Numerical controller

The numerical controller of the invention receives input of a technique for operating a plurality of tools and an operation condition of the operation technique, calculates movement command data including speed information and position information on the plurality of tools, such that respective cutting paths of the plurality of tools intersect, based on the input operation method and operation condition, generates interpolation data based on the movement command data, and controls a motor for driving a machine based on the interpolation data.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Phase application of PCT/JP2021/001053, filed Jan. 14, 2021 which claims priority to Japanese Patent Application No. 2020-005491, filed Jan. 16, 2020, the disclosures of these applications being incorporated herein by reference in their entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates to a numerical controller, and more particularly to a numerical controller having a function of performing threading with a plurality of cooperating tools.

BACKGROUND OF THE INVENTION

In a case where threading is performed on a workpiece, the threading is performed by a blade making a predetermined cut on the workpiece while the workpiece is rotated and the blade being relatively moved in the axial direction of the workpiece. Although the machining may be performed by one tool being moved relative to the workpiece rotation at this time, in many cases, a machine tool equipped with a plurality of shafts is used and a plurality of tools cooperate and move relative to the workpiece to perform the threading.

In conventional threading and turning machining, a tool continues to cut into a workpiece in one direction, and thus the chips resulting from the machining are not divided and are continuously generated as the tool moves. On condition that the machining continues without chip removal, problems arise in the form of chip entanglement in the tool and chip-workpiece contact leading to workpiece damage. Various methods have been used to solve such problems.

International Publication No. 2016/056526, Japanese Unexamined Patent Publication No. 2019-185780, and so on disclose arts for solving the problems by such methods.

SUMMARY OF THE INVENTION

The chips can be divided by adding a swinging operation to the tool movement during the machining. However, the swinging operation leads to an increase in mechanical load, and thus there is a problem that a machine life (ball screw, bearing, and so on) and a tool life are adversely affected. In addition, machining process addition for chip division causes the machining time to become longer than in the case of normal threading. Further, an increase in motor speed is required for a machining time equal to that in the case of normal threading, and then the load of the machining needs to be higher than that in the case of normal threading and another problem arises as the life of the tool tip tends to decrease.

In this regard, there is a demand for a technique with which it is possible to cut off cut chips without causing an increase in machining time and achieve machine and tool life extension.

The numerical controller according to the invention solves the above problem by performing threading while controlling the relative speeds and positions of a plurality of tools such that chips can be divided in a machining method for performing cutting with a machine configured to be capable of controlling the plurality of tools at the same time.

Further, the numerical controller according to the invention controls threading of a workpiece by a machine provided with a plurality of tools based on a program and includes: a chip division information input unit configured to receive input of a technique for operating the plurality of tools and an operation condition of the operation method; a multi-tool operation calculation unit configured to calculate movement command data including speed information and position information on the plurality of tools, such that respective cutting paths of the plurality of tools intersect, based on the operation technique and the operation condition input by the chip division information input unit; an interpolation unit configured to generate interpolation data based on the movement command data; and a servo control unit configured to control a motor for driving the machine based on the interpolation data.

According to the invention, it is possible to perform threading while cutting the cut chips without causing an increase in machining time and achieve machine and tool life extension.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG.1is a schematic hardware configuration diagram illustrating a main part of a numerical controller according to an embodiment of the invention. A numerical controller1according to the invention can be mounted as a numerical controller that controls a lathe machine tool based on a program or the like.

A central processing unit (CPU)11in the numerical controller1according to the present embodiment is a processor that controls the numerical controller1as a whole. The numerical controller1according to the present embodiment further includes a read only memory (ROM)12and a random access memory (RAM)13. Under such a configuration, the CPU11reads out a system program stored in the ROM12via a bus20and then controls the entire numerical controller1in accordance with the system program. Various data are temporarily stored in the RAM13. Examples of data that can be temporarily stored in the RAM13include temporary calculation data and display data and various data input from the outside.

