Machining path generation device, machining path generation method, and computer program

Abstract

To provide a machining path generation device, a machining path generation method, and a computer program that prevent portions of a tool, other than a blade, from interfering with a workpiece.SOLUTION: A machining path generation device includes: a first direction acquisition unit that acquires a first direction that is a direction of a force applied to the workpiece by the tool at a first point in time; a second direction acquisition unit that acquires a second direction that is a direction of a force applied to the workpiece by the tool at a second point in time after the first point in time; an angle change degree calculation unit that calculates an angle change degree in a direction around a predetermined axis of the tool, based on a difference between the first direction and the second direction; a target direction calculation unit that calculates a target direction around the predetermined axis, based on a position of the tool around the predetermined axis at the first point in time and the angle change degree calculated by the angle change degree calculation unit; and a first correction angle calculation unit that calculates a correction angle around the predetermined axis of the tool, based on a difference between the target direction calculated by the target direction calculation unit and a direction around the predetermined axis of the tool at the second point in time.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The present technology relates to a machining path generation device that generates a machining path for a tool that machines a workpiece, and the like.

Background Art

[0002] There is a robot device including a robot hand that holds a tool, a force sensor attached to the robot hand, and a control device. The robot device performs a deburring operation on a workpiece. An operator performs a teaching operation on the robot device before the deburring operation. In the teaching operation, the control device stores a plurality of teaching points on the workpiece, a unit vector of the force acting on each teaching point, a feed rate of the robot hand, and the like.

[0003] Based on the stored teaching points, unit vectors of forces, feed rates, etc., the control device moves the robot hand. The control device calculates interpolation points between the teaching points, calculates the unit vector of the force at the interpolation points, and can realize a uniform deburring operation on the workpiece regardless of the presence or absence of a shape error of the workpiece (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the teaching operation for the robot device, the tool edge is brought into contact with the workpiece. However, when the tool is moved along the surface of the workpiece, depending on the posture of the tool, parts other than the tool edge interfere with the workpiece, and the accuracy of the machining path for realizing the generated deburring operation decreases.

[0006] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a machining path generation apparatus, a machining path generation method, and a computer program that can realize highly accurate deburring work.

Means for Solving the Problems

[0007] A machining path generation apparatus according to an embodiment of the present disclosure is a machining path generation apparatus that mounts a tool for machining a workpiece and can change the position of the tool around a predetermined axis, and includes a first direction acquisition unit that acquires a first direction that is the direction of the force applied by the tool to the workpiece at a first time point, a second direction acquisition unit that acquires a second direction that is the direction of the force applied by the tool to the workpiece at a second time point after the first time point, an angle change amount calculation unit that calculates an angle change amount of the direction of the tool around the predetermined axis based on a difference between the first direction and the second direction, a target direction calculation unit that calculates a target direction around the predetermined axis based on the position of the tool around the predetermined axis at the first time point and the angle change amount calculated by the angle change amount calculation unit, and a first correction angle calculation unit that calculates a correction angle of the tool around the predetermined axis based on a difference between the target direction calculated by the target direction calculation unit and the direction of the tool around the predetermined axis at the second time point.

[0008] In the present disclosure, since the posture of the tool is automatically controlled each time the tool is moved along the surface of the workpiece, it is possible to prevent the portion other than the blade of the tool from interfering with the workpiece and to generate a machining path that can realize highly accurate deburring work.

[0009] The machining path generation device according to an embodiment of the present disclosure includes a third direction acquisition unit that acquires a third direction, which is the direction of the force applied by the tool to the workpiece at a third time point after the second time point; a second angle change amount calculation unit that calculates a second angle change amount of the direction of the tool around the predetermined axis based on the difference between the first direction and the third direction; an addition unit that adds an adjustment angle based on the correction angle calculated by the first correction angle calculation unit to the second angle change amount calculated by the second angle change amount calculation unit; a second target direction calculation unit that calculates a target direction around the predetermined axis based on the position of the tool around the predetermined axis at the first time point and the addition result of the addition unit; and a second correction angle calculation unit that calculates a correction angle of the tool around the predetermined axis based on the difference between the target direction calculated by the second target direction calculation unit and the direction of the tool around the predetermined axis at the third time point.

[0010] In the present disclosure, when automatically controlling the posture of the tool while continuously moving the tool along the surface of the workpiece, the deviation between the direction of the force applied by the tool to the workpiece and the direction of the tool around the predetermined axis due to the delay of the tool rotation with respect to the tool movement is suppressed.

[0011] In an embodiment of the present disclosure, the adjustment angle is calculated by multiplying the correction angle by a predetermined coefficient.

[0012] In the present disclosure, the deviation between the direction of the force applied by the tool to the workpiece and the direction of the tool around the predetermined axis can be suppressed with high accuracy.

[0013] A machining path generation method according to an embodiment of the present disclosure is a machining path generation method for generating a machining path of a machine tool that mounts a tool for machining a workpiece and can change the position of the tool around a predetermined axis. At a first time point, a first direction that is the direction of the force applied by the tool to the workpiece is obtained. At a second time point after the first time point when the tool has moved, a second direction that is the direction of the force applied by the tool to the workpiece is obtained. Based on the difference between the first direction and the second direction, an angular change amount of the position of the tool around the predetermined axis is calculated. Based on the position of the tool around the predetermined axis at the first time point and the calculated angular change amount, a target direction around the predetermined axis is calculated. Based on the difference between the calculated target direction and the position of the tool around the predetermined axis at the second time point, a correction angle of the tool around the predetermined axis is calculated.

[0014] In the present disclosure, since the posture of the tool is automatically controlled each time the tool is moved along the surface of the workpiece, it is possible to prevent parts other than the cutting edge of the tool from interfering with the workpiece and to generate a machining path that realizes highly accurate deburring work.

