Machine tool control device

Abstract

Provided is a technology with which it is possible to calculate surface roughness, and to easily set machining conditions and oscillation conditions while checking the calculated surface roughness. A control device 1 of a machine tool is for machining a workpiece while oscillating a cutting tool and the workpiece relative to each other, and comprises: a condition acquiring unit 12 that acquires machining conditions and oscillation conditions; a surface roughness calculation unit 13 that calculates surface roughness on the basis of the machining conditions and oscillation conditions acquired by the condition acquiring unit 12; and a surface roughness output unit 14 that outputs the surface roughness calculated by the surface roughness calculation unit 13.

Description

[Technical Field]

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

[0002] Conventionally, to prevent chips continuously generated during cutting from becoming entangled in the workpiece or cutting tool, which can cause machining defects or machine failures, a known method is oscillation cutting, in which the cutting tool and workpiece are oscillated relative to each other while cutting the workpiece. In this oscillation cutting, the tool path, which is the trajectory of the cutting tool, is set to partially overlap the previous tool path by adjusting the oscillation frequency and oscillation amplitude. This causes a missed cut, called an air cut, in which the cutting edge of the cutting tool separates from the surface of the workpiece, shredding the chips.

[0003] However, when orbital cutting is applied, the surface roughness of the machined workpiece often worsens compared to when orbital cutting is not applied. This is because the path of the cutting tool when orbital cutting is applied is the trajectory of the orbital motion according to the specified orbital conditions. Therefore, a technique has been proposed to calculate the surface roughness from, for example, the shape of the cutting tool's cutting edge, the rotational speed of the spindle, and the feed rate (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-114614 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because the calculation of surface roughness depends on the machining conditions and oscillation conditions, it has been difficult to set the machining conditions and oscillation conditions while taking surface roughness into consideration. Therefore, a technology that can calculate surface roughness and easily set the machining conditions and oscillation conditions while checking the calculated surface roughness is desired.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technology that can calculate surface roughness and easily set processing conditions and oscillation conditions while checking the calculated surface roughness. [Means for solving the problem]

[0007] The present disclosure relates to a control device for a machine tool that performs machining while oscillating a cutting tool and a workpiece relative to one another, and includes a condition acquisition unit that acquires machining conditions and oscillation conditions, a surface roughness calculation unit that calculates surface roughness based on the machining conditions and oscillation conditions acquired by the condition acquisition unit, and a surface roughness output unit that outputs the surface roughness calculated by the surface roughness calculation unit. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a technology that can calculate surface roughness and easily set processing conditions and oscillation conditions while checking the calculated surface roughness. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is a diagram for explaining swing cutting. [Figure 2] FIG. 2 is a functional block diagram of the control device for the machine tool according to the first embodiment. [Figure 3] FIG. 10 is a diagram showing a surface roughness confirmation screen on which processing conditions and oscillation conditions have been input. [Figure 4] FIG. [Figure 5] FIG. 10 is a diagram showing a surface roughness confirmation screen on which the calculated surface roughness is displayed. [Figure 6] FIG. 10 is a diagram showing a phase for acquiring a roughness curve. [Figure 7] FIG. 1 is a diagram showing a roughness curve. [Figure 8] FIG. 10 is a functional block diagram of a control device for a machine tool according to a second embodiment. [Figure 9] FIG. 10 is a diagram showing a first example of a surface roughness correction table. [Figure 10]FIG. 10 is a diagram showing a first example of a surface roughness correction table. [Figure 11] FIG. 10 is a diagram showing a surface roughness confirmation screen on which the calculated surface roughness is displayed. [Figure 12] FIG. 10 is a diagram showing a surface roughness confirmation screen on which the surface roughness corrected based on the surface roughness correction coefficient is displayed. [Figure 13] FIG. 10 is a diagram showing a second example of a surface roughness correction table. [Figure 14] FIG. 10 is a diagram showing a second example of a surface roughness correction table. [Figure 15] FIG. 10 is a diagram showing a surface roughness confirmation screen on which the calculated surface roughness is displayed. [Figure 16] FIG. 10 is a diagram showing a surface roughness confirmation screen on which the corrected surface roughness for each type of workpiece is displayed. [Figure 17] FIG. 10 is a functional block diagram of a control device for a machine tool according to a third embodiment. [Figure 18] FIG. 10 is a diagram showing the attenuation rate of the actually measured value of the oscillation amplitude relative to the command value. [Figure 19] FIG. 10 is a diagram showing a surface roughness confirmation screen on which the attenuation rate of the oscillation amplitude is input. [Figure 20] FIG. 10 is a diagram showing a surface roughness confirmation screen on which the surface roughness corrected based on the attenuation rate of the oscillation amplitude is displayed. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 embodiment, and the description thereof will be omitted as appropriate.