The numerical controller1according to the present embodiment further includes a non-volatile memory14. The non-volatile memory14may be configured by a memory backed up by a battery (not shown), a solid state drive (SSD), or the like. By such a configuration, a storage state is maintained even when the numerical controller1is off. The non-volatile memory14stores a program read from an external device72via an interface15, a program input via a display/MDI unit70, and the like. The program and various data stored in the non-volatile memory14may be loaded into the RAM13during executed or used. In addition, various system programs such as a known analysis program are written in advance in the ROM12.

The numerical controller1according to the present embodiment further includes the interface15provided for connecting the CPU11in the numerical controller1with the external device72such as a USB device. A program, various parameters, and the like used for controlling the lathe machine tool are read from the external device72. In addition, the program, the parameters, and the like edited in the numerical controller1can be stored in external storage means via the external device72. The numerical controller1according to the present embodiment further includes a programmable machine controller (PMC)16and an input/output unit (I/O unit)17. The PMC16performs control by outputting a signal via the I/O unit17to the lathe machine tool and a peripheral device for the lathe machine tool with a sequence program built in the numerical controller1. It should be noted that examples of the peripheral device for the lathe machine tool include a tool changer, an actuator for a robot or the like, and a sensor attached to the lathe machine tool. In addition, the PMC16receives a signal from, for example, the peripheral device or various switches in an operation panel in the main body of the lathe machine tool, performs necessary signal processing, and then passes the signal to the CPU11.

The display/MDI unit70is a manual data input device including a display, a keyboard, and the like, and an interface18receives a command and data from the keyboard of the display/MDI unit70and passes the command and data to the CPU11. The numerical controller1further includes an interface19connected to an operation panel71having, for example, a manual pulse generator used in manually driving each shaft.

The numerical controller1according to the present embodiment further includes a shaft control circuit30provided for controlling a shaft of the lathe machine tool and a servo amplifier40connected to the shaft control circuit30. In addition, the servo amplifier40is further connected to a servomotor50moving the shaft of the lathe machine tool. The shaft control circuit30receives a shaft movement command amount from the CPU11and outputs a shaft command to the servo amplifier40. The servo amplifier40receives this command to drive the servomotor50. The shaft servomotor50has a built-in position and speed detector. A position and speed feedback signal from the position and speed detector is fed back to the shaft control circuit30to perform position and speed feedback control. It should be noted that although one shaft control circuit30, one servo amplifier40, and one servomotor50are shown in the hardware configuration diagram ofFIG.1, the actual numbers thereof are equal to the number of shafts in the lathe machine tool to be controlled. For example, in the case of controlling a lathe machine tool provided with two cutter holders as in the embodiment of the present application that can be used to execute the operation examples illustrated inFIGS.3to20, two sets of the shaft control circuits30, the servo amplifiers40, and the servomotors50that respectively drive a first cutter holder to which a first tool is attached in the X-axis and Z-axis directions are prepared along with two sets of the shaft control circuits30, the servo amplifiers40, and the servomotors50that respectively drive a second cutter holder to which a second tool is attached in the X-axis and Z-axis directions.

The numerical controller1according to the present embodiment further includes a spindle control circuit60and a spindle amplifier61connected to the spindle control circuit. The spindle amplifier61is further connected to a spindle motor62in the lathe machine tool. The spindle control circuit60receives a spindle rotation command and outputs a spindle speed signal to the spindle amplifier61.

In response to this spindle speed signal, the spindle amplifier61rotates the spindle motor62in the lathe machine tool at a commanded rotation speed to drive a workpiece. To the spindle motor62, a position coder63is coupled. The position coder63outputs a feedback pulse in synchronization with spindle rotation, and this feedback pulse is read by the CPU11via the spindle control circuit60.

FIG.2is a schematic functional block diagram of the numerical controller1according to one embodiment of the invention.

