Control system for a machine tool

Abstract

A control system (100) for a machine tool machining a workpiece (W), the control system comprising: a control device (50) which controls drive axes of the machine tool (10) based on control data, a machining surface measuring device (20) which measures a machined surface of the workpiece (W), and an analysis device (30) which analyses a defect on the machined surface of the workpiece (W), wherein the analysis device (30) contains: a first detection part (31) which receives the chronological control data from the control device (50) during the machining of the workpiece (W), a second detection part (32) which receives spatial machining surface measurement data measured by the machining surface measuring device (20) after machining of the workpiece (W), a storage part (33) which stores the chronological control data received by the first detection part (31) and the spatial machining area measurement data received by the second detection part (32) during machining of the workpiece in at least two machining directions, a data association processing part (34) which associates the chronological control data and the spatial machining area measurement data stored in the storage part (33) with each other when the workpiece is machined in the at least two machining directions, a machining surface error detection part (35) which detects the error on the machined surface of the workpiece (W) and its position based on the spatial machining surface measurement data stored in the storage part (33) when the workpiece is machined in the at least two machining directions, and an identification part (36) that identifies the drive axis causing an error detected by the machining surface error detection part (35) based on the chronological control data and the spatial machining surface measurement data associated with each other by the data association processing part (34), from the error detected by the machining surface error detection part (35) and the machining direction of the control data in correspondence to the error position detected by the machining surface error detection part (35).

Description

BACKGROUND OF THE INVENTIONField of invention

[0001] The present invention relates to a control system for a machine tool that machines a workpiece. State of the art

[0002] A machine tool machines a workpiece while moving the workpiece (the element to be machined) and / or a tool along predetermined drive axes. In other words, the machine tool machines the workpiece while varying the relative position of the workpiece and the tool.

[0003] When the workpiece is machined with the machine tool described above, a striped pattern (defect) may appear on the machined surface of the workpiece. In other words, stripes may appear at predetermined intervals. Furthermore, protrusions may appear on the machined surface of the workpiece due to a delay in the reversal of the drive axis caused by backlash or other reasons.

[0004] For example, Patent Documents 1 and 2 disclose technologies in which a stripe pattern (defect) on the machined surface of a workpiece is detected based on the movement path of the tip of a tool during machining of a workpiece. Patent Document 1: Unexamined Japanese Patent Application Publication No. 2016-57843 Patent Document 2: Unexamined Japanese Patent Application Publication No. 2017-13178 SUMMARY OF THE INVENTION

[0005] The inventors of the present application adopted a different approach from the technologies of Patent Documents 1 and 2 to detect a defect on the machined surface of a workpiece. Specifically, another method for detecting a defect on the machined surface after machining the workpiece uses a vision sensor or the like to capture an image of the machined surface of the workpiece, performs image processing on the captured image data, and thus detects a defect (streaks or protrusions) on the machined surface. In other words, a defect on the machined surface is detected from spatial machined surface measurement data after machining the workpiece.

[0006] It is an object of the present invention to provide a control system for a machine tool that identifies a drive axis that causes the occurrence of a defect on the machined surface of the workpiece based on defect information obtained from spatial machining surface measurement data after machining of a workpiece.

[0007] (1) A control system (for example, a numerical control system 100 of a machine tool described below) of a machine tool according to the present invention that machines a workpiece (for example, a workpiece W described below) includes: a control device (for example, a numerical control device 50 described below) that controls drive axes of the machine tool (for example, a machine tool 10 described below) based on control data; a machined surface measuring device (for example, a machined surface measuring device 20 described below) that measures a machined surface of the workpiece; andand an analysis device (for example, a machining surface error analysis device 30 described below) that analyzes an error on the machined surface of the workpiece, the analysis device including: a first acquisition part (for example, a drive axis control data acquisition part 31 described below) that receives the chronological control data from the control device during machining of the workpiece; a second acquisition part (for example, a machining surface measurement data acquisition part 32 described below) that receives spatial machining surface measurement data measured by the machining surface measurement device after machining of the workpiece;a storage part (for example, a storage part 33 described below) that stores the chronological control data obtained by the first detection part and the spatial machining area measurement data obtained by the second detection part during machining of the workpiece in at least two machining directions; a data association processing part (for example, a data association processing part 34 described below) that associates the chronological control data and the spatial machining area measurement data stored in the storage part when the workpiece is machined in the at least two machining directions;a machining surface error detection part (for example, a machining surface error detection part 35 described below) that detects an error on the machined surface of the workpiece and its position based on the spatial machining surface measurement data stored in the storage part when the workpiece is machined in the at least two machining directions;and an identification part 36 (for example, a drive axis identification part 36 described below) that identifies the drive axis that causes an error detected by the machining surface error detection part, based on the control data and the machining surface measurement data associated with each other by the data association processing part, from the error detected by the machining surface error detection part, and the machining direction of the control data in correspondence with the error position detected by the machining surface error detection part.

[0008] (2) In the control system for a machine tool according to (1), the analysis device may further include a machining program analysis part (for example, a machining program analysis part 38 described below) that analyzes a machining program in the control device to set at least the two machining directions, and the control device may change the machining program in accordance with the machining directions set by the machining program analysis part to change the machining direction.

[0009] (3) In the control system for a machine tool according to (1), the analysis device may further include a machining direction determining part (for example, an optimal machining direction determining part 37 described below) that determines the machining direction so as to reduce a drive ratio of the drive axis causing the error identified by the identification part, and the control device may change the machining program in accordance with the machining direction determined by the machining direction determining part to change the machining direction.