[0011] [First embodiment] A machine tool control device according to a first embodiment performs swing cutting, which cuts a workpiece while swinging the cutting tool and the workpiece relative to each other. FIG. 1 is a diagram illustrating swing cutting. In the example of swing cutting shown in FIG. 1, at least one spindle S that rotates the cutting tool T and the workpiece W relative to each other and at least one feed axis (not shown) that moves the cutting tool T relative to the workpiece W are operated to rotate the cutting tool T and the workpiece W relative to each other and to swing the cutting tool T and the workpiece W relative to each other in the feed direction while performing cutting. At this time, the tool path, which is the trajectory of the cutting tool T, is set so that the current path partially overlaps the previous path. In other words, because the current path partially includes a portion that has already been machined in the previous path, a missed cut known as an air cut occurs, in which the cutting edge of the cutting tool T separates from the surface of the workpiece W, shredding chips.

[0012] The shape of the workpiece is not limited in the swing cutting performed in this embodiment. That is, it can be applied to cases where the workpiece has a tapered or arc-shaped portion on the machining surface, requiring multiple feed axes (Z-axis and X-axis), or to cases where the workpiece is columnar or cylindrical and only one specific feed axis (Z-axis) is sufficient.

[0013] Fig. 2 is a functional block diagram of the machine tool control device 1 according to the first embodiment. As shown in Fig. 2, the machine tool control device 1 according to the first embodiment includes an input unit 11, a condition acquisition unit 12, a surface roughness calculation unit 13, a surface roughness output unit 14, and a surface roughness display unit 15. The machine tool control device 1 is configured using a computer including memories such as a ROM (read only memory) and a RAM (random access memory), a CPU (control processing unit), and a communication control unit, all connected to each other via a bus, for example. The functions and operations of the above functional units are achieved by cooperation between the CPU and memory installed in the computer, and the control program stored in the memory.

[0014] The control device 1 of the machine tool may be configured with a CNC (Computer Numerical Controller), and may be connected to a host computer (not shown) such as a CNC or a PLC (Programmable Logic Controller). In addition to a machining program, machining conditions such as rotation speed and feed rate, and oscillation conditions such as oscillation amplitude and oscillation frequency are input to the control device 1 of the machine tool from the host computer.

[0015] The input unit 11 inputs information about the machining conditions and the oscillation conditions in response to an operator's input operation on an input means (not shown), such as a keyboard or a touch panel. The information about the machining conditions and the oscillation conditions input by the input unit 11 is output to the condition acquisition unit 12, which will be described later.

[0016] The condition acquisition unit 12 acquires the machining conditions and oscillation conditions input by the input unit 11. The condition acquisition unit 12 outputs the acquired machining conditions and oscillation conditions to the surface roughness calculation unit 13, which will be described later.

[0017] Here, the machining conditions include at least information regarding the relative feed rate per revolution between the cutting tool and the workpiece, and information regarding the shape of the cutting tool cutting edge, as well as information regarding the spindle speed S (1 / min), cutting tool feed rate (mm / min), workpiece diameter (mm), cutting tool clearance angle (°), etc. Note that information regarding the relative feed rate per revolution between the cutting tool and the workpiece includes feed rate per revolution F (mm / rev), and information regarding the shape of the cutting tool cutting edge includes radius (mm) of the cutting edge.

[0018] The oscillation conditions include information about the relative oscillation frequency per rotation between the cutting tool and the workpiece, and information about the oscillation amplitude relative to the feed rate per rotation between the cutting tool and the workpiece. The information about the relative oscillation frequency per rotation between the cutting tool and the workpiece includes an oscillation frequency magnification I (times), which indicates the oscillation frequency per rotation of the spindle. The information about the oscillation amplitude relative to the feed rate per rotation between the cutting tool and the workpiece includes an oscillation amplitude magnification K (times), which indicates the magnitude of the oscillation amplitude relative to the magnitude of the feed rate per rotation of the spindle. The oscillation frequency magnification I (times) may be specified directly, or it may be calculated from the oscillation frequency (Hz) and the spindle rotation speed S (1 / min) after specifying the oscillation frequency (Hz). Similarly, the oscillation amplitude magnification K (times) may be specified directly, or it may be calculated from the oscillation amplitude (mm), the feed rate (mm / min), and the spindle rotation speed S (1 / min) after specifying the oscillation amplitude (mm).

[0019] The surface roughness calculation unit 13 calculates the surface roughness based on the machining conditions and oscillation conditions acquired by the condition acquisition unit 12. The surface roughness calculated by the surface roughness calculation unit 13 includes at least one of, for example, arithmetic mean roughness, maximum height which is the maximum distance between peaks and valleys, maximum peak height which is the maximum height from the mean line of the surface, maximum valley depth which is the absolute value of the minimum height from the mean line of the surface, average height which is the average height of the profile elements consisting of a pair of adjacent peaks and valleys, maximum cross-sectional height which is the sum of the maximum peak height and the maximum valley depth of the profile elements, and load length ratio which is the ratio of the load length of the profile elements at a predetermined cutting level (height % or μm) to the evaluation reference length. Specific methods for calculating these surface roughnesses will be described in detail later.

