Cutting device and cutting method

Abstract

To provide a cutting device and a cutting method that are able to sufficiently prevent chatter vibration.SOLUTION: A cutting device includes; an angle changing device 20 that changes a workpiece cutting angle that is an angle at which a cutting tool makes a cut toward a workpiece axis; a loop dynamic rigidity acquisition unit 52 that acquires loop dynamic rigidity from a workpiece to the cutting tool; a cutting force direction acquisition unit 51 that acquires a direction of a cutting force; a chatter suppression angle prediction device 50 that predicts a chatter suppression angle by using the loop dynamic rigidity and the direction of the cutting force; a drive control unit 43 that controls the angle changing device 20 so that the workpiece cutting angle becomes equal to the chatter suppression angle and that cuts the workpiece by means of the cutting tool while maintaining the controlled workpiece cutting angle.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a cutting device and a cutting method that are less susceptible to chatter vibration and enable highly accurate cutting. [Background technology]

[0002] When cutting is performed using a machine tool (cutting device) equipped with a motor-driven spindle on which a tool or workpiece is attached, so-called "chatter vibration" may occur if the dynamic rigidity of the workpiece or cutting tool is low. Chatter vibration can cause problems such as tool breakage and deterioration of the surface accuracy of the workpiece. As a technique for suppressing this chatter vibration, for example, Patent Document 1 proposes suppressing chatter vibration by periodically varying the rotation speed of the workpiece, that is, the rotation speed of the spindle. However, the method described in Patent Document 1 has the problem that, because the rotation speed of the spindle is changed during machining, streaks are likely to remain on the machined surface of the workpiece due to the change in rotation speed, and the finishing accuracy is deteriorated. In response to this problem, Patent Document 2 focuses on the anisotropy of the workpiece dynamic rigidity, which is the tendency of the workpiece to vibrate, and proposes suppressing chatter vibration by setting the angle of cutting toward the center of rotation of the workpiece during cutting in the direction in which the workpiece dynamic rigidity is high. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 49-105277 [Patent Document 2] JP 2010-17801 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the cutting direction in which chatter vibration is reduced does not necessarily coincide with the direction in which the dynamic stiffness of the workpiece is high. Therefore, the method of Patent Document 2 has a problem in that chatter vibration cannot be sufficiently suppressed.

[0005] Therefore, the present disclosure has been made in consideration of the above problems, and has an object to provide a cutting apparatus and a cutting method that can sufficiently suppress chatter vibrations. [Means for solving the problem]