[0010] (4) In the control system for a machine tool according to (3), the control means can change the angle of the workpiece in accordance with the change in the machining direction.

[0011] (5) In the control system for a machine tool according to any one of (1) to (4), the control data obtained by the first acquisition part may be position control data of the drive axes of the machine tool, the data association processing part may generate a first workpiece shape image based on the chronological position control data, generate a second workpiece shape image based on the spatial machining surface measurement data, and associate the chronological position control data and the spatial machining surface measurement data with each other to superimpose the first workpiece shape image and the second workpiece shape image.

[0012] (6) In the control system for a machine tool according to (5), the chronological position control data may be machining coordinate information, and the spatial machining surface measurement data may be machining coordinate information calculated based on a machining coordinate of the machining surface measuring device.

[0013] (7) In the control system for a machine tool according to any one of (1) to (4), the first acquisition part may receive from the controller chronological position control data and chronological speed control data when the workpiece is machined, which are position control data and speed control data of the drive axes of the machine tool associated with each other, and the data association processing part may acquire, based on a variation in the chronological speed control data as an edge position of the workpiece, a machining start position and a machining completion position to generate a first workpiece shape image; may acquire, based on the spatial machining surface measurement data, an edge position of the workpiece to generate a second workpiece shape image; may associate the chronological speed control data and the spatial machining surface measurement data with each other;to superimpose the edge position of the first workpiece shape image and the edge position of the second workpiece shape image, and can associate the chronological speed control data and the chronological position control data with each other to associate the chronological position control data and the spatial machining surface measurement data with each other.,

[0014] (8) In the control system for a machine tool according to any one of (1) to (4), the first detection part may obtain from the controller chronological position control data and chronological speed control data when the workpiece is machined, which are position control data and speed control data of the drive axes of the machine tool associated with each other, and the data association part may detect, based on a variation in a value obtained by subtracting a value corresponding to a variation in acceleration / deceleration from the chronological speed control data, as an edge position of the workpiece to generate a first workpiece shape image; may detect, based on the spatial machining surface measurement data, an edge position of the workpiece to generate a second workpiece shape image;may associate the chronological speed control data and the spatial machining surface measurement data to superimpose the edge position of the first workpiece shape image and the edge position of the second workpiece shape image, and may associate the chronological speed control data and the chronological position control data to associate the chronological position control data and the spatial machining surface measurement data.

[0015] (9) In the control system for a machine tool according to any one of (1) to (8), the defect on the machined surface of the workpiece may be a streak or a projection.

[0016] (10) In the control system for a machine tool according to (1), the control data may be a command value or a feedback value, the command value may be a position command value, a speed command value or a torque command value, and the feedback value may be a position feedback value, a speed feedback value or a current feedback value.

[0017] According to the present invention, there can be provided a control system for a machine tool that identifies a drive axis that causes the occurrence of a defect on the machined surface of the workpiece based on defect information acquired from image data of the machined surface of a workpiece. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing an example of the configuration of a machine tool according to an embodiment of the present invention. Fig. 2 is a schematic view showing the configuration of a numerical control system in the machine tool according to the embodiment of the present invention. Fig. 3 is a schematic view showing the configuration of a machining surface failure analysis device of Fig. 2 shows. Fig. 4 is a flowchart showing the data association processing performed by the machining surface failure analysis device of the numerical control system in the machine tool according to the embodiment of the present invention. Fig. 5 is a flowchart showing machining surface failure analysis processing performed by the machining surface failure analysis device of the numerical control system in the machine tool according to the embodiment of the present invention. Fig. Figure 6 is a schematic view showing data association processing. Fig. 7 is a schematic view showing the data association processing and the machining surface error analysis processing. Fig. 8 is a schematic view showing the configuration of a numerical control system in a machine tool according to a variation of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Examples of embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, like or corresponding parts are designated by like reference numerals. (machine tool)

[0019] First, an example of a machine tool in a numerical control system according to the embodiment of the present invention will be described below. Fig. Figure 1 is a perspective view showing an example of the configuration of the machine tool according to the embodiment of the present invention. This machine tool 10 is a machine tool that performs machining. The machine tool in the numerical control system of the present invention is not limited to this machine tool and can be any industrial machine.

[0020] The Fig. The machine tool 10 shown in FIG. 1 includes a head 2, a support member 3 that movably supports the head 2, a support column 4 that movably supports the support member 3, a base 5 that supports the support column 4, and a table 6. A tool T such as an end mill is attached to the head 2, and a workpiece W is mounted on the table 6. The machine tool 10 includes a drive device (not shown) and a numerical control device (not shown).

[0021] The drive device includes servo motors, which are described below. The drive device moves the base 5 in the X-axis direction (arrow X), moves the table 6 in the Y-axis direction (arrow Y), and moves the holding member 3 in the Z-axis direction (arrow Z). Furthermore, the drive device rotates the tool T in the A-axis direction (arrow A) with respect to the head 2, rotates the head 2 in the B-axis direction (arrow B) with respect to the holding member 3, and rotates the table 6 in the C-axis direction (arrow C) with respect to the head 2.

[0022] The numerical control device controls the drive device to drive the three directly moving axes (the X-axis, the Y-axis, and the Z-axis) and the three rotary axes (the X-axis, the B-axis, and the C-axis), thereby controlling the relative position of the tool T with respect to the workpiece W and its posture. In this way, the machine tool 10 machines the workpiece 10 while changing the relative position of the tool T with respect to the workpiece W and its posture.

