece W1 and the first tool TO1, and locks the Z1 axis (S218). If the workpiece W1 retracts until it is released from the guide bush 14, cutting oil will enter the space on the headstock 11 side, and the headstock 11 gripping the workpiece W1 will move in the -Z1 direction within a range that prevents the workpiece W1 from releasing from the guide bush 14. Locking the Z1 axis means that the drive of the headstock 10 is stopped, thereby prohibiting movement of the headstock 10 along the Z1 axis. When the Z1 axis is locked, the headstock 10 will not move even if the coordinate of the headstock 10 is changed along the Z1 axis by the machining program PR2. In system 1, the X1-axis and Y1-axis are not locked, so movement of the first tool post 30 along the X1-axis and Y1-axis is permitted. The processing of S218 makes it possible to prevent interference between the workpiece W1 held by the front spindle 11 and the first tool TO1 attached to the first tool post 30.

[0062] After locking the Z1 axis, the NC device 70 simultaneously operates both systems 1 and 2 to perform back machining of the in-process workpiece W2 using at least the back tool TO1b in accordance with the machining program PR2 for continuous machining, operates system 2 to eject the product, and prevents the gripper 17 of the back spindle 16 from closing after the product is ejected (S220). As shown in FIG. 5 , in the machining program PR2 for performing back machining of the in-process workpiece W2, system 1 controls the movement of back tool TO1b using commands such as those for indexing the T3000-series back tool TO1b. Furthermore, system 2 controls the drive of the back spindle stock 15, including the back spindle 16, using commands for controlling the rotation speed and position of the back spindle 16. Therefore, during back machining, the NC device 70 drives the first tool rest 30 in system 1 to move the back tool TO1b, and simultaneously drives the back spindle stock 15, including the back spindle 16, in system 2. When the second tool TO2 attached to the second tool rest 40 included in the system 2 is also used for back machining, the NC device 70 drives the second tool rest 40 in the system 2 so that the second tool TO2 moves, and drives the back spindle stock 15 including the back spindle 16. In the machining program for path 2, the pick-up command after product discharge has a " / " added to it, which indicates a skip function that does not execute subsequent commands in block units when the back spindle 16 is not gripping a workpiece. After the product is discharged, the gripper 17 of the back spindle 16 is not closed, so the pick-up command is not executed. In this way, when the NC device 70 ends continuous machining of the workpiece W1, it drives the back spindle stock 15, including the back spindle 16 gripping the workpiece W2 in the middle of machining, in path 2 to machine the workpiece W2 in the middle of machining, and then stops the operation of receiving the next workpiece W2 in the middle of machining from the front spindle 11. As a result, unnecessary operations are eliminated in path 2, and back machining and product discharge are performed efficiently.

[0063] When the readout of the commands in the machining program PR2 as shown in Fig. 5 returns to the beginning, the machining cycle is stopped in accordance with the cycle stop command, thereby completing the machining process shown in Figs. By the processing of S218 to S220, when continuous machining is completed, the NC device 70 simultaneously advances both systems 1 and 2 according to the machining program PR2 while preventing the workpiece W1 held by the front spindle 11 from being machined. As a result, when the first tool rest 30 is used for back machining of the workpiece W2 that is currently being machined, machining of the workpiece W2 that is currently being machined is completed without using a special machining program, and continuous machining ends.

[0064] On the other hand, if the first tool rest 30 is not to be used to machine the workpiece W2 in the middle of machining, the NC device 70 stops the first path (S222). After stopping the first path, the NC device 70 causes the second path 2 to proceed so that the second tool TO2 attached to the second tool rest 40 performs back machining of the workpiece W2 in the middle of machining in accordance with the machining program PR2 for continuous machining, causes the second path 2 to proceed so that the product is discharged, and prevents the gripper 17 of the back spindle 16 from closing after the product is discharged (S224). As shown in FIG. 4 , in the machining program for performing back machining of the workpiece W2 in the middle of machining in the second path 2, the movement of the second tool TO2 is controlled by commands such as those for indexing the second tool TO2 in the T2000 series. In addition, the drive of the back spindle stock 15 including the back spindle 16 is controlled by commands for controlling the rotation speed and position of the back spindle 16. Therefore, during back surface machining, the NC device 70 drives the second tool rest 40 in the system 2 so that the second tool TO2 moves, and drives the back surface headstock 15 including the back surface spindle 16. In the machining program for path 2, the pick-up command after product discharge has a " / " added to it, which indicates a skip function that does not execute subsequent commands in block units when the back spindle 16 is not gripping a workpiece. After the product is discharged, the gripper 17 of the back spindle 16 is not closed, so the pick-up command is not executed. In this way, when the NC device 70 ends continuous machining of the workpiece W1, it drives the back spindle stock 15, including the back spindle 16 gripping the workpiece W2 in the middle of machining, in path 2 to machine the workpiece W2 in the middle of machining, and then stops the operation of receiving the next workpiece W2 in the middle of machining from the front spindle 11. As a result, unnecessary operations are eliminated in path 2, and back machining and product discharge are performed efficiently.