[0020] The surface roughness output unit 14 outputs to the outside the surface roughness calculated by the surface roughness calculation unit 13. In this embodiment, the surface roughness output unit 14 outputs the calculated surface roughness to a surface roughness display unit 15, which will be described later.

[0021] The surface roughness display unit 15 displays the surface roughness output by the surface roughness output unit 14. Specifically, the surface roughness display unit 15 displays the surface roughness calculated by the surface roughness calculation unit 13 on a surface roughness confirmation screen, which will be described in detail later.

[0022] Next, a method for calculating surface roughness by the surface roughness calculation unit 13 will be described in detail with reference to Figs. 3 to 5. Fig. 3 is a diagram showing a surface roughness confirmation screen on which machining conditions and oscillation conditions are input. Fig. 4 is a diagram showing a cutting path. Fig. 5 is a diagram showing a surface roughness confirmation screen on which the calculated surface roughness is displayed.

[0023] As shown in Fig. 3, first, the operator inputs the machining conditions and oscillation conditions by operating the input means of the input unit 11 using the surface roughness confirmation screen on the surface roughness display unit 15. For example, as in the example shown in Fig. 3, the operator inputs, as machining conditions, the feed rate per revolution F (mm / rev), which is information regarding the relative feed rate per revolution between the cutting tool and the workpiece, and the cutting edge R (mm), which is information regarding the shape of the cutting edge of the cutting tool, as well as the oscillation frequency magnification I and oscillation amplitude magnification K, which are oscillation conditions.

[0024] The input machining conditions and oscillation conditions are then acquired by the condition acquisition unit 12, and the surface roughness calculation unit 13 automatically calculates the surface roughness based on the acquired machining conditions and oscillation conditions. Specifically, the surface roughness calculation unit 13 calculates the coordinate value Y (mm) in the feed direction of the cutting pass using the following formula (1), and searches for the point where the distance between the cutting passes is maximum.

[0025]

number

[0026] In formula (1), Y is the coordinate value in the feed direction (mm), f is the feed amount per revolution of the spindle (mm / rev), S is the spindle rotation speed (1 / min), I is the oscillation frequency magnification (times), K is the oscillation amplitude magnification (times), and t is the time (sec).

[0027] 4 shows the point where the distance between cutting passes is the longest. In this embodiment, the coordinate values ​​Y of the points where the distance between cutting passes is the longest are calculated using the above formula (1), and the distance between the calculated coordinate values ​​is set as the maximum distance between cutting passes. Then, when calculating the maximum height Rz, which is the maximum distance between peaks and valleys as surface roughness, for example, the maximum height Rz can be calculated by substituting the R (mm) of the cutting edge and the maximum distance between cutting passes calculated as described above into the following formula (2).

[0028]

number

[0029] In conventional techniques, the surface roughness after swing cutting is calculated from machining conditions such as the shape of the cutting tool's cutting edge, the rotational speed of the spindle, and the feed rate. In contrast, as is clear from the above-mentioned method of calculating surface roughness, the surface roughness calculation unit 13 of this embodiment calculates surface roughness by including the swing frequency magnification I and the swing amplitude magnification K as calculation conditions. Therefore, the surface roughness calculation unit 13 of this embodiment can calculate surface roughness more accurately than conventional techniques.

[0030] The surface roughness calculated by the surface roughness calculation unit 13 as described above is automatically displayed on a surface roughness confirmation screen, as shown in Fig. 5. In Fig. 5, the maximum height is displayed as the surface roughness. This allows the operator to set the machining conditions and oscillation conditions while checking the surface roughness that has been calculated more accurately than before, making it easier to set the machining conditions and oscillation conditions.

[0031] Further, for example, a case where the arithmetic mean roughness Ra is calculated as the surface roughness will be described in detail with reference to Fig. 6 and Fig. 7. Fig. 6 is a diagram showing a phase for acquiring a roughness curve. Fig. 7 is a diagram showing a roughness curve.

[0032] Figure 6 shows the cutting path shown in Figure 4 rotated 90 degrees, and is an example in which the phase where the distance between the cutting paths is greatest is used as the phase for obtaining the roughness curve of the machined surface of the workpiece. By arranging an arc with the cutting edge radius R at the coordinate values ​​of the cutting path in this phase, the roughness curve shown in Figure 7 can be obtained. In this way, a roughness curve of the machined surface of the workpiece that takes into account the cutting edge R of the cutting tool can be obtained, and the arithmetic mean roughness Ra can be calculated by substituting the Z value of the obtained roughness curve in Figure 7 into the following formula (3).