[0006] In order to achieve the above object, a first configuration of the present disclosure is a cutting apparatus in which a cutting tool is disposed toward a workpiece axis line from a direction perpendicular to the workpiece axis line, and at least one of the workpiece and the cutting tool is rotated to cut the workpiece, An angle changing means for changing a workpiece cutting angle which is an angle at which the cutting tool cuts toward the workpiece axis; a loop dynamic stiffness acquisition means for acquiring a loop dynamic stiffness from the workpiece to the cutting tool; A cutting force direction acquisition means for acquiring a direction of a cutting force; a chatter suppression angle prediction means for predicting a chatter suppression angle using the loop dynamic stiffness and the direction of the cutting force; An angle control means for controlling the angle changing means so that the workpiece cutting angle becomes the chatter suppression angle; and cutting control means for cutting the workpiece with the cutting tool while maintaining the workpiece cutting angle controlled by the angle control means. Another aspect of the first configuration of the present disclosure is the above-mentioned configuration, wherein the cutting force direction acquisition means includes cutting edge information acquisition means for acquiring cutting edge information of the cutting tool, and cutting condition acquisition means for acquiring cutting conditions, The cutting force direction acquisition means acquires the direction of the cutting force based on the cutting edge information and the cutting conditions. Another aspect of the first configuration of the present disclosure is the above-mentioned configuration, wherein the loop dynamic stiffness acquisition means includes a work information acquisition means for acquiring work information, and a cutting tool information acquisition means for acquiring cutting tool information, The loop dynamic stiffness acquisition means acquires the loop dynamic stiffness based on the workpiece information and the cutting tool information. Another aspect of the first configuration of the present disclosure is characterized in that, in the above configuration, it further comprises a positional relationship display means that enables visual confirmation of the relative positional relationship between the workpiece cutting angle and the machine coordinate system. Another aspect of the first configuration of the present disclosure is characterized in that, in the above configuration, it further comprises a processing point photographing means for photographing a cutting processing point where the workpiece and the cutting tool contact each other, and a processing point display means for displaying the photographed cutting processing point. In order to achieve the above object, a second configuration of the present disclosure is an angle changing means for changing a workpiece cutting angle, which is an angle at which the cutting tool cuts into the workpiece axis, by disposing a cutting tool toward the workpiece axis from a direction perpendicular to the workpiece axis. and an angle control means for controlling the angle changing means. A cutting method in which at least one of the workpiece and the cutting tool is rotated to cut the workpiece, a loop dynamic stiffness acquisition step of acquiring a loop dynamic stiffness from the workpiece to the cutting tool; A cutting force direction acquisition step of acquiring a direction of the cutting force; a chatter suppression angle prediction step of predicting a chatter suppression angle using the loop dynamic stiffness and the direction of the cutting force; The workpiece cutting angle is adjusted to the chatter suppression angle. The angle control means a cutting angle control step of adjusting the angle changing means; and a cutting step of cutting the workpiece with the cutting tool while maintaining the workpiece cutting angle controlled by the angle control means. Another aspect of the second configuration of the present disclosure is characterized in that, in the above configuration, in the cutting force direction acquisition step, cutting edge information and cutting conditions of the cutting tool are acquired, and the direction of the cutting force is acquired based on the cutting edge information and the cutting conditions. Another aspect of the second configuration of the present disclosure is characterized in that, in the above configuration, in the loop dynamic stiffness acquisition step, work information and cutting tool information are acquired, and the loop dynamic stiffness is acquired based on the work information and the cutting tool information. Effect of the Invention

[0007] According to the present disclosure, since the chatter suppression angle is predicted taking into consideration the direction of the cutting force in addition to the loop dynamic stiffness, it is possible to determine the cutting angle toward the center of rotation of the workpiece at an angle that can sufficiently suppress chatter vibrations, thereby making it possible to suppress the occurrence of chatter vibrations and perform machining with high finished surface accuracy. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory plan view showing an embodiment of a cutting device. [Diagram 2] FIG. 2 is an explanatory side view of FIG. [Diagram 3] FIG. 2 is a block diagram of a control device for the cutting device. [Figure 4] 4 is a flowchart of a chatter suppression angle prediction method. [Diagram 5] FIG. 11 is a prediction diagram showing the relationship between the workpiece cutting angle and chatter stability. [Figure 6] FIG. 13 is an explanatory diagram showing a positional relationship displayed on a monitor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. 1 to 3 are explanatory diagrams showing an example of a cutting apparatus (e.g., a machine tool such as an NC lathe) according to the present disclosure, in which FIG. 1 is a plan view seen from the Y-axis direction, and FIG. 2 is a side view seen from the axial direction of the workpiece. In Figures 1 and 2, reference numeral 1 denotes a headstock of a cutting device, 2 a spindle rotatably supported on the headstock 1, 3 a chuck provided at the tip of the spindle 2 and having jaws 4 for gripping a workpiece 5, 6 a cutting tool, 7 a tool spindle to which the cutting tool 6 is attached, 8 a Y-axis movement mechanism for translationally moving the tool spindle 7 in the Y-axis direction, 9 a saddle provided on a base (not shown) of the cutting device to enable movement of the tool spindle 7 in the X-axis direction, and 10 an X-axis movement mechanism for translationally moving the saddle 9 in the X-axis direction.

