CONTROL DEVICE, MACHINE SYSTEM, AND PROGRAM

Abstract

To provide a control device, a machining system, and a program that are able to improve accuracy in machining a workpiece to be machined, without requiring a measuring tool.SOLUTION: A control device 4 according to the present disclosure, which is a control device 4 that controls an operation of a machine tool that, using a tool, machines a workpiece to be machined into a target shape, includes: a storage unit (an information storage unit 431) that stores a filter for correcting a detected value of a force and a tool in association with each other; a detection unit (a force sensor 12) that detects a force generated when a tool used by the machine tool comes into contact with a master workpiece having the target shape; a correction unit (a control unit 41) that, using the filter stored in the storage unit in association with the tool, corrects the detection value of the force detected by the detection unit; and a path generation unit (a control unit 41) that, using the detection value corrected by the correction unit, determines a machining path to be followed by the tool when the workpiece to be machined is machined.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a control device, a machining system, and a program. [Background technology]

[0002] The machining system includes a machine tool and a control device, and uses a tool to machine a workpiece into a target shape. The tool has a blade and cuts the workpiece by rotating and coming into contact with the workpiece.

[0003] The finishing device (machining system) described in Patent Document 1 performs force control so that a machining tool contacts a workpiece with a predetermined force, and performs tracing control so that the machining tool follows a given machining path. The finishing device compares the actual movement path of the machining tool by force control and tracing control with a given movement path based on CAD data of a target shape, detects burrs based on the comparison result, and generates a cutting path pattern (machining path) for removing the detected burrs with the machining tool. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-58961 A Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, a control device may determine a machining path using a master workpiece having a target shape. The control device determines the machining path so that a tool moves at a predetermined speed while in contact with the master workpiece, and the force generated by the tool contacting the master workpiece is constant.

[0006] The machine tool is equipped with a motor that rotates the tool, but the motor does not rotate the tool while the machining path is being generated. However, the tool rotates naturally due to contact with the master workpiece, so the blade of the tool comes into contact with the master workpiece. Since the blade is likely to get caught on the master workpiece, the detection value of the force generated by the tool contacting the master workpiece contains an error caused by the blade. If the machining path is obtained based on the detection value containing the error, there is a risk that the machining accuracy of the workpiece to be machined will deteriorate. In addition, it is possible to obtain a machining path with high accuracy by using a measuring tool such as a probe, but it is necessary to prepare the measuring tool separately from the machining tool, and in addition, the tool diameter and tool length are often different from the tool actually used for machining, so correction for them is required.

[0007] An object of the present disclosure is to provide a control device, a machining system, and a program that can improve the machining accuracy of a workpiece without requiring a measurement tool. [Means for solving the problem]

[0008] The control device of the present disclosure is a control device that controls the operation of a machine tool that uses a tool to machine a workpiece into a target shape, and is characterized in that it comprises a memory unit that stores a filter for correcting a force detection value in association with the tool, a detection unit that detects a force generated when a tool used by the machine tool comes into contact with a master workpiece having a target shape, a correction unit that corrects the force detection value detected by the detection unit using a filter stored in the memory unit in association with the tool, and a path generation unit that uses the detection value corrected by the correction unit to determine the machining path to be followed by the tool when machining the workpiece.

[0009] In the present disclosure, the detection unit detects a force. This force is generated when a tool used by a machine tool comes into contact with a master workpiece. The detection value by the detection unit includes an error caused by the blade of the tool. When the blade of the tool comes into periodic contact with the master workpiece, the error caused by the blade of the tool is considered to have periodicity.

[0010] The correction unit corrects the detection value by the detection unit. When making the correction, the correction unit uses a filter stored in the memory unit in association with the tool used by the machine tool. As a result, errors can be removed from the detection value by the detection unit. The path generation unit determines the machining path using the detection value corrected by the correction unit. When the machining path is determined based on the detection value that does not include errors, the machining accuracy of the workpiece to be machined can be improved. Since the machining path can be determined with the tool actually used attached to the machine tool, no measuring tool is required.

[0011] The control device according to the present disclosure further includes a calculation unit that calculates a cutoff frequency based on the diameter and number of teeth of a tool used by the machine tool and the moving speed during the machining, the memory unit stores a notch filter as the filter, and the correction unit has a first correction unit that corrects the detection value of the force detected by the detection unit using the notch filter of the cutoff frequency calculated by the calculation unit.

[0012] In the present disclosure, the calculation unit calculates the cutoff frequency based on the diameter and number of teeth of the tool used by the machine tool, and the moving speed during machining of the workpiece. If the tool is rod-shaped, the diameter of the tool is constant in the axial direction of the tool, and the number of tool teeth is easy to count, the period in which the tool blade contacts the master workpiece can be calculated. The frequency component corresponding to the calculated period is considered to be an error caused by the tool blade. The correction unit corrects the detection value by the detection unit using a notch filter of the cutoff frequency calculated by the calculation unit.