Each functional block shown inFIG.2is actualized by the CPU11in the numerical controller1shown inFIG.1executing a system program and controlling the operation of each part of the numerical controller1. The numerical controller1according to the present embodiment controls the lathe machine tool machining the workpiece attached to the spindle by driving the first cutter holder to which the first tool is attached and the second cutter holder to which the second tool is attached, respectively.

The numerical controller1of the present embodiment includes an analysis unit100, an information input unit102(more specifically, chip division information input unit102configured to input chip division-related information), and an operation calculation unit104(more specifically, multi-tool operation calculation unit104configured to execute calculation related to the operation of a plurality of tools). In addition, the numerical controller1of the present embodiment includes a first interpolation unit122, a second interpolation unit124, servo control units130x1,130z1,130x2, and130z2, and a spindle control unit140. In addition, the non-volatile memory14in the numerical controller1stores in advance a program200provided for executing the control of machining the workpiece by driving the tools attached to the two cutter holders.

The analysis unit100is actualized by the CPU11in the numerical controller1shown inFIG.1executing a system program read from the ROM12and arithmetic processing using the RAM13and the non-volatile memory14being performed mainly by the CPU11. The analysis unit100reads out and analyzes blocks of the program200and then generates movement command data for the respective servomotors driving the first and second cutter holders and spindle command data for commanding the rotation speed of the spindle. The analysis unit100generates, based on a feed command commanded by the block of the program200, the movement command data for servomotors50x1and50z1driving the first cutter holder and the movement command data for servomotors50x2and50z2driving the second cutter holder. In addition, the analysis unit100generates the spindle command data based on the spindle rotation command commanded by the block of the program200.

The chip division information input unit102is actualized by the CPU11in the numerical controller1shown inFIG.1executing a system program read from the ROM12and arithmetic processing using the RAM13and the non-volatile memory14and input/output processing using the interface18and the display/MDI unit70being performed mainly by the CPU11. The chip division information input unit102displays a setting screen to a worker via the display/MDI unit70for the worker to input how to operate the first and second cutter holders and conditions required for the operation. With the chip division information input unit102, the worker can select an operation technique such as (1) tool front insertion technique, (2) tool vibration technique, (3) tool rear insertion technique, and (4) combination technique, which will be described later. In addition, the chip division information input unit102allows the worker to set a chip division length (so to speak, chip length). The chip length may be set by specifying a lead count or a coordinate value. The information input by the chip division information input unit102is output to the multi-tool operation calculation unit104.

The multi-tool operation calculation unit104is actualized by the CPU11of the numerical controller1shown inFIG.1executing a system program read from the ROM12and arithmetic processing using the RAM13and the non-volatile memory14being performed mainly by the CPU11. The multi-tool operation calculation unit104calculates the operation of each tool corresponding to the information input from the chip division information input unit102based on the movement command data generated by the analysis unit100. It should be noted that examples of the information input from the chip division information input unit102include the selected operation method. However, the chip length and various types of information not limited to these examples can also be input from the chip division information input unit102. The multi-tool operation calculation unit104calculates the operation of each tool by calculating the speeds and positions of the tools at which the respective cutting paths of the tools intersect. The operation of each tool calculated by the multi-tool operation calculation unit104is one in which the chips generated as a result of machining by each tool are divided at the chip length input by the chip division information input unit102. The operation of each tool calculated by the multi-tool operation calculation unit104is output to the first interpolation unit122and the second interpolation unit124as movement command data. The operation of each tool calculated by the multi-tool operation calculation unit104will be described later.

The first interpolation unit122and the second interpolation unit124are actualized by the CPU11of the numerical controller1shown inFIG.1executing a system program read from the ROM12and arithmetic processing using the RAM13and the non-volatile memory14being performed mainly by the CPU11.