[0015] A computer program according to an embodiment of the present disclosure is a program executable by a machining path generation device that generates a machining path of a machine tool that mounts a tool for machining a workpiece and can change the position of the tool around a predetermined axis. At a first time point, a first direction that is the direction of the force applied by the tool to the workpiece is obtained. At a second time point after the first time point, a second direction that is the direction of the force applied by the tool to the workpiece is obtained. Based on the difference between the first direction and the second direction, an angular change amount of the position of the tool around the predetermined axis is calculated. Based on the position of the tool around the predetermined axis at the first time point and the calculated angular change amount, a target direction around the predetermined axis is calculated. Based on the difference between the calculated target direction and the position of the tool around the predetermined axis at the second time point, the machining path generation device is caused to execute a process of calculating a correction angle of the tool around the predetermined axis.

[0016] In the present disclosure, every time the tool is moved along the surface of the workpiece, the posture of the tool is automatically controlled, so that parts other than the cutting edge of the tool are prevented from interfering with the workpiece, and a machining path that realizes highly accurate deburring work can be generated.

Effect of the Invention

[0017] In a machining path generation device, a machining path generation method, and a computer program according to an embodiment of the present disclosure, a machining path that appropriately realizes deburring work is generated.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

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Figure 8

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Figure 10

Figure 11

Figure 12

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Figure 15

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Figure 17

Mode for Carrying Out the Invention

[0019] (Embodiment 1) Hereinafter, the present invention will be described based on the drawings showing the machine tool and the machining path generation device according to Embodiment 1. In the following description, the up-down, front-back, left-right shown in the drawings are used. The left-right direction corresponds to the X direction, the front-back direction corresponds to the Y direction, and the up-down direction corresponds to the Z direction. FIG. 1 is an external perspective view of the machine tool, and FIG. 2 is a schematic perspective view of the machine tool inside the cover.

[0020] The machine tool includes a holding table 1. The upper surface of the holding table 1 holds the workpiece. A cover 2 is provided around the holding table 1. The cover 2 has a rectangular parallelepiped shape extending vertically, and includes a front surface portion 2a, a right surface portion 2b, a left surface portion 2c, a rear surface portion 2d, and an upper surface portion 2e. An opening / closing door 3 is provided in the front surface portion 2a, and transparent windows 4 are provided in the right surface portion 2b and the left surface portion 2c.

[0021] Inside the cover 2, three columns 5 extending in the vertical direction are provided. The three columns 5 are arranged around the holding table 1 with a phase interval of about 120 degrees in plan view. A rail 6 is provided on the side surface of each column 5 on the side of the holding table 1. The rail 6 extends in the vertical direction. A moving part 7 and a drive mechanism (not shown) are provided on the rail 6, and the drive mechanism is composed of a ball screw mechanism or the like. A motor 8 for supplying power to the drive mechanism is provided at the upper end of the column 5. By driving the motor 8, the moving part 7 moves in the vertical direction along the rail 6. The motor 8 is provided above the upper surface portion 2e and is located outside the cover 2.

[0022] As shown in Fig. 2, the upper surface portion 2e includes a support plate 2f having a triangular shape in plan view. A motor 10 and a speed reducer 11 are provided on the support plate 2f. The three columns 5 are respectively adjacent to the three corner portions of the support plate 2f. The upper end portions of the three columns 5 project upward from the upper surface portion 2e. The upper end portions and the corner portions of the support plate 2f are connected via a connecting plate 9. In Fig. 1, the description of the upper end portions, the support plate 2f, and the connecting plate 9 is omitted.

[0023] A spindle unit 20 is disposed above the holding table 1. The spindle unit 20 is connected to the speed reducer 11 via a ball spline 12 extending vertically. The rotation of the motor 10 is decelerated by the speed reducer 11 and then transmitted to the ball spline 12. The ball spline 12 rotates about an axis.

[0024] The spindle unit 20 faces each column 5. The spindle unit 20 and the moving portion 7 are connected by two parallel links 13. The links 13 are rod-shaped. One end portions of the two links 13 are connected to the first housing 21 of the spindle unit 20 via a rotatable joint 14. The other end portions of the two links 13 are connected to the moving portion 7 via a joint 14. The joint 14 is a universal joint or the like. By changing the vertical positions of the three moving portions 7, the spindle unit 20 moves vertically, forward and backward, and left and right.

[0025] Fig. 3 is a longitudinal sectional view of the spindle unit. The spindle unit 20 includes a frustum-shaped first housing 21. The first housing 21 is arranged with the smaller-diameter side facing upward and the larger-diameter side facing downward. The entire lower surface of the first housing 21 is open. A link 13 (see Fig. 2) is connected to the lower edge portion of the first housing 21.

[0026] The second housing 22 is provided at the lower surface opening of the first housing 21. The second housing 22 has a cylindrical shape with a hollow interior and is arranged with the vertical direction as the axial direction. The upper edge portion of the second housing 22 is arranged inside the lower edge portion of the first housing 21. A cross roller bearing 23 is provided between the upper edge portion of the second housing 22 and the lower edge portion of the first housing 21. The cross roller bearing 23 rotatably supports the second housing 22. The second housing 22 rotates around the vertical axis. The central axes of the first housing 21 and the second housing 22 extending in the vertical direction are at the same position. Hereinafter, the central axes of the first housing 21 and the second housing 22 are referred to as the C axis. The C axis corresponds to a predetermined axis.

