Control device for machine tool

Abstract

Provided is a technology for easily setting a processing program and reliably executing air cutting in a control device for a machine tool that controls thread cutting with and without oscillation. The control device 1 for a machine tool comprises: a cutting position acquisition unit 11 that acquires a cutting position for thread cutting; a margin acquisition unit 12 that acquires a margin set so that the cutting tool oscillates beyond the cutting position in thread cutting with oscillation; an oscillation amplitude information acquisition unit 13 that acquires oscillation amplitude information indicating the oscillation amplitude of the thread cutting with oscillation; and a thread cutting command generation unit 20 that generates a thread cutting command to oscillate so that at least one end position in the oscillation direction exceeds the cutting position on the basis of the cutting position, the margin, and the oscillation amplitude information.

Description

Machine tool control device

[0001] The present disclosure relates to a control device for a machine tool.

[0002] Conventionally, machine tools have performed swing machining, in which the tool and workpiece are swung relative to each other, to prevent chips that are continuously generated during machining from becoming entangled in the workpiece or cutting tool, which could result in machining defects or machine failure (see, for example, Patent Documents 1 and 2).

[0003] In this type of swing machining, the tool path, which is the trajectory of the tool, is set to partially overlap the previous tool path, causing an air cut in which the tool separates from the surface of the workpiece, shredding the chips.

[0004] JP 2020-124793 A International Publication No. 2016 / 067372

[0005] In thread cutting, both swing and non-swing machining are performed as a set. When both swing and non-swing machining are performed, the cutting position (for example, the X-axis position) is often specified to be the same in order to simplify the machining program.

[0006] However, when performing swing thread cutting so that the cutting position specified by the operator is one end position of the swing (for example, the bottom end position), although programming is easy, since one end position of the swing is specified, it is not possible to take a margin for air cutting. In actual machining, since the swing amplitude is often attenuated in response to the swing command, there is a risk that air cutting will not be performed appropriately unless a margin that takes attenuation into account can be secured.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technology that can easily set a machining program and reliably perform air cutting in a control device of a machine tool that controls thread cutting both with and without swinging.

[0008] The present disclosure relates to a control device for a machine tool that performs thread cutting on a workpiece using a cutting tool, the control device for a machine tool including: a cutting position acquisition unit that acquires a cutting position for thread cutting; a margin acquisition unit that acquires a margin that is set to swing beyond the cutting position in thread cutting with swing; a swing amplitude information acquisition unit that acquires swing amplitude information that indicates the swing amplitude for thread cutting with swing; and a thread cutting command generation unit that generates a thread cutting command to swing so that at least one end position in the swing direction swings beyond the cutting position based on the cutting position, the margin, and the swing amplitude information.

[0009] According to the present disclosure, it is possible to provide a technology that allows for easy setting of machining programs and reliable execution of air cutting in a control device of a machine tool that controls thread cutting both with and without swinging.

[0010] 8 is a functional block diagram of a control device for a machine tool according to a first embodiment of the present invention. FIG. 9 is a diagram showing an example of a machining program according to the first embodiment. FIG. 10 is a graph showing the positional relationship between a workpiece and a cutting tool in the first embodiment. FIG. 11 is an enlarged view of the graph of FIG. 3 showing the upper end position and lower end position of oscillation in the first embodiment. FIG. 12 is a graph showing the positional relationship between a workpiece and a cutting tool over multiple cycles in the first embodiment. FIG. 13 is a graph showing the path of the cutting tool in thread cutting with oscillation and thread cutting without oscillation in the prior art. FIG. 14 is a graph showing the path of the cutting tool in thread cutting with oscillation and thread cutting without oscillation in the present embodiment. FIG. 15 is a graph showing the positional relationship between a workpiece and a cutting tool in a second embodiment. FIG. 16 is an enlarged view of the graph of FIG. 8 showing the upper end position and lower end position of oscillation in the second embodiment. FIG. 17 is a graph showing the positional relationship between a workpiece and a cutting tool over multiple cycles in the second embodiment. FIG. 18 is a functional block diagram showing the configuration of a thread cutting command generation unit according to a third embodiment. FIG. 19 is a graph showing the positional relationship between a workpiece and a cutting tool in a thread cutting command generation method according to the third embodiment. FIG. 19 is a graph showing the positional relationship between a workpiece and a cutting tool in a thread cutting command generation method according to a fourth embodiment. FIG. 10 is a graph showing the positional relationship between a workpiece and a cutting tool in a method for generating a threading command according to a fifth embodiment. FIG. 11 is a functional block diagram showing the configuration of a threading command generating unit according to a sixth embodiment. FIG. 12 is a graph showing the positional relationship between a workpiece and a cutting tool in a method for generating a threading command according to a sixth embodiment. FIG. 13 is a functional block diagram showing the configuration of a threading command generating unit according to a seventh embodiment. FIG. 14 is a graph showing the positional relationship between a workpiece and a cutting tool in a method for generating a threading command according to a seventh embodiment. FIG. 15 is a functional block diagram of a control device for a machine tool according to an eighth embodiment.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the second and subsequent embodiments, the same reference numerals will be used to designate components common to the first and second embodiments, and the description thereof will be omitted as appropriate.