[0013] The control device according to the present disclosure further includes an acquisition unit that acquires a correction value for the cutoff frequency, and the calculation unit calculates a cutoff frequency by correcting the frequency calculated based on the diameter, number of teeth, and moving speed of a tool used by the machine tool with the correction value acquired by the acquisition unit.

[0014] In the present disclosure, an acquisition unit acquires a correction value for the cutoff frequency. A calculation unit calculates a cutoff frequency by correcting a frequency calculated based on a diameter of a tool used by a machine tool, a number of teeth, and a moving speed during machining of a workpiece, using the correction value acquired by the acquisition unit. By appropriately correcting the cutoff frequency mechanically determined from the tool parameters, the cutoff frequency determined by the calculation unit approaches the frequency of the actual error, so that the error can be reliably removed from the detection value by the detection unit.

[0015] The control device according to the present disclosure further includes a selection unit for selecting one of a plurality of frequencies, the memory unit stores a low-pass filter as the filter, and the correction unit has a second correction unit that corrects the detection value of the force detected by the detection unit using a low-pass filter whose upper limit is the frequency selected by the selection unit.

[0016] In the present disclosure, the correction unit corrects the detection value by the detection unit using a low-pass filter whose upper limit is the frequency selected by the selection unit. If the diameter of the tool changes in the axial direction of the tool or if it is difficult to count the number of teeth of the tool, the cutoff frequency cannot be obtained from the parameters related to the tool. However, since it has been experimentally found that the error caused by the teeth is a high-frequency component, the error can be removed from the value detected by the detector by using a low-pass filter.

[0017] The machining system disclosed herein is a machining system having a machine tool that uses a tool to machine a workpiece into a target shape, and a control device that controls the operation of the machine tool, and has a memory unit that associates and stores a filter for correcting a force detection value with the tool, and the control device is characterized in that it has a detection unit that detects a force generated when a tool used by the machine tool comes into contact with a master workpiece having a target shape, a correction unit that corrects the force detection value detected by the detection unit using a filter stored in the memory unit in association with the tool, and a path generation unit that uses the detection value corrected by the correction unit to determine the machining path to be followed by the tool when machining the workpiece.

[0018] In the present disclosure, the control device is equipped with a detection unit, a correction unit, and a path generation unit, and by using a memory unit, the machining accuracy of the workpiece can be improved without the need for a measurement tool.

[0019] The program disclosed herein is a program executable by a control device that controls the operation of a machine tool that uses a tool to machine a workpiece into a target shape, and is characterized in that it detects a force generated when the tool used by the machine tool comes into contact with a master workpiece having a target shape, acquires the filter corresponding to the tool used by the machine tool from a memory unit that associates and stores filters for correcting the detected force values ​​with the tools, corrects the detected force detection value using the acquired filter, and uses the corrected detection value to cause the control device to execute a process of determining the machining path to be followed by the tool when machining the workpiece.

[0020] In the present disclosure, by having the control device execute the program according to the present disclosure, it is possible to improve the machining accuracy of the workpiece without requiring a measurement tool. Effect of the Invention

[0021] According to the control device, machining system, and program disclosed herein, it is possible to improve the machining accuracy of a workpiece without requiring a measuring tool. [Brief description of the drawings]

[0022] [Figure 1] 1 is an external perspective view of a machining system according to an embodiment; [Diagram 2] FIG. 1 is a schematic perspective view of a machine tool. [Diagram 3] FIG. 2 is a vertical sectional view of the spindle unit. [Figure 4] FIG. 2 is a block diagram showing a control device, a force sensor, and the like. [Diagram 5] FIG. 2 is a schematic plan view of a master work. [Figure 6] FIG. 13 is a simplified partial enlarged plan view of the master workpiece with the tool in contact with the starting point. [Figure 7] 4 is a schematic diagram showing an example of data stored in a tool information storage unit; FIG. [Figure 8] 13 is a flowchart showing a procedure for a filter preparation process. [Figure 9] 13 is a flowchart showing a procedure for a processing path generation process. [Figure 10] FIG. 11 is a characteristic diagram showing a change over time in the magnitude of the force from the tool to the master workpiece. [Figure 11] FIG. 11 is a characteristic diagram showing a change over time in the magnitude of the force from the tool to the master workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present disclosure will be described. In the following description, up, down, front, back, left and right are indicated by arrows in the drawings. The left and right direction corresponds to the X direction, the front and back direction corresponds to the Y direction, and the up and down direction corresponds to the Z direction.

[0024] 1 is a perspective view of the appearance of a machining system according to an embodiment of the present invention. In the drawing, reference numeral 1 denotes the machining system, and the machining system 1 includes a cover 2, a machine tool 3, and a control device 4. The cover 2 is a vertically extending rectangular parallelepiped and has a front surface 2a, a right surface 2b, a left surface 2c, a rear surface 2d, and a top surface 2e. The cover 2 covers the machine tool 3 from the front, rear, left and right, and from above. An opening / closing door 21 is provided on the front surface 2a. Transparent windows 22 are provided on the right surface 2b and the left surface 2c. The top surface 2e is provided with a support plate 2f that is triangular in plan view. The machine tool 3 includes a holder 31. The upper surface of the holder 31 holds a workpiece to be machined or a master workpiece 61 (not shown) (see FIGS. 5 and 6 described later).