[0027] A part of the circumferential surface of the second housing 22 protrudes radially outward and obliquely downward. Hereinafter, this protruding portion is referred to as the protruding portion 22a. The lower end of the protruding portion 22a is open. The angle formed between the protruding portion 22a and the circumferential surface of the second housing 22 is an acute angle, for example, about 30 degrees. The first arm 40 is provided at the lower end of the protruding portion 22a. The first arm 40 includes a cylindrical housing 40a extending vertically. The upper end portion of the housing 40a is connected to the protruding portion 22a, and the housing 40a extends obliquely downward from the protruding portion 22a.

[0028] An opening 41 is formed on the side surface of the lower end portion of the housing 40a. The second arm 42 is rotatably connected to the peripheral edge of the opening 41. The second arm 42 includes an arm portion 43 and a support cylinder 44. The arm portion 43 has a shape like bending the center of a rod and includes a first portion 43a extending in a direction parallel to the housing 40a and a second portion 43b extending in a direction intersecting the first portion 43a. One end of the first portion 43a and one end of the second portion 43b are integrally connected. The other end of the first portion 43a is rotatably connected to the peripheral edge of the opening 41 around the A axis. The inner angle between the A axis and the C axis is less than 90°, for example, about 60°. A support cylinder 44 is provided at the other end of the second portion 43b.

[0029] The support cylinder 44 is arranged such that the axis of the support cylinder 44 coincides with the C-axis. A motor and a main shaft (both not shown) are housed in the support cylinder 44. A cylindrical tool 45 is attached to the lower end of the main shaft. The tool 45 protrudes downward from the support cylinder 44, and the axis of the tool 45 coincides with the C-axis. The machine tool can change the angle of the axis of the tool 45 with respect to the workpiece to be worked by the movement of the moving part 7, the rotation of the second housing 22 around the C-axis, or the rotation of the second arm 42 around the A-axis, and change the posture of the tool 45. The tip of the tool 45 is located at the intersection of the C-axis and the A-axis. The motor housed in the support cylinder 44 supplies power to the main shaft, and the main shaft and the tool 45 rotate around the C-axis. The support cylinder 44 houses a force sensor 44a. The force sensor 44a detects the magnitude and direction of the force acting on the tool 45. The measurement method of the force sensor 44a is not limited, and examples of the force sensor 44a include a strain gauge type force sensor, a piezoelectric type force sensor, an optical type force sensor, or a capacitance type force sensor, etc.

[0030] The first housing 21 houses a switching mechanism 28. The first housing 21 and the second housing 22 house a first transmission mechanism 26. The first housing 21, the second housing 22, and the housing 40a house a second transmission mechanism 27. An air cylinder 50 is attached to the outside of the first housing 21. The air cylinder 50 has a rod (not shown).

[0031] By the movement of the rod, the switching mechanism 28 switches the transmission destination of the rotation of the ball spline 12 to the first transmission mechanism 26 or the second transmission mechanism 27. The first transmission mechanism 26 transmits the rotation of the ball spline 12 to the second housing 22. The second transmission mechanism 27 is connected to the other end of the first part 43a. The second transmission mechanism 27 transmits the rotation of the ball spline 12 to the second arm 42. Note that the switching mechanism 28 can also be switched to a neutral state in which it does not transmit rotation to either the first transmission mechanism 26 or the second transmission mechanism 27.

[0032] When the switching mechanism 28 switches the rotation transmission destination of the ball spline 12 to the first transmission mechanism 26, the second housing 22, the first arm 40, and the second arm 42 rotate about the C axis. At this time, the second arm 42 does not rotate about the A axis. When the switching mechanism 28 switches the rotation transmission destination of the ball spline 12 to the second transmission mechanism 27, the second arm 42 rotates about the A axis. At this time, the second housing 22, the first arm 40, and the second arm 42 do not rotate about the C axis.

[0033] FIG. 4 is a block diagram showing the control device 60, the force sensor 44a, etc. The machine tool includes a control device 60 that controls the driving of the motor 8, the motor 10, the air cylinder 50, etc. The control device 60 constitutes a machining path generation device. The control device 60 includes a CPU 61, a RAM 62, a storage unit 63, etc. The storage unit 63 has a rewritable storage medium such as an EEPROM, an EPROM, or a hard disk. The storage unit 63 stores a machining path generation program for generating a machining path, a machining program for machining a workpiece, a threshold value, a target value, etc. The machining path generation program and the machining program (program product) stored in the portable storage medium 63a, such as a CD-ROM and a flash memory, may be stored in the storage unit 63, or each program may be stored in the storage unit 63 from a server via a network. The CPU 61 reads the machining path generation program and the machining program into the RAM 62 and executes the machining path generation process and the machining program.

[0034] The force sensor 44a outputs a signal indicating the direction and magnitude of the force acting on the tool 45 to the control device 60. The motor 8 has an encoder 8a. The encoder 8a outputs a signal indicating the rotational position of the motor 8 to the control device 60. The motor 10 has an encoder 10a. The encoder 10a outputs a signal indicating the rotational position of the motor 10 to the control device 60. The control device 60 executes a machining path generation process based on the inputs from the force sensor 44a, the encoder 8a, and the encoder 10a.

[0035] FIG. 5 is a schematic plan view of the master workpiece 70. In this embodiment, a method for generating a machining path in the XY plane will be described. However, by specifying a plane, it is possible to generate a machining path not only in the XY plane but also in an arbitrary plane in three-dimensional space. When performing the machining path generation process, the operator installs the master workpiece 70 on the holding table 1 and sets the start point S and the end point E of the machining path. The operator manually operates the tool 45 to bring it into contact with a desired position on the master workpiece 70. The CPU 61 stores in the storage unit 63 the position where the tool 45 contacts, that is, the front, rear, left, right, up, and down positions of the start point S and the end point E. In this embodiment, the end point E is provided on the right side of the start point S.