[0012] First Embodiment FIG. 1 is a functional block diagram of a machine tool control device 1 according to a first embodiment of the present invention. The machine tool control device 1 shown in FIG. 1 is used to perform thread cutting using a cutting tool that oscillates radially relative to a workpiece. For convenience, FIG. 1 only shows a motor 3 that drives one feed axis. Furthermore, the cutting process according to this embodiment is not limited to a specific workpiece shape. That is, the present invention is applicable to cases where the workpiece has a tapered or arc-shaped portion on the cutting surface, requiring multiple feed axes (Z-axis and X-axis), and cases where the workpiece is columnar or cylindrical and only one specific feed axis (Z-axis) is sufficient.

[0013] The machine tool control device 1 of this embodiment is configured using a computer including memories such as ROM (read only memory) and RAM (random access memory), a CPU (control processing unit), and a communication control unit, all connected via a bus. The functions and operations of each functional unit, which will be described later, are achieved by cooperation between the CPU and memory installed in the computer and the control program stored in the memory. The machine tool control device 1 may also be configured with a CNC (computer numerical controller) or PLC (programmable logic controller), or may be connected to a higher-level computer that outputs machining conditions such as rotational speed in addition to the machining program.

[0014] As shown in FIG. 1, the machine tool control device 1 includes a cutting position acquisition unit 11, a margin acquisition unit 12, a swing amplitude information acquisition unit 13, a thread cutting command generation unit 20, a machining control unit 21, a memory unit 14, an input unit 15, and a display unit 16.

[0015] The cutting position acquisition unit 11 acquires the cutting position of the cutting tool relative to the workpiece during thread cutting. The cutting position may be stored in the storage unit 14, for example, or may be output from an external computer.

[0016] The margin acquisition unit 12 acquires a margin as information for setting an oscillation waveform so that the oscillation exceeds the incision position acquired by the incision position acquisition unit 11. The margin is, for example, information that determines the width of the oscillation beyond the incision position. The margin may be, for example, stored in the storage unit 14 or may be output from an external computer.

[0017] The oscillation amplitude information acquisition unit 13 acquires oscillation amplitude information indicating the oscillation amplitude from processing conditions, etc., which will be described later. The oscillation amplitude may be stored in the storage unit 14, for example, or may be output from an external computer.

[0018] The thread cutting command generating unit 20 generates a thread cutting command for executing thread cutting. The thread cutting command is generated by the thread cutting command generating unit 20 based on the cutting position acquired by the cutting position acquiring unit 11, the margin acquired by the margin acquiring unit 12, and the oscillation amplitude acquired by the oscillation amplitude information acquiring unit 13. Details of the thread cutting command generation process will be described later.

[0019] The machining control unit 21 performs operation control based on the thread cutting command generated by the thread cutting command generating unit 20. The operation control drives the motor 3 and the like, moves the workpiece and the cutting tool, and performs thread cutting.

[0020] The storage unit 14 stores various information for controlling and machining the machine tool. In this embodiment, the storage unit 14 stores machining conditions and oscillation conditions. The machining conditions and oscillation conditions are, for example, those input by an operator into a machining program or those specified as machine tool parameters. The storage unit 14 may be configured to be located outside the control device 1 rather than inside it.

[0021] The oscillation conditions stored in the memory unit 14 include information relating to the number of oscillations in the radial direction of the workpiece and information relating to the oscillation amplitude in the radial direction of the workpiece. The information relating to the number of oscillations in the radial direction of the workpiece includes an oscillation frequency magnification I (times), which indicates the oscillation frequency per rotation of the spindle. Furthermore, the information relating to the oscillation amplitude in the radial direction of the workpiece relative to the cutting tool and the workpiece includes an oscillation amplitude magnification K (times), which indicates the magnitude of the oscillation amplitude relative to the cutting depth in the radial direction of the workpiece during thread cutting.