[0010] The Y-axis moving mechanism 8 and the X-axis moving mechanism 10 are constituted by a ball screw mechanism, the Y-axis moving mechanism 8 is driven by a Y-axis motor 8a installed on the saddle 9, and the X-axis moving mechanism 10 is driven by an X-axis motor 10a installed on the base. M1 indicates the work axis which is the rotation center of the work, M2 indicates the tool spindle axis, and M3 indicates the tool axis, and the plane perpendicular to the work axis M1 is the XY plane. The tool spindle 7 is provided at its tip with a tool spindle rotating part L for holding the cutting tool 6 in a manner that allows rotational indexing in a manner in which the tool spindle axis M2 and the tool axis M3 intersect, and for enabling the cutting tool 6 to change the work cutting angle. The angle changing device 20 is constituted by the tool spindle 7, the Y-axis moving mechanism 8, the saddle 9, and the X-axis moving mechanism 10.

[0011] Fig. 3 shows a control device that controls this cutting device. As shown in Fig. 3, the control device includes a numerical control device 40 for controlling various motors, and a chatter suppression angle prediction device 50 for predicting a chatter suppression angle at which chatter vibration is unlikely to occur. Reference numeral 2a denotes a spindle motor that rotates the spindle 2, and 7a denotes a tool spindle motor that drives the tool spindle rotating part L. The numerical control device 40 includes a program storage unit 41 that stores a workpiece machining program, a program analysis unit 42 that analyzes the machining program, and a drive control unit 43 that controls various motors. The chatter suppression angle prediction device 50 includes a cutting force direction acquisition unit 51 that acquires the direction of the cutting force, a loop dynamic stiffness acquisition unit 52 that acquires the loop dynamic stiffness from the workpiece 5 to the cutting tool 6, and a calculation unit 53 that calculates the chatter suppression angle at which chatter stability is maximized from the loop dynamic stiffness and the direction of the cutting force.

[0012] Furthermore, the cutting force direction acquisition unit 51 includes a cutting force direction memory unit 54 that stores a database of the cutting force direction, a cutting edge information acquisition unit 55 that acquires cutting edge information of the cutting tool 6 that affects the direction of the cutting force, and a cutting condition acquisition unit 56 that acquires cutting conditions that affect the direction of the cutting force. The loop dynamic stiffness acquisition unit 52 includes a loop dynamic stiffness memory unit 57 that stores a database of loop dynamic stiffness, a work information acquisition unit 58 that acquires work information that affects the dynamic stiffness of the workpiece 5, and a cutting tool information acquisition unit 59 that acquires cutting tool information that affects the dynamic stiffness of the cutting tool 6. The chatter suppression angle predicted by the calculation unit 53 is sent to the drive control unit 43, which combines it with a control command generated by analyzing a normal machining program to generate a motor drive signal to control each motor.

[0013] The cutting method using the cutting apparatus configured as above is carried out as follows. First, the direction of the cutting force is acquired (cutting force direction acquisition step), and the loop dynamic stiffness from the workpiece 5 to the cutting tool 6 is acquired (loop dynamic stiffness acquisition step). Next, the angle (θ) at which chatter stability is maximized is predicted based on the obtained cutting force direction and loop dynamic stiffness (chatter suppression angle prediction step). Details of the steps up to this point will be described later. Next, based on the prediction results, if the direction with high chatter stability is at an angle of θ from the X-axis direction, the tool spindle rotation unit L of the tool spindle 7 is controlled by the numerical control device 40 to set the cutting angle toward the workpiece axis M1, i.e., toward the rotation center, to θ (state shown in FIG. 2: Cutting angle control steps). Thereafter, the numerical control device 40 controls the X-axis motor 10a and the Y-axis motor 8a to maintain the state in which the tool axis M3 of the cutting tool 6 intersects with the workpiece axis M1 at the workpiece cutting angle θ, and performs cutting control (turning control) to cut the cutting tool 6 toward the workpiece axis M1 (cutting step).

