Patent Application
20250205844
The present invention relates to a machine tool that processes workpieces (machining objects or measurement objects), such as NC (numerical control) processing machines and machining centers. In particular, the present invention relates to a tool holder attachment state detection method and a tool holder attachment state detection device for determining an attachment abnormality indicating whether a tool holder to which a tool is attached is properly attached to a spindle in a machine tool having an automatic tool changer (ATC) that selects tools as appropriate and performs the attachment and detachment, and a machine tool having the tool holder attachment state detection device. Further, the present invention relates to a displacement detection method and a displacement detection device for detecting a displacement from a reference state of a tool holder to which a tool is attached and a machine tool having the displacement detection device.
A machining center (MC) is a device that automatically selects various tools according to a machining process, automatically attaches the selected tools to a spindle, and performs various types of machining. In the MC, tools are changed using an automatic tool change (ATC: automatic tool holder change) device. The ATC device automatically takes out a tool holder to which a tool is attached, from a tool magazine and automatically attaches the taken-out tool holder to a spindle. The tool holder to which the tool is attached has a tapered fitting portion, and this fitting portion is fitted into a tapered fitted portion formed in the spindle of the MC. However, if chips or the like adhere to the fitting portion of a tool holder, a tool holder may be attached in a state that an axis of a tool holder is tilted. If machining is performed in this state, a shake (displacement from a reference state) will occur in the tool with rotation, and the machining accuracy of the workpiece will drop significantly.
As a technology for detecting a displacement from a reference state of a tool holder which occurs due to an abnormal attachment state (chuck error) or the like of the tool holder, PTL 1 discloses “a machine tool in which a tool holder to which a tool is attached is attached to a spindle, the spindle is rotationally driven to process a workpiece, the machine tool including a measuring means for measuring a displacement of an outer circumferential surface of a flange of the tool holder attached to the spindle and a determination means for determining an abnormality in the machine tool from measurement data obtained from the measuring means”. Furthermore, PTL 1 also discloses that “the machine tool further includes a basic data storage means for storing measurement data of the displacement of the outer circumferential surface of the flange of the tool holder attached to the spindle as basic data, and a true measurement data calculation means to calculate true measurement data by comparing the basic data with the measurement data measured by the measuring means, and the determination means determines an abnormality in the machine tool from the true measurement data calculated by the true measurement data calculation means”.
In addition, PTL 1 also discloses that “if the tool holder 2 has a notch, as shown in FIG. 10(b), the phase of the measurement data is corrected so that the center of any one notch 2C of the two notches 2C is 0° ”, and “a calculated magnetic uneven pattern (magnetic pattern during machining) and a magnetic uneven pattern during setup (magnetic pattern during setup) stored in a memory 20 are compared and a position of the calculated magnetic uneven pattern corresponding to 0° is determined”.
Further, according to PTL 2, an eddy current sensor is provided as an outer circumferential surface detection means provided close to an outer circumferential surface of a flange, and when there is a notch in the flange portion of a tool holder, the detection data of the surface position of the outer circumferential surface of the flange detected by the sensor at a predetermined period is interpolated to calculate interpolated detection data with an interpolation period shorter than a predetermined period and generate interpolated data.
Furthermore, in paragraph 0026 and the like of PTL 2, it is stated that the detection accuracy and resolution of detectors such as eddy current sensors decrease as the detection distance increases, and that the distance of the notch portion changes rapidly in the detection direction, so that when the average distance of this portion is detected, the detection signal becomes dull. Therefore, PTL 2 describes that correction is performed so that the larger the detection distance becomes, the smaller the value of the detection data of the notch portion becomes.
In the method of measuring the displacement of the outer circumferential surface of the flange of the tool holder and detecting the displacement from the reference state caused by chuck errors or the like, or in the method of detecting chuck errors using this, it is necessary to find the relative difference between pieces of measurement data from a sensor. For this purpose, it is necessary to perform phase correction on each piece of measurement data. Regarding this phase correction, PTL 1 describes a method that uses a signal derived from a notch in a flange or a characteristic magnetic uneven pattern.
