JP7444697B2 - Numerical control device, control program and control method - Google Patents

Description

The present invention relates to a numerical control device, a control program, and a control method.

Conventionally, a cutting tool has a main shaft that rotates a cutting tool or a workpiece to be machined, and a feed shaft that moves the cutting tool relative to the workpiece, and the main shaft and feed shaft operate in coordination to cut the workpiece with the cutting tool. For example, a machine tool such as a lathe is used. In such machine tools, the main spindle, feed axis, and other drive axes are often controlled by numerical control devices.

In addition, with machine tools such as lathes, the cutting edge of the cutting tool usually scrapes off material on the surface of the workpiece continuously, so depending on the material of the workpiece, the scraped material becomes elongated shavings (chips) that can be removed by the cutting tool. There is a possibility that it will stick and interfere with the machining of the workpiece. On the other hand, as described in Patent Document 1, for example, a technique is known in which a numerical control device is used to perform swing cutting in which a cutting tool is reciprocated with respect to a workpiece at a predetermined number of vibrations. In oscillating cutting, the cutting tool is periodically moved away from the workpiece by reciprocating, so that the chips are cut at a constant length.

JP2018-94690A

As mentioned above, when performing swing cutting in which the cutting tool is moved back and forth, the swing period of the cutting tool is determined according to the rotation period of the spindle, and the swing amplitude of the cutting tool is determined according to the feed rate of the cutting tool. It is determined by The cutting speed in oscillating cutting is a speed in which the circumferential speed due to rotation of the spindle, the feed rate of the tool, and the speed of reciprocating movement for oscillating cutting are superimposed. Specifically, the maximum value V [mm/s] of the cutting speed is the feed rate v1 [mm/s] of the tool, the diameter L [mm] of the workpiece W, the spindle speed f1 [rev/s], and the amount transferred each time. Using the amount F [mm/rev], the swing frequency f2 [Hz], and the swing amplitude magnification k1, which is a constant that is appropriately set, V=v1+π・L・f1+(k1・F)/2・2π・f2 It is expressed as
That is, it can be seen that the cutting speed V changes depending on the swing frequency f2.

Generally, the range of cutting speeds that allow appropriate cutting is limited depending on various conditions such as the material of the cutting tool and the workpiece. If the cutting speed becomes too high, various problems may occur, such as roughening of the machined surface of the workpiece due to occurrence of chatter vibration, overload and fatigue of the drive mechanism of the machine tool, and abnormal wear and tear of the cutting tool. Therefore, a technique is desired that can prevent the cutting speed from becoming excessive by suppressing the oscillation frequency.

A numerical control device according to an aspect of the present disclosure includes a main shaft that rotates a cutting tool or a workpiece to be processed, and a feed axis that moves the cutting tool relative to the workpiece, the main shaft and the feed axis. A numerical control device that controls a machine tool that cuts the workpiece with the cutting tool by cooperatively operating the machine tools, the spindle speed being the rotational speed of the spindle according to a machining program, and the movement of the feed axis according to the machining program. a reference speed calculation unit that calculates a feed rate that is a speed; and a periodic fluctuation component that is superimposed on the feed axis command based on the spindle speed, the feed rate, and a preset swing frequency multiplier. a swing command calculation unit that calculates a swing command that is a swing command; a setting acquisition unit that obtains an upper limit value of the frequency of the swing command; An adjustment unit that adjusts the frequency of the command, or adjusts at least one of the spindle speed and the swing frequency multiplier.

A control program according to another aspect of the present disclosure includes a main shaft that rotates a cutting tool or a workpiece to be processed, and a feed axis that moves the cutting tool relatively to the workpiece, the main shaft and the feed axis. A control program for controlling a machine tool that cuts the workpiece with the cutting tool by operating in a coordinated manner, the main spindle speed being the rotational speed of the main spindle according to the machining program, and the movement speed of the feed axis according to the machining program. a reference speed calculation control unit that calculates a feed speed that is, and a periodic fluctuation component that is superimposed on the feed axis command based on the spindle speed, the feed speed, and a preset swing frequency multiplier. a swing command calculation control unit that calculates a swing command that is a swing command; a setting acquisition control unit that obtains an upper limit value of the frequency of the swing command; An adjustment control section that adjusts the frequency of the rocking command, or adjusts at least one of the spindle speed and the rocking frequency multiplier.