[0065] When the readout of the commands in the machining program PR2 as shown in Fig. 4 returns to the beginning, the machining cycle is stopped in accordance with the cycle stop command, thereby completing the machining process shown in Figs. As described above, when the first tool rest 30 is not used for machining the back surface of the workpiece W2 in the middle of machining, machining of the workpiece W2 in the middle of machining is completed without using a special machining program, and continuous machining ends.

[0066] As explained above, the present lathe 1 does not require a special machining program to complete machining of the workpiece W2 in the middle of machining and end continuous machining, whether or not a separate tool post is used for machining the back surface of the workpiece W2 in the middle of machining.

[0067] (5) Variation: The present invention can be modified in various ways. For example, the machine tool to which the present technology can be applied is not limited to a lathe, but may also be a machining center or the like.

[0068] (6) Conclusion: As explained above, according to various aspects of the present invention, it is possible to provide a technology for a machine tool or the like that does not require a special machining program for completing the machining of a workpiece in the middle of machining and terminating continuous machining, both in the case where a tool post of a different system is used for machining the workpiece in the middle of machining and in the case where a tool post of a different system is not used for machining the workpiece in the middle of machining. Of course, even a technology that consists only of the constituent elements of the independent claims can achieve the basic functions and effects described above. Furthermore, it is possible to implement configurations in which the components disclosed in the above examples are substituted with each other or the combination is changed, or configurations in which the components disclosed in the publicly known techniques and the above examples are substituted with each other or the combination is changed, etc. The present invention also includes these configurations. [Explanation of symbols]

[0069] 1...Lathe (example of machine tool), 10...Front headstock (example of first headstock), 11...Front spindle (example of first spindle), 12...gripping section, 13...front headstock drive section, 15... Back headstock (example of second headstock), 16... Back spindle (example of second spindle), 17...gripping section, 18...rear headstock drive section, 30...first tool post, 31...first tool post drive unit, 40... second tool post, 41... second tool post drive unit, 70...NC device (example of control unit), PR2... Machining program, TO1...First tool, TO1a...Front side tool, TO1b...Back side tool, TO2...Second tool, W1...workpiece, W2...workpiece in the middle of machining.

Claims

1. A machine tool that performs continuous machining of a workpiece, a first headstock provided with a first spindle that grips the workpiece; a second headstock provided with a second spindle that grips the workpiece being processed and transferred from the first spindle; a first tool rest to which a first tool is attached that machines the workpiece held by at least one of the first spindle and the second spindle; a second tool rest to which a second tool is attached that machines the workpiece in the middle of machining held by the second spindle; a control unit that simultaneously causes a first system that drives the first headstock including the first spindle and the first tool rest, and a second system that drives the second headstock including the second spindle and the second tool rest, in accordance with a machining program for performing the continuous machining, which is created by an operator, The control unit determining whether or not the first tool rest will be used to machine the workpiece in the middle of machining based on a description of the machining program; When completing the machining of the workpiece in the middle of machining and terminating the continuous machining, if the first tool post is used to machine the workpiece in the middle of machining, the first system and the second system are simultaneously advanced while following the description of the machining program for performing the continuous machining, the description of the first tool post in the first system and the description of the second system, the first headstock is retracted to a position that prevents contact between the workpiece and the first tool, and the driving of the first headstock is stopped, thereby preventing the workpiece held by the first spindle from being machined; When completing the machining of the workpiece in the middle of machining and ending the continuous machining, if the first tool post is not used to machine the workpiece in the middle of machining, the machine tool follows the description of the second system in the machining program for performing the continuous machining, while stopping the first system, thereby allowing the second system to proceed.

2. 2. The machine tool according to claim 1, wherein the control unit accepts a setting indicating whether or not to complete machining of the workpiece in the middle of machining when the continuous machining is terminated, and if the setting indicates that machining of the workpiece in the middle of machining will not be completed, stops the first system and the second system without completing machining of the workpiece in the middle of machining when the continuous machining is terminated.

3. When the control unit completes machining of the workpiece in the middle of machining and ends the continuous machining, if the first tool rest is used for machining the workpiece in the middle of machining, in the first system, the first headstock including the first spindle gripping the workpiece is retracted to a position where the workpiece and the first tool are prevented from coming into contact with each other, and then driving of the first headstock is stopped and the first tool rest is driven; 3. The machine tool according to claim 1, wherein the second system drives at least the second headstock including the second spindle gripping the workpiece in the middle of machining.

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