[0023] When the workpiece W is machined in the machine tool 10 described above, a defect (streak) may occur on the machined surface of the workpiece W due to, for example, vibration. For example, vibrations are transmitted to the head 2 holding the tool T or the table 6 holding the workpiece W, so that the tool T or the workpiece W may vibrate. For example, when the movement direction of the head 2 or the table 6 is changed during machining, vibrations occur. Vibrations are also transmitted from a fan motor in an inverter or the like in the machine tool 10 or in various machines or the like outside the machine tool 10. If the tool T or the workpiece W vibrates due to the vibration of the machine tool 10 as described above, a defect may occur on the machined surface of the workpiece W.

[0024] The defect (streak) can be detected as described above by using a vision sensor or the like after machining the workpiece W to acquire an image of the machined surface of the workpiece W, and performing image processing on the acquired image data. Based on the defect on the machined surface of the workpiece W being machined by changing the machining direction and the machining direction based on the control data at this time, a drive axis causing the defect can be identified.

[0025] The present invention relates to a numerical control system in a machine tool that identifies a drive axis causing the occurrence of a defect on the machined surface of the workpiece based on defect information obtained from spatial machining surface measurement data such as image data after machining of a workpiece. (Numerical control system for a machine tool)

[0026] The numerical control system for a machine tool according to the embodiment of the present invention will be described below. Fig. 2 is a schematic view showing the configuration of the numerical control system in the machine tool according to the embodiment of the present invention. Fig. 3 is a schematic view showing the configuration of a machining surface failure analysis device of Fig. 2. The numerical control system 100 of the machine tool of Fig. 2 and Fig. 3 includes the machine tool 10 described above, a machining surface measuring device 20 and a machining surface error analysis device 30.

[0027] While the machine tool 10 described above has six drive axes (the X-axis, the Y-axis, the Z-axis, the A-axis, the B-axis, and the C-axis), the machine tool 10 of this embodiment has n drive axes. The machine tool 10 includes n servomotors M1, M2, ..., and Mn corresponding to the above-mentioned drive device, encoders (position / speed detectors) E1, E2, ..., and En provided in the servomotors, current detectors CT1, CT2, ..., and CTn, a scale (position detector) 16, and a numerical control device (CNC) 50. Fig. 2, only the configuration of the machine tool 10 relevant to the features of the present invention is shown, while the other configurations are not shown.

[0028] The servomotors M1, M2, ..., and Mn each drive the n drive axes under the control of the numerical controller 50. The encoders E1, E2, ..., and En each detect the rotational positions of the servomotors M1, M2, ..., and Mn and send the detected rotational positions to the numerical controller 50 as position feedback values. The encoders E1, E2, ..., and En each detect the rotational speeds of the servomotors M1, M2, ..., and Mn and send the detected rotational speeds to the numerical controller 50 as speed feedback values.

[0029] The current detectors CT1, CT2 ... and CTn detect the drive current values of the servo motors M1, M2 ... and Mn, respectively, and send the detected current values to the numerical controller 50 as current feedback values (actual current values).

[0030] The scale 16 is provided in the table 6 on which the above-mentioned workpiece W is mounted. The scale 16 detects the position of the workpiece W and sends the detected position to the numerical controller 50 as a position feedback value.

[0031] The numerical controller 50 generates torque command values (current command values) for the drive axes based on position command values (movement command values) for the drive axes based on a machining program for machining the workpiece W, the position feedback value from the scale 16 or the position feedback values from the encoders E1, E2 ... and En, the speed feedback values from the encoders E1, E2 ... and En and the current feedback values from the current detectors CT1, CT2 and CTn, and drives the servomotors M1, M2 and Mn with these torque command values.

[0032] Specifically, the numerical controller 50 includes a machining program generation part 51, a position command generation part 52, an individual-axis control part 53, and a storage part 54. The machining program generation part 51 generates a machining program for machining the workpiece W. The machining program generation part 51 changes the machining program to change the machining direction (machining angle) based on machining direction information from the machining surface error analysis device 30. The position command generation part 52 generates the position command values (movement command values) for the drive axes based on the machining program generated by the machining program generation part 51.The individual-axis control section 53 generates speed command values for the drive axes based on the differences between the position command values and the position feedback values, and generates torque command values (current command values) for the drive axes based on the differences between the speed command values and the speed feedback values. The individual-axis control section 53 generates drive currents for the drive axes based on the differences between the torque command values (current command values) and the current feedback values.

[0033] The storage section 54 stores control data for the individual axes from the individual-axis control section 53. The control data includes position control data (position command values, position feedback values), speed control data (speed command values, speed feedback values), and torque control data (torque command values, torque feedback values). The storage section 54 is, for example, a rewritable memory such as an EEPROM.

[0034] The numerical control device 50 is formed, for example, by a computing processor such as a DSP (digital signal processor) or an FPGA (field-programmable gate array). The various types of functions of the numerical control device 50 are realized by executing predetermined software (programs and applications) stored in the memory portion. The various types of functions of the numerical control device 50 can be realized through the interaction of hardware and software or solely through hardware (electronic circuitry).

[0035] The machining surface measuring device 20 is a device that measures the workpiece W to measure the machined surface of the workpiece W. Specific examples of the machining surface measuring device 20 include a vision sensor, an optical microscope, a laser microscope, and a three-dimensional coordinate measuring device. The machining surface measuring device 20 sends the image data or the position data of the measured workpiece W to the machining surface error analysis device 30. The machining surface measuring device 20 is provided, for example, in a measuring stage, a fixing stage, or a final stage of a robot external to the machine tool 10. The machining surface measuring device 20 can be integrated into the machine tool 10.