[0014] The outer diameter cutting of the workpiece 5 is performed by rotating the workpiece 5 together with the spindle 2, keeping the workpiece cutting angle θ of the cutting tool 6 constant, and translating the cutting tool 6 while maintaining the state in which the tool axis M3 intersects with the workpiece axis M1. That is, the cutting tool 6 cuts into the workpiece 5 toward the workpiece axis M1 to cut it. The translation operation of the cutting tool 6 is performed by cooperatively operating the X-axis motor 10a and the Y-axis motor 8a to move the tool spindle 7, and thus the outer peripheral surface of the workpiece 5 is cut. Next, the tool spindle 7 is fed along the workpiece axis M1 to perform the outer diameter cutting. The same is true when performing grooving on the outer periphery of the workpiece. As with external diameter cutting, the angle of the cutting tool 6 is calculated, and the tool spindle 7 is fed along the tool axis M3 by a movement motion resulting from the combination of the X and Y axes, thereby performing cutting.

[0015] Here, a method for predicting the chatter suppression angle by the chatter suppression angle prediction device 50 will be described in detail with reference to the flowchart of FIG. First, the operator inputs cutting edge information of the cutting tool 6 that affects the direction of the cutting force, such as the cutting face shape, clearance angle, nose R, tool apex angle, cutting edge tip shape, etc., to the cutting edge information acquisition unit 55, and inputs cutting conditions that affect the direction of the cutting force, such as the work rotation direction, feed direction, feed amount, cutting depth (during external diameter cutting) or cutting width (during grooving), the presence and type of cutting fluid, etc., to the cutting condition acquisition unit 56 (S1). Next, the cutting force direction acquisition unit 51 acquires the direction of the cutting force from the cutting force direction storage unit 54 based on the input cutting edge information and cutting conditions (S2: cutting force direction acquisition step).

[0016] Next, the operator inputs information that affects the dynamic rigidity of the workpiece 5, such as the material, shape, and fixing method, to the workpiece information acquisition unit 58, and inputs information that affects the dynamic rigidity of the cutting tool 6, such as the material, shape, and fixing method, to the cutting tool information acquisition unit 59 (S3). Next, the loop dynamic stiffness acquisition unit 52 acquires the loop dynamic stiffness from the loop dynamic stiffness storage unit 57 based on the input workpiece information and cutting tool information (S4: loop dynamic stiffness acquisition step). Next, the calculation unit 53 calculates chatter stability for each workpiece cutting angle based on the loop dynamic stiffness and the direction of the cutting force (S5: chatter suppression angle prediction step). For example, in the case of grooving, the chatter stability limit cutting width, which is the critical condition for whether chatter vibration occurs or not, can be calculated by the following formula using the maximum negative real part of the composite compliance calculated from the dynamic compliance, which is the reciprocal of the dynamic stiffness, and the ratio of the thrust force to the principal force of the cutting force, i.e., the cutting force ratio, which indicates the direction of the cutting force.

[0017]

number

[0018] The composite compliance can be calculated using Equation 2 when the workpiece rotation direction is positive as shown in Figure 2, and using Equation 3 when the workpiece rotation direction is negative.

[0019]

number

[0020]

number

[0021] FIG. 5 shows an example of the chatter stability limit cutting width for each workpiece cutting angle in grooving. From this figure, it can be seen that the chatter stability is high in the +30° angle direction (chatter vibration is unlikely to occur even with a large cutting width), and is low in the -25° angle direction (chatter vibration is likely to occur even with a small cutting width). In this way, chatter stability is usually anisotropic, and the value changes depending on the angle. This is the same even if the workpiece 5 itself is cylindrical and isotropic, because it is affected by the anisotropy inherent in the headstock 1. Therefore, in this example, the chatter suppression angle is predicted to be in the +30° direction and output (S6: chatter suppression angle prediction step).