[0025] Fig. 2 is a schematic perspective view of the machine tool 3. In Fig. 2, the illustration of the support table 31 is omitted. The machine tool 3 has three upright pillars 32. The three upright pillars 32 extend in the vertical direction inside the cover 2 (see FIG. 1). The three upright pillars 32 are arranged around the support base 31 with a phase interval of approximately 120 degrees in a plan view. The three upright pillars 32 are adjacent to three corners of the support plate 2f, respectively. The upper parts of the three upright pillars 32 are connected to the corners of the support plate 2f via connecting plates 320. The upper parts of the upright pillars 32 and the connecting plates 320 are omitted from FIG. 1.

[0026] A track 321 is provided on the side surface of each upright pillar 32 facing the support base 31. The track 321 extends in the vertical direction. A moving part 322 and a drive mechanism (not shown) are provided on the track 321, and the drive mechanism is composed of a ball screw mechanism or the like. A motor 323 that supplies power to the drive mechanism is provided on the upper end of the upright pillar 32. When driven by the motor 323, the moving part 322 moves in the vertical direction along the track 321. The motor 323 is provided on the upper surface part 2e and is located outside the cover 2 (see FIG. 1).

[0027] The machine tool 3 includes a motor 33 and a reducer 34. The motor 33 and the reducer 34 are provided on a support plate 2f (see FIG. 1). The machine tool 3 includes a spindle unit 5. The spindle unit 5 is disposed above the support table 31. The spindle unit 5 is connected to a reducer 34 via a ball spline 35 extending vertically. The rotation of a motor 33 is reduced in speed by the reducer 34 and then transmitted to the ball spline 35. The ball spline 35 rotates around its axis.

[0028] The spindle unit 5 faces each of the upright pillars 32. The spindle unit 5 and the moving part 322 are connected by two parallel links 36. The links 36 are rod-shaped. One end of each of the two links 36 is connected to the first housing 51 of the spindle unit 5 via a rotatable joint 361. The other end of each of the two links 36 is connected to the moving part 322 via the joint 361. The joint 361 is a universal joint or the like. As the up-down positions of the three moving parts 322 change, the spindle unit 5 moves up-down, forward-backward, left-right and right-left.

[0029] FIG. 3 is a vertical sectional view of the spindle unit 5. As shown in FIG. The spindle unit 5 includes a first housing 51 having a truncated cone shape. The first housing 51 is disposed with its small diameter side facing upward and its large diameter side facing downward. The entire bottom surface of the first housing 51 is open. The link 36 is connected to the lower edge of the first housing 51 (see FIG. 2).

[0030] The second housing 52 is provided at the bottom opening of the first housing 51. The second housing 52 is cylindrical with a hollow interior and is disposed with the vertical direction as the axial direction. The upper edge of the second housing 52 is disposed inside the lower edge of the first housing 51. A cross roller bearing 53 is provided between the upper edge of the second housing 52 and the lower edge of the first housing 51. The cross roller bearing 53 rotatably supports the second housing 52. The second housing 52 rotates around a vertical axis. The central axes of the first housing 51 and the second housing 52 extending in the vertical direction are in the same position. Hereinafter, the central axis of the first housing 51 and the second housing 52 will be referred to as the C axis.

[0031] A part of the peripheral surface of the second housing 52 protrudes radially outward and obliquely downward. Hereinafter, this protruding portion will be referred to as a protruding portion 521. A lower end of the protruding portion 521 is open. The angle between the protruding portion 521 and the peripheral surface of the second housing 52 is an acute angle, for example, about 30 degrees. A first arm 54 is provided at the lower end of the protruding portion 521. The first arm 54 includes a cylindrical housing 541. An upper end of the housing 541 is connected to the protruding portion 521, and the housing 541 extends obliquely downward from the protruding portion 521.

[0032] An opening 55 is formed on the side surface of the lower end of the housing 541. A second arm 56 is connected to the periphery of the opening 55. The second arm 56 includes an arm portion 561 and a support tube 562. The arm portion 561 has a shape like a bent rod, and includes a first portion 56a extending in a direction parallel to the housing 541 and a second portion 56b extending in a direction intersecting the first portion 56a. One end of the first portion 56a and one end of the second portion 56b are integrally connected. The other end of the first portion 56a is connected to the periphery of the opening 55 so as to be rotatable around the A-axis shown in the figure. The interior angle between the A-axis and the C-axis is less than 90°, for example, about 60°. A support tube 562 is provided at the other end of the second portion 56b.

[0033] The support cylinder 562 is arranged so that its axis coincides with the C-axis. A motor 563 (see FIG. 4 described below) and a spindle (not shown) are housed in the support cylinder 562. A cylindrical tool 11 is attached to the lower end of the spindle. The tool 11 protrudes downward from the support cylinder 562, and the axis of the tool 11 coincides with the C-axis. The tip of the tool 11 is located at the intersection of the C-axis and the A-axis. The motor 563 housed in the support cylinder 562 supplies power to the spindle, and the spindle and tool 11 rotate around the C-axis. The support cylinder 562 houses a force sensor 12. The force sensor 12 detects the magnitude and direction of a force acting on the tool 11.