[0036] The machining surface error analysis device 30 is a device that analyzes the error on the machined surface of the workpiece W. The machining surface error analysis device 30 includes a drive-axis control data acquisition part (first acquisition part) 31, a machining surface measurement data acquisition part (second acquisition part) 32, a storage part 33, a data association processing part 34, a machining surface error detection part 35, an error-causing drive-axis identification part 36, an optimal machining direction determination part 37, and a machining program analysis part 38.

[0037] The drive-axis control data acquisition part 31 acquires chronological drive-axis control data stored in the storage part 54 of the numerical controller 50 when the workpiece W is machined. Specifically, the drive-axis control data acquisition part 31 obtains, as the drive-axis control data, the position control data (the position command values, the position feedback values of the workpiece W acquired by the scale 16, or the position feedback values of the servomotors M1, M2, Mn acquired by the encoders E1, E2, ..., and En) (position information (machining information) of the drive axes).

[0038] The machining surface measurement data acquisition part 32 obtains the spatial machining surface measurement data after machining of the workpiece W, which is measured by the machining surface measuring device 20. Specifically, the machining surface measurement data acquisition part 32 obtains three-dimensional image data or position data (coordinate data) as the machining surface measurement data.

[0039] The storage section 33 stores the chronological position control data obtained by the drive-axis control data acquisition section 31 and the spatial machining surface measurement data measured by the machining surface measuring device 20. Specifically, the storage section 33 stores the chronological position control data and the spatial machining surface measurement data when the workpiece W is machined in two different machining directions α and β. The storage section 33 is, for example, a rewritable memory such as an EEPROM.

[0040] The data association processing part 34 associates the chronological position control data and the spatial machining area measurement data in the machining direction α stored in the storage part 33. The data association processing part 34 also associates the chronological position control data and the spatial machining area measurement data in the machining direction β stored in the storage part 33. Furthermore, the data association processing part 34 associates the association data of the chronological position control data and the spatial machining area measurement data in the machining direction α and the association data of the chronological position control data and the spatial machining area measurement data in the machining direction β. Details of the data association processing will be described below.

[0041] The machining surface error detection part 35 detects the error (streak) on the machined surface of the workpiece W when the workpiece W is machined in the machining direction α and its position based on the spatial machining surface measurement data in the machining direction α stored in the storage part 33. The machining surface error detection part 35 also detects the error (streak) on the machined surface of the workpiece W when the workpiece W is machined in the machining direction β and its position based on the spatial machining surface measurement data in the machining direction β stored in the storage part 33.

[0042] The error-causing drive axis identification part 36 identifies the drive axis that causes the error based on the position control data and the machining surface measurement data associated with each other by the data association processing part 34, from the error detected by the machining error detection part 35 and the machining direction of the position control data corresponding to the error position.

[0043] The optimal machining direction determining part 37 determines the machining direction to reduce a drive ratio of the drive axis identified by the error-causing drive axis identifying part 36 and causing the error.

[0044] The machining program analysis part 38 analyzes the machining program in the numerical control device 50 to determine the machining direction β, which is different from the machining direction α based on the current machining program. The machining program analysis part 38 sends the machining direction determined by the optimal machining direction determination part 37 to the numerical control device 50.

[0045] The machining surface failure analysis part 30 is constituted, for example, by a computing processor such as a DSP (Digital Signal Processor) or an FPGA (Field Programmable Gate Array). The various types of functions of the machining surface failure analysis device 30 are realized by executing predetermined software (programs and applications) stored in the memory part (not shown). The various types of functions of the machining surface failure analysis device 30 can be realized through the cooperation of hardware and software or solely through hardware (electronic circuitry).

[0046] The various types of functions of the machining surface error analysis device 30 can be realized in the numerical control device 50 of the machine tool 10.

[0047] The data association processing and the machining surface error analysis processing performed by the machining surface error analysis device 30 of the numerical control system 100 in the machine tool of the present embodiment will be described below with reference to Fig. 4 to 7. Fig. 4 is a flowchart showing the data association processing performed by the machining surface error analysis device 30 of the numerical control system 100 in the machine tool of the present embodiment. Fig. 5 is a flowchart showing the machining surface error analysis processing performed by the machining surface error analysis device 30 of the numerical control system 100 in the machine tool of the present embodiment. Fig. Figure 6 is a schematic view showing data association processing. Fig. 7 is a schematic view showing the data association processing and the machining surface error analysis processing. [Data association processing]

[0048] The machining program generation section 51 of the numerical control system 50 first generates a machining program for machining the workpiece W in the machining direction α (machining angle). Thus, the workpiece W is machined in the machining direction α by the machining tool 10.

[0049] When the workpiece W is machined, the numerical controller 50 controls the drive axes based on the position command values, the speed command values, and the torque command values (current command values) for the drive axes based on the machining program, the position feedback values from the scale 16 (or the position feedback values from the encoders E1, E2 ... and En), the speed feedback values from the encoders E1, E2 ... and En, and the current feedback values (actual current values and actual torque values) from the current detectors CT1, CT2, and CTn, and thereby controls the relative position of the tool T with respect to the workpiece W and its posture so that the workpiece W is machined in the machining direction α.

