Numerical control device

Abstract

This numerical control device comprises: a program analysis unit that acquires, by analyzing a machining program, a reference cutting point through which a movement path of a cutting point, which is a relative position where a tool comes into contact with a workpiece, should pass, and a reference relative orientation, which is a relative orientation of the tool with respect to the workpiece at the reference cutting point; a tool data acquisition unit that acquires tool data including an ideal shape of the tool and an actual shape of the tool; an interpolation unit that, on the basis of the reference cutting point and the reference relative orientation, calculates a command cutting point and a command relative orientation specifying a cutting point and a relative orientation for each control cycle; a relative orientation correction unit that corrects the command relative orientation on the basis of the ideal shape, the command cutting point, and the command relative orientation; and a relative position correction unit that, on the basis of the corrected command relative orientation and the actual shape, corrects the command cutting point so that a point corresponding to the command cutting point on the actual shape approaches the command cutting point calculated by the interpolation unit.

Description

Numerical Control Device

[0001] The present disclosure relates to a numerical control device.

[0002] Numerical control devices that control machine tools to cut workpieces by relatively moving a tool and a workpiece in accordance with a machining program are widely used. It has been proposed to set a usable part of a tool excluding a worn part and create a machining program for machining using the usable part (see, for example, Patent Document 1).

[0003] International Publication No. 2014 / 068667

[0004] A numerical control device operates a machine tool by interpolating the relative position of a tool and a workpiece between a plurality of cutting points described in a machining program. Even when using a machining program created to perform machining using a usable part of a tool, it is not guaranteed that machining is performed with the usable part at an interpolated relative position. Therefore, a technique capable of performing appropriate machining according to the state of a tool is desired.

[0005] A numerical control device according to one aspect of the present disclosure is a numerical control device that controls a machine tool that performs cutting by changing a relative position and a relative posture between a tool and a workpiece based on a machining program, the numerical control device comprising: a program analysis unit that acquires, through analysis of the machining program, a reference cutting point that a movement path of a cutting point, which is a relative position where the tool contacts the workpiece, should pass through, and a reference relative posture that is a relative posture of the tool with respect to the workpiece at the reference cutting point; a tool data acquisition unit that acquires tool data including an ideal shape of the tool and an actual shape of the tool; an interpolation unit that calculates a commanded cutting point designating the cutting point and a commanded relative posture designating the relative posture for each control cycle based on the reference cutting point and the reference relative posture; a relative posture correction unit that corrects the commanded relative posture based on the ideal shape, the commanded cutting point and the commanded relative posture; and a relative position correction unit that corrects the commanded cutting point based on the corrected commanded relative posture and the actual shape such that a point on the actual shape corresponding to the commanded cutting point approaches the commanded cutting point calculated by the interpolation unit.

[0006] This is a block diagram illustrating the configuration of a numerical control device according to one embodiment of the present disclosure. This is a schematic diagram illustrating cutting operations using the numerical control device of Figure 1. This is a schematic diagram illustrating the correction of the command relative posture by the numerical control device of Figure 1. This is a schematic diagram illustrating the tool shape data acquired by the numerical control device of Figure 1.

[0007] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Figure 1 is a block diagram showing the configuration of a numerical control device 1 according to one embodiment of the present disclosure. Figure 2 is a schematic diagram illustrating cutting operations performed by the numerical control device 1.

[0008] The numerical control device 1 controls a machine tool that performs cutting by changing the relative position and relative orientation of the tool 2 and the workpiece 3 based on a machining program. The numerical control device 1 includes a program storage unit 11, a surface finish information storage unit 12, a program analysis unit 13, a tool data acquisition unit 14, an interpolation unit 15, a relative orientation correction unit 16, and a relative position correction unit 17. The numerical control device 1 can be implemented by one or more computer devices that have, for example, memory, a processor, an input / output interface, etc., and execute an appropriate control program. The above-described components of the numerical control device 1 are classifications of the functions of the numerical control device 1 and do not necessarily have to be clearly distinguishable in terms of physical configuration and program configuration.

[0009] The program storage unit 11 stores a machining program that describes the changes in the relative position and relative orientation of the tool 2 and the workpiece 3, for example, according to the numerical control program format specified in JIS-B6315-1 (2003). The machining program includes, as illustrated below, the coordinates (words described by addresses X, Y, Z) of the reference cutting point Pn (where n is the line number of the machining program) that the movement path of the cutting point, which is the relative position where the tool 2 contacts the workpiece 3, should pass through, and a vector (words described by addresses I, J, K) that indicates the reference relative orientation Vn, which is the relative orientation of the tool 2 with respect to the workpiece 3 at the reference cutting point Pn. The machining program may also include the number of the tool 2 to be used (word described by address H), the vector Un perpendicular to the cutting surface at the reference cutting point Pn (words described by addresses I, J, K after address L2), and so on.