[0034] The first housing 51 houses a switching mechanism 511. An air cylinder 512 is attached to the outside of the first housing 51. The air cylinder 512 has a rod (not shown). The first housing 51 and the second housing 52 house a first transmission mechanism 57. The first housing 51, the second housing 52, and the housing 541 house a second transmission mechanism 58.

[0035] By movement of the rod of the air cylinder 512, the switching mechanism 511 switches the transmission destination of the rotation of the ball spline 35 to the first transmission mechanism 57 or the second transmission mechanism 58. The first transmission mechanism 57 transmits the rotation of the ball spline 35 to the second housing 52. The second transmission mechanism 58 is connected to the other end of the first portion 56a and transmits the rotation of the ball spline 35 to the second arm 56. The switching mechanism 511 can also be switched to a neutral state in which it does not transmit rotation to either the first transmission mechanism 57 or the second transmission mechanism 58.

[0036] When the switching mechanism 511 switches the destination of the rotation of the ball spline 35 to the first transmission mechanism 57, the second housing 52, the first arm 54, and the second arm 56 rotate around the C axis. At this time, the second arm 56 does not rotate around the A axis. When the switching mechanism 511 switches the destination of the rotation of the ball spline 35 to the second transmission mechanism 58, the second arm 56 rotates around the A axis. At this time, the second housing 52, the first arm 54, and the second arm 56 do not rotate around the C axis.

[0037] FIG. 4 is a block diagram showing the control device 4, the force sensor 12, and the like. The control device 4 controls the driving of the motor 323, the air cylinder 512, etc., to machine the workpiece into a target shape using the tool 11. The tool 11 has a blade, and is driven by a motor 563 housed in a support cylinder 562. The tool 11 comes into contact with the workpiece while rotating, thereby performing cutting on the workpiece. Before machining the workpiece, the control device 4 uses a master workpiece 61 (see FIG. 5) having a target shape to generate a machining path that the tool 11 will follow when machining the workpiece.

[0038] The control device 4 includes a control unit 41, a main memory unit 42, and an auxiliary memory unit 43, which are connected to each other via a bus. The control unit 41 includes one or more processors such as a CPU, an MPU, and a GPU. The main memory unit 42 is volatile, for example, a RAM. The auxiliary memory unit 43 is nonvolatile, for example, an EEPROM, a flash memory, a hard disk, or an SSD. The auxiliary memory unit 43 pre-stores a program 4P for controlling the operation of the control device 4, and various data required for executing the program 4P. The program 4P (program product) includes a machining path generation program for generating a machining path, and a machining program for machining a workpiece. A part of the memory area of ​​the auxiliary memory unit 43 is an information memory unit 431, which will be described later.

[0039] The control unit 41 uses the main memory unit 42 as a working area and executes various calculation processes and control processes, etc., according to the program 4P stored in the auxiliary memory unit 43. For example, the control unit 41 determines a machining path such that the tool 11 moves at a predetermined feed speed V while in contact with the master workpiece 61, and the force generated by the tool 11 contacting the master workpiece 61 is constant. The feed speed V is the moving speed of the tool 11 when machining the workpiece.

[0040] The auxiliary memory unit 43 may store a program 4P or data stored on a portable recording medium 62 such as a CD-ROM or flash memory, or may store a program 4P or data received from a server via a network. The information storage unit 431 is not limited to being provided in the control device 4. The information storage unit 431 may be provided in a server that communicates with the control device 4 via a network, for example.

[0041] The force sensor 12 outputs a signal indicating the direction and magnitude of the force acting on the tool 11 to the control device 4. The motor 323 has an encoder 13. The encoder 13 outputs a signal indicating the position of the motor 323 to the control device 4. The control device 4 executes a machining path generation process based on inputs from the force sensor 12 and the encoder 13.

[0042] The machining system 1 includes a display unit 14 and an operation unit 15. The display unit 14 and the operation unit 15 are provided, for example, on the outer surface of the cover 2. The display unit 14 displays images. The operation unit 15 has a plurality of operation keys. An operator operates the operation keys of the operation unit 15 while looking at the image displayed by the display unit 14, thereby providing the control device 4 with commands or data, etc., required for machining the workpiece or generating a machining path.

[0043] 5 is a schematic plan view of the master workpiece 61. Although the present embodiment describes a method for generating a machining path on the XY plane, by specifying the plane, it is possible to generate a machining path on any plane in three-dimensional space, not limited to the XY plane. When performing machining path generation processing, the worker places the master workpiece 61 on the holding table 31 and sets the start point S and end point E of the machining path. The worker manually operates the tool 11 to bring it into contact with two desired positions on the master workpiece 61. The control unit 41 stores the positions where the tool 11 makes contact, that is, the front / back, left / right, top / bottom positions of the start point S and end point E, in the auxiliary storage unit 43. In this embodiment, the end point E is set to the right of the start point S.