[0050] When the workpiece W in step S11 of Fig. 4 is machined, the drive-axis control data acquisition part 31 obtains the chronological position control data (the position command values, the position feedback values of the workpiece W detected by the scale 16, or the position feedback values of the servomotors M1, M2 ... and Mn detected by the encoders E1, E2 ... and En) (position information (machining information) of the drive axes) in the machining direction α stored in the storage part 54 of the numerical controller 50, and stores them in the storage part 33.

[0051] When the machining of the workpiece W is completed, the machining surface measuring device 20 measures the machined surface of the workpiece W. At this time, in step S12, the machining surface measurement data acquisition part 32 obtains the spatial machining surface measurement data in the machining direction α from the machining surface measuring device 20 and stores it in the storage part 33. Specifically, the machining surface measurement data acquisition part 32 obtains the three-dimensional image data or the position data (coordinate data) as the machining surface measurement data.

[0052] Then, the data association processing part 34 associates the chronological position control data and the spatial machining surface measurement data in the machining direction α stored in the storage part 33. For example, after machining the workpiece, the data of an image captured by a vision sensor is three-dimensional data, while the position control data obtained from the numerical controller 50 during machining of the workpiece is chronological data, so it is not easy to associate these types of data. The inventors of the present application use the following method to associate these types of data.

[0053] Specifically, the data association processing section 34 first converts the machining surface measurement data into machining coordinate data. For example, if the machining surface measuring device 20 is a vision sensor, the machining surface measurement data is image data. In this case, the data association processing section 34 uses an image processing technique to determine the coordinate data of the workpiece W from the image data. The data association processing section 34 then converts the coordinate data of the workpiece W into machining coordinate data based on the distance between the machining surface measuring device 20 and the workpiece W, and on the position (machining coordinates) and angle (view angle) of the machining surface measuring device 20.On the other hand, if the machining surface measuring device 20 is an optical microscope, a laser microscope, or a three-dimensional coordinate measuring device, the machining surface measurement data is position data (coordinate data). In this case, the data association processing part 34 converts the position data (coordinate data) of the workpiece W into machining coordinate data based on the distance between the machining surface measuring device 20 and the workpiece W and on the position (machining coordinates) and angle (viewing angle) of the machining surface measuring device 20.

[0054] Then, the data association processing part 34 associates the chronological position control data (machining coordinates) when the workpiece W is machined in the machining direction α and the spatial position data (machining coordinates) of the machining surface after machining the workpiece W in the machining direction α. For example, as shown in Fig. 6, the data association processing part 34 generates a first workpiece shape image W1α in the machining direction α based on the chronological position control data (machining coordinates) when the workpiece W is machined in the machining direction α. Accordingly, the data association processing part 34 generates a second workpiece shape image W2α in the machining direction α based on the spatial position data (machining coordinates) of the machined surface after machining the workpiece W in the machining direction α. Then, the data association processing part 34 associates the chronological position control data and the spatial position data of the machined surface in the machining direction α with each other to superimpose the first workpiece shape image W1α and the second workpiece shape image W2α.

[0055] Then, in step S14, the machining program analysis part 38 reads the machining program from the machining program generation part 51 of the numerical controller 50 and analyzes the machining program. Specifically, the machining program analysis part 38 determines the machining direction (machining angle) β, which differs by 90 degrees from the machining direction α, based on the machining program and sends it to the machining program generation part 51 of the numerical controller 50. At this time, the machining program generation part 51 of the numerical controller 50 changes the machining program such that the machining direction α is changed to the machining direction β. In this way, a workpiece W (another workpiece on which the same machining is performed) is machined in the machining direction β by the machine tool 10.

[0056] When the workpiece W is machined in step S15, the drive-axis control data acquisition part 31 accordingly obtains the chronological position control data (position information (machining information) of the drive axes) in the machining direction β stored in the storage part 54 of the numerical controller 50 and stores it in the storage part 33.

[0057] When the machining of the workpiece W is completed, the machining surface measuring device 20 measures the machined surface of the workpiece W. At this time, the machining surface measurement data acquisition part 32 also receives the spatial machining surface measurement data in the machining direction β from the machining surface measuring device 20 and stores it in the storage part 33.

[0058] Then, in step S17, the data association processing part 34 also associates the chronological position control data (machining coordinates) when the workpiece W is machined in the machining direction β and the spatial position data (machining coordinates) of the machined surface after machining the workpiece W in the machining direction β with each other. For example, as shown in Fig. 6, the data association processing part 34 generates a first workpiece shape image W1β in the machining direction β based on the chronological position control data (machining coordinates) when the workpiece W is machined in the machining direction β. Similarly, the data association processing part 34 generates a second workpiece shape image W2β in the machining direction β based on the spatial position data (machining coordinates) of the machined surface after machining the workpiece W in the machining direction β. Then, the data association processing part 34 associates the chronological position control data and the spatial position data of the machined surface in the machining direction β with each other to superimpose the first workpiece shape image W1β and the second workpiece shape image W2β.