However, in recent years, as the machining accuracy of tool holders has improved, the shape deviation of the flange portion has become significantly smaller than before. Therefore, the present inventors have found that it is becoming difficult to find a characteristic magnetic uneven pattern unique to a tool holder, as in the method described in PTL 1. This is because the characteristic magnetic uneven pattern is obtained due to the non-uniformity (deviation) in shape inherent to each tool holder (typically the flange portion).
Furthermore, the present inventors have also found that even if an attempt is made to perform phase correction using a signal derived from the notch, for example, if a flange portion has two notches and the notches are arranged at 180-degree symmetrical positions, a magnetic uneven pattern that is close to the 180-degree rotational symmetry occurs. Thus, for example, the phase cannot be determined only by comparing the magnetic pattern during machining and the magnetic pattern during setup.
In addition, according to PTL 2, interpolation of data can reduce errors in shake measurement due to the influence of notches in the flange portion. However, if there is a deviation in the sampling start position or unevenness in the rotation speed, the detection data of the surface position of the outer circumferential surface of the flange may become inaccurate and the eccentricity may not be calculated with high accuracy.
Further, for example, if a shake occurs due to the trapping of chips, complicated processing is required when there are two notches and the sampling start position is largely shifted, or when there is a lot of noise or the like. Therefore, detectors such as eddy current sensors must be installed in locations where they are not affected by coolant to ensure more stable and highly accurate measurements.
The present invention has been made to solve the above-mentioned problems of the prior art, and enable matching phases of pieces of measurement data in the reference state and during displacement detection easily and accurately regardless of sensor types, the number of notches in the outer circumferential surface of a flange of a tool holder, the symmetry of a rotation direction, changes in the shape of a flange portion 11B (particularly the thickness of a measurement portion), magnetization, quenching depth, engraving, environment, and the like, and improve the detection accuracy of the displacement from a reference state of a tool holder, which occurs due to a chuck error (attachment abnormality) of a spindle of a tool holder, or the like. Another object of the present invention is to improve the detection accuracy of a chuck error detection method that applies the displacement detection described above to detect an attachment abnormality of the tool holder attached to a spindle.
The configuration of the present invention for achieving the above-mentioned objects is as follows.
[10] A machine tool that is equipped with a tool holder attachment state detection device that determines whether a chuck error indicating whether a tool holder with a tool attached thereto is properly attached to a spindle has occurred, a sensor that measures an outer circumferential shape of a flange portion of the tool holder; means for, during setup, attaching the tool holder to the spindle without the chuck error, starting rotation of the tool holder after stopping the tool holder at a predetermined angle, starting counting the number of notches formed in the flange portion based on a change in a signal from the sensor, and storing a time T taken to obtain measurement data during setup from the sensor from the notch detected last and a count N at that time after rotating the tool holder at least once; and means for, during machining, starting rotation of the tool holder after stopping the tool holder at the predetermined angle, starting counting notches formed in the flange portion based on a change in the signal from the sensor, making the count N and the time T stored during the setup correspond to each other, and obtaining measurement data during machining from the sensor; and a data processing device that determines the chuck error based on the measurement data during setup and the measurement data during machining.
[11] A displacement detection method for detecting a displacement from a reference state of a tool holder that is attached to a spindle and rotates integrally with the spindle by a comparison of measurement data from a sensor that measures an outer circumferential shape of a flange portion of the tool holder with measurement data in the reference state, wherein each piece of the measurement data is obtained by rotating the tool holder after stopping the tool holder at a predetermined angle, starting counting the number of notches formed in the flange portion, and making a time T taken to obtain the pieces of measurement data from the sensor from the notch detected last and a count N at that time after rotating the tool holder at least once correspond to each other.
[12] The displacement detection method according to [11], wherein the comparison is performed by comparing each of eccentricity vectors which are obtained by performing Fourier analysis on the each piece of measurement data and calculating an amplitude and a phase of one peak component.