[0036] P(t in FIG. 6 k ) is the contact position of the tool 45 with the master workpiece 70 at time t. k The V-axis is an axis indicating the direction of the force applied by the tool 45 to the master workpiece 70 at the contact position at time t. k The V-axis has the master workpiece 70 side as the positive side. The U-axis is an axis orthogonal to the V-axis and indicates the direction in which the tool 45 moves. In this embodiment, the U-axis extends substantially in the front-rear direction, and since the tool 45 moves backward, the U-axis has the rear as positive. The start point S and the contact position P(t k ) correspond to the first position.

[0037] At the start point S, based on the detected value of the force sensor 44a, the CPU 61 acquires the magnitude and direction of the force f(t k ) applied by the tool 45 to the contact position P(t k ) of the master workpiece 70, that is, the information regarding the V-axis. The CPU 61 calculates the difference between the acquired magnitude of the force f(t k ) and the target value f d (t k ). The target value f d (t k ) is stored in advance in the storage unit 63. The target value f d (t k ) is the target value of the force in the V-axis direction.

[0038] The CPU 61 multiplies the calculated difference by the coefficient κ to obtain the position deviation amount ΔPf in the V-axis direction.d (t k ) is obtained. The CPU 61 determines the position deviation amount ΔP d (t k ) so as to be the feed amount n stored in advance in the storage unit 63 in the same direction as the U-axis direction. For example, the position deviation amount ΔP d (t k ) is obtained by multiplying the unit vector of the U-axis by the feed amount n. However, the feed amount n does not have to be in the same direction as the U-axis direction. In that case, the position deviation amount ΔPf d (t k ) includes a component in the U-axis direction, and the position deviation amount ΔP d (t k ) includes a component in the V-axis direction. The position deviation amount (ΔPf d (t k ) 、 ΔP d (t k )) with the components of the other axes removed is the V-axis direction error F err , and the U-axis direction error P err . Note that the position obtained by moving from the first position P(t k ) by the position deviation amount ΔP d (t k ) corresponds to the second position. The position deviation amount ΔP d (t k ) in the U-axis direction is the moving distance in the U-axis direction when the tool 45 moves from the starting point S, i.e., the current position, to the next position. The position deviation amount ΔPf d (t k ) in the V-axis direction is the moving distance in the V-axis direction when the tool 45 moves from the starting point S, i.e., the current position, to the next position.

[0039] The CPU 61 obtains the V-axis direction error F err using the following Equation 1.

[0040]

Equation

[0041] The CPU 61 obtains the U-axis direction error P err using the following Equation 2.

[0042]

Equation

[0043] The CPU 61 calculates the first control amount for the V-axis direction error F err using PID control. PID control is a common feedback control method. The first control amount corresponds to the pressing amount of the tool 45. Also, the CPU 61 calculates the second control amount for the U-axis direction error P err using PID control. The second control amount corresponds to the feed amount of the tool 45. The CPU 61 calculates the first control amount and the second control amount independently. That is, it calculates based on hybrid control. Hybrid control means calculating and controlling the control amounts in each direction independently in the control directions of position and force respectively. Note that it is not necessarily required to calculate the first control amount and the second control amount using PID control. For example, the V-axis direction error F err can be used as the first control amount, and the U-axis direction error P err can be used as the second control amount. The CPU 61 adds the first control amount and the second control amount to obtain the combined control amount in the XY coordinate system, that is, the target position.

[0044] For the movement from the position P(t k ) to the next position P(t k+1 ), the same calculation is performed to obtain the target position of the tool 45. In this case, the position P(t k ) corresponds to the first position, and the position P(t k+1 ) corresponds to the target position.

[0045] P(t) in FIG. 7 k is the position of the tool 45 at time point t, and is a position non-contact with the master workpiece 70. Hereinafter, P(t k ) is referred to as a non-contact position. P(t k ) is the contact position of the tool 45 with the master workpiece 70 at time point t k-1 , that is, at the time point immediately before time point t k-1 . The V' axis is the axis indicating the direction of the force applied by the tool 45 to the master workpiece 70 at the contact position at time point t k . The V' axis has the master workpiece 70 side as the positive side. The U' axis is an axis orthogonal to the V' axis and is the axis indicating the direction in which the tool 45 moves. In this embodiment, since the tool 45 moves to the right, the U' axis has the right side as the positive side. k-1

[0046] At time point t k , the tool 45 is non-contact with the master workpiece 70, that is, at the position P(t k ). In this case, the detected value of the force sensor 44a becomes 0, and the direction of the force acting from the master workpiece 70 on the tool 45, that is, the V-axis direction, cannot be obtained.

[0047] In this case, the CPU 61 determines the axis obtained by rotating the V' axis at the contact position P(t k-1 ) at time point t k-1 by an angle θ as the V axis at the non-contact position P(t k ) at time point t k . The U axis is determined based on this V axis. The angle θ is stored in the storage unit 63 in advance. Also, a threshold value regarding the detected value of the force sensor 44a is stored in the storage unit 63 in advance. When the magnitude of the force indicated by the detected value is less than or equal to the threshold value, the CPU 61 determines that the magnitude of the detected force is 0 and the V-axis direction cannot be obtained. Incidentally, the axis obtained by rotating the U' axis at the contact position P(t k-1 ) at time point t k-1 by an angle θ may be determined as the U axis at the non-contact position P(t k ) at time point t k , and the V axis may be determined based on this U axis.

[0048] FIG. 8 is a flowchart for explaining a machining path generation process. The CPU 61 moves the tool 45 to the starting point S (S1). The CPU 61 obtains the detected value of the force sensor 44a, that is, the magnitude and direction of the force f(t k ) (S2), and the CPU 61 stores the direction of the force f(t k ) in the storage unit 63 as the V axis or the V' axis (S3). The CPU 61 determines whether or not the magnitude of the detected force is less than or equal to a threshold value (S4).