[0010] (Example of machining program) O0001 N1 G54 G90 G00 X0 Y0 Z0 A0 C0 N2 G43.9 H1 N3 G01 X3.5721 Y0 Z7.6604 I-0.6428 J0 K0.766, L2 I-0.1736 J0 K0.9848 N4 G01 X5.0 Y0 Z8.6603 I0 J0 K1, L2 I-0.5 J0 K0.866 N5 G01 X6.5798 Y0 Z9.3969 I0.1736 J0 K0.9848, L2 I-0.3420 J0 K0.9397 N6 G01 X8.2635 Y0 Z9.8481 I0.342 J0 K0.9397, L2 I-0.1736 J0 K0.9848 N7 G01 X10.0 Y0 Z10.0 I0.5 J0 K0.866, L2 I0 J0 K1

[0011] The surface finish information storage unit 12 stores surface finish information that identifies the shape of the finished surface, which is the shape of the workpiece 3 after cutting. The shape of the finished surface is the shape formed when an ideal tool 2 is precisely moved relative to it according to the machining program, and as shown in Figure 3, it can be a wave shape with grooves that reflect the shape of the tool 2. Surface finish information can be generated by simulating the machining program.

[0012] The program analysis unit 13 obtains the reference cutting point Pn and reference relative posture Vn specified by the machining program by analyzing the machining program. Preferably, the program analysis unit 13 further obtains the type of tool 2 and the cutting surface perpendicular vector Un by analyzing the machining program.

[0013] The tool data acquisition unit 14 acquires tool data including the ideal shape of the tool 2 and the actual shape of the tool 2. The actual shape of the tool 2 can be measured using a laser measuring instrument or the like. The actual shape of the tool 2 is the shape that acts on the workpiece 3 and can be represented as the shape of a rotating body obtained by rotating the tool 2. Therefore, the data may be a representation of the shape of the outer edge within a 90° range from the tip of the outer edge of the cross-section. Although the actual shape of the tool 2 is a shape that has receded from the ideal shape due to wear, by setting a reference point so that it visually overlaps with the actual shape, it is possible to have a shape that has a portion protruding from the ideal shape, as shown in Figure 4. The tool data acquired by the tool data acquisition unit 14 may further include cutting edge information that identifies the cutting edge portion (the area shown by hatching in Figure 3) of the ideal shape that can cut the workpiece 3. For example, the cutting edge portion may be a region that excludes the area near the tip where the cutting speed is low and the area near the outer circumference where deflection of the tool 2 may occur due to the reaction force from the workpiece 3. Furthermore, the tool data may further include the type of tool 2 (e.g., ball end mill, square end mill, radius end mill), and may further include at least one of the values ​​of length, diameter, and corner radius.

[0014] The interpolation unit 15 calculates a command cutting point Qm (where m is a number indicating the control cycle) and a command relative posture Wm, which specify the cutting point and relative posture for each control cycle, based on the reference cutting point Pn and the reference relative posture Vn, as shown in Figure 2. Since the interpolation by the interpolation unit 15 is the same as the interpolation in conventional numerical control devices, a detailed explanation is omitted.

[0015] The relative posture correction unit 16 corrects the commanded relative posture Wm based on the ideal shape, the commanded cutting point Qm, and the commanded relative posture Wm. Specifically, the relative posture correction unit 16 may be configured to correct the commanded relative posture Wm so that the cutting edge of the tool 2 contacts the commanded cutting point Qm in order to ensure that the workpiece 3 is cut using the cutting edge of the tool 2. Furthermore, it may be configured to acquire surface finish information from the surface finish information storage unit 12 and correct the commanded relative posture Wm so that only the cutting edge of the ideal shape contacts the surface. Furthermore, the relative posture correction unit 16 may be configured to correct the command relative posture Wm so that the range in which the difference between the ideal shape and the actual shape satisfies a predetermined standard (for example, the range shown by hatching in Figure 4) contacts the command cutting point Qm, in order to prevent excessive cutting in accordance with the missing portion by reflecting the actual shape of the tool 2. In addition, it may be configured to acquire surface finish information and correct the command relative posture Wm so that only the range in which the difference between the ideal shape and the actual shape satisfies a predetermined standard contacts the finished surface, as shown in Figure 3 (in Figure 3, command relative posture Wm+1 shows the uncorrected state). The range in which the difference between the ideal shape and the actual shape satisfies a predetermined standard may be the range in which the difference from the actual shape is less than or equal to a preset threshold, the range in which the rate of change of the difference from the actual shape is less than or equal to a preset threshold, etc. The relative posture correction unit 16 may also modify the command relative posture Wm so that only the range in which the difference between the ideal shape and the actual shape satisfies a predetermined standard contacts the command cutting point Qm, preferably the finished surface.