[0022] In this way, the cutting processing apparatus of the above-mentioned form is equipped with an angle changing device 20 that changes the work cutting angle θ, which is the angle at which the cutting tool 6 is cut toward the work axis M1, a loop dynamic stiffness acquisition unit 52 that acquires the loop dynamic stiffness from the work 5 to the cutting tool 6, a cutting force direction acquisition unit 51 that acquires the direction of the cutting force, a chatter suppression angle prediction device 50 that predicts the chatter suppression angle using the loop dynamic stiffness and the direction of the cutting force, and a drive control unit 43 that controls the angle changing device 20 so that the work cutting angle θ becomes the chatter suppression angle and maintains the controlled work cutting angle θ to cut the work 5 with the cutting tool 6, and performs the above-mentioned cutting method. According to this configuration, since the chatter suppression angle is predicted taking into consideration the direction of the cutting force in addition to the loop dynamic stiffness, it is possible to determine the angle of cutting toward the rotation center of the workpiece 5 at an angle that can sufficiently suppress chatter vibrations during machining. Therefore, it is possible to suppress the occurrence of chatter vibrations and perform machining with high finished surface accuracy.

[0023] The numerical control device 40 may be provided with a monitor (positional relationship display means) that displays the cutting angle into the workpiece and the relative positional relationship with the machine coordinate system, as shown in Fig. 6. By making the relative positional relationship visually identifiable in this way, it is possible to prevent the cutting tool 6 from cutting into the workpiece 5 from a direction different from that understood by the operator. In addition, the numerical control device 40 may be provided with a monitor (machining point display means) not shown that displays an image of the cutting point photographed by a camera or the like (machining point photographing means) attached to the cutting device. By using these means as an alternative confirmation means when the machining point cannot be visually observed during cutting, it is possible to reduce the psychological stress of the operator that a machining defect may occur in a place that cannot be visually observed.

[0024] Furthermore, the configurations of the cutting processing apparatus and cutting processing method disclosed herein are not limited to the aspects described in the above embodiments, and can be appropriately modified as necessary without departing from the spirit of the present disclosure. For example, the cutting tool 6 is indexed by driving the tool spindle rotation part L by the tool spindle motor 7a, but the tool spindle motor 7a may not be provided and the operator may manually index the cutting tool 6 and fix it with a bolt. In addition, an extraction unit (not shown) may be provided that extracts information possessed by the cutting processing device and acquires cutting edge information, cutting conditions, workpiece information, and cutting tool information, and the acquired information may be automatically input by the control device to the cutting edge information acquisition unit, cutting conditions acquisition unit, workpiece information acquisition unit, and cutting tool information on behalf of the operator. In addition, in the process shown in FIG. 4, the input of work information and cutting tool information (S3) and the acquisition of loop dynamic stiffness (S4) may be performed prior to the input of cutting edge information and cutting conditions (S1) and the acquisition of the cutting force direction (S2).

[0025] Furthermore, the cutting force direction acquisition unit 51 acquires the cutting force direction from the database stored in the cutting force direction storage unit 54 based on the cutting edge information and the cutting conditions, but the cutting force direction may also be acquired using a simulation or the like. Furthermore, the loop dynamic stiffness acquisition unit 52 acquires the loop dynamic stiffness from the database stored in the loop dynamic stiffness storage unit 57 based on the workpiece information and cutting tool information, but it may also be acquired using a simulation or the like. Furthermore, the operator may directly input the direction of the cutting force obtained by a separate measurement or simulation to the cutting force direction acquisition unit 51 without using the cutting edge information acquisition unit 55 and the cutting condition acquisition unit 56 . Furthermore, the operator may directly input the loop dynamic stiffness obtained by separate measurement or simulation to the loop dynamic stiffness obtaining unit 52 without using the workpiece information obtaining unit 58 and the cutting tool information obtaining unit 59 . [Explanation of symbols]