[0059] Then, the data association processing part 34 associates in step S18 as shown in Fig. 7, the association data of the chronological position control data and the spatial position data of the machined surface in the machining direction α, and the association data of the chronological position control data and the spatial position data of the machined surface in the machining direction β, are superimposed on each other to superimpose the first workpiece shape image W1α and the second workpiece shape image W2α in the machining direction α, and the first workpiece shape image W1β and the second workpiece shape image W2β in the machining direction β. The method for superimposing the workpiece shape images and associating the types of data with each other may be the same as described above. The associated types of data may be temporarily stored in the storage part 33. (Machining surface error analysis processing)

[0060] In step S21 of Fig. 5, the machining surface defect analysis part 35 detects the defect (streak) on the machined surface of the workpiece W in the machining direction α and its position based on the spatial machining surface measurement data in the machining direction α stored in the storage part 33. Then, in step S22, the machining surface defect detection part 35 detects the defect (streak) on the machined surface of the workpiece W in the machining direction β and its position based on the spatial machining surface measurement data in the machining direction β stored in the storage part 33. Specifically, when the machining surface measurement device 20 is a vision sensor, the machining surface measurement data is image data.In this case, the machined surface defect detection part 35 detects the defect on the machined surface and its position from the characteristic size of the stripe on the machined surface in the image data. On the other hand, if the machined surface measuring device 20 is an optical microscope, a laser microscope, or a three-dimensional coordinate measuring device, the machined surface measurement data is position data (coordinate data). In this case, the machined surface defect detection part 35 detects the defect on the machined surface and its position from a small variation (such as vibration) in the position data (coordinate data) of the machined surface.

[0061] Then, the error-causing drive axis identification part 36 identifies the drive axis causing the error based on the position control data and the machining surface measurement data associated with each other by the data association processing part 34, from the error detected by the machining surface error detection part 35 and the machining direction of the position control data corresponding to the error position. Specifically, in step S23, the error-causing drive axis identification part 36 compares, at an error position Dα detected by the machining surface error detection part 35 when the workpiece is machined in the machining direction α, the extent of the error during machining in the machining direction α (such as the size, the depth, or the number) (the error position Dα of the second workpiece shape image W2α in Fig. 7) with the extent of the error during machining in the machining direction β (the error position Dα of the second workpiece shape image W2β in Fig. 7). In step S24, the error-causing drive axis identification part 36 compares, at an error position Dβ detected by the machining surface error detection part 35 when the workpiece is machined in the machining direction β, the extent of the error during machining in the machining direction β (the error position Dβ of the second workpiece shape image W2β in Fig. 7) with the extent of the error during machining in the machining direction α (the error position Dβ of the second workpiece shape image W2α in Fig. 7). Then, in step S25, the error-causing drive axis identification part 36 identifies, based on the comparison results, the drive axis causing the error based on the machining direction of the position control data corresponding to the error position at which the degree of the error is greater.

[0062] Then, the optimal machining direction determining part 37 determines the optimal machining direction (machining angle) to reduce the drive ratio of the drive axis identified by the error-causing drive axis identifying part 36 and causing the error.

[0063] Then, in step S27, the machining program analysis part 38 sends the machining direction determined by the optimal machining direction determination part 37 to the numerical controller 50. In this way, in the machining program generation part 51 of the numerical controller 50, the machining program is changed to set the determined machining direction.

[0064] As described above, in the numerical control system 100 in the machine tool of the present embodiment, the machining surface error analysis device 30 associates the chronological control data and the spatial machining surface measurement data when the workpiece W is machined in at least two machining directions α and β with each other, detects the error on the machined surface of the workpiece W and its position based on the spatial machining surface measurement data when the workpiece W is machined in at least two machining directions α and β, and identifies the drive axis that causes the error based on the control data and the machining surface measurement data associated with each other from the detected error and the machining direction of the control data in accordance with the error position.In this way, the drive axis that causes the occurrence of the defect (stripe) on the machined surface of the workpiece W can be identified.

[0065] In the numerical control system 100 in the machine tool of this embodiment, the machining surface error analysis device 30 determines the machining direction to reduce the drive ratio of the identified drive axis causing the error. Then, according to the machining direction determined by the machining surface error analysis device 30, the numerical control device 50 changes the machining program to change the machining direction. In this way, the occurrence of the error (streak) on the machined surface can be reduced in subsequent machining passes, thereby improving the quality of the machined surface.

[0066] The present invention is not limited to the above-described embodiment of the invention. The effects described for this embodiment are merely some of the most advantageous effects of the present invention, and the effects of the present invention are not limited to those described for this embodiment.

[0067] For example, in the embodiment described above, only the machining direction is changed without rotating the workpiece. In other words, the machining direction is changed with respect to the workpiece. However, the present invention is not limited to this configuration; for example, the workpiece may be rotated according to the change in the machining direction, so that the machining direction with respect to the workpiece is not changed. For example, the machine tool 10 includes, as shown in Fig. 8 shows a plurality of servo motors M1R, M2R ... and MnR for rotation in the direction of the C-axis (see Fig. 1) of the table 6 on which the workpiece W is mounted, and the numerical controller 50 includes the individual rotary axis control part 53 for driving and controlling the servomotors M1R, M2R, ..., and MnR. Then, the machining program generation part 51 of the numerical controller 50 controls the individual rotary axis control part 53 to rotate the table 6 according to the change in the machining direction.

[0068] In the above-described embodiment, the machining program generation part 51 of the numerical controller 50 changes the machining program, but a CAM system that generates the machining program from a CAD drawing may also generate the changed machining program.

[0069] In the embodiment described above, when the workpiece is machined in the machining directions α and β different by 90 degrees, the machining surface measurement data is used to identify the driving axis that causes the occurrence of the defect on the machined surface, but machining surface measurement data when the workpiece is machined in machining directions different from each other by an angle other than 90 degrees can also be used to identify the driving axis that causes the occurrence of the defect on the machined surface.

[0070] In the embodiment described above, the machining surface measurement data when the workpiece is machined in the two different machining directions α and β is used to identify the driving axis that causes the occurrence of the defect on the machined surface, but machining surface measurement data when the workpiece is machined in three or more different machining directions may also be used to identify the driving axis that causes the occurrence of the defect on the machined surface.