[0016] The relative posture correction unit 16 may be configured to acquire the operating range of the machine tool and correct the command relative posture Wm so as not to deviate from the operating range. In order to avoid abrupt changes in the posture of the tool 2 that may reduce machining quality due to vibration, etc., the relative posture correction unit 16 preferably uses the correction candidate that is closest to the command relative posture Wm calculated by the interpolation unit 15 as the corrected command relative posture Wm when there are multiple correction candidates for the command relative posture Wm. Furthermore, the relative posture correction unit 16 may smooth the corrected command relative posture Wm so that the corrected command relative posture Wm does not change discontinuously.

[0017] The relative position correction unit 17 corrects the command cutting point Qm to be shown as a white dot, as shown in Figure 4, based on the corrected command relative posture Wm and the actual shape, so that the point Rm corresponding to the command cutting point Qm on the actual shape of the tool 2 approaches the command cutting point Qm calculated by the interpolation unit. Note that the point Rm corresponding to the command cutting point Qm on the actual shape may be a point that lies on the normal to the command cutting point Qm of the theoretical shape of the tool 2, or a point that lies perpendicular to the cutting surface of the command cutting point Qm.

[0018] The numerical control device 1 having the above configuration corrects the command relative posture Wm for each control cycle interpolated by the interpolation unit 15 using the relative posture correction unit 16 so that a part of the tool 2 capable of normal cutting can be used, and corrects the command cutting point Qm according to the actual shape of the tool 2 so that the position indicated by the command cutting point Qm for each control cycle interpolated by the interpolation unit 15 can be cut, thereby enabling accurate machining of the workpiece 3.

[0019] The following further notes are disclosed regarding the above embodiments and modifications. (Note 1) The numerical control device (1) is a numerical control device (1) that controls a machine tool that performs cutting by changing the relative position and relative orientation of a tool (T) and a workpiece (W) based on a machining program, and comprises a program analysis unit (13) that acquires, by analysis of the machining program, a reference cutting point (Pn) that the movement path of the cutting point, which is the relative position where the tool (T) contacts the workpiece (W), should pass through, and a base relative orientation (Vn) which is the relative orientation of the tool (T) with respect to the workpiece (W) at the reference cutting point (Pn), and a tool data acquisition unit (14) that acquires tool data including the ideal shape of the tool (T) and the actual shape of the tool (T), The system includes: an interpolation unit (15) that calculates command cutting point (Qm) and command relative posture (Wm) that specify the cutting point and relative posture for each control cycle based on a reference cutting point (Pn) and a reference relative posture (Vn); a relative posture correction unit (16) that corrects the command relative posture (Wm) based on the ideal shape, command cutting point (Qm), and command relative posture (Wm); and a relative position correction unit (17) that corrects the command cutting point (Qm) based on the corrected command relative posture (Wm) and the actual shape so that the point (Rm) corresponding to the command cutting point (Qm) on the actual shape approaches the command cutting point (Qm) calculated by the interpolation unit (15).

[0020] (Note 2) In the numerical control device (1) of Note 1, the tool data further includes cutting edge information that identifies the cutting edge portion capable of cutting the workpiece (W) from the ideal shape, and the relative posture correction unit (16) may correct the command relative posture (Wm) so that the cutting edge portion is in contact with the command cutting point (Qm) based on the ideal shape, command cutting point (Qm), command relative posture (Wm), and cutting edge information.

[0021] (Note 3) In the numerical control device (1) of Notes 1 to 2, the relative posture correction unit (16) may acquire surface finish information that identifies the finished surface shape, which is the shape of the workpiece (W) after cutting, and correct the command relative posture (Wm) so that only the cutting edge portion of the ideal shape contacts the finished surface.

[0022] (Note 4) In the numerical control device (1) of Notes 1 to 3, the relative attitude correction unit (16) may correct the command relative attitude (Wm) so that only the range within which the difference between the ideal shape and the actual shape satisfies a predetermined standard contacts the command cutting point (Qm).

[0023] (Note 5) In the numerical control device (1) of Note 4, the relative posture correction unit (16) may acquire surface finish information that identifies the shape of the finished surface, which is the shape of the workpiece (W) after cutting, and correct the command relative posture (Wm) so that only the range in which the difference between the ideal shape and the actual shape satisfies a predetermined standard contacts the finished surface.