[13] A displacement detection device that detects a displacement from a reference state of a tool holder that is attached to a spindle and rotates integrally with the spindle, the device including: a data comparison unit that detects a displacement by comparing measurement data from a sensor that measures an outer circumferential shape of a flange portion of the tool holder with measurement data in the reference state; and a phase adjustment unit that adjusts an acquisition timing of the measurement data, wherein the phase adjustment unit rotates the tool holder after stopping the tool holder at a predetermined angle, starts counting the number of notches formed in the flange portion, makes a time T taken to obtain each piece of measurement data from the sensor from the notch detected last and a count N at that time correspond to each other after rotating the tool holder at least once so that the sensor acquires the each piece of measurement data.
[14] The displacement detection device according to [13], wherein the data comparison unit performs Fourier analysis on each piece of the measurement data, calculates eccentricity vectors from an amplitude and a phase of one peak component, and compares the eccentricity vectors.
[15] A machine tool including the displacement detection device according to or [14].
According to the present invention, it is possible to match phases of measurement data in the reference state and during displacement detection easily and accurately regardless of sensor types, the number of notches in the outer circumferential surface of a flange of a tool holder, the symmetry of a rotation direction, changes in the shape of a flange portion 11B (particularly the thickness of a measurement portion), magnetization, quenching depth, engraving, environment, and the like, and improve the detection accuracy of the displacement from a reference state of a tool holder which occurs due to a chuck error (attachment abnormality) or the like. Another object of the present invention, it is also possible to improve the detection accuracy of a chuck error detection method that applies the displacement detection described above to detect an attachment abnormality of the tool holder attached to a spindle.
For example, the reference state is assumed to be “during setup” where chuck errors do not occur. During setup, the tool holder is attached to the spindle without any chuck errors, and rotation of the tool (that is, the tool holder) is started. Next, a change in the signal from the sensor is detected and counting of the number of notches formed in the flange portion is started. After rotating the tool holder at least once, the time T taken to obtain the measurement data during setup (in the reference state) from the sensor from the notch detected last and the count N at that time are stored. Next, the displacement is detected “during machining”. During machining, the rotation of the tool is started in the same procedure as during setup, and the count N and time T are made to correspond to each other to obtain measurement data. Since the measurement data during setup and the measurement data during machining are obtained in a state where the time T and the count N correspond to each other, the pieces of measurement data are in phase and therefore, the pieces of data can be compared easily without comparing the data waveforms. Based on the results of this comparison, a displacement can be detected and chuck errors can be determined accordingly.
First, the terms used in the present specification will be explained. Note that terms not explained below shall be used with meanings commonly understood by those skilled in the art based on the common general knowledge at the time of filing of this application.
In the present specification, the term “reference state” refers to a state that serves as a relative reference for displacement detection. That is, the displacement detection method of the present invention is for detecting a relative displacement from the position of a tool holder in this reference state. The reference state is not particularly limited and may be any state, but when the detected displacement of the tool holder is used to determine chuck errors, it is preferable that the reference state is a state in which no chuck errors occur. Preferably, such a state is during setup of a machine tool, that is, before machining a workpiece.
However, the “reference state” in the displacement detection method in the present specification is not limited to the above, and may include a state in which machining of a workpiece has already started, and a state in which no tool is attached to the tool holder (a state in which a tool holder without tool is attached to a spindle).
Furthermore, in the present specification, “displacement” refers to a relative change in the rotational position during displacement detection (during chuck error detection) from the rotational position in the reference state of the tool holder. Typically, the “displacement” refers to a state in which the rotation axis of the tool holder is tilted or moved compared to the reference state, causing a “shake” in its rotation.
Furthermore, in the present specification, “measurement data A” means measurement data in the reference state, and “measurement data B” means measurement data during displacement detection. By comparing the measurement data A and the measurement data B, a displacement of the tool holder can be detected. Furthermore, by acquiring the measurement data A “during setup” and acquiring the measurement data B “during machining,” chuck errors can be determined based on the displacement described above.
A typical example of the tool holder being displaced when compared with the reference state is a state in which a chuck error of the tool holder occurs during machining, that is during displacement detection, with respect to the reference state, that is during setup.