[0071] In the above-described embodiment, the numerical control system 100 is described, which identifies the drive axis that causes the occurrence of a defect such as streaks on the machined surface of the workpiece W (due to vibration). However, the present invention is not limited to this and can also be applied to the identification of drive axes that cause the occurrence of various defects on the machined surface. For example, the machined surface defect analysis device 30 can identify a drive axis that causes the occurrence of a defect in the form of protrusions on the machined surface of the workpiece W (due to a delay in reversing the drive direction of the drive axis caused by, for example, backlash).The inventors of the present application found that when the error is caused by a delay in reversal resulting from backlash, the drive direction of the drive axis (the machining direction) can be slightly changed (for example, by a few degrees) to reduce the occurrence of protrusions. Accordingly, the machining surface error analysis device 30 can change the machining direction by only a few degrees to prevent the occurrence of protrusions.

[0072] In the above-described embodiment, the data association processing part 34 of the machining surface error analysis device 30 directly associates the position control data itself from the numerical controller 50 and the machining surface measurement data from the machining surface measurement device 20 to identify the position control data corresponding to the machining surface measurement data of the error position. However, the data association processing part 34 may also associate the speed control data from the numerical controller 50 and the machining surface measurement data, identify the speed control data corresponding to the machining surface measurement data of the error position, and identify the position control data corresponding to the speed control data.In this case, the drive axis control data acquisition part 31 and the data association processing part 34 on the machining surface failure analysis device 30 can also be operated as follows.

[0073] The drive axis control data acquisition part 31 receives from the numerical controller 50 as the chronological drive axis control data when the workpiece W is processed, the speed control data (speed command values, speed feedback values) and the position control data (position command values, position feedback values) and stores them in the storage part 33 (steps S11 and S15 of Fig. 4).

[0074] The data association processing part 34 associates the chronological speed control data stored in the storage part 33 and the spatial machining area measurement data with each other (steps S13 and S17 of Fig. 4). For example, the machine tool machines the entire workpiece W while moving the tool T back and forth with respect to the workpiece W. When the tool T makes contact with the workpiece W and when the tool T separates from the workpiece W, the speed command values and the speed feedback values are varied. In this way, the point of variation in the speed command values or the point of variation in the speed feedback values is detected, and the edge position of the workpiece W and thus the outline of the workpiece W can be detected.

[0075] Because the speed command values and the speed feedback values in this embodiment also vary according to the acceleration / deceleration, a value obtained by subtracting a value corresponding to a variation in acceleration / deceleration from the speed command values and the current feedback values is used. This prevents a reversal point when the tool T is reciprocated with respect to the workpiece W from being incorrectly detected as the edge position of the workpiece W. When the tool T is not reciprocated with respect to the workpiece W, the speed command values and the speed feedback values can be used without any processing.

[0076] Specifically, the data association processing part 34 detects, based on the point of variation in the value obtained by subtracting the value corresponding to a variation in acceleration / deceleration from the chronological speed control data as the edge position of the workpiece W, a machining start position and a machining completion position, and thereby generates the first workpiece shape images (outline images) W1α and W1β as shown in Fig. 6 shown.

[0077] The data association processing part 34 also obtains the edge position of the workpiece based on the spatial machining surface measurement data after machining the workpiece W, and thereby generates the second workpiece shape images (outline images) W2α and W2β as shown in Fig.6. For example, when the machining surface measuring device 20 is a vision sensor, the machining surface measurement data is image data. In this case, the data association processing part 34 uses image processing technology to detect the edge position of the workpiece W from the image data, thereby generating the second workpiece shape images (outline images) W2α and W2β. On the other hand, when the machining surface measuring device 20 is an optical microscope, a laser microscope, or a three-dimensional coordinate measuring device, the machining surface measurement data is position data (coordinate data). In this case, the data association processing part 34 detects the edge position of the workpiece W from the position data (coordinate data), thereby generating the second workpiece shape images (outline images) W2α and W2β.

[0078] Then, the data association processing part 34 associates the chronological speed control data and the spatial machining area measurement data of the machined surface with each other to superimpose the first workpiece shape images W1α and W1β and the second workpiece shape images W2α and W2β.

[0079] In the numerical control device 50, the speed control data and the position control data are associated with each other. In this way, the data association processing section 34 associates the chronological speed control data and the position control data stored in the storage section 33 to associate the chronological position control data and the spatial machining area measurement data of the machined surface.

[0080] In the above-described embodiment, the data association processing part 34 can indirectly associate the torque control data from the numerical controller 50 and the machining surface measurement data, identify the torque control data corresponding to the machining surface measurement data of the error position, and identify the position control data corresponding to the torque control data. In this case, as in the above-described case of the speed control data, the torque control data corresponding to the machining surface measurement data of the error position can be identified based on the point of variation in the torque control data.