[0024] (Note 6) In the numerical control device (1) of Notes 1 to 5, the relative attitude correction unit (16) may acquire the operating range of the machine tool and correct the command relative attitude (Wm) so as not to deviate from the operating range.

[0025] (Note 7) In the numerical control device (1) of Notes 1 to 6, if there are multiple correction candidates for the command relative attitude (Wm), the relative attitude correction unit (16) may use the correction candidate that is closest to the command relative attitude (Wm) calculated by the interpolation unit (15) as the corrected command relative attitude (Wm).

[0026] (Note 8) In the numerical control device (1) of Notes 1 to 7, the relative attitude correction unit (16) may smooth the corrected command relative attitude (Wm) so that the corrected command relative attitude (Wm) does not change discontinuously.

[0027] (Note 9) In the numerical control device (1) of Notes 1 to 8, the program analysis unit (13) may further acquire the type of tool (T) and the vector perpendicular to the cutting surface at the reference cutting point (Pn) by analyzing the machining program.

[0028] (Note 10) In the numerical control device (1) of Notes 1 to 9, the tool data may further include at least one of the tool (T) type, length, diameter, and corner radius.

[0029] Although the present disclosure has been described in detail above, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the present disclosure or from the spirit of the present disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0030] 1 Numerical control device 11 Program storage unit 12 Surface finish information storage unit 13 Program analysis unit 14 Tool data acquisition unit 15 Interpolation unit 16 Relative posture correction unit 17 Relative position correction unit 2 Tool 3 Workpiece Pn Reference cutting point Qm Command cutting point Rm Corresponding point Vn Reference relative posture Wm Command relative posture Un Cutting surface perpendicular vector T Tool

Claims

1. A numerical control device for controlling a machine tool that performs cutting by changing the relative position and relative orientation of a tool and a workpiece based on a machining program, comprising: a program analysis unit that, by analyzing the machining program, acquires a reference cutting point that the movement path of the cutting point, which is the relative position where the tool contacts the workpiece, should pass through, and a reference relative orientation, which is the relative orientation of the tool with respect to the workpiece at the reference cutting point; a tool data acquisition unit that acquires tool data including the ideal shape of the tool and the actual shape of the tool; an interpolation unit that calculates a command cutting point and a command relative orientation that specify the cutting point and the relative orientation for each control cycle based on the reference cutting point and the reference relative orientation; a relative orientation correction unit that corrects the command relative orientation based on the ideal shape, the command cutting point and the command relative orientation; and a relative position correction unit that corrects the command cutting point so that the point corresponding to the command cutting point on the actual shape approaches the command cutting point calculated by the interpolation unit, based on the corrected command relative orientation and the actual shape.

2. The numerical control device according to claim 1, wherein the tool data further includes cutting edge information that identifies a cutting edge portion of the ideal shape capable of cutting the workpiece, and the relative posture correction unit corrects the command relative posture so that the cutting edge portion is in contact with the command cutting point, based on the ideal shape, the command cutting point, the command relative posture, and the cutting edge information.

3. The numerical control device according to claim 2, wherein the relative posture correction unit acquires surface finish information that identifies the shape of the finished surface, which is the shape of the workpiece after cutting, and corrects the command relative posture so that only the cutting edge portion of the ideal shape contacts the finished surface.

4. The numerical control device according to any one of claims 1 to 3, wherein the relative posture correction unit corrects the command relative posture so that the range in which the difference between the ideal shape and the actual shape satisfies a predetermined standard contacts the command cutting point.

5. The numerical control device according to claim 4, wherein the relative posture correction unit acquires surface finish information that identifies the shape of the finished surface, which is the shape of the workpiece after cutting, and corrects the command relative posture so that only the range in which the difference between the ideal shape and the actual shape satisfies a predetermined standard contacts the finished surface.

6. The numerical control device according to any one of claims 1 to 5, wherein the relative attitude correction unit acquires the operating range of the machine tool and corrects the command relative attitude so as not to deviate from the operating range.

7. The numerical control device according to any one of claims 1 to 6, wherein, when there are multiple correction candidates for the command relative attitude, the correction candidate that is closest to the command relative attitude calculated by the interpolation unit is set as the corrected command relative attitude.

8. The numerical control device according to any one of claims 1 to 7, wherein the relative attitude correction unit smooths the corrected command relative attitude so that the corrected command relative attitude does not change discontinuously.

9. The numerical control device according to any one of claims 1 to 8, wherein the program analysis unit further obtains the type of tool and the vector perpendicular to the cutting surface at the reference cutting point by analyzing the machining program.

10. The numerical control device according to any one of claims 1 to 9, wherein the tool data further includes at least one of the tool type, length, diameter, and corner radius.

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