[0022] The machining conditions stored in the memory unit 14 include information about the shape of the thread and cutting conditions for the workpiece. For example, information about the shape of the thread includes the thread lead (mm), thread diameter (mm), and thread angle (°). Cutting conditions for the workpiece include the spindle rotation speed S (1 / min), finishing allowance (mm), the number of finishing passes (times), and cutting position (mm). The cutting position is a reference position such as one end position (e.g., the lower end position) or the other end position (the upper end position) in the swing direction, and is not particularly limited to a specific position. Furthermore, the cutting position may be any information that can identify the cutting position, such as the cutting area. In this way, the cutting amount may be a length or an area, or may be information that identifies a position.

[0023] The input unit 15 inputs information related to processing in response to an operator's input operation on an input means (not shown), such as a keyboard or a touch panel. The information related to processing input by the input unit 15 is stored in the storage unit 14 or the like, or input to each unit of the control device 1.

[0024] The display unit 16 displays various information related to the machine tool, the control device 1, and machining. The display unit 16 is configured by, for example, a display.

[0025] The above has described the overall configuration of the control device 1. Next, the flow of the process of generating a swing command by the control device 1 of this embodiment will be described.

[0026] 2 is a diagram showing an example of a machining program of the first embodiment. "I5.0 K1.2" following the code "G8.5" in the machining program indicates oscillation conditions such as oscillation frequency and oscillation amplitude. "G92" is a code that generates one cycle of thread cutting operations with one block of commands. "X10.00 Z10.00 F2.0" following "G92" indicates thread cutting machining conditions indicating position and feed amount.

[0027] The process of generating a swing command will now be described. In the process of generating a swing command, first, the swing amplitude information acquisition unit 13 acquires swing amplitude information indicating an amplitude of 1.2 [mm] from "K1.2" in the machining program.

[0028] Next, the cutting position acquisition unit 11 acquires the thread cutting conditions (thread pitch, lead, etc.) from "G92 X10.00 Z10.00 F2.0" in the processing program. Then, the cutting position acquisition unit 11 analyzes from the description of "X10.00" that the cutting position in the thread cutting is X = 10.0 [mm].

[0029] Then, the margin acquisition unit 12 acquires the margin from "G8.5 P3 I5.0 K1.2 L0.1" in the machining program. Note that in this example, the margin is acquired from the machining program, but this is not limiting. For example, the margin may be acquired from parameters set in the machine tool. Furthermore, the margin does not have to be directly specified. A multiplier for each thread cutting depth may be acquired as information indicating the margin.

[0030] Next, the threading command generating unit 20 will be described with reference to Figures 3 and 4. Figure 3 is a graph showing the positional relationship between the workpiece and the cutting tool T in the first embodiment. Figure 4 is an enlarged view of the graph in Figure 3 showing the upper and lower end positions of the swing in the first embodiment.

[0031] The threading command generating unit 20 determines an upper end position, which is one end position of the swinging motion, and a lower end position, which is the other end position of the swinging motion.

[0032] The thread cutting command generating unit 20 first sets the bottom end position of the swing operation based on the cutting position acquired by the cutting position acquiring unit 11 and the margin acquired by the margin acquiring unit 12. In this example, as shown in Figures 3 and 4, 9.9, which is the cutting position X = 10.0 [mm] minus the margin 0.1 [mm], is determined as the bottom end position.

[0033] The thread cutting command generating unit 20 determines the upper end position based on the swing amplitude acquired by the swing amplitude information acquiring unit 13. In this example, the upper end position is determined to be 11.2 mm, which is the sum of the swing amplitude of 1.2 mm and the cutting position of 10.0 mm.

[0034] The thread cutting command generating unit 20 generates a swing command based on the swing conditions acquired from the machining program and the upper and lower end positions of the generated swing. The swing may be performed using a sine wave, for example, but a triangular wave or the like may also be used as long as it is a periodic signal.

[0035] Next, an example of generating a swing command for multiple cycles will be described with reference to Fig. 5. Fig. 5 is a graph showing the positional relationship between the workpiece and the cutting tool T for multiple cycles in the first embodiment. One cycle is, for example, a series of operations from the start point of the cutting tool T shown in Fig. 5, where the cutting tool T comes into contact with the workpiece to perform machining, and then returns to the start point. As shown in Fig. 5, the threading command generating unit 20 generates a threading command for performing threading machining for multiple cycles.

[0036] In the example of Figure 5, cutting is performed in two steps: a step of making a cut by swinging in the X-axis direction, and a step of making a cut without swinging after the cut. Thread cutting with swinging is performed in the first, third, fifth, and seventh cycles. The depth of the cut increases as the cycle progresses from the first to the third, fifth, and seventh cycles. For each swinging cut, swing conditions such as amplitude are set so that the cut trajectory is located radially outward from the surface of the workpiece. Then, thread cutting without swinging is performed in the second, fourth, sixth, and eighth cycles.