A control method according to yet another aspect of the present disclosure includes a main shaft that rotates a cutting tool or a workpiece to be processed, and a feed axis that moves the cutting tool relative to the workpiece, the main shaft and the feed shaft. A control method for controlling a machine tool that cuts the workpiece using the cutting tool by cooperating axes, the method comprising: a spindle speed, which is the rotational speed of the spindle according to a machining program; and movement of the feed axis according to the machining program. A step of calculating a feed rate, which is a speed, and a process of calculating a oscillation, which is a periodic fluctuation component, superimposed on the command of the feed axis, based on the spindle speed, the feed rate, and a preset oscillation frequency multiplier. a step of calculating a motion command; a step of obtaining an upper limit value of the frequency of the rocking command; and a step of adjusting the frequency of the rocking command so that the frequency of the rocking command does not exceed the upper limit value; and adjusting at least one of the spindle speed and the oscillation frequency magnification.

According to the numerical control device, control program, and control method according to the present disclosure, it is possible to prevent the cutting speed from becoming excessive.

FIG. 1 is a block diagram showing the configuration of a machine tool including a numerical control device according to an embodiment of the present disclosure. FIG. 2 is a diagram showing a trajectory of a cutting tool on a workpiece surface during machining by the machine tool of FIG. 1; 2 is a flowchart showing a control procedure for swing cutting in the machine tool of FIG. 1. FIG.

Embodiments of the present disclosure will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a machine tool 100 including a numerical control device 1 according to an embodiment of the present disclosure.

The machine tool 100 is an NC lathe that uses a cutting tool T to cut a workpiece W to be machined. The machine tool 100 includes a main axis Ac that rotates a cutting tool T or a workpiece W (rotates the workpiece W in this embodiment), and a main axis Ac that moves the cutting tool T relative to the workpiece W in a direction parallel to the rotational axis of the main axis Ac. The feed axis Az moves the cutting tool T (in the embodiment), and the cutting axis Ax moves the cutting tool T relative to the work W in the radial direction of the main axis Ac (moves the cutting tool T in the embodiment). It has a control axis. Therefore, the machine tool 100 applies drive current to the drive motors (main spindle motor Mc, feed axis motor Mz, and cutting axis motor Mx) that drive these control axes Ac, Az, and Ax, and to each of the drive motors Mc, Mz, and Mx. It has servo amplifiers (main axis amplifier Sc, feed axis amplifier Sz, and cutting axis amplifier Sx) that apply .

The numerical control device 1 controls the machine tool 100 to cut the workpiece W with the cutting tool T by cooperatively operating the main axis Ac, the feed axis Az, and the cutting axis Ax. The numerical control device 1 includes a program storage section 11, a data storage section 12, a setting acquisition section 13, a reference speed calculation section 14, a swing command calculation section 15, an adjustment section 16, a drive output section 17, and an input device 18.

The numerical control device 1 is a device that implements the control method according to the present disclosure. Further, the numerical control device 1 can be realized by, for example, loading a control program according to the present disclosure into a computer device having a CPU, a memory, and the like. The control program according to the present disclosure may be provided by being recorded on a non-temporary recording medium. Each component of the numerical control device 1 is functionally distinct, and does not need to be clearly distinguishable in terms of physical configuration and structure of a control program for realizing the numerical control device 1.

The program storage unit 11 stores machining programs input from the outside. The machining program is written, for example, in G code. The numerical control device 1 processes the workpiece W into a desired shape by controlling control axes Ac, Az, and Ax of the machine tool 100 according to a processing program.