[0044] The control device 4 in this embodiment acquires the direction and magnitude of the force applied to the first position of the master workpiece 61. Based on the direction and magnitude of the force applied to the first position, the control device 4 automatically calculates the feed direction of the tool 11 from the first position to the second position, the feed amount of the tool 11 from the first position to the second position, and the distance by which the tool 11 approaches the master workpiece 61 at the second position, i.e., the pressing amount.

[0045] Here, the first position is the current position of the tool 11, and the tool 11 at the first position is in contact with the master workpiece 61. The feed direction of the tool 11 is a direction perpendicular to the direction of the force applied to the first position. The feed amount of the tool 11 is the amount that the tool 11 moves in the feed direction. The second position is a position away from the first position by the feed amount in the feed direction. The feed amount is sufficiently small. The distance by which the tool 11 approaches the master workpiece 61 at the second position is the pressing amount of the tool 11 at the second position in the direction of the force applied to the first position.

[0046] FIG. 6 is a schematic partial enlarged plan view of the master work 61 where the tool 11 is in contact with the starting point S. k ) is at time t k The V axis is the contact position of the tool 11 with the master workpiece 61 at time t k The V-axis indicates the direction of the force applied by the tool 11 to the master workpiece 61 at the contact position in the drawing. The master workpiece 61 side is the positive side of the V-axis. The U-axis is an axis perpendicular to the V-axis, and indicates the feed direction of the tool 11. In this embodiment, since the tool 11 moves to the right, the right side of the U-axis is the positive side.

[0047] Time t k The contact position P(t k ) to the next time t k+1 Position P(t k+1 ), P(t k ) corresponds to the first position, the position away by the feed amount is the second position, and P(t k+1 For example, the starting point S corresponds to the first position at time t0, and P(t1) at time t1 corresponds to the target position.

[0048] First position P(t k ), the control unit 41 acquires the detection value of the force sensor 12. Based on the direction indicated by the detection value of the force sensor 12, the control unit 41 determines whether the tool 11 is at the first position P(t k ) to the force f(t kThe control unit 41 determines whether the tool 11 is in the first position P(t k ) to the force f(t k The force sensor 12 in the machining path generation process functions as a detection unit that detects the force generated when the tool 11 comes into contact with the master workpiece 61.

[0049] The control unit 41 determines the force f(t k ) and the target value f d (t k ) and calculate the difference between the target value f d (t k ) is a target value of the force in the V-axis direction, and is stored in advance in the auxiliary storage unit 43. The control unit 41 multiplies the calculated difference by a coefficient κ to obtain the position deviation amount ΔPf d (t k The coefficient κ is stored in advance in the auxiliary storage unit 43. The position deviation amount ΔPf d (t k ) is the moving distance in the V-axis direction when the tool 11 moves from the current position to the next position. The control unit 41 adjusts the position deviation amount ΔP so as to be equal to the feed amount n prestored in the auxiliary storage unit 43 in the same direction as the U-axis direction. d (t k For example, multiply the unit vector of the U axis by the feed amount n to obtain the position deviation amount ΔP d (t k 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 in the V-axis direction is calculated. d (t k ) contains a component in the U-axis direction, and the position deviation in the U-axis direction ΔP d (t k ) contains a component in the V-axis direction. The position deviation amount (ΔPf d (t k ), ΔP d (t k )) with the other axis components deleted, the V axis direction error F err , U-axis direction error P err The position deviation amount in the U-axis direction ΔP d(t k ) is the moving distance in the U-axis direction when the tool 11 moves from the current position to the next position.

[0050] The control unit 41 calculates the V-axis direction error F err Request.

[0051]

number

[0052] The control unit 41 calculates the U-axis direction error P err Request.

[0053]

number

[0054] The control unit 41 detects the V-axis error F err The first controlled variable is calculated using PID control. PID control is a common feedback control method. The first controlled variable is the position P(t k ) corresponds to the pressing amount of the tool 11 in the V-axis direction. err The control unit 41 obtains a second control amount by using PID control. The second control amount is the first position P(t k ) to position P(t k+1) corresponds to the feed amount of the tool 11 to the V-axis direction. The control unit 41 determines the first control amount and the second control amount independently (i.e., determines them based on hybrid control). Hybrid control refers to controlling the control amounts in the respective control directions of position and force independently of each other. It is not necessary to calculate the first control amount and the second control amount by PID control. For example, err is the first control variable, and U is the axial direction error P err The control unit 41 adds the first control amount and the second control amount to obtain a composite control amount in the XY coordinate system, that is, the target position.

[0055] After calculating the target position, the control unit 41 moves the tool 11 to the target position at a feed speed V. The operator gives the feed speed V to the control device 4 by operating the operation unit 15 before starting generation of the machining path. The control unit 41 determines the position P(t k ) to the next position P(t k+1 In the case of the movement to the position P(t), the target position of the tool 11 is obtained by performing the same calculation processing, and the tool 11 is moved to the obtained target position. k ) corresponds to the first position, and position P(t k+1 ) corresponds to the target position. By repeatedly executing the above-mentioned calculation of the target position, the control unit 41 generates the machining path.