[0037] The intersection of the thread cutting path with oscillation and the thread cutting path without oscillation realizes air cutting, which cuts off chips. For example, an oscillation command is generated so that the depth of the bottom end of the first thread cutting with oscillation intersects with the depth of the second thread cutting. This allows chips to be cut off even in each cutting with oscillation. Even in the cutting of the final thread groove, which does not involve oscillation, chips can be cut off and a highly accurate machined surface can be achieved.

[0038] Here, the conventional technology will be described with reference to FIG. 6 . FIG. 6 is a graph showing the paths of the cutting tool T in thread cutting with and without swinging according to the conventional technology. As shown in FIG. 6 , in thread cutting with swinging according to the conventional technology, the amplitude of the waveform showing the actual path of the cutting tool T is attenuated, and the amplitude of the waveform showing the commanded path of the cutting tool T is reduced. In the example of FIG. 6 , the path of the sixth thread cutting without swinging and the path of the seventh thread cutting with swinging intersect, allowing air cutting. However, due to the attenuation of the amplitude, the path of the seventh thread cutting with swinging and the path of the eighth thread cutting without swinging do not actually intersect, although they intersect in the command, and air cutting is not possible.

[0039] To ensure air cutting, it is possible to generate a command with a larger swing amplitude and ensure a margin for air cutting. However, at the bottom end of the swing, the position is directly specified in the program, so it is not possible to ensure a margin for air cutting at the bottom end of the swing.

[0040] 7 is a graph showing the paths of the cutting tool T in thread cutting with and without swing according to this embodiment. According to the configuration of this embodiment, as shown in FIG. 7, even if the actual swing amplitude is attenuated below the commanded swing amplitude, the swing command is generated in advance taking the attenuation into account, so the paths of the thread cutting with and without swing intersect. In this example, the path of the seventh thread cutting with swing and the path of the eighth thread cutting without swing intersect, whereas in the prior art they did not intersect, and air cutting is performed.

[0041] According to the control device 1 of the first embodiment of the machine tool that performs thread cutting on a workpiece using the cutting tool T described above, the following effects are achieved.

[0042] The machine tool control device 1 according to this embodiment includes an infeed position acquisition unit 11 that acquires the infeed position for thread cutting, a margin acquisition unit 12 that acquires a margin that is set so that the cutting tool T swings beyond the infeed position in thread cutting with swing, a swing amplitude information acquisition unit 13 that acquires swing amplitude information that indicates the swing amplitude for thread cutting with swing, and a thread cutting command generation unit 20 that generates a thread cutting command to swing so that at least one end position in the swing direction passes beyond the infeed position based on the infeed position, the margin, and the swing amplitude information. This makes it possible to realize a machine tool control device 1 that maintains ease of programming the machining program while also reliably performing air cutting because the swing waveform is set taking the margin into consideration.

[0043] The thread cutting command generating unit 20 determines one end position (lower end position) in the oscillation direction based on the cutting position and margin, and determines the other end position (upper end position) in the oscillation direction based on the oscillation amplitude information, and generates a thread cutting command based on the one end position and the other end position. This allows the one end position and the other end position of the amplitude oscillation to be determined without complex processing, effectively reducing the calculation cost for setting the oscillation waveform to a position where air cutting can be reliably performed.

[0044] Although the control device 1 for a machine tool according to the first embodiment has been described above, the present invention is not limited to the configuration of the above embodiment. Below, an embodiment different from the above embodiment will be described.

[0045] Second Embodiment Next, a control device 1 according to a second embodiment will be described. The control device 1 according to the second embodiment has the same configuration as that of the first embodiment, except for the processing for generating a swing command by the threading command generating unit 20. In the first embodiment, the lower end position is determined first, and then the upper end position is determined based on the lower end position and the swing amplitude, but in the second embodiment, the upper end position is determined first.

[0046] The process of generating a swing command by the threading command generator 20 of the second embodiment will be described with reference to Figures 8 and 9. Figure 8 is a graph showing the positional relationship between the workpiece and the cutting tool T in the second embodiment. Figure 9 is an enlarged view of the graph of Figure 8 showing the upper and lower end positions of the swing in the second embodiment.

[0047] The thread cutting command generating unit 20 first sets the upper end position of the swing operation based on the cutting position acquired by the cutting position acquiring unit 11 and the margin acquired by the margin acquiring unit 12. In this example, as shown in Figures 8 and 9, 10.1, which is the cutting position X = 10.0 [mm] plus a margin of 0.1 [mm], is determined as the upper end position.