The data storage unit 12 stores general information necessary for processing the workpiece W. The information stored in the data storage unit 12 includes, for example, the upper limit value (f2 _limit [Hz]) of the oscillation frequency f2 [Hz] for each combination of the materials of the plurality of workpieces W and the types of the plurality of cutting tools T. ), etc. can be included.

The setting acquisition unit 13 refers to the information in the program storage unit 11 and the data storage unit 12 to acquire the upper limit value f2 _limit of the oscillation frequency for the combination of the cutting tool T and workpiece W to be used. Further, the setting acquisition unit 13 refers to information in the program storage unit 11 and the data storage unit 12, and determines the initial values of parameters used in the swing command calculation unit 15, which will be described later, and the priority of parameters to be adjusted by the adjustment unit 16. Obtain ranking etc.

The reference speed calculation unit 14 calculates the spindle speed (f1 [rev/s]), which is the rotational speed of the spindle Ac according to the machining program, and the feed rate (v1 [mm/s]), which is the moving speed of the feed axis Az according to the machining program. Calculate. More specifically, the reference speed calculation unit 14 calculates the spindle speed f1 and the feed speed v1 that are optimal when the swing control is not performed according to the machining shape of the workpiece W described in the machining program.

The swing command calculation unit 15 calculates periodic fluctuations that are superimposed on the feed rate v1 based on the spindle speed f1 and the feed rate v1 calculated by the reference speed calculation unit 14 and the parameters acquired by the setting acquisition unit 13. A swing command (vo(t) [mm]), which is a component, is calculated. Specifically, the swing command calculation unit 15 calculates the swing command vo(t) as a sinusoidal command whose amplitude is the swing amplitude r [mm] and whose frequency is the swing frequency f2.

The swing amplitude r is calculated by multiplying the value obtained by dividing the feed speed v1 by the spindle speed f1 by a preset swing amplitude magnification k1. That is, it is expressed as r=(k1·v1/f1)/2. Further, the swing frequency f2 is calculated by multiplying the spindle speed f1 by a swing frequency multiplier k2 set in advance. That is, the swing frequency f2 is expressed as f2=k2·f1.

In addition, the cutting speed is the sum of the tool feed rate (v1), the circumferential speed of the workpiece W (π×L×f1), and the tool swing speed (r×2π×f2) (L is the diameter of the workpiece [mm]). That is, the maximum value V [mm/s] of the cutting speed is expressed as V=v1+π·L·f1+r·2π·f2. Alternatively, it may be expressed as V=v1+π·L·f1+r·2π·k2·f1 using the main shaft speed f1 and the swing frequency magnification k2.

The position of the cutting tool T in the feed axis Az direction is expressed as the sum of the integral value of the feed speed v1 and the swing command vo(t). If this is shown as a change with respect to the rotation angle of the spindle Ac, as shown in FIG. The phase differs from the trajectory by 180° when the swing frequency multiplier k2 is an odd multiple of 0.5. Therefore, the circumferential position of the workpiece W at which the position of the cutting tool T in the feed direction becomes the maximum during the n-th rotation, and the circumferential position of the workpiece W at which the position of the cutting tool T in the feed direction becomes the minimum during the n+1st rotation. The position matches.

In the section where the trajectory of the cutting tool T during the nth rotation of the spindle Ac overlaps the trajectory of the cutting tool T during the n+1st rotation of the spindle Ac, the cutting tool T separates from the workpiece W in the direction of the feed axis Az. The state will be as follows. The generation of chips formed from the material scraped off the workpiece W by the cutting tool T ends at the moment the cutting tool T separates from the workpiece W. That is, chips are cut every time the locus of the cutting tool T overlaps with the previous locus.