[0049] When the magnitude of the detected force is not less than or equal to the threshold value (S4: NO), the CPU 61 determines the U axis based on the stored V axis (S5). Still, when the magnitude of the detected force is not less than or equal to the threshold value (S4: NO), the direction of the force f(t k ) in step S3 is the V axis. The U axis is an axis orthogonal to the V axis, and the CPU 61 determines the direction orthogonal to the direction of the force f(t k ) as the U axis. The CPU 61 calculates a first control amount and a second control amount, that is, a pressing amount and a feed amount (S6). The CPU 61 adds the first control amount and the second control amount to calculate a combined control amount, that is, a target position (S7).

[0050] The CPU 61 moves the tool 45 to the target position (S8). By feedback control, the tool 45 moves to the target position. After the movement of the tool 45 is completed, the CPU 61 obtains the rotational position of the motor 8 from the encoder 8a (S9), and determines whether or not the tool 45 is at the end point E from the obtained rotational position of the motor 8 (S10). Note that the CPU 61 determines that the tool 45 is at the end point E when the difference between the position of the tool 45 obtained from the encoder 8a and the position of the end point E is less than or equal to a predetermined value. The predetermined value is stored in advance in the storage unit 63.

[0051] When the tool 45 is not at the end point E (S10: NO), the CPU 61 returns the process to step S2. That is, the CPU 61 obtains the magnitude and direction of the force f(t k+1 ) at the target position (S2) and repeats the process. When the tool 45 is at the end point E (S10: YES), the CPU 61 ends the process.

[0052] In step S4, when the magnitude of the detected force is equal to or less than the threshold value (S4: YES), the CPU 61 determines the V-axis and the U-axis based on the information of the V'-axis stored in the storage unit 63 in step S2 (S11), and proceeds to step S6. When the magnitude of the detected force is equal to or less than the threshold value (S4: YES), the force f(t k ) in step S3 is in the direction of the V'-axis.

[0053] In the machine tool according to the embodiment, by simply acquiring the direction and magnitude of the force applied to the first position, for example, the starting point S, the feed direction and feed amount of the tool from the starting point S to the second position, that is, the next position P(t k ) and the distance at which the tool 45 approaches the master workpiece 70 at the position P(t k ), that is, the pressing amount, are automatically calculated. Therefore, it is not necessary to store a large number of teaching points in advance, and the time required for generating the machining path of the tool can be shortened.

[0054] Also, the pressing amount can be calculated so that the force for pressing the tool 45 against the master workpiece 70 approaches the target value at the second position.

[0055] Also, by hybrid control, the pressing amount of the tool 45 can be calculated without being affected by the feed amount of the tool 45.

[0056] Although the force magnitude and direction are detected using the force sensor 44a, the present invention is not limited to this. The load acting on each motor 8, for example, torque, may be detected, and the force magnitude and direction may be calculated based on the detected torque.

[0057] The CPU 61 controls the tool to move along the circumferential direction of the master workpiece 70 as described above. Also, the CPU 61 controls the tool to rotate about the C-axis simultaneously with the control of the movement of the tool. Hereinafter, the control of the rotation of the tool about the C-axis by the CPU 61 will be described.

[0058] Figure 9 is a schematic partial enlarged view of the master workpiece contacted by the tool in state 0. Figure 9A shows the pressing direction, and Figure 9B shows the tool rotation direction. The tool 45 is cylindrical as described above and contacts the master workpiece 70 on its side surface. As shown in Figure 9A, when the operator contacts the tool 45 with the master workpiece 70, the CPU 61 starts creating the machining generation path. The state of the tool 45 at the start of machining path generation is defined as state 0. M(0) is the position where the tool 45 (in state 0) contacts the master workpiece 70 at the start of machining path generation. In state 0, the CPU 61 stores the direction F(0) (hereinafter referred to as the initial pressing direction) in which the tool 45 is pressed from the C-axis toward M(0) based on the detected value of the force sensor 44a. As shown in Figure 9B, with M(0) as the reference point B, the CPU 61 calculates the tool rotation direction G, that is, the direction from the C-axis toward the reference point B. However, the reference point B does not necessarily have to be M(0), and it can be in any direction. The CPU 61 stores the direction G(0) (hereinafter referred to as the initial tool rotation direction) from the C-axis to the reference point B in state 0 based on the detected value of the encoder 10a. After storing the initial pressing direction F(0) and the initial tool rotation direction G(0), the CPU 61 moves the tool 45 along the circumferential direction of the master workpiece 70 without rotating the tool 45 around the C-axis.

[0059] Figure 10 is a schematic partial enlarged view of the master workpiece contacted by the tool in state 1. Figure 10A shows the pressing direction, and Figure 10B shows the tool rotation direction. As shown by the white arrow in Figure 10, when the tool 45 moves a predetermined distance from state 0, the tool 45 enters state 1. Hereinafter, in a certain state k (k = 1, 2, ···), the contact position between the tool 45 and the master workpiece 70 is denoted as M(k), and the direction in which the tool 45 is pressed against the master workpiece 70 from the C-axis toward M(k) is denoted as the pressing direction F(k). Also, the direction from the C-axis toward the reference point B is denoted as the tool rotation direction G(k). In state 1, the CPU 61 obtains F(1) based on the detected value of the force sensor 44a. As shown in FIG. 10A, the CPU 61 calculates the angular change amount around the C-axis of the pressing direction of the tool 45 with respect to the master workpiece from state 0 to state 1 based on the initially stored initial pressing direction F(0) and the obtained F(1). Hereinafter, the angular change amount around the C-axis from state 0 to a certain state k is defined as the pressing angle change amount φk.