The first interpolation unit122generates, based on the movement command data generated by the analysis unit100, interpolation data in which a point on the command path of the first tool attached to the first cutter holder commanded by the movement command data is interpolation-calculated with an interpolation cycle (so to speak, control cycle). In addition, the second interpolation unit124generates, based on the movement command data generated by the analysis unit100, interpolation data in which a point on the command path of the second tool attached to the second cutter holder commanded by the movement command data is interpolation-calculated with an interpolation cycle. The interpolation processing by the first interpolation unit122and the second interpolation unit124is executed every interpolation cycle.

The servo control units130x1and130z1are actualized by the CPU11in the numerical controller1shown inFIG.1executing a system program read from the ROM12, arithmetic processing using the RAM13and the non-volatile memory14being performed mainly by the CPU11, and the shaft control circuit30and the servo amplifier40performing control processing on the servomotor50. The servo control units130x1and130z1drive the first cutter holder in the machine to be controlled by controlling each of the servomotor50x1that drives the first cutter holder in the X-axis direction and the servomotor50z1that drives the first cutter holder in the Z-axis direction based on the interpolation data generated by the first interpolation unit122.

In addition, the servo control units130x2and130z2are actualized by the CPU11in the numerical controller1shown inFIG.1executing a system program read from the ROM12, arithmetic processing using the RAM13and the non-volatile memory14being performed mainly by the CPU11, and the shaft control circuit30and the servo amplifier40performing control processing on the servomotor50. The servo control units130x2and130z2drive the second cutter holder of the machine to be controlled by controlling each of the servomotor50x2that drives the first cutter holder in the X-axis direction and the servomotor50z2that drives the first cutter holder in the Z-axis direction based on the interpolation data generated by the second interpolation unit124.

The spindle control unit140is realized by the CPU11of the numerical controller1illustrated inFIG.1executing a system program read from the ROM12, arithmetic processing using the RAM13and the non-volatile memory14being performed mainly by the CPU11, and the spindle control circuit60and the spindle amplifier61performing control processing on the spindle motor62. The spindle control unit140controls the spindle motor62that rotates the spindle of the machine to be controlled based on the spindle command data generated by the analysis unit100.

The followings are some examples of the operation of each tool calculated by the multi-tool operation calculation unit104provided in the embodiment of the invention.

FIGS.3to8are a series of diagrams illustrating states where a workpiece7is machined using the (1) tool front insertion technique calculated by the multi-tool operation calculation unit104with a first tool5attached to a first cutter holder3, and a second tool6attached to a second cutter holder4.

As for the tool front insertion method, threading is first started by one of the tools. In the state illustrated inFIG.3, the workpiece7attached to a headstock2and rotating is cut (that is, threaded) by the first tool5attached to the first cutter holder3. At this time, the second tool6attached to the second cutter holder moves in the Z-axis direction in a non-cutting state at a speed overtaking the first tool5at an X-axis position of non-contact with the workpiece7. In this state, chips8are generated from the threading position of the first tool5.

Next, as illustrated inFIG.4, when the second tool6reaches the cutting start point positioned ahead by half rotation of the spindle when viewed from the first tool5while the first tool5cuts the workpiece7, the second cutter holder4moves in the X-axis direction after setting the speed of movement in the Z-axis direction to the speed of cutting, and the second tool6starts cutting the workpiece7. The cutting start point of the second tool6is a position where the cutting length from the cutting start position of the first tool5is substantially the same as the chip length input by the chip division information input unit102. At this stage, the workpiece7is machined by both the first tool5and the second tool6.

Subsequently, as illustrated inFIG.5, when the first tool5reaches the cutting start point of the second tool6, the chips generated as a result of the cutting by the first tool5are divided by the cutting groove of the second tool6. When the cutting point of the first tool5reaches the cutting start point of the second tool6, the first cutter holder3moves in the X-axis direction, thereby the first tool5enters a non-cutting state.