[0033]

number

[0034] The machine tool control device 1 according to the first embodiment provides the following effects.

[0035] The machine tool control device 1 according to this embodiment is provided with a condition acquisition unit 12 that acquires machining conditions and oscillation conditions, a surface roughness calculation unit 13 that calculates surface roughness based on the machining conditions and oscillation conditions, and a surface roughness output unit 14 that outputs the calculated surface roughness. As a result, while surface roughness depends on the machining conditions and oscillation conditions and it has conventionally been difficult to set machining conditions and oscillation conditions while taking surface roughness into consideration, according to this embodiment, surface roughness can be calculated based on the machining conditions and oscillation conditions, and machining conditions and oscillation conditions can be easily set while checking the surface roughness that is calculated and output to an external device, etc.

[0036] Furthermore, the machine tool control device 1 according to this embodiment is further provided with a surface roughness display unit 15 that displays the surface roughness output by the surface roughness output unit 14. This allows the operator to more easily set the machining conditions and oscillation conditions while checking the surface roughness displayed on a display screen or the like by the surface roughness display unit 15.

[0037] Furthermore, the machine tool control device 1 according to this embodiment is configured to acquire, as machining conditions, information on the relative feed rate per rotation between the cutting tool and the workpiece and information on the shape of the cutting tool cutting edge, and, as oscillation conditions, information on the relative oscillation rate per rotation between the cutting tool and the workpiece and information on the oscillation amplitude for the relative feed rate per rotation between the cutting tool and the workpiece, and calculate surface roughness based on these machining conditions and oscillation conditions. As a result, although surface roughness depends on the oscillation conditions, in the past the oscillation conditions were not taken into consideration, but according to this embodiment, surface roughness can be calculated by including the oscillation conditions in the calculation conditions, allowing for more accurate calculation of surface roughness.

[0038] [Second embodiment] Fig. 8 is a functional block diagram of a machine tool control device 1A according to the second embodiment. As shown in Fig. 8, the machine tool control device 1A according to the second embodiment differs from the machine tool control device 1 according to the first embodiment in that it further includes a correction value calculation unit 16 and an actual surface roughness acquisition unit 17, and in that, unlike the surface roughness calculation unit 13 of the first embodiment, the surface roughness calculation unit 13A also corrects the surface roughness, but the other configurations are the same as those of the first embodiment.

[0039] The actual surface roughness acquisition unit 17 acquires the actual surface roughness by actually measuring the surface roughness of the workpiece machined surface obtained by actually performing the swing cutting. The acquired actual surface roughness is output to the correction value calculation unit 16, which will be described later.

[0040] The correction value calculation unit 16 calculates a correction value used to correct the surface roughness. Specifically, the correction value calculation unit 16 calculates the correction value based on the theoretical surface roughness calculated by the surface roughness calculation unit 13A and the measured actual surface roughness acquired by the actual surface roughness acquisition unit 17. For example, the correction value calculation unit 16 calculates a correction coefficient or correction amount based on the deviation magnification or difference between the theoretical surface roughness and the actual surface roughness obtained by actually performing oscillation cutting under the machining conditions and oscillation conditions used for the calculation. The calculated correction value is output to the surface roughness calculation unit 13A, which will be described later.

[0041] It is also preferable that the correction value calculation unit 16 calculates the correction value for each machining condition. Specifically, it is preferable that the correction value calculation unit 16 calculates the correction value for each machining condition including, for example, at least one of the material of the cutting tool tip, the shape of the cutting tool tip, the material of the workpiece, the cutting speed, the cutting depth, and the cutting angle.

[0042] The surface roughness calculation unit 13A calculates the surface roughness based on the machining conditions and oscillation conditions acquired by the condition acquisition unit 12 using the same calculation method as the surface roughness calculation unit 13 of the first embodiment. Moreover, unlike the surface roughness calculation unit 13 of the first embodiment, the surface roughness calculation unit 13A corrects the calculated theoretical surface roughness using a correction value calculated by the correction value calculation unit 16.

[0043] Next, a first example of a method for correcting surface roughness by the surface roughness calculation unit 13A will be described in detail with reference to Figs. 9 to 12. Figs. 9 and 10 are diagrams showing a first example of a surface roughness correction table. Fig. 11 is a diagram showing a surface roughness confirmation screen on which the calculated surface roughness is displayed. Fig. 10 is a diagram showing a surface roughness confirmation screen on which the surface roughness corrected based on the surface roughness correction coefficient is displayed.