[0060] As shown in FIG. 10B, the CPU 61 calculates the target tool rotation direction Gd(1) in state 1 based on the initially stored initial tool rotation direction G(0) and the pressing angle change amount φ1. The target tool rotation direction Gd(1) and the current pressing direction F(1) are the same. The CPU 61 obtains the tool rotation direction G(1) based on the detected value of the encoder 10a. Since the tool 45 does not rotate around the C-axis when moving from state 0 to state 1, G(0) and G(1) are in the same direction. The CPU 61 calculates the tool correction rotation angle around the C-axis based on the tool rotation direction G(1) and the target tool rotation direction Gd(1). Hereinafter, the tool correction rotation angle calculated based on the tool rotation direction G(k) and the target tool rotation direction Gd(k) in a certain state k is defined as ψk.

[0061] FIG. 11 is a schematic partially enlarged view of the master workpiece contacted by the tool in state 2. FIG. 11A shows the pressing direction, and FIG. 11B shows the tool rotation direction. As shown by the arrow in FIG. 11, the CPU 61 rotates the tool 45 around the C-axis by the same angle as the tool correction rotation angle ψ1. The state of the tool 45 after rotation is defined as state 2. In state 2, the direction from the C-axis to the reference point B, that is, the tool rotation direction G(2), coincides with the tool pressing direction F(2). That is, the reference point B and M(2) coincide. After rotating the tool 45 around the C-axis, the CPU 61 moves the tool 45 along the circumferential direction of the master workpiece 70 without rotating it around the C-axis.

[0062] FIG. 12 is a schematic partially enlarged view of the master workpiece contacted by the tool in state 3. FIG. 12A shows the pressing direction, and FIG. 12B shows the tool rotation direction. As shown by the white arrow in Fig. 12, when the tool 45 moves a predetermined distance from state 2, the tool 45 enters state 3. In state 3, the CPU 61 obtains F(3) based on the detected value of the force sensor 44a. As shown in Fig. 12A, the CPU 61 calculates the pressing angle change amount φ3 based on the initially stored pressing direction F(0) and the obtained F(3).

[0063] As shown in Fig. 12B, the CPU 61 calculates the target tool rotation direction Gd(3) in state 3 based on the initially stored initial tool rotation direction G(0) and the pressing angle change amount φ3. The target tool rotation direction Gd(3) and the current pressing direction F(3) coincide. The CPU 61 obtains the tool rotation direction G(3) based on the detected value of the encoder 10a. Since the tool 45 does not rotate around the C-axis when moving from state 2 to state 3, G(3) and G(2) are in the same direction. The CPU 61 calculates the tool correction rotation angle ψ3 around the C-axis based on the tool rotation direction G(3) and the target tool rotation direction Gd(3).

[0064] Fig. 13 is a schematic partial enlarged view of the master workpiece contacted by the tool in state 4. Fig. 13A shows the pressing direction, and Fig. 13B shows the tool direction. As shown by the arrow in Fig. 13, the CPU 61 rotates the tool 45 by the same angle as the tool correction rotation angle ψ3 around the C-axis. The state of the tool 45 after rotation is set as state 4. In state 4, the direction from the C-axis to the reference point B, that is, the tool rotation direction G(4), coincides with the tool pressing direction F(4). That is, the reference point B and M(4) coincide. After rotating the tool 45 around the C-axis, the CPU 61 moves the tool 45 along the circumferential direction of the master workpiece 70 without rotating the tool 45 around the C-axis.

[0065] Thereafter, the CPU 61 repeats the same processes and controls as those from state 2 to state 4. When the tool 45 reaches the end point E, the processes and controls are terminated.

[0066] FIG. 14 is a flowchart for explaining the tool rotation control process according to Embodiment 1. Note that the tool 45 becomes in state 0 at the first time point and becomes in state k at the second time point. The CPU 61 moves the tool 45 to the starting point S (S11). The CPU 61 acquires and stores the initial pressing direction F(0) based on the detected value of the force sensor 44a (S12). The initial pressing direction F(0) corresponds to the first direction. The CPU 61 acquires and stores the direction of the initial tool rotation direction G(0) based on the detected value of the encoder 10a (S13).

[0067] The CPU 61 moves the tool 45 along the circumferential direction of the master workpiece 70 by a predetermined distance (S14). At this time, the state of the tool 45 is set to state k (k = 1, 2,...). After the movement of the tool 45 is completed, the CPU 61 acquires the pressing direction F(k) based on the detected value of the force sensor 44a (S15). The pressing direction F(k) corresponds to the second direction. Also, the CPU 61 acquires the tool rotation direction G(k) (S16).

[0068] The CPU 61 calculates the pressing angle change amount based on the pressing direction F(k) and the initial pressing direction F(0) (S17). The CPU 61 calculates the target tool rotation direction Gd(k) based on the pressing angle change amount and the initial tool rotation direction G(0) (S18). The CPU 61 calculates the tool correction rotation angle from the target tool rotation direction Gd(k) and the tool rotation direction G(k) (S19), and rotates the tool 45 by the same angle around the C-axis as the tool correction rotation angle (S20).

[0069] After the CPU 61 rotates the tool 45 and the state becomes k + 1, it acquires the position of the tool 45 from the encoder 8a and determines whether the tool 45 is at the end point E (S21). Note that the CPU 61 determines that the tool 45 is at the end point E when the difference between the position of the tool 45 acquired from the encoder 8a and the position of the end point E is equal to or less than a predetermined value. The predetermined value is stored in advance in the storage unit 63.

[0070] When the tool 45 is not at the end point E (S21: NO), the CPU 61 returns the process to step S14. That is, the tool 45 is moved a predetermined distance along the circumferential direction of the master workpiece 70 (S14), and the process is repeated for the state k+2 of the next tool. When the tool 45 is at the end point E (S21: YES), the CPU 61 ends the process.