[0081] In the above-described embodiment, the machining surface defect detection part 35 of the machining surface defect analysis device 30 automatically detects the defect on the machined surface and its position from the image data or the position data (coordinate data) of the workpiece W (machined surface) from the machining surface measuring device 20, but these may also be manually detected. For example, the measurement result (three-dimensional image data or position data) of the machining surface measuring device 20 may be displayed on a monitor or the like, the defect and its position may be visually recognized by the user, and the detected defect position may be manually input to the machining surface defect analysis device 30. LIST OF REFERENCE SYMBOLS 2 heads 3 Holding link 4 support column 5 Base 6 table 10 Machine tool 16 scale 20 Working area measuring device 30 Machining surface error analysis device (analysis device) 31 Drive axle control data acquisition part (first acquisition part) 32 Working area measurement data acquisition part (second acquisition part) 33, 54 storage part 34 Data association processing part 35 Machining surface error detection part 36 Fault-causing drive axle identification part (identification part) 37 Optimal machining direction determination part (machining direction determination part) 38 Machining program analysis part 50 numerical control device (control device) 51 Machining program generation part 52 Position command generation part 53 Individual axis control section 100 numerical control system (control system) CT1, CT2 ... and CTn current detector E1, E2 ... and En encoders M1, M2 ... and Mn servo motors T tool W workpiece

Claims

[1] A control system (100) for a machine tool machining a workpiece (W), the control system comprising: a control device (50) which controls drive axes of the machine tool (10) based on control data, a machining surface measuring device (20) which measures a machined surface of the workpiece (W), and an analysis device (30) which analyses a defect on the machined surface of the workpiece (W), wherein the analysis device (30) contains: a first detection part (31) which receives the chronological control data from the control device (50) during the machining of the workpiece (W), a second detection part (32) which receives spatial machining surface measurement data measured by the machining surface measuring device (20) after machining of the workpiece (W), a storage part (33) which stores the chronological control data received by the first detection part (31) and the spatial machining area measurement data received by the second detection part (32) during machining of the workpiece in at least two machining directions, a data association processing part (34) which associates the chronological control data and the spatial machining area measurement data stored in the storage part (33) with each other when the workpiece is machined in the at least two machining directions, a machining surface error detection part (35) which detects the error on the machined surface of the workpiece (W) and its position based on the spatial machining surface measurement data stored in the storage part (33) when the workpiece is machined in the at least two machining directions, and an identification part (36) that identifies the drive axis causing an error detected by the machining surface error detection part (35) based on the chronological control data and the spatial machining surface measurement data associated with each other by the data association processing part (34), from the error detected by the machining surface error detection part (35) and the machining direction of the control data in correspondence to the error position detected by the machining surface error detection part (35). [2] A control system (100) for a machine tool according to claim 1, wherein the analysis means (30) further includes a machining program analysis part (38) that analyzes a machining program in the control means (50) to set at least the two machining directions, and the control means (50) changes the machining program in accordance with the machining directions set by the machining program analysis part (38) to change the machining direction. [3] The control system (100) for a machine tool according to claim 1, wherein the analysis means further includes a machining direction determining part (37) that determines the machining direction so as to reduce a drive ratio of the drive axis causing the error identified by the identification part, and the control means (50) changes the machining program in accordance with the machining direction determined by the machining direction determining part (37) to change the machining direction. [4] A control system (100) for a machine tool according to claim 3, wherein the control means (50) changes the angle of the workpiece (W) in accordance with the change in the machining direction. [5] A control system (100) for a machine tool according to any one of claims 1 to 4, wherein the control data received by the first detection part (31) is position control data of the drive axes of the machine tool (10), wherein the data association processing part (34): a first workpiece shape image is generated based on the chronological position control data, a second workpiece shape image is generated based on the spatial machining surface measurement data, and the chronological position control data and the spatial machining surface measurement data are associated with each other to superimpose the first workpiece shape image and the second workpiece shape image. [6] A control system (100) for a machine tool according to claim 5, wherein the chronological position control data is machining coordinate information, and the spatial machining surface measurement data is machining coordinate information calculated based on a machining coordinate of the machining surface measuring device (20). [7] A control system (100) for a machine tool according to any one of claims 1 to 4, wherein the first acquisition part (31) receives from the control device (50) chronological position control data and chronological speed control data when the workpiece (W) is machined, which are associated position control data and speed control data of the drive axes of the machine tool (10), wherein the data association processing part (34): based on a variation in the chronological speed control data, a machining start position and a machining end position are detected as an edge position of the workpiece (W) to generate a first workpiece shape image, based on the spatial machining surface measurement data, an edge position of the workpiece (W) is detected in order to generate a second workpiece shape image, the chronological speed control data and the spatial machining area measurement data are associated with each other to superimpose the edge position of the first workpiece shape image and the edge position of the second workpiece shape image, and the chronological speed control data and the chronological position control data are associated with each other in order to associate the chronological position control data and the spatial machining area measurement data with each other. [8] A control system (100) for a machine tool according to any one of claims 1 to 4, wherein the first acquisition part (31) receives from the control device (50) chronological position control data and chronological speed control data when the workpiece (W) is machined, which are associated position control data and speed control data of the drive axes of the machine tool (10), wherein the data association processing part (34): based on a variation in a value received by subtracting a value corresponding to a variation in acceleration / deceleration from the chronological speed control data as an edge position of the workpiece (W), a machining start position and a machining completion position are detected to generate a first workpiece shape image, based on the spatial machining surface measurement data, an edge position of the workpiece (W) is detected in order to generate a second workpiece shape image, the chronological speed control data and the spatial machining area measurement data are associated with each other to superimpose the edge position of the first workpiece shape image and the edge position of the second workpiece shape image, and the chronological speed control data and the chronological position control data are associated with each other in order to associate the chronological position control data and the spatial machining area measurement data with each other. [9] A control system (100) for a machine tool according to any one of claims 1 to 8, wherein the defect on the machined surface of the workpiece is a streak or a projection. [10] A control system (100) for a machine tool according to claim 1, wherein the control data is a command value or a feedback value, where the command value is a position command value, a speed command value or a torque command value, and where the feedback value is a position feedback value, a velocity feedback value, or a current feedback value.

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