In the following, one application example of a displacement detection method of the present invention will be described, in which the reference state is taken as the setup time, and detects whether a displacement has occurred in the tool holder during machining, and this is used to determine a chuck error of the tool holder, and the configuration of a displacement detection device for detecting this will be explained.
A machining center (MC) is a numerically controlled machine tool that performs various types of machining such as milling, drilling, boring, and screw tapping with a workpiece attached thereto by only one machine. A large number of cutting tools 9 are stored in a tool magazine of the MC, and the tools 9 are automatically changed under computer control to perform machining of the workpiece. Since the main purpose is machining, the environment in which the MC is installed often contains fine particles of oil mist and dust, and in addition, there are often dust and chips around the workpiece and the spindle.
The tool 9 is automatically attached to and detached from the spindle 26 by the ATC device. The attachment and detachment is performed by a control device 22 of the MC executing a program. The tool 9 can be integrally attached to the tool holder 11. A fitting portion 11A of the tool holder 11 is pressed against a tapered fitted portion 26A of the spindle 26. As a result, the fitting portion 11A and the fitted portion 26A come into close contact, and the tool holder 11 is attached (chucked) to the spindle 26, and as a result, the tool 9 is fixed to the spindle 26.
The sensor 1 is a measuring means that measures the distance d to the outer circumferential surface of the flange portion 11B of the tool holder 11 as an electrical signal. The sensor 1 may be an eddy current sensor. The sensor 1 is not limited to an eddy current sensor, and may be any other sensor type as long as the sensor 1 can measure the distance d from a certain measurement point to the outer circumferential surface of the tool holder 11. In this case, the sensor 1 is not limited to a non-contact-type sensor, but may be a contact-type sensor. Further, the MC uses various types of tools 9 depending on the machining content. Therefore, the number of tool holders 11 increases according to the number of tools 9. The sensor 1 is required to be compatible with these many tool holders 11.
An eddy current sensor is a sensor that uses a high-frequency magnetic field to measure the distance d. An eddy current sensor generates a high-frequency magnetic field by passing a high-frequency current through an internal coil. A feature of eddy current sensors is that it requires a linearization circuit to correct the linearity, so the measured distance d is short, but it is resistant to harsh environments where water, oil, and the like are scattered.
An optical sensor is a sensor that emits visible light, infrared rays, and the like from a light projector, detects changes in the light reflected by a detection object with a light receiver, and obtains an output signal. A laser sensor is a sensor that uses laser light instead of visible light or infrared light. A feature of optical sensors and laser sensors is that they can increase the measured distance d, but they are vulnerable to harsh environments where water, oil, and the like are scattered.
Contact-type sensors are resistant to harsh environments where water, oil, and the like are scattered, but it is difficult to install them at arbitrary locations. Therefore, non-contact-type sensors such as eddy current sensors, optical sensors, laser sensors, and the like, which can perform accurate measurements even in harsh environments where water, oil, and the like are scattered, and whose attachment position can be freely set are preferred as the sensor 1.
When an eddy current sensor is used as the sensor 1, since the measurement distance is short, it is desirable to attach a head 27 to which the spindle 26 is attached.
When using an eddy current sensor, when the outer circumferential surface of the flange portion 11B is measured, the shape to be measured, that is, the outer circumferential shape of the flange portion 11B estimated from the change in the distance d, may not be a perfect circle due to the influence of magnetization, the thickness (area) of the measurement portion and the like. Therefore, when an eddy current sensor is used as the sensor 1, simply measuring the outer circumferential surface of the flange portion 11B only during machining may include an error when calculating the eccentricity, and the detection accuracy may deteriorate.
The data processing device 3 detects the attachment state of the tool holder 11 based on the distance d measured by the sensor 1, and includes an A/D converter 4, a CPU 6, a memory 5, an input/output circuit 7, and the like. The A/D converter 4 converts the electrical signal indicating the distance d outputted from the sensor 1 into a digital signal and outputs the digital signal to the CPU 6. The CPU 6 determines the eccentricity based on the measurement data from the sensor 1 converted into this digital signal. Then, the calculated eccentricity is compared with an allowable value, and if the eccentricity exceeds the allowable value, it is determined that a chuck error (attachment abnormality) has occurred. The data processing device 3 then outputs the result to the control device 22 that controls the MC via the input/output circuit 7.