[0044] First, the operator inputs the cutting conditions, such as the feed rate F (mm / rev), which is information about the relative feed rate per revolution between the cutting tool and the workpiece, the cutting edge R (mm), which is information about the shape of the cutting tool's cutting edge, and the spindle rotation speed S (1 / min), as well as the oscillation conditions, such as the oscillation frequency magnification I and the oscillation amplitude magnification K. Then, as shown in FIG. 11, the theoretical surface roughness automatically calculated by the surface roughness calculation unit 13A is displayed as the surface roughness on the surface roughness confirmation screen. In FIG. 11, the maximum height Rz is displayed as the surface roughness (similarly shown in FIG. 12). Before and after the above input operation, the operator operates the machine tool control device 1A to actually perform oscillation cutting under the cutting conditions and oscillation conditions used to calculate the theoretical surface roughness, and measure the surface roughness of the workpiece's machined surface.

[0045] Next, in order to correct the calculated theoretical surface roughness, the operator operates the input means of input unit 11 to open a surface roughness correction table such as that shown in Fig. 9. Then, as shown in Fig. 9, the surface roughness correction table automatically displays the calculated theoretical surface roughness in addition to the feed rate F per cut, R of the cutting edge, spindle rotation speed S, oscillation frequency magnification I, and oscillation amplitude magnification K that were input on the surface roughness confirmation screen. In Fig. 9, the theoretical maximum height Rz is displayed as the calculated theoretical surface roughness (similar to Fig. 10).

[0046] Therefore, the operator operates the input means of the input unit 11 to input the actual surface roughness obtained by actual measurement. In FIG. 9, the actual maximum height Rz is displayed as the actual surface roughness (similar to FIG. 10). Then, the correction value calculation unit 16 automatically calculates a correction coefficient based on, for example, the deviation magnification between the theoretical surface roughness and the actual surface roughness, and the calculated correction coefficient is automatically displayed in the surface roughness correction table. Also, as shown in FIG. 12, the surface roughness display on the surface roughness confirmation screen is changed to the surface roughness value corrected using the correction coefficient.

[0047] 9 and 10, when there are multiple combinations of machining conditions and oscillation conditions to be input, and multiple combinations of theoretical surface roughness and actual surface roughness exist for each combination of conditions, it is preferable that the correction value calculation unit 16 automatically calculates the correction coefficient based on the arithmetic mean of the deviation magnifications between the theoretical surface roughness and the actual surface roughness calculated for each combination. When deriving the correction coefficient from the deviation magnification, other data analysis methods such as the geometric mean, harmonic mean, median, and mode may also be used.

[0048] Next, a second example of the method of correcting surface roughness by the surface roughness calculation unit 13A will be described in detail with reference to Figs. 13 to 16. Figs. 13 and 14 are diagrams showing a second example of a surface roughness correction table. Fig. 15 is a diagram showing a surface roughness confirmation screen on which the calculated surface roughness is displayed. Fig. 16 is a diagram showing a surface roughness confirmation screen on which the corrected surface roughness for each type of workpiece is displayed.

[0049] First, the operator inputs the cutting conditions, such as the feed rate F (mm / rev), which is information about the relative feed rate per revolution between the cutting tool and the workpiece, the cutting edge R (mm), which is information about the shape of the cutting edge of the cutting tool, and the type (material) of the workpiece, as well as the oscillation conditions, such as the oscillation frequency magnification I and the oscillation amplitude magnification K. Then, as shown in FIG. 15, the theoretical surface roughness automatically calculated by the surface roughness calculation unit 13A corresponding to the selected type of workpiece is displayed as the surface roughness on the surface roughness confirmation screen. In FIG. 15, the maximum height Rz is displayed as the surface roughness (similar to FIG. 16). Before and after the above input operation, the operator operates the machine tool control device 1A to actually perform oscillation cutting under the cutting conditions and oscillation conditions used to calculate the theoretical surface roughness, and measure the surface roughness of the machined surface of the workpiece obtained by the actual execution of oscillation cutting.

[0050] Next, in order to correct the calculated theoretical surface roughness, the operator operates the input means of the input unit 11 to open a surface roughness correction table as shown in Fig. 13. Then, as shown in Fig. 13, the surface roughness correction table automatically displays the calculated theoretical surface roughness in addition to the feed rate F per cut, cutting edge R, workpiece type, oscillation frequency magnification I, and oscillation amplitude magnification K entered on the surface roughness confirmation screen. In Fig. 13, the theoretical maximum height Rz is displayed as the calculated theoretical surface roughness (similar to Fig. 14).

[0051] Therefore, the operator operates the input means of the input unit 11 to input the actual surface roughness obtained by actual measurement. In FIG. 13, the actual maximum height Rz is displayed as the actual surface roughness (similar to FIG. 14). Then, the correction value calculation unit 16 automatically calculates a correction coefficient based on, for example, the deviation magnification between the theoretical surface roughness and the actual surface roughness, and the calculated correction coefficient is automatically displayed in the surface roughness correction table. Also, as shown in FIG. 16, the surface roughness display on the surface roughness confirmation screen is changed to the surface roughness value corrected using the correction coefficient.