With the first tool5in the non-cutting state, as illustrated inFIG.6, the first cutter holder3moves in the Z-axis direction in the non-cutting state at a speed overtaking the second tool6. Then, when the first tool5reaches the cutting start point positioned ahead by half rotation of the spindle when viewed from the second tool6, the first cutter holder3moves in the X-axis direction after setting the speed of movement in the Z-axis direction to the speed of cutting and then the first tool5starts cutting as illustrated inFIG.7. The cutting start point of the first tool5is a position where the cutting length from the cutting start position of the second tool6is substantially the same as the chip length input by the chip division information input unit102. At this stage, the workpiece7is re-machined by both the first tool5and the second tool6.

Subsequently, as illustrated inFIG.8, when the second tool6reaches the cutting start point of the first tool5, the chips generated as a result of the cutting by the second tool6are divided by the cutting groove of the first tool5. When the cutting point of the second tool6reaches the cutting start point of the first tool5, the second cutter holder4moves in the X-axis direction and then the second tool6enters a non-cutting state.

As described above, by the tool front insertion technique, the first tool5and the second tool6alternately machine the workpiece7by repeating the operations illustrated inFIGS.3to8. By this operation method, the chips generated as a result of the cutting by the first tool5are divided by the cutting groove by the second tool6. In addition, the chips generated as a result of the cutting by the second tool6are divided by the cutting groove by the first tool5. By setting the Z-axis-direction movement speeds of the first cutter holder3and the second cutter holder4in machining the workpiece7to cutting feed rates commanded by the program200or the like, the machining time is almost the same as that in the case of normal threading (strictly speaking, the machining time slightly decreases to the extent of the front insertion). In addition, it is not necessary to perform a swinging operation or an operation similar thereto, and thus no heavy load is applied to the turning machine tool and each tool. Further, because the machining of the workpiece7is alternately performed by the first tool5and the second tool6, machining burden can be distributed to the respective tools. For example, the non-cutting time of the tool is longer than in the case of continuous machining, and thus the heat generated during the machining can be sufficiently removed and tool life extension is also expectable by this technique.

FIGS.9to11are a series of diagrams illustrating states where the workpiece7is machined using the (2) tool vibration technique calculated by the multi-tool operation calculation unit104with the first tool5attached to the first cutter holder3and the second tool6attached to the second cutter holder4.

As for the tool vibration technique, one tool performs threading for the most part. In the state illustrated inFIG.9, the workpiece7attached to the headstock2and rotating is cut (threaded) by the first tool5attached to the first cutter holder3. At this time, the second tool6attached to the second cutter holder moves in the Z-axis direction in a non-cutting state at a speed overtaking the first tool5at an X-axis position of non-contact with the workpiece7. In this state, the chips8are generated from the threading position of the first tool5.

Next, as illustrated inFIG.10, when the second tool6reaches the cutting start point ahead by half rotation of the spindle when viewed from the first tool5while the first tool5cuts the workpiece7, the second cutter holder4moves in the X-axis direction after setting the speed of movement in the Z-axis direction to the speed of cutting, and the second tool6starts cutting the workpiece7. The cutting start point of the second tool6is a position where the cutting length from the cutting start position of the first tool5is substantially the same as the chip length input by the chip division information input unit102. At this stage, the workpiece7is machined by both the first tool5and the second tool6.

Subsequently, as illustrated inFIG.11, the second cutter holder4moves in the X-axis direction and the second tool6reenters a non-cutting state. When the first tool5reaches the cutting start point of the second tool6, the chips generated as a result of the cutting by the first tool5are divided by the cutting groove of the second tool6.

As described above, in the tool vibration technique, the workpiece7is machined by the first tool5and the chips are divided by the second tool6with repeating the operations illustrated inFIGS.9to11. By setting the Z-axis-direction movement speed of the first cutter holder3in machining the workpiece7to a cutting feed rate commanded by the program200or the like, the machining time of the workpiece7is the same as that in the case of normal threading. The second tool6performs the chip division operation within the range of a normal cutter holder operation, and thus no heavy load is applied to the turning machine tool or each tool. In addition, by using a tool resistant to vibration as the second tool6, the burden on the machine as a whole can be reduced. It should be noted that the roles of the first tool5and the second tool6may be reversed although only the first tool5is configured to perform continuous cutting and the second tool6is configured to temporarily enter a cutting point in the above example. In addition, by switching the roles of the first tool5and the second tool6at a tool load accumulation timing, burden dispersion to the respective tools is also possible.