[0048] The thread cutting command generating unit 20 determines the lower end position based on the oscillation amplitude acquired by the oscillation amplitude information acquiring unit 13. In this example, the lower end position is determined to be 8.8 mm, which is the cutting position of 10.0 mm minus the oscillation amplitude of 1.2 mm.

[0049] In this way, the thread cutting command generating unit 20 generates a command to execute thread cutting with swing so that the upper end position X=10.1 [mm] and the lower end position X=8.8 [mm].

[0050] Next, an example of generating a swing command for multiple cycles will be described with reference to FIG. 10 . FIG. 10 is a graph showing the positional relationship between the workpiece and the cutting tool T for multiple cycles in the first embodiment. The threading command generating unit 20 generates a swing command for performing cutting in a step of making a cut by swinging in the X-axis direction and a step of making a cut without swinging after the cut. In the example of FIG. 10 , threading without swinging is performed in the first, third, fifth, and seventh cycles. Then, threading with swinging is performed in the second, fourth, and sixth cycles. The intersection of the path for threading with swinging and the path for threading without swinging achieves air cutting, which cuts off chips.

[0051] [Third Embodiment] Next, a method of generating a threading command different from that of the first embodiment will be described. Fig. 11 is a functional block diagram showing the configuration of a threading command generating unit 20a of the third embodiment. Fig. 12 is a graph showing the positional relationship between a workpiece and a cutting tool T in the method of generating a threading command of the third embodiment. Note that in the third embodiment, the configuration other than the threading command generating unit 20a is the same as that of the above-mentioned embodiments.

[0052] As shown in FIG. 11, the threading command generating unit 20a has a movement command generating unit 25 that generates a movement command, and a swing command generating unit 26 that generates a swing command.

[0053] The movement command generating unit 25 generates a movement command for controlling the position of the cutting tool T. The movement command is generated so that the cutting tool T moves the cutting position in thread cutting. The swing command generating unit 26 generates a swing command for swinging the cutting tool T relative to the workpiece. The swing command is generated taking a margin into consideration.

[0054] In the example of Fig. 12, the movement command generator 25 generates a movement command F1 based on a cutting position of 10 mm. The swing command generator 26 calculates a swing command F2 using the following equation 1. In equation 1, A represents the amplitude [mm], L represents the margin [mm], and θ represents the swing phase [deg]. In the example of Fig. 12, it is assumed that the swing amplitude A is set to 1.0 mm and the margin L is set to 0.1 mm.

[0055]

[0056] The threading command generating unit 20a generates a threading command for performing threading with swing by superimposing the swing command F2 calculated by the swing command generating unit 26 using the above-mentioned equation 1 and the movement command F1 generated by the movement command generating unit 25. As shown in equation 1 and in Fig. 12, "A + L" is the swing amplitude indicated by the swing command, and "L" therein is the offset amount. In this way, the machining operation is performed based on the threading command in which the movement command and swing command are superimposed.

[0057] [Fourth Embodiment] A fourth embodiment will be described in which a threading command is generated by issuing a movement command and a swing command in a manner different from that of the third embodiment. Fig. 13 is a graph showing the positional relationship between the workpiece and the cutting tool T in the threading command generation method of the fourth embodiment.

[0058] In the example shown in Fig. 13, F2 can be expressed by the following formula 2. In formula 2, A represents the amplitude [mm], L represents the margin [mm], and θ represents the oscillation phase [deg]. In the example of Fig. 13, it is assumed that the oscillation amplitude A is set to 1.1 mm and the margin L is set to 0.1 mm.

[0059]

[0060] The thread cutting command generating unit 20a generates a thread cutting command for performing thread cutting with swing by superimposing the swing command F2 calculated by the swing command generating unit 26 using the above-mentioned formula 2 and the movement command F1 generated by the movement command generating unit 25. As shown in formula 2 and in FIG. 13, "A" directly becomes the swing amplitude. In this way, the machining operation is performed based on the thread cutting command in which the movement command and swing command are superimposed.

[0061] According to the control device 1 of the machine tool of the third and fourth embodiments, which performs thread cutting on a workpiece using the cutting tool T described above, the following effects are achieved.

[0062] In the third and fourth embodiments, the thread cutting command generating unit 20a has a movement command generating unit 25 that generates a movement command for moving the cutting tool T in thread cutting, and a swing command generating unit 26 that generates a swing command that determines the operation of the swing amplitude in thread cutting based on swing amplitude information, and generates a thread cutting command by superimposing the swing command offset by the margin L on the movement command. This makes it possible to easily set the swing waveform to a position where air cutting can be reliably performed using the process of superimposing the movement command and the swing command.