[0052] As shown in Figures 13 and 14, the correction coefficient is calculated for each type of workpiece. In the second example, the correction coefficient is calculated for each type of workpiece. However, correction values ​​such as the correction coefficient may be calculated for each machining condition, including not only the type of workpiece but also at least one of the material of the cutting tool cutting edge, the shape of the cutting tool cutting edge, the cutting speed, the cutting depth, and the cutting depth angle. As in the first example, when multiple combinations of machining conditions and oscillation conditions are input and multiple combinations of theoretical surface roughness and actual surface roughness are obtained for each combination of conditions, it is preferable that the correction value calculation unit 16 automatically calculates the correction coefficient based on the arithmetic mean of the deviation factors between the theoretical surface roughness and the actual surface roughness calculated for each combination. When deriving the correction coefficient from the deviation factor, other data analysis methods such as the geometric mean, harmonic mean, median, and mode may also be used.

[0053] The machine tool control device 1A according to the second embodiment provides the following effects.

[0054] The machine tool control device 1A according to the second embodiment is further provided with a correction value calculation unit 16 that calculates a correction value used to correct the surface roughness, and is configured to correct the calculated surface roughness using the correction value calculated by the correction value calculation unit 16. More specifically, it is further provided with an actual surface roughness acquisition unit 17 that acquires the actual surface roughness obtained by actually performing machining, and is configured to calculate the correction value based on the calculated theoretical surface roughness and actual surface roughness. This makes it possible to calculate a more accurate surface roughness.

[0055] Furthermore, in the machine tool control device 1A according to the second embodiment, the correction value calculation unit 16 is configured to calculate a correction value for each machining condition. More specifically, the correction value calculation unit 16 is configured to calculate a correction value for each machining condition including at least one of the material of the cutting tool tip, the shape of the cutting tool tip, the material of the workpiece, the cutting speed, the cutting depth, and the cutting angle. This allows for even more accurate calculation of surface roughness.

[0056] [Third embodiment] Fig. 17 is a functional block diagram of a machine tool control device 1B according to the third embodiment. As shown in Fig. 15, the machine tool control device 1B according to the third embodiment differs from the machine tool control device 1 according to the first embodiment in that it further includes a correction value calculation unit 16A and an actual oscillation amplitude acquisition unit 18, and in that, unlike the surface roughness calculation unit 13 of the first embodiment, surface roughness calculation unit 13B also corrects surface roughness, but the other configurations are the same as those of the first embodiment.

[0057] The actual oscillation amplitude acquisition unit 18 acquires, as the actual oscillation amplitude, the oscillation amplitude of the cutting path measured by actually performing oscillation cutting under the machining conditions and oscillation conditions used to calculate the theoretical surface roughness. The actual measurement value of the cutting path can be acquired by a position detector such as an encoder that is normally provided in a servo motor. The acquired actual oscillation amplitude is output to the correction value calculation unit 16A, which will be described later.

[0058] The correction value calculation unit 16A calculates a correction value used to correct the surface roughness. Specifically, the correction value calculation unit 16A calculates the correction value based on the attenuation rate of the actual oscillation amplitude acquired by the actual oscillation amplitude acquisition unit 18 relative to the oscillation amplitude acquired by the condition acquisition unit 12, i.e., the oscillation amplitude command value. For example, the attenuation rate itself is used as the correction value. The calculated correction value is output to the surface roughness calculation unit 13B, which will be described later.

[0059] Furthermore, similar to the correction value calculation unit 16 of the second embodiment, it is preferable that the correction value calculation unit 16A calculates a correction value for each machining condition, specifically for each machining condition including at least one of the material of the cutting tool cutting edge, the shape of the cutting tool cutting edge, the material of the workpiece, the cutting speed, the cutting depth, and the cutting angle.

[0060] The surface roughness calculation unit 13B calculates the theoretical surface roughness based on the machining conditions and oscillation conditions acquired by the condition acquisition unit 12 using the same calculation method as the surface roughness calculation unit 13 of the first embodiment. Furthermore, when calculating the surface roughness using the above-mentioned formula (1), the surface roughness calculation unit 13B calculates the surface roughness by substituting a value obtained by multiplying the oscillation amplitude magnification K by an attenuation rate as a correction value into formula (1) instead of the oscillation amplitude magnification K. This makes it possible to calculate the surface roughness corrected based on the attenuation rate.

[0061] Next, the method of correcting surface roughness by the surface roughness calculation unit 13B will be described in detail with reference to Figs. 18 to 20. Fig. 18 is a diagram showing the attenuation rate of the actual measurement value relative to the command value of the oscillation amplitude. Fig. 19 is a diagram showing a surface roughness confirmation screen on which the attenuation rate of the oscillation amplitude has been input. Fig. 20 is a diagram showing a surface roughness confirmation screen on which the surface roughness corrected based on the attenuation rate of the oscillation amplitude is displayed.