The shape of the tool holder 11 is approximately the same because the outer circumferential shapes of the fitting portion 11A and the flange portion 11B are standardized. Therefore, by measuring the outer circumferential shape of the flange portion 11B, the attachment state of the tool holder 11 can be determined. The outer circumferential shape is determined by rotating the tool holder 11 once and measuring the distance d. As shown in
The CPU 6 obtains and stores a basic eccentricity vector unique to the tool holder from measurement data during setup (measurement data A) of the tool holder 11 attached without any chuck errors (attachment abnormalities). Then, the CPU 6 obtains a measured eccentricity vector from the measurement data during machining (measurement data B). The CPU 6 compares the basic eccentricity vector and the measured eccentricity vector to calculate a true eccentricity vector. Then, the CPU 6 determines the eccentricity from the true eccentricity vector, and determines whether there is a chuck error (attachment abnormality). By doing the above, even if the sensor 1 is an eddy current sensor, the eccentricity inherent in the tool holder 11 due to magnetization, thickness, and the like can be canceled, and the eccentricity related to displacement can be calculated more accurately.
By the way, in order to compare the measurement data during setup (measurement data A) and the measurement data during machining (measurement data B), it is necessary to match their phases (the angle of the tool holder, which is the starting point of comparison). When the tool holder 11 has a notch 11C, the phase can be corrected (specifically, the 0-degree position can be determined) based on the detection signal from the notch 11C.
However, when there are two or more notches 11C, it is necessary to determine which of the two notches 11C to correct the phase based on (which one is located at the 0-degree position). However, the measurement by the sensor 1 may cause fluctuations or timing shifts. In addition, if the notches 11C are located at 180-degree symmetrical positions, measurement data close to 180-degree rotational symmetry will appear, and it is difficult to determine the phase simply by comparing the measurement data during setup and the measurement data during machining.
First, setup is performed to obtain a basic eccentricity vector (step S30). The setup is performed before the MC starts machining the workpiece. First, the tool holder 11 is attached to the spindle 26 (step S31). Since this is before the start of machining, chips will not be caught between the fitting portion 11A and the fitted portion 26A, and the tool holder 11 will be attached to the spindle 26 without chuck errors (attachment abnormalities). The control device 22 once rotates the tool holder 11 in this state, and stops the tool 9 (that is, the tool holder 11) at a predetermined angle (step S32).
Next, the control device 22 outputs a trigger signal for starting counting the number of notches 11C to the data processing device 3 (step S33), and starts rotating the tool holder 11 and the tool 9 (step S34). The measurement data from the sensor 1 changes from ON to OFF at the position of the notch 11C, as shown in
The data processing device 3 stores the time T taken for the sensor to the measurement data during setup (measurement data A) from the time when the notch 11C is detected last and the count N at that time after rotating the tool holder 11 at least once (step S36). In other words, the notch count N counted until the measurement data during setup (measurement data A) is acquired and the time T that has elapsed until the measurement data A is acquired after the notch is detected last are stored.
The measurement data during setup is the measurement data from the sensor 1 after step S36. This measurement data is obtained after rotating the tool holder 11 at least once, but may be obtained after rotating the tool holder 11 multiple times in order to improve accuracy. Alternatively, the measurement data may be an average of a plurality of pieces of measurement data.
Even if the tool 9 (that is, the tool holder 11) is stopped at a predetermined angle and the rotation of the tool holder 11 is started, the measurement for determining a chuck error is performed after the rotation becomes stable. Therefore, in order to compare the measurement data A during setup and the measurement data B during machining, it is necessary to find the starting position for acquiring the pieces of measurement data in a stable rotation state, that is, a state where the tool holder 11 is rotated, and match the pieces of