[0063] Fifth Embodiment A fifth embodiment will now be described in which a threading command is generated directly without superimposing a movement command and a swing command. Fig. 14 is a graph showing the positional relationship between the workpiece and the cutting tool T in a method for generating a threading command according to the fifth embodiment. As shown in Fig. 14, a threading command is generated directly, rather than by superimposing a movement command and a swing command. In this example, the swing amplitude A is set to 1.0 mm, and the margin L is set to 0.1 mm, so that "A + L" is the swing amplitude.

[0064] Sixth Embodiment Next, a sixth embodiment will be described in which a threading command is generated by a method different from that of the above-described embodiments. In the sixth embodiment, the threading command generator 20b generates a threading command such that the infeed position for threading with oscillation differs from the infeed position for threading without oscillation.

[0065] Fig. 15 is a functional block diagram showing the configuration of a threading command generating unit 20b according to the sixth embodiment. Fig. 16 is a graph showing the positional relationship between the workpiece and the cutting tool T in the threading command generating method according to the sixth embodiment.

[0066] 15, the thread cutting command generating unit 20b includes a no-swing infeed position determining unit 30. The no-swing infeed position determining unit 30 determines the no-swing infeed position based on the infeed position acquired by the infeed position acquiring unit 11 and the margin acquired by the margin acquiring unit 12.

[0067] In this embodiment, the margin acquisition unit 12 functions as a shift amount acquisition unit that acquires a shift amount for changing the cutting position as a margin for changing the position of the oscillation waveform. In the example shown in Fig. 16, a margin of 0.1 mm is added to the cutting position X = 10.00 mm, and 10.10 mm is determined as the cutting position during thread cutting without oscillation.

[0068] According to the control device 1 of the sixth embodiment of the machine tool that performs thread cutting on a workpiece using the cutting tool T described above, the following effects are achieved.

[0069] The threading command generating unit 20b of the sixth embodiment has a no-swing infeed position determining unit 30 that sets the infeed position for no swing during threading without swing based on the infeed position and margin, and in threading with swing, executes threading based on the infeed position acquired by the infeed position acquiring unit 11, and in threading without swing, generates a threading command that executes threading based on the infeed position for no swing set by the no-swing infeed position determining unit 30. This makes it possible to realize a configuration that can ensure a margin for air cutting through the simple process of adjusting the infeed position for threading without swing.

[0070] [Seventh Embodiment] Next, a seventh embodiment will be described, in which a threading command is generated by a method different from the above-described embodiments. Fig. 17 is a functional block diagram showing the configuration of a threading command generation unit 20b of the seventh embodiment. Fig. 18 is a graph showing the positional relationship between the workpiece and the cutting tool T in the threading command generation method of the seventh embodiment.

[0071] 17, the thread cutting command generating unit 20c includes a pre-machining infeed position determining unit 31. The pre-machining infeed position determining unit 31 determines the infeed position without oscillation based on the infeed position acquired by the infeed position acquiring unit 11 and the margin acquired by the margin acquiring unit 12.

[0072] In this embodiment, the margin acquisition unit 12 also functions as a shift amount acquisition unit that acquires a shift amount for changing the cutting position as a margin for changing the position of the oscillation waveform. In the example shown in Fig. 18, 9.9 mm, which is obtained by subtracting a margin of 0.1 mm from X = 10.00 mm, is determined as the cutting position before the start of machining.

[0073] The pre-machining infeed position determiner 31 determines the infeed position at a timing before the execution of the thread cutting with oscillation. The thread cutting command generator 20 generates a thread cutting command based on the infeed position and outputs it to the machining control unit 21. The machining control unit 21 executes a positioning process based on the infeed position determined by the pre-machining infeed position determiner 31, and then executes the oscillation cutting.

[0074] According to the control device 1 of the seventh embodiment of the machine tool that performs thread cutting on a workpiece using the cutting tool T described above, the following effects are achieved.

[0075] The thread cutting command generation unit 20c of the seventh embodiment has a pre-machining infeed position determination unit 31 that sets the infeed position for oscillation during thread cutting with oscillation based on the infeed position and margin, and generates a thread cutting command to perform thread cutting with oscillation after positioning the workpiece at the infeed position determined by the pre-machining infeed position determination unit 31 before the start of machining.

[0076] Eighth Embodiment Next, a control device 1a according to an eighth embodiment will be described with reference to Fig. 19. Fig. 19 is a functional block diagram of a control device for a machine tool according to the eighth embodiment. The control device 1a according to the eighth embodiment differs from the control device 1 according to the above-described embodiments in that it further includes a machining accuracy determination unit 35 and in the processing of a threading command generation unit 20d.