[0026] 1...headstock, 2...spindle, 2a...spindle motor, 3...chuck, 4...jaw, 5...workpiece, 6...cutting tool, 7...tool spindle, 7a...tool spindle motor, 8...Y-axis movement mechanism, 8a...Y-axis motor, 9...saddle, 10...X-axis movement mechanism, 10a...X-axis motor, 20...angle change device (angle change means), 40...numerical control device, 41...program storage unit, 42...program analysis unit, 43...drive control unit (angle control means, cutting control means), 50...chatter suppression angle prediction device (chatter suppression angle prediction means), 51··Cutting force direction acquisition unit (cutting force direction acquisition means), 52··Loop dynamic stiffness acquisition unit (loop dynamic stiffness acquisition means), 53··Calculation unit, 54··Cutting force direction storage unit, 55··Cutting edge information acquisition unit (cutting edge information acquisition means), 56··Cutting condition acquisition unit (cutting condition acquisition means), 57··Loop dynamic stiffness storage unit, 58··Workpiece information acquisition unit (workpiece information acquisition means), 59··Cutting tool information acquisition unit (cutting tool information acquisition means), M1··Workpiece axis, M2··Tool spindle axis, M3··Tool axis, L··Tool spindle rotation unit.

Claims

1. A cutting processing device in which a cutting tool is disposed toward a workpiece axis line from a direction perpendicular to the workpiece axis line, and at least one of the workpiece and the cutting tool is rotated to cut the workpiece, An angle changing means for changing a workpiece cutting angle which is an angle at which the cutting tool cuts toward the workpiece axis; a loop dynamic stiffness acquisition means for acquiring a loop dynamic stiffness from the workpiece to the cutting tool; A cutting force direction acquisition means for acquiring a direction of a cutting force; a chatter suppression angle prediction means for predicting a chatter suppression angle using the loop dynamic stiffness and the direction of the cutting force; An angle control means for controlling the angle changing means so that the workpiece cutting angle becomes the chatter suppression angle; a cutting control means for cutting the workpiece with the cutting tool while maintaining the workpiece cutting angle controlled by the angle control means; A cutting apparatus comprising:

2. The cutting force direction acquisition means includes a cutting edge information acquisition means for acquiring cutting edge information of the cutting tool, and a cutting condition acquisition means for acquiring cutting conditions, 2. The cutting device according to claim 1, wherein the cutting force direction acquisition means acquires the direction of the cutting force based on the cutting edge information and the cutting conditions.

3. The loop dynamic stiffness acquisition means includes a workpiece information acquisition means for acquiring workpiece information, and a cutting tool information acquisition means for acquiring cutting tool information.

3. The cutting apparatus according to claim 1, wherein the loop dynamic stiffness acquisition means acquires the loop dynamic stiffness based on the workpiece information and the cutting tool information.

4. 4. The cutting device according to claim 1, further comprising a positional relationship display means for enabling a relative positional relationship between the workpiece cutting angle and a machine coordinate system to be visually confirmed.

5. The cutting processing device according to any one of claims 1 to 4, further comprising a processing point photographing means for photographing a cutting processing point where the workpiece and the cutting tool come into contact, and a processing point display means for displaying the photographed cutting processing point.

6. A cutting method comprising: an angle changer for disposing a cutting tool toward a workpiece axis from a direction perpendicular to the workpiece axis; and an angle control unit for controlling the angle changer for changing a workpiece cutting angle at which the cutting tool cuts toward the workpiece axis; and an angle control unit for controlling the angle changer, wherein at least one of the workpiece and the cutting tool rotates to cut the workpiece, a loop dynamic stiffness acquisition step of acquiring a loop dynamic stiffness from the workpiece to the cutting tool; A cutting force direction acquisition step of acquiring a direction of the cutting force; a chatter suppression angle prediction step of predicting a chatter suppression angle using the loop dynamic stiffness and the direction of the cutting force; a cutting angle control step of adjusting the angle changing means by the angle control means so that the workpiece cutting angle becomes the chatter suppression angle; a cutting step of cutting the workpiece with the cutting tool while maintaining the workpiece cutting angle controlled by the angle control means; A cutting method comprising the steps of:

7. The cutting method according to claim 6, characterized in that in the cutting force direction acquisition step, cutting edge information and cutting conditions of the cutting tool are acquired, and the direction of the cutting force is acquired based on the cutting edge information and the cutting conditions.

8. 8. The cutting method according to claim 6, wherein in the loop dynamic stiffness acquisition step, workpiece information and cutting tool information are acquired, and the loop dynamic stiffness is acquired based on the workpiece information and the cutting tool information.

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