FIGS.12to15are diagrams illustrating states where the workpiece7is machined using the (3) tool rear insertion technique calculated by the multi-tool operation calculation unit104with the first tool5attached to the first cutter holder3and the second tool6attached to the second cutter holder4.

As for the tool rear insertion technique, threading is first started by one of the tools. In the state illustrated inFIG.12, the workpiece7attached to the headstock2and rotating is cut (threaded) by the first tool5attached to the first cutter holder3. At this time, the second tool6attached to the second cutter holder moves in the Z-axis direction in a non-cutting state behind the first tool5at an X-axis position of non-contact with the workpiece7. In this state, the chips8are generated from the threading position of the first tool5.

Next, as illustrated inFIG.13, when the second tool6approaches the cutting start point, the first cutter holder3moves in the X-axis direction and then the first tool5enters a non-cutting state. Then, until the workpiece7rotates half, the second cutter holder4moves in the X-axis direction after setting the speed of movement in the Z-axis direction to the speed of cutting, and the second tool6is inserted into the cutting groove cut by the first tool5. Then, when the workpiece7rotates half, the second tool6starts cutting at the position where the cutting by the first tool5is interrupted.

The chips generated as a result of the cutting by the first tool5are divided when the first tool5is retracted. The cutting start point of the second tool6is a position where the cutting length from the cutting start position of the first tool5is substantially the same as the chip length input by the chip division information input unit102.

With the first tool5in the non-cutting state, the first cutter holder3moves in the Z-axis direction while adjusting the speed as illustrated inFIG.14. Then, when the first tool5approaches the next cutting start point, the second cutter holder4moves in the X-axis direction and the second tool6enters a non-cutting state as illustrated inFIG.15. Then, until the workpiece7rotates half, the first cutter holder3moves in the X-axis direction after setting the speed of movement in the Z-axis direction to the speed of cutting, and the first tool5is inserted into the cutting groove cut by the second tool6. Then, when the workpiece7rotates half, the first tool5starts cutting at the position where the cutting by the second tool6is interrupted. The chips generated as a result of the cutting by the second tool6are divided when the second tool6is retracted. The cutting start point of the first tool5is a position where the cutting length from the cutting start position of the second tool6is substantially the same as the chip length input by the chip division information input unit102.

As described above, by the tool rear insertion technique, the first tool5and the second tool6alternately machine the workpiece7by repeating the operations illustrated inFIGS.12to15. By this operation technique, the chips generated as a result of the cutting by the first tool5are divided when the first tool5is retracted. In addition, the chips generated as a result of the cutting by the second tool6are divided when the second tool6is retracted. By setting the Z-axis-direction movement speeds of the first cutter holder3and the second cutter holder4in machining the workpiece7to cutting feed rates commanded by the program200or the like, the machining time of the workpiece7is substantially the same as that in the case of normal threading.

In addition, it is not necessary to perform a swinging operation or the like, and thus no heavy load is applied to the turning machine tool or each tool. Further, because the machining of the workpiece7is alternately performed by the first tool and the second tool, machining burden can be distributed to the respective tools. For example, the non-cutting time of the tool is longer than in the case of continuous machining, and thus sufficient heat can be taken off during the machining and tool life extension is also expectable. In addition, no machining is performed in the direction of cutting by the tool (workpiece radial direction), and thus burden on the tools is particularly reduced.

FIGS.16to20are diagrams illustrating states where the workpiece7is machined using the (4) combination technique calculated by the multi-tool operation calculation unit104, the first tool5attached to the first cutter holder3, and the second tool6attached to the second cutter holder4. The combination technique is a combination of the tool operations of the (1) tool front insertion technique and the (3) tool rear insertion technique.