[0077] The machining accuracy determination unit 35 determines the degree of machining accuracy from the description of the machining program. The degree of machining accuracy determined by the machining accuracy determination unit 35 is determined based on, for example, the type of code described in the machining program or a dedicated determination code attached near the code.

[0078] This section explains a case where the degree of machining accuracy is determined based on the type of code. For example, the code "G76" is a code that generates multiple thread cutting movement blocks with one block of commands in a machining program. When the code "G76" is written in a machining program, the importance of the machining accuracy of the thread cutting in each cycle can be determined based on the target value written in the block following "G76." For example, the final finishing machining can be set as the most important machining, and the importance of machining accuracy can be set to increase as the final finishing machining is approached over multiple cycles.

[0079] The following describes a case where the degree of machining accuracy is determined using a dedicated judgment code. For example, if a dedicated discrimination code (e.g., a character such as "L0") is assigned to a block such as "G32" or "G92" in a machining program, the degree of machining accuracy is determined based on the discrimination code. In this case, the discrimination code itself contains information indicating the importance of machining accuracy.

[0080] The threading command generating unit 20d executes a process of correcting the margin in accordance with the degree of machining accuracy determined by the machining accuracy determining unit 35. For example, in the case of final finish machining, the importance of machining accuracy is highest, so the threading command generating unit 20d sets the margin to 0, and reduces the margin in the stage immediately preceding the final finish machining. The margin reduction amount may be reduced as the stage approaches the stage immediately preceding the final finish machining. In this case, the margin becomes relatively larger as the stage approaches the stage immediately preceding the final finish machining.

[0081] According to the control device 1a of the machine tool of the eighth embodiment, which performs thread cutting on a workpiece using the cutting tool T described above, the following effects are achieved.

[0082] The control device 1a for the machine tool according to this embodiment further includes a machining accuracy determination unit 35 that determines the level of machining accuracy, and the threading command generation unit 20d sets a margin value according to the level of machining accuracy determined by the machining accuracy determination unit 35. This allows the machining accuracy to be reflected in the margin, making it possible to achieve both high machining accuracy and reliable execution of air cutting at a high level.

[0083] In the above embodiment, a command is automatically generated to alternately repeat thread cutting with swing and thread cutting without swing, but the present invention is not limited to this.

[0084] For example, a configuration may be adopted in which thread cutting with oscillation is performed multiple times, followed by thread cutting without oscillation at least once. In this case, in order to perform air cutting, it is preferable to perform machining control by adjusting the oscillation conditions so that the peaks and valleys of successive thread cuttings with oscillation overlap. For example, the thread cutting command generation units 20, 20a to 20d can overlap the peaks and valleys of successive thread cuttings with oscillation by performing processing to shift the phase of the oscillation conditions by 180 degrees.

[0085] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0086] The following supplementary note is further disclosed regarding the above embodiment and modified examples. (Supplementary Note 1) A control device (1, 1a) for a machine tool that performs thread cutting on a workpiece with a cutting tool (T), comprising: an infeed position acquisition unit (11) that acquires an infeed position for thread cutting, a margin acquisition unit (12) that acquires a margin that is set so that the cutting tool (T) swings beyond the infeed position in thread cutting with swing, an oscillation amplitude information acquisition unit (13) that acquires oscillation amplitude information that indicates the oscillation amplitude for thread cutting with swing, and a thread cutting command generation unit (20, 20a to 20d) that generates a thread cutting command to swing so that at least one end position in the swing direction passes beyond the infeed position, based on the infeed position, the margin, and the oscillation amplitude information.

[0087] (Supplementary Note 2) In the control device (1) of a machine tool, the thread cutting command generation unit (20) determines one end position of the oscillation direction based on the cutting position and the margin, and determines the other end position of the oscillation direction based on the oscillation amplitude information, and generates a thread cutting command based on the one end position and the other end position.

[0088] (Supplementary Note 3) In the control device (1) for a machine tool, the thread cutting command generation unit (20a) has: a movement command generation unit (25) that generates a movement command to move the cutting tool (T) in thread cutting; and a swing command generation unit (26) that generates a swing command that determines the operation of the swing amplitude in thread cutting based on the swing amplitude information, and generates a thread cutting command by superimposing the swing command and the movement command that are offset based on the margin.

[0089] (Supplementary Note 4) In the control device (1) of the machine tool, the thread cutting command generation unit (20c) has a pre-machining infeed position determination unit (31) that sets an infeed position for oscillation during thread cutting with oscillation based on the infeed position and the margin, and generates a thread cutting command to perform thread cutting with oscillation after positioning the infeed position determined by the pre-machining infeed position determination unit (31) before the start of machining.