[0071] In the machining path generation device according to the first embodiment, every time the tool 45 moves, the tool rotation direction is corrected to match the pressing direction. As a result, the angle of the tool 45 with respect to the master workpiece 70 at the start point and any arbitrary point becomes the same. Further, by repeating the same process, the angle of the tool 45 with respect to the master workpiece 70 can be made constant.

[0072] FIG. 15 is a schematic cross-sectional view when the tool contacts the master workpiece. In FIG. 15A, the tool 45 in the state 0 and the state k when the tool 45 is moved along the circumferential direction of the master workpiece 70 without performing the process and control according to the present embodiment are shown. In FIG. 15B, the tool 45 in the state 0 and the state k when the tool 45 is moved along the circumferential direction of the master workpiece 70 while performing the process and control according to the present embodiment are shown. As shown in FIG. 15A, after the tool edge portion 45a is brought into contact with the master workpiece 70 in the state 0, when the tool 45 is moved along the circumferential direction of the master workpiece 70 without rotating the tool 45 around the C axis, in the state k, an unintended portion of the tool 45 hits the master workpiece 70 and interferes, and the tool edge portion 45a does not contact the master workpiece 70, and a correct machining path cannot be generated. On the other hand, when the tool 45 is moved along the circumferential direction of the master workpiece 70 while performing the process and control according to the present embodiment, as shown in FIG. 15B, the direction of the C axis changes so as to prevent an unintended portion of the tool 45 from hitting the master workpiece 70 and interfering, and also in the state k, the tool edge portion 45a contacts the master workpiece in the same manner as in the state 0. Therefore, a correct machining path can be generated without an unintended portion of the tool 45 hitting the master workpiece 70 and interfering.

[0073] (Embodiment 2) Hereinafter, regarding Embodiment 2, the differences from Embodiment 1 will be described. The same reference numerals as those in Embodiment 1 are given to the processes and configurations common to Embodiment 1, and the description thereof will be omitted. FIG. 16 is a schematic partial enlarged view of the master workpiece contacted by the tool in states k, k + 1, and k + 2 according to Embodiment 2. FIG. 16A shows the pressing direction, and FIG. 16B shows the tool rotation direction. After the start of movement, the tool 45 always moves along the circumferential direction of the master workpiece 70 until the end of movement. However, in FIG. 16, for convenience of explanation, the tools 45 in the three states are superimposed and displayed. As shown in FIG. 16B, in state k, G(k) is on the G(0) side in the rotational direction about the C-axis rather than F(k).

[0074] The machining path generation device according to Embodiment 1 rotates the tool 45 about the C-axis so that the difference between the pressing direction and the tool rotation direction disappears every time the tool 45 moves along the circumferential direction of the master workpiece 70. On the other hand, in Embodiment 2, as shown in FIG. 16, the tool 45 is rotated about the C-axis while moving the tool 45 in the direction of the white arrow in order to reduce the machining path generation time. At this time, since the rotation of the tool 45 about the C-axis is delayed with respect to the movement in the circumferential direction of the master workpiece 70, the pressing direction and the tool rotation direction cannot be made to coincide. Therefore, the machining path generation device according to Embodiment 2 sets the direction rotated about the C-axis by an angle larger than φk from the initial tool rotation direction G(0) as the target tool rotation direction Gd(k), and while moving the tool 45 in the circumferential direction of the master workpiece 70, controls so that the difference between the pressing direction and the tool rotation direction of the tool 45 does not increase. That is, the CPU 61 sets Gd(k) in state k not in the same direction as F(k), but in the direction rotated clockwise on the drawing rather than F(k) about the C-axis.

[0075] In state k + 1, the CPU 61 acquires G(k + 1) and F(k + 1). Then, while moving the tool 45 along the circumferential direction of the master workpiece 70, the CPU 61 calculates the target tool rotation direction Gd(k + 1). At this time, in addition to the pre-stored G(0), F(0), and the acquired F(k + 1), the CPU 61 calculates the target tool rotation direction Gd(k + 1) based on the previously calculated previous tool correction rotation angle ψk in state k. Specifically, an adjustment angle obtained by multiplying the previously calculated previous tool correction rotation angle ψk in state k by a predetermined coefficient α is added to the pressing angle change amount φk + 1 calculated in state k + 1, and the adjusted angle change amount φ'k + 1 (φ'k + 1 = φk + 1 + α·ψk) is obtained. The direction of the tool rotated by the same angle as the adjusted angle change amount φ'k + 1 from the initial tool rotation direction G(0) around the C-axis is set as the target tool rotation direction Gd(k + 1) in state k + 1.

[0076] After calculating Gd(k + 1), the CPU 61 calculates the tool correction rotation angle ψk + 1 based on the difference between G(k + 1) and Gd(k + 1). While advancing the movement of the tool 45 along the circumferential direction of the master workpiece 70, the CPU 61 rotates the tool 45 by the same angle as the tool correction rotation angle ψk + 1 around the C-axis. After the rotation of the tool 45, the tool 45 enters state k + 2, and the CPU 61 repeats the same processing and control as in the processing and control in state k + 1.