[0062] First, the operator inputs, as machining conditions, the feed rate per revolution F (mm / rev), which is information about the relative feed rate per revolution between the cutting tool and the workpiece, and the cutting edge R (mm), which is information about the shape of the cutting edge of the cutting tool, as well as the oscillation frequency magnification I and oscillation amplitude magnification K, which are oscillation conditions. Then, as shown in FIG. 19, the theoretical surface roughness automatically calculated by the surface roughness calculation unit 13B is displayed as the surface roughness on the surface roughness confirmation screen. In FIG. 19, the maximum height Rz is displayed as the surface roughness (similarly shown in FIG. 20). The operator also operates the machine tool control device 1A before and after the above input operation to actually perform oscillation cutting under the machining conditions and oscillation conditions used to calculate the theoretical surface roughness, and obtains actual measured values ​​of the cutting path.

[0063] Next, the correction value calculation unit 16A calculates the attenuation rate of the actual measurement value for the oscillation amplitude relative to the command value by comparing the command value and the actual measurement value of the cutting path, and sets the calculated attenuation rate itself as the correction value, as shown in Fig. 18. Then, the surface roughness calculation unit 13B calculates the surface roughness corrected based on the attenuation rate, and as shown in Fig. 20, the attenuation rate of the amplitude is displayed on the surface roughness confirmation screen, and the display of the surface roughness is changed to the surface roughness value corrected based on the attenuation rate.

[0064] According to the machine tool control device 1B of the third embodiment, the following effects are achieved.

[0065] The machine tool control device 1B according to the third embodiment is further provided with an actual oscillation amplitude acquisition unit 18 that acquires an actual oscillation amplitude obtained by actually performing oscillation cutting, and the correction value calculation unit 16A is configured to calculate a correction value based on the attenuation rate of the actual oscillation amplitude acquired by the actual oscillation amplitude acquisition unit 18 relative to the oscillation amplitude acquired by the condition acquisition unit 12. This makes it possible to calculate a more accurate surface roughness.

[0066] The present disclosure is not limited to the above-described embodiments, and includes modifications and improvements within the scope of achieving the object of the present disclosure.

[0067] For example, in the second and third embodiments, the correction values ​​are automatically calculated by the correction value calculation units 16 and 16A, but the present invention is not limited to this. The correction values ​​may be calculated by an external computer or otherwise acquired, and then manually input and set by an operator.

[0068] For example, in the third embodiment, if the attenuation rate of the actual oscillation amplitude is known from the results of the frequency response of the machine, the correction value may be calculated based on that attenuation rate. [Explanation of symbols]

[0069] 1,1A,1B Machine tool control device 11 Input section 12 Condition acquisition section 13, 13A, 13B Surface roughness calculation section 14 Surface roughness output section 15 Surface roughness display 16,16A Correction value calculation section 17 Actual surface roughness acquisition unit 18 Actual oscillation amplitude acquisition unit

Claims

1. A control device for a machine tool that performs machining while swinging a cutting tool and a workpiece relative to each other, a condition acquisition unit that acquires processing conditions and swing conditions; a surface roughness calculation unit that calculates surface roughness based on the machining conditions and the oscillation conditions acquired by the condition acquisition unit; a surface roughness output unit that outputs the surface roughness calculated by the surface roughness calculation unit, The surface roughness calculation unit calculates the surface roughness based on the location where the distance between cutting paths under the machining conditions and the swing conditions is maximum.

2. A control device for a machine tool that performs machining while swinging a cutting tool and a workpiece relative to each other, comprising: a condition acquisition unit that acquires processing conditions and swing conditions; a surface roughness calculation unit that calculates surface roughness based on the machining conditions and the oscillation conditions acquired by the condition acquisition unit; a surface roughness output unit that outputs the surface roughness calculated by the surface roughness calculation unit; a correction value calculation unit that calculates a correction value used to correct the surface roughness; an actual surface roughness acquisition unit that acquires an actual surface roughness obtained by actually performing the processing; the surface roughness calculation unit corrects the surface roughness calculated based on the machining conditions and the oscillation conditions acquired by the condition acquisition unit using the correction value calculated by the correction value calculation unit; A control device for a machine tool, wherein the correction value calculation unit calculates the correction value based on the surface roughness calculated by the surface roughness calculation unit and the actual surface roughness acquired by the actual surface roughness acquisition unit.