[0090] (Supplementary Note 5) A control device (1, 1a) for a machine tool that performs thread cutting on a workpiece with a cutting tool (T), comprising: an infeed position acquisition unit (11) that acquires an infeed position for thread cutting; a margin acquisition unit (12) that acquires a margin that is set so that the cutting tool (T) exceeds the infeed position in thread cutting without swing; a swing amplitude information acquisition unit (13) that acquires swing amplitude information that indicates swing amplitude for thread cutting with swing; and a thread cutting command generation unit (20, 20a to 20d) that generates a thread cutting command based on the infeed position, the margin, and the swing amplitude information, wherein the thread cutting command generation unit (20b) has a no-swing infeed position determination unit (30) that sets an infeed position for no swing during thread cutting without swing based on the infeed position and the margin, In thread cutting with swing, thread cutting is performed based on the cutting position acquired based on the cutting position acquisition unit (11), and in thread cutting without swing, a thread cutting command is generated to perform thread cutting based on the cutting position without swing set by the cutting position determination unit (30) for cutting without swing.

[0091] (Supplementary Note 6) The control device (1, 1a) of the machine tool further comprises a machining accuracy determination unit (35) that determines the degree of machining accuracy, and the thread cutting command generation unit (20d) sets the margin value according to the degree of machining accuracy determined by the machining accuracy determination unit (35).

[0092] REFERENCE SIGNS LIST 1, 1a Machine tool control device 11 Cutting position acquisition unit 12 Margin acquisition unit 13 Vibration amplitude information acquisition unit 20, 20a to 20d Thread cutting command generation unit 25 Movement command generation unit 26 Swing command generation unit 30 Cutting position determination unit for no swing 31 Pre-machining cutting position determination unit 35 Machining accuracy determination unit T Cutting tool

Claims

1. A control device for a machine tool that performs thread cutting on a workpiece using a cutting tool, a cutting position acquisition unit that acquires a cutting position of a thread cutting process; a margin acquisition unit that acquires a margin that is set so that the cutting tool swings beyond the cutting position in a swing-type thread cutting process; a swing amplitude information acquisition unit that acquires swing amplitude information indicating the swing amplitude of thread cutting with swing; a threading command generating unit that generates a threading command to swing so that at least one end position in the swing direction exceeds the cutting position, based on the cutting position, the margin, and the swing amplitude information.

2. The thread cutting command generation unit 2. The control device for a machine tool according to claim 1, wherein one end position of the swing direction is determined based on the cutting position and the margin, and the other end position of the swing direction is determined based on the swing amplitude information, and a thread cutting command is generated based on the one end position and the other end position.

3. The thread cutting command generation unit a movement command generating unit that generates a movement command for moving the cutting tool in thread cutting; a swing command generating unit that generates a swing command that determines the operation of the swing amplitude in thread cutting based on the swing amplitude information, 2. The control device for a machine tool according to claim 1, wherein the swing command offset based on the margin and the movement command are superimposed to generate a thread cutting command.

4. The thread cutting command generation unit a pre-machining infeed position determining unit that sets an infeed position for swinging during thread cutting with swinging based on the infeed position and the margin; 2. The control device for a machine tool according to claim 1, wherein a threading command is generated to perform threading with oscillation after positioning to the infeed position determined by the pre-machining infeed position determining unit before machining starts.

5. A control device for a machine tool that performs thread cutting on a workpiece using a cutting tool, a cutting position acquisition unit that acquires a cutting position of a thread cutting process; a margin acquisition unit that acquires a margin that is set so that the cutting tool exceeds the cutting position in thread cutting without swinging; a swing amplitude information acquisition unit that acquires swing amplitude information indicating the swing amplitude of thread cutting with swing; a thread cutting command generating unit that generates a thread cutting command based on the cutting position, the margin, and the swing amplitude information, The thread cutting command generation unit a no-swing infeed position determining unit that sets an infeed position for no swing during thread cutting without swing based on the infeed position and the margin, A control device for a machine tool that, in thread cutting with swing, performs thread cutting based on the cutting position acquired by the cutting position acquisition unit, and, in thread cutting without swing, generates a thread cutting command to perform thread cutting based on the cutting position for without swing set by the cutting position determination unit for without swing.

6. Further provided is a machining accuracy determination unit that determines the degree of machining accuracy, The thread cutting command generation unit 3. The control device for a machine tool according to claim 1, wherein the margin value is set in accordance with the degree of machining accuracy determined by the machining accuracy determination unit.