The adjustment unit 16 performs adjustment so that the swing frequency f2 calculated by the swing command calculation unit 15 does not exceed the upper limit value f2 _limit acquired by the setting acquisition unit 13. The adjustment may be performed by adjusting the swing frequency f2, or by adjusting at least one of the spindle speed f1 and the swing frequency magnification k2. That is, when the swing frequency f2 calculated by the swing command calculation unit 15 exceeds the upper limit f2 _limit , the adjustment unit 16 changes the swing frequency f2 or changes at least one of the spindle speed f1 and the feed speed v1. Then, the reference speed calculation section 14 and the swing command calculation section 15 are caused to recalculate.

The adjustment unit 16 may adjust only one of the spindle speed f1 and the swing frequency magnification k2, or may adjust both. When adjusting both the spindle speed f1 and the swing frequency multiplier k2, the adjustment unit 16 adjusts the ratio of the adjustment amounts of the spindle speed f1 and the swing frequency multiplier k2, or the spindle speed f1 and the swing frequency relative to the amount of change in the swing frequency f2. The spindle speed f1 and the swing frequency multiplier k2 may be adjusted so that the degree of contribution of the adjustment amount of the dynamic frequency multiplier k2 is constant, and the main shaft speed f1 and the swing frequency multiplier k2 may be roughly adjusted. , the other may be configured to perform fine adjustment, or the other may be configured to be adjusted only when the adjustment amount of one of the spindle speed f1 and the swing frequency magnification k2 reaches a predetermined upper limit.

The selection of which of the spindle speed f1 and the swing frequency multiplier k2 to adjust, the ratio of the amount of adjustment of the spindle speed f1 and the swing frequency multiplier k2, the priority order, etc. are specified in the machining program and acquired by the setting acquisition unit 13. It may be configured to allow an operator to input via the input device 18. In this way, by changing the ratio of the adjustment amount of the spindle speed f1 and the swing frequency multiplier k2 in adjusting the swing frequency f2, each machining condition (such as the material and machining shape of the work W, the type of cutting tool, etc.) ), for example, the influence on machining accuracy, machining time, etc. can be minimized. In particular, by changing the ratio of the adjustment amounts of the spindle speed f1 and the swing frequency multiplier k2 according to the machining program, each machining process can be reliably optimized. In addition, such parameters can be described by selecting one of the spindle speed f1 and the swing frequency multiplier k2, or by changing the ratio of the adjustment amounts of the spindle speed f1 and the swing frequency multiplier k2, according to the operator's input. Machining can be optimized even when using a machining program that is not

The change in the ratio of the adjustment amount of the spindle speed f1 and the swing frequency multiplier k2 can be done not only by directly specifying the ratio of the adjustment amount of the spindle speed f1 and the swing frequency multiplier k2, but also by, for example, changing the ratio of the adjustment amount of the spindle speed f1 and the swing frequency multiplier k2. It is also possible to set the upper limit of the adjustment amount (including the case where one is not adjustable), or to specify the degree of contribution of the adjustment amount of the spindle speed f1 and feed speed v1 to the amount of change in the oscillation frequency f2. may be caused.

The drive output unit 17 outputs a main spindle amplifier Sc, a feed axis amplifier Sz, and a cutting axis amplifier Sx so as to relatively move the workpiece W and the cutting tool T at the adjusted spindle speed f1, swing command vo(t), and feed rate v1. Input the command signal to.

The input device 18 may be any device that allows input by the user, and may have, for example, a keyboard, a touch panel, a switch, etc., and may be an interface for communicating with a terminal used by the user or a higher-level control device. There may be.

As is clear from the above description, the control program of the embodiment of the present disclosure that realizes the numerical control device 1 is configured to control the spindle speed f1, which is the rotational speed of the spindle Ac according to the machining program, and the movement of the feed axis according to the machining program. A reference speed calculation control unit that realizes a reference speed calculation unit 14 that calculates the feed speed v1, which is a speed, and a reference speed calculation control unit that realizes a reference speed calculation unit 14 that calculates the feed speed v1, and a A swing command calculation control unit that realizes a swing command calculation unit 15 that calculates a swing command vo(t) that is a periodic speed fluctuation component that is superimposed on the swing command, and obtains an upper limit value f2 _limit of the swing frequency f2. A settings acquisition control unit that realizes a settings acquisition unit 13 that adjusts the swing frequency f2 so that the swing frequency f2 does not exceed an upper limit value f2 _limit , or at least one of the spindle speed f1 and the swing frequency multiplier k2. and an adjustment control section that implements the adjustment section 16 that adjusts the.