[0077] FIG. 17 is a flowchart for explaining the tool rotation control process according to Embodiment 2. The tool 45 becomes in state k+1 at the third time point, and the pressing direction F(k+1) corresponds to the third direction. In S31 to S33, the same processes as S11 to S13 are performed. After the CPU 61 stores the initial tool rotation direction G(0) (S33), it starts the continuous movement of the tool 45 (S34). In state k+1, the CPU 61 acquires the pressing direction F(k+1) (S35) and acquires the tool rotation direction G(k+1) (S36). The CPU 61 multiplies the previous tool correction rotation angle ψk in state k by a predetermined coefficient α to calculate the adjustment angle α·ψk (S37). The CPU 61 calculates the pressing angle change amount φk+1 from the pressing direction F(k+1) and the initial pressing direction F(0) (S38), adds the adjustment angle α·ψk to the pressing angle change amount φk+1 to obtain the adjusted angle change amount φ'k+1, and calculates the target tool rotation direction Gd(k+1) based on the initial tool rotation direction G(0) and the adjusted angle change amount φ'k+1 (S39). The CPU 61 calculates the tool correction rotation angle ψk+1 from the target tool rotation direction Gd(k) and the tool rotation direction G(k) (S40), and rotates the tool 45 by the same angle as the tool correction rotation angle ψk+1 around the C axis (S41).

[0078] The CPU 61 determines whether the tool 45 is at the end point E (S42). If the tool 45 is not at the end point E (S42: NO), the CPU 61 returns the process to step S35. That is, it acquires the pressing direction in the next state k+1 (S35) and repeats the same process. If the tool 45 is at the end point E (S42: YES), the CPU 61 ends the process.

[0079] In the machining path generation device according to Embodiment 2, by moving the tool 45 along the circumferential direction of the master workpiece 70, it is possible to shorten the machining path generation time and minimize the deviation between the pressing direction and the tool rotation direction.

[0080] (Modification example) In Embodiments 1 and 2, the axis of the C-axis and the tool 45 coincide, and the predetermined axis corresponds to the C-axis. However, when the second arm 44 rotates around the A-axis, the axis of the C-axis and the tool 45 do not coincide. At this time, the predetermined axis shall correspond to the axis of the tool 45, and the CPU 61 may perform the same control as in Embodiments 1 and 2.

[0081] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and the scope equivalent to the claims.

Explanation of Reference Numerals

[0082] 8 Motor 8a Encoder 10 Motor 10a Encoder 20 Spindle Unit 45 Tool 60 Control Device 61 CPU 62 RAM 63 Storage Unit 63a Storage Medium 70 Master Workpiece

Claims

1. In a machining path generation device that generates a machining path for a machine tool that mounts a tool for machining a workpiece and can change the position of a predetermined point with respect to a predetermined axis in the tool and the posture of the tool with respect to the workpiece, a first direction acquisition unit that acquires a first direction that is the direction of the force applied by the tool to the workpiece at a first time point; a second direction acquisition unit that acquires a second direction that is the direction of the force applied by the tool to the workpiece at a second time point when the tool moves after the first time point; an angle change amount calculation unit that calculates an amount of angle change in the direction around the predetermined axis of the tool based on the difference between the first direction and the second direction; a target direction calculation unit that calculates a target direction around the predetermined axis based on the direction of the position of the predetermined point with respect to the predetermined axis in the tool at the first time point and the amount of angle change calculated by the angle change amount calculation unit; a first correction angle calculation unit that calculates a correction angle around the predetermined axis of the tool based on the difference between the target direction calculated by the target direction calculation unit and the direction around the predetermined axis of the tool at the second time point A machining path generation device comprising.

2. a third direction acquisition unit that acquires a third direction that is the direction of the force applied by the tool to the workpiece at a third time point after the second time point; a second angle change amount calculation unit that calculates a second amount of angle change in the direction around the predetermined axis of the tool based on the difference between the first direction and the third direction; an addition unit that adds an adjustment angle based on the correction angle calculated at the second time point, which is the previous time point of the third time point, to the second amount of angle change calculated by the second angle change amount calculation unit; a second target direction calculation unit that calculates a target direction around the predetermined axis based on the direction of the position of the predetermined point with respect to the predetermined axis in the tool at the first time point and the addition result of the addition unit; a second correction angle calculation unit that calculates a correction angle around the predetermined axis of the tool based on the difference between the target direction calculated by the second target direction calculation unit and the direction around the predetermined axis of the tool at the third time point; The machining path generation device according to claim 1, comprising.

3. The addition unit adds an adjustment angle calculated by multiplying the correction angle by a predetermined coefficient to the second amount of angle change The machining path generation device according to claim 2.

4. In a machining path generation method for generating a machining path of a machine tool that mounts a tool for machining a workpiece and can change the position of a predetermined point with respect to a predetermined axis in the tool and the attitude of the tool with respect to the workpiece, obtain a first direction that is the direction of the force applied by the tool to the workpiece at a first point in time, obtain a second direction that is the direction of the force applied by the tool to the workpiece at a second point in time after the first point in time, calculate an amount of angular change in the direction around the predetermined axis of the tool based on the difference between the first direction and the second direction, calculate a target direction around the predetermined axis based on the direction of the position of the predetermined point with respect to the predetermined axis in the tool at the first point in time and the calculated amount of angular change, calculate a correction angle around the predetermined axis of the tool based on the difference between the calculated target direction and the direction around the predetermined axis of the tool at the second point in time Machining path generation method.

5. In a program executable by a machining path generation device for generating a machining path of a machine tool that mounts a tool for machining a workpiece and can change the position of a predetermined point with respect to a predetermined axis in the tool and the attitude of the tool with respect to the workpiece, obtain a first direction that is the direction of the force applied by the tool to the workpiece at a first point in time, obtain a second direction that is the direction of the force applied by the tool to the workpiece at a second point in time after the first point in time, calculate an amount of angular change in the direction around the predetermined axis of the tool based on the difference between the first direction and the second direction, calculate a target direction around the predetermined axis based on the direction of the position of the predetermined point with respect to the predetermined axis in the tool at the first point in time and the calculated amount of angular change, calculate a correction angle around the predetermined axis of the tool based on the difference between the calculated target direction and the direction around the predetermined axis of the tool at the second point in time A computer program that causes the machining path generation device to execute the process.

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