As for the combination technique, threading is started by both the first tool5and the second tool6as illustrated inFIG.16. InFIG.16, the cutting position of the first tool5is disposed so as to be positioned in front of the cutting position of the second tool6in the Z-axis direction. The cutting position of each of the first tool5and then the second tool6is a position where the cutting length is substantially the same as the chip length input by the chip division information input unit102.

When the cutting position of the second tool6reaches the cutting start position of the first tool5, as illustrated inFIG.17, each of the first cutter holder3and the second cutter holder4moves in the X-axis direction and then the first tool5and the second tool6enter a non-cutting state. At this time, the chips8generated as a result of the cutting by the first tool5and the second tool6are divided respectively.

Subsequently, as illustrated inFIG.18, the second tool6is moved to the cutting end point of the first tool5with the relative front-back relationship between the first tool5and the second tool6maintained. Then, at the respective positions, the first cutter holder3and the second cutter holder4move in the X-axis direction and the first tool5and the second tool6start cutting (seeFIG.19).

Then, when the cutting position of the second tool6reaches the cutting start position of the first tool5, the first cutter holder3and then the second cutter holder4move in the X-axis direction and the first tool5and the second tool6enter a non-cutting state as illustrated inFIG.20. At this time, the chips8generated as a result of the cutting by the first tool5and the second tool6are divided respectively.

As described above, in the combination technique, each of the first tool5and the second tool6machines the workpiece7by repeating the operations illustrated inFIGS.16to20. By this operation technique, the chips generated as a result of the cutting by the first tool5are divided when the first tool5is retracted. In addition, the chips generated as a result of the cutting by the second tool6are divided by the cutting groove by the first tool5. The time for machining the workpiece7is sufficiently shorter than in the case of single-tool machining even with the tool movement time in the non-cutting state (that is, rapid traverse time) taken into consideration. In particular, machining can be efficiently performed when the cutting distance in single cutting is long. By setting to the cutting feed rate commanded by the threading program200or the like, the machining time is approximately halved as compared with the case of normal threading. In addition, because it is not necessary to perform a swinging operation or the like, no heavy load is applied to the turning machine tool and each tool. Further, because the machining of the workpiece7is distributed to the first tool and the second tool, the burden of machining can be distributed to the respective tools. In addition, by this technique, the machining heat can be sufficiently removed during the non-cutting time of the tool and thus tool life extension is also expectable.

One embodiment of the invention has been described above together with some tool operation examples actualized by the embodiment. However, the invention is not limited to the above description of the embodiment and operation examples and can be implemented in various aspects by being changed appropriately.

For example, in the exemplary configuration of the embodiment and the operation examples described above, the machine to be controlled by the numerical controller1is configured such that the first cutter holder3and the second cutter holder4are at opposite positions. However, the cutter holders and the tools may be disposed in any manner insofar as the first tool5and the second tool6are capable of performing threading in cooperation with each other.

In addition, in the exemplary configuration of the embodiment and the operation examples described above, the machine to be controlled by the numerical controller1is configured to perform threading using two cutter holders and two tools. However, in an alternative configuration, threading may be performed using three or more cutter holders and three or more tools. Even in this case, the multi-tool operation calculation unit104in the numerical controller1may create movement command data for each tool such that the cutting paths of the respective tools intersect.

In addition, in the exemplary configuration of the embodiment and the operation examples described above, a machine configured to perform threading using two movable cutter holders is controlled by the numerical controller1. However, regardless of the above description, threading may be performed using one movable cutter holder, one fixed cutter holder, and one movable headstock. Even in this case, the multi-tool operation calculation unit104may create movement command data for each tool such that the cutting paths of the respective tools intersect. Even in this case, it is a matter of course that the number of cutter holders used for threading may be 3 or more.