[0056] The tool 11 moves from the first position to the second position while in contact with the master workpiece 61. The tool 11 is not rotated while the machining path is being generated. However, the tool 11 naturally rotates due to contact with the master workpiece 61, and the blade of the tool 11 comes into contact with the master workpiece 61. Since the blade is likely to get caught on the master workpiece 61, the detection value of the force sensor 12 contains an error caused by the blade. If the machining path is obtained based on detection values ​​containing an error, there is a risk that the machining accuracy of the workpiece will deteriorate, and therefore it is necessary to remove the error.

[0057] FIG. 7 is a schematic diagram showing an example of data stored in the information storage unit 431. As shown in FIG. The information storage unit 431 is a storage unit that stores a filter for correcting a force detection value and the tool 11 in association with each other. The information storage unit 431 stores identification information for identifying the tool 11 and the type of the tool in association with each other. The information storage unit 431 stores at least one of the tool diameter and the number of teeth of the tool 11 in association with the identification information of the tool 11, or stores neither of them.

[0058] The information storage unit 431 stores a function representing a notch filter (hereinafter simply referred to as a notch filter) in association with identification information of the tool 11 that stores both the tool diameter and the number of teeth. The information storage unit 431 may store an offset value ("F" in the figure), which will be described later, in association with identification information of the tool 11 that stores the notch filter. The information storage unit 431 stores a function representing a low-pass filter (hereinafter simply referred to as a low-pass filter) in association with identification information of a tool 11 that does not store at least one of the tool diameter and the number of teeth. The information storage unit 431 stores multiple frequencies ("f1, f2, f3" in the figure) in association with identification information of a tool 11 that stores a low-pass filter. For example, the multiple frequencies are common to all tools 11.

[0059] The display unit 14 displays a plurality of frequencies, and the worker selects one of the plurality of frequencies by operating the operation unit 15. At this time, the operation unit 15 functions as a selection unit in the embodiment. The options displayed by the display unit 14 are not limited to the numerical values ​​of the plurality of frequencies themselves, and may be, for example, information indicating the magnitude of the plurality of frequencies ("large", "medium", "small"). The information storage unit 431 stores a flag indicating the selection made by the worker ("*" in the figure) in association with the frequency selected by the worker.

[0060] FIG. 8 is a flowchart showing the procedure of the filter preparation process. The control unit 41 receives the identification information and the feed speed V of the tool 11 (S11). In S11, the control unit 41 controls the operation of the display unit 14, so that the display unit 14 displays an image for receiving the identification information and the feed speed V of the tool 11. The worker provides the identification information and the feed speed V of the tool 11 to the control device 4 by operating the operation unit 15 while looking at the image displayed by the display unit 14. The control unit 41, which receives the identification information and feed speed V of the tool 11, refers to the information storage unit 431 and determines whether the information storage unit 431 stores both the tool diameter and the number of blades of the tool 11 in association with the received identification information (S12).

[0061] If both the tool diameter and the number of teeth of the tool 11 are stored (YES in S12), the control unit 41 reads out the tool diameter and the number of teeth stored in the information storage unit 431 in association with the identification information received in S11 (S13).

[0062] If it is easy to know the tool diameter of the position of the tool 11 where it contacts the master workpiece 61 and the number of teeth of the tool 11, it is possible to obtain the period in which the teeth of the tool 11 contact the master workpiece 61. For example, if the tool diameter of the tool 11 is φn [mm] and the number of teeth is m [pieces], the circumference of the tool 11 is nπ [mm], so that the teeth of the tool 11 contact the master workpiece 61 every time the tool 11 rotates nπ / m, causing an error. When the feed rate is V [mm / min] = V / 60 [mm / sec], an error occurs in the detection value of the force sensor 12 every nπ / m [mm] ÷ V / 60 [mm / sec] = 60nπ / mV [sec.]. Therefore, by using a notch filter with a cutoff frequency of mV / 60nπ [Hz], the error is removed from the detection value of the force sensor 12.

[0063] After the process of S13 is completed, the control unit 41 judges whether or not the information storage unit 431 stores an offset value in association with the identification information received in S11 (S14). In the case of the information storage unit 431 shown in Fig. 7, the control unit 41 in S14 judges YES when the offset value field stores the real number F, and judges NO when the offset value field stores "-".

[0064] If the information storage unit 431 does not store an offset value (NO in S14), the control unit 41 calculates the cutoff frequency mV / 60nπ based on the feed rate V received in S11 and the tool diameter φn and number of teeth m read in S13 (S15). The control unit 41 writes the cutoff frequency calculated in the process of S15 in association with the identification information received in S11 in the main storage unit 42 (S16), and ends the filter preparation process.