Further, as shown in FIG. 3, the control method according to an embodiment of the present disclosure performed by the numerical control device 1 includes a step of acquiring an upper limit value f2 _limit of the oscillation frequency f2 (step S1: upper limit value acquisition step). and a step of calculating the spindle speed f1 and feed speed v1 according to the machining program (step S2: reference speed calculation step), and a swing command based on the spindle speed f1 and feed speed v1 and a preset swing frequency multiplier k2. vo(t) (step S3: oscillation command calculation step); and a step of adjusting at least one of the spindle speed f1 and the oscillation frequency magnification k2 so that the oscillation frequency f2 does not exceed the upper limit value f2 _limit . (Step S4: Adjustment step) and a step of storing the spindle speed f1 and the swing command vo(t) (Step S5: Storage step).

The adjustment step of step S4 includes a step of checking whether the swing frequency f2 exceeds the upper limit value f2 _limit (step S41: swing frequency confirmation step), and a step of checking whether the swing frequency f2 exceeds the upper limit value f2 limit in the confirmation step of step S41. If it is determined that the oscillation frequency multiplier k2 exceeds the f2 _limit , a step of confirming whether the oscillation frequency multiplier k2 exceeds a preset lower limit k2 _limit (step S42: oscillation frequency multiplier confirmation step); A step of changing the rocking frequency magnification k2 to a smaller value when it is determined _that the magnification k2 exceeds the lower limit value k2 _limit (step S43: rocking magnification changing step); If it is determined that the spindle speed f1 is not exceeded, the spindle speed f1 may be changed to a smaller value (step S44: spindle speed changing step).

In the control method of FIG. 3, if the swing frequency f2 is equal to or lower than the upper limit value f2 _limit in the swing frequency confirmation step, the process proceeds to the storage step of step S5, and the spindle speed f1 and the swing command vo(t) are Remember. On the other hand, if the swing frequency f2 exceeds the upper limit value f2 _limit in the swing frequency confirmation process and the swing frequency f2 is adjusted in the swing magnification change process or the spindle speed f1 is changed in the spindle speed change process, step Returning to the swing command calculation step of S3, recalculation is performed.

In the control method of FIG. 3, in the adjustment process, the oscillation frequency multiplier k2 is preferentially set in order to prevent the oscillation frequency f2 when the machine tool 100 finally performs machining from exceeding the upper limit value f2 _limit . After the oscillation frequency magnification k2 reaches the lower limit value k2 _limit , the spindle speed f1 is adjusted. By preferentially adjusting the swing frequency magnification k2, a decrease in the spindle speed f1 is suppressed, thereby suppressing a decrease in machining efficiency.

The numerical control device 1, the control program that implements the numerical control device 1, and the control method implemented by the numerical control device 1 suppress the oscillation frequency f2 to below the upper limit value f2 _limit when performing oscillation cutting on the machine tool 100. By doing so, it is possible to suppress periodic fluctuation components and prevent the cutting speed from becoming excessive.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above. Further, the effects described in this embodiment are only a list of the most preferable effects resulting from the present disclosure, and the effects due to the present disclosure are not limited to those described in this embodiment.

For example, the numerical control device, control program, and control method according to the present disclosure may adjust only one of the spindle speed and the swing frequency multiplier, or may adjust the spindle speed and the swing frequency multiplier simultaneously, The spindle speed may be adjusted with priority, and the swing frequency magnification may be adjusted when the spindle speed adjustment reaches a limit.