3. A control device for a machine tool that performs machining while swinging a cutting tool and a workpiece relative to each other, comprising: a condition acquisition unit that acquires processing conditions and swing conditions; a surface roughness calculation unit that calculates surface roughness based on the machining conditions and the oscillation conditions acquired by the condition acquisition unit; a surface roughness output unit that outputs the surface roughness calculated by the surface roughness calculation unit; a correction value calculation unit that calculates a correction value used to correct the surface roughness; an actual surface roughness acquisition unit that acquires an actual surface roughness obtained by actually performing the processing; the surface roughness calculation unit corrects the surface roughness calculated based on the machining conditions and the oscillation conditions acquired by the condition acquisition unit using the correction value calculated by the correction value calculation unit; The correction value calculation unit calculates the correction value based on a damping rate of an actual swing amplitude relative to a swing amplitude.

4. A control device for a machine tool that performs machining while swinging a cutting tool and a workpiece relative to each other, comprising: a condition acquisition unit that acquires processing conditions and swing conditions; a surface roughness calculation unit that calculates surface roughness based on the machining conditions and the oscillation conditions acquired by the condition acquisition unit; a surface roughness output unit that outputs the surface roughness calculated by the surface roughness calculation unit; a correction value calculation unit that calculates a correction value used to correct the surface roughness; an actual surface roughness acquisition unit that acquires an actual surface roughness obtained by actually performing the processing; the surface roughness calculation unit corrects the surface roughness calculated based on the machining conditions and the oscillation conditions acquired by the condition acquisition unit using the correction value calculated by the correction value calculation unit; The correction value calculation unit calculates the correction value for each of the machining conditions.

5. A control device for a machine tool described in any one of claims 1 to 4, further comprising a surface roughness display unit that displays the surface roughness output by the surface roughness output unit.

6. The condition acquisition unit: As the machining conditions, information regarding the relative feed amount per rotation of the cutting tool and the workpiece and information regarding the shape of the cutting edge of the cutting tool are acquired, 5. The control device for a machine tool according to claim 1, wherein the oscillation conditions include information regarding the relative number of oscillations per rotation between the cutting tool and the workpiece, and information regarding the oscillation amplitude relative to the relative feed amount per rotation between the cutting tool and the workpiece.

7. A control device for a machine tool described in any one of claims 1 to 4, wherein the surface roughness includes at least one of arithmetic mean roughness, maximum height, maximum peak height, maximum valley depth, average height, maximum cross-sectional height and load length ratio.

8. Further comprising a correction value calculation unit that calculates a correction value used to correct the surface roughness, 2. The control device for a machine tool according to claim 1, wherein the surface roughness calculation unit corrects the surface roughness calculated based on the machining conditions and the swing conditions acquired by the condition acquisition unit using the correction value calculated by the correction value calculation unit.

9. Further comprising an actual surface roughness acquisition unit that acquires an actual surface roughness obtained by actually performing the processing, 9. The control device for a machine tool according to claim 3, 4 or 8, wherein the correction value calculation unit calculates the correction value based on the surface roughness calculated by the surface roughness calculation unit and the actual surface roughness acquired by the actual surface roughness acquisition unit.

10. A control device for a machine tool as described in Claim 4, wherein the correction value calculation unit calculates the correction value based on the attenuation rate of the actual oscillation amplitude relative to the oscillation amplitude.

11. A control device for a machine tool as described in Claim 9, wherein the correction value calculation unit calculates the correction value based on the attenuation rate of the actual oscillation amplitude relative to the oscillation amplitude.

12. Further comprising an actual oscillation amplitude acquisition unit that acquires an actual oscillation amplitude obtained by actually performing the machining, the condition acquisition unit acquires an oscillation amplitude; The control device for a machine tool according to claim 10, wherein the attenuation rate of the actual swing amplitude relative to the swing amplitude is calculated based on the swing amplitude acquired by the condition acquisition unit and the actual swing amplitude acquired by the actual swing amplitude acquisition unit.

13. Further comprising an actual oscillation amplitude acquisition unit that acquires an actual oscillation amplitude obtained by actually performing the machining, the condition acquisition unit acquires an oscillation amplitude; The control device for a machine tool according to claim 11, wherein the attenuation rate of the actual swing amplitude relative to the swing amplitude is calculated based on the swing amplitude acquired by the condition acquisition unit and the actual swing amplitude acquired by the actual swing amplitude acquisition unit.

14. A control device for a machine tool as described in claim 2, 3 or 8, wherein the correction value calculation unit calculates the correction value for each of the machining conditions.

15. A control device for a machine tool as described in Claim 4, wherein the correction value calculation unit calculates the correction value for each of the machining conditions including at least one of the material of the cutting tool cutting edge, the shape of the cutting tool cutting edge, the material of the workpiece, the cutting speed, the cutting depth, and the cutting angle.

16. A control device for a machine tool as described in Claim 14, wherein the correction value calculation unit calculates the correction value for each of the machining conditions including at least one of the material of the cutting tool cutting edge, the shape of the cutting tool cutting edge, the material of the workpiece, the cutting speed, the cutting depth, and the cutting angle.

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