[0065] If the information storage unit 431 stores an offset value (YES in S14), the control unit 41 calculates the cutoff frequency mV / 60nπ in the same manner as in the process of S15, and writes it to the main storage unit 42 (S17). It is empirically known that, depending on the tool 11, an error occurs at a frequency slightly deviated from the cutoff frequency calculated in S17. The operator operates the operation unit 15 to provide the error amount as an offset value to the information storage unit 431 before the control unit 41 executes the filter preparation process.

[0066] The control unit 41 reads out the offset value from the information storage unit 431 (S18), and adds or subtracts the read cutoff frequency to or from the cutoff frequency calculated in S17 (S19). However, whether or not to add or subtract the offset value may be specified by the operator in the machining program, or the operator may directly specify the cutoff frequency in the machining program.

[0067] After completing the process of S19, the control unit 41 shifts the process to S16, and writes the cutoff frequency determined in the process of S19 in association with the identification information received in S11 into the main storage unit 42, thereby completing the filter preparation process. The control unit 41 in S15 functions as a calculation unit in the embodiment. The control unit 41 in S18 functions as an acquisition unit in the embodiment, and the control unit 41 in S17 and S19 functions as a calculation unit in the embodiment. The offset value used in S19 functions as a correction value for the cutoff frequency.

[0068] When it is difficult to calculate the tool diameter at the position where the tool 11 contacts the master workpiece 61, or when it is difficult to count the number of teeth of the tool 11, the cutoff frequency cannot be obtained from the parameters related to the tool 11. However, it has been experimentally found that the error caused by the teeth is a high-frequency component. Therefore, when at least one of the tool diameter and the number of teeth of the tool 11 is not stored (NO in S12), the control unit 41 reads out the frequency stored in the information storage unit 431 in association with a flag indicating that the operator has selected it (S21). In the case of FIG. 7, the control unit 41 reads out the frequency "f2".

[0069] The control unit 41 reads out a low-pass filter by referring to the information storage unit 431 (S22), and writes the low-pass filter into which the frequency read out in S21 has been assigned, in association with the identification information received in S11, into the main storage unit 42 (S23), and terminates the filter preparation process.

[0070] FIG. 9 is a flowchart showing the procedure of the machining path generation process. The control unit 41 calculates a filter stored in the main storage unit 42 (S31). If the result of S12 of the filter preparation process is YES, the control unit 41 in S31 reads out the cutoff frequency written in the main storage unit 42 in the process of S16 of the filter preparation process, and calculates a notch filter based on the read-out cutoff frequency. If the result of S12 of the filter preparation process is NO, the control unit 41 in S31 reads out the low-pass filter stored in the main storage unit 42 in the process of S23 of the filter preparation process. The control unit 41 performs processing for moving the tool 11 to the start point S (S32). In S32, the control unit 41 controls the driving of the motor 323, the air cylinder 512, etc., so that the tool 11 moves to the start point S.

[0071] The control unit 41 acquires the detection value of the force sensor 12 (S33), and corrects the acquired detection value with the filter read out in S31 (S34).

[0072] 10 and 11 are characteristic diagrams showing the change over time in the magnitude of the force from the tool 11 to the master workpiece 61. In FIG. The horizontal axis in Figures 10 and 11 represents time. The vertical axis represents the magnitude of force. The magnitude of force in the V-axis direction is shown by a thick solid line. The magnitude of force in the U-axis direction is shown by a dashed line. The magnitude of force in the direction perpendicular to both the V-axis and the U-axis is shown by a thin solid line. The magnitudes of the forces shown in Figures 10A and 11A are values ​​obtained from the detection values ​​of the force sensor 12. The magnitudes of the forces shown in Figures 10B and 11B are values ​​after correction by a filter.

[0073] Figure 10 relates to a tool 11 with identification information "N1" shown in Figure 7. As can be seen from Figure 10A, the waveform of the detected value is periodically disturbed. Figure 10B shows the value after correction by a notch filter. It can be seen from the figure that the notch filter has removed the disturbance of the waveform. FIG. 11 relates to a tool 11 such as the identification information "L1" shown in FIG. 7. As can be seen from FIG. 11A, the waveform of the detected value contains high frequency noise. FIG. 11B shows the value after application of the low pass filter. As can be seen from the figure, the low pass filter has removed the high frequency noise.

[0074] The control unit 41 calculates the force f(t k ) and find the magnitude of the force f(t k ) (i.e., the V axis) is found (S35). The control unit 41 calculates the U-axis perpendicular to the V-axis based on the V-axis calculated in S35 (S36), and calculates the first control amount and the second control amount, i.e., the pressing amount and the feed amount (S37). The control unit 41 adds the first control amount and the second control amount to calculate a composite control amount, i.e., the target position, and writes the calculated target position to the auxiliary storage unit 43 (S38).

[0075] The control unit 41 performs processing to move the tool 11 to the target position (S39). The tool 11 moves to the target position by feedback control. After the movement of the tool 11 is completed, the control unit 41 acquires the current position of the tool 11 from the encoder 13 (S40) and determines whether the tool 11 is at the end point E or not (S41). Note that the control unit 41 determines that the tool 11 is at the end point E if the difference between the current position of the tool 11 acquired from the encoder 13 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 auxiliary memory unit 43.