In the numerical control device, control program, and control method according to the present disclosure, the adjustment unit may directly adjust the frequency of the rocking command. For example, if the frequency of the rocking command input from the rocking command calculation unit exceeds the upper limit value, the adjustment unit may be configured to correct the frequency of the rocking command to the upper limit value and output it. .

In the numerical control device, control program, and control method according to the present disclosure, the waveform of the swing command is not limited to a sine wave, but may be a waveform that fluctuates periodically, such as a sawtooth wave, a triangular wave, a trapezoidal wave, or a rectangular wave. Good to have.

The numerical control device, control program, and control method according to the present disclosure are not limited to lathes, but can also be applied to, for example, controlling a drilling machine.

1 Numerical control device 13 Setting acquisition unit 14 Reference speed calculation unit 15 Oscillation command calculation unit 16 Adjustment unit 17 Drive output unit 100 Machine tool Ac main axis Az feed axis,
T Cutting tool W Workpiece

Claims (4)

It has a main shaft for rotating a cutting tool or a workpiece to be machined, and a feed shaft for moving the cutting tool relative to the workpiece, and the main shaft and the feed shaft are operated cooperatively to move the workpiece by the cutting tool. A numerical control device that controls a machine tool that performs cutting,
a reference speed calculation unit that calculates a spindle speed that is a rotational speed of the spindle according to a machining program, and a feed rate that is a movement speed of the feed axis according to the machining program;
a swing command calculation unit that calculates a swing command, which is a periodic fluctuation component superimposed on the feed axis command, based on the spindle speed, the feed speed, and a preset swing frequency multiplier; ,
a setting acquisition unit that acquires an upper limit value set for the frequency of the rocking command;
an adjustment unit that adjusts the spindle speed and the swing frequency multiplier so that the ratio of the adjustment amount of the spindle speed and the swing frequency multiplier is constant so that the frequency of the swing command does not exceed the upper limit value; ,
A numerical control device equipped with. The numerical control device according to claim 1 , wherein the setting acquisition unit acquires a ratio between the spindle speed and the adjustment amount of the oscillation frequency multiplier specified in the machining program . It has a main shaft for rotating a cutting tool or a workpiece to be machined, and a feed shaft for moving the cutting tool relative to the workpiece, and the main shaft and the feed shaft are operated cooperatively to move the workpiece by the cutting tool. A control program that controls a machine tool that performs cutting,
a reference speed calculation control unit that calculates a spindle speed that is a rotational speed of the spindle according to a machining program, and a feed rate that is a movement speed of the feed axis according to the machining program;
A swing command calculation control unit that calculates a swing command that is a periodic fluctuation component superimposed on the feed axis command based on the spindle speed, the feed speed, and a preset swing frequency multiplier. and,
a setting acquisition control unit that acquires an upper limit value set for the frequency of the rocking command;
an adjustment control unit that adjusts the spindle speed and the swing frequency multiplier so that the ratio of the adjustment amount of the spindle speed and the swing frequency multiplier is constant so that the frequency of the swing command does not exceed the upper limit value; and,
A control program with It has a main shaft for rotating a cutting tool or a workpiece to be machined, and a feed shaft for moving the cutting tool relative to the workpiece, and the main shaft and the feed shaft are operated cooperatively to move the workpiece by the cutting tool. A control method for controlling a machine tool that performs cutting,
calculating a spindle speed, which is the rotational speed of the spindle according to the machining program, and a feed rate, which is the movement speed of the feed axis according to the machining program;
Calculating a swing command that is a periodic fluctuation component superimposed on the feed axis command based on the spindle speed, the feed speed, and a preset swing frequency multiplier;
obtaining an upper limit value set for the frequency of the rocking command;
adjusting the spindle speed and the swing frequency multiplier so that the ratio of the adjustment amount of the spindle speed and the swing frequency multiplier is constant so that the frequency of the swing command does not exceed the upper limit;
A control method comprising:

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