[0076] If the tool 11 is not at the end point E (NO in S41), the control unit 41 returns the process to S33 and again acquires the detection value of the force sensor 12. If the tool 11 is at the end point E (YES in S41), the control unit 41 ends the machining path generation process. The series of target positions stored in the auxiliary storage unit 43 in S38 while the processes of S33 to S41 are repeated is the machining path generated by the control unit 41.

[0077] The control unit 41 in S34 functions as a correction unit in the embodiment. When the control unit 41 in S31 calculates a notch filter, the control unit 41 in S34 functions as a first correction unit. When the control unit 41 in S31 calculates a low-pass filter, the control unit 41 in S34 functions as a second correction unit. The control unit 41 in S38 functions as a route generating unit in the embodiment.

[0078] According to the control device 4 as described above, it is possible to remove errors from the detection values ​​of the force sensor 12. Since the machining path is obtained based on the detection values ​​that do not include errors, when the operation of the tool 11 is controlled based on the obtained machining path, it is possible to improve the machining accuracy of the workpiece without requiring a measuring tool.

[0079] If the machining path generated based on the offset value given by the worker to the control device 4 is inappropriate, the worker inputs a new offset value to the control device 4, and the control unit 41 starts over from executing the filter preparation process again. The suitability of the machining path may be determined by the control unit 41 based on a given criterion, or may be determined by the worker. Similarly, if the machining path generated based on the frequency selected by the worker is inappropriate, the worker selects another frequency, and the control unit 41 starts over from executing the filter preparation process again.

[0080] In this embodiment, the force sensor 12 detects the magnitude and direction of the force, but this is not limiting, and for example, the torque acting on each motor 323 may be detected, and the control unit 41 may calculate the magnitude and direction of the force based on the detected torque. In this case, the control unit 41 functions as a detection unit. The tool diameter and the number of teeth of the tool 11 may be input by an operator to the control device 4. The control device 4 may have a feed speed V in advance. The process of generating the processing path is not limited to the above-mentioned process.

[0081] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is intended to include not only the above-mentioned meaning, but also the meaning equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0082] 1. Crafting System 11 Tools 12 Force sensor (detection part) 3 Machine tools 4. Control device 4P Program 41 control unit (correction unit, path generation unit, calculation unit, first correction unit, acquisition unit, second correction unit) 431 Information storage unit (storage unit) 61 Masterwork

Claims

1. A control device for controlling an operation of a machine tool that uses a tool to machine a workpiece into a target shape, a storage unit that stores a filter for correcting a detected value of force in association with a tool; a detection unit that detects a force generated when a tool used by the machine tool comes into contact with a master workpiece having a target shape; a correction unit that corrects a detection value of the force detected by the detection unit by using a filter that is associated with the tool and stored in the storage unit; a path generating unit that uses the detection value corrected by the correction unit to determine a machining path that the tool will follow when machining a workpiece; A control device comprising:

2. A calculation unit is further provided to calculate a cutoff frequency based on a diameter and a number of teeth of a tool used by the machine tool and a moving speed during the machining, the storage unit stores a notch filter as the filter, 2. The control device according to claim 1, wherein the correction unit includes a first correction unit that corrects the detection value of the force detected by the detection unit using a notch filter having a cutoff frequency determined by the calculation unit.

3. An acquisition unit that acquires a correction value of the cutoff frequency, The control device according to claim 2, characterized in that the calculation unit calculates a cutoff frequency by correcting a frequency calculated based on the diameter, number of teeth, and moving speed of a tool used by the machine tool with a correction value acquired by the acquisition unit.

4. A selection unit for selecting one of a plurality of frequencies, the storage unit stores a low-pass filter as the filter, The control device according to any one of claims 1 to 3, characterized in that the correction unit has a second correction unit that corrects the detection value of the force detected by the detection unit using a low-pass filter with an upper limit of the frequency selected by the selection unit.

5. A machine tool that uses a tool to machine a workpiece into a target shape; A control device for controlling the operation of the machine tool; In a machining system having a storage unit that stores a filter for correcting a detected value of a force in association with a tool; The control device includes: a detection unit that detects a force generated when a tool used by the machine tool comes into contact with a master workpiece having a target shape; a correction unit that corrects a detection value of the force detected by the detection unit by using a filter that is associated with the tool and stored in the storage unit; a path generating unit that uses the detection value corrected by the correction unit to determine a machining path that the tool will follow when machining a workpiece; A machining system comprising:

6. A program executable by a control device that controls an operation of a machine tool that uses a tool to machine a workpiece into a target shape, Detecting a force generated when a tool used by the machine tool comes into contact with a master workpiece having a target shape; acquiring a filter corresponding to a tool used by the machine tool from a storage unit that stores a filter for correcting a force detection value in association with a tool; The detected force value is corrected using the obtained filter. The corrected detection value is used to determine the machining path that the tool follows when machining the workpiece. A program for causing the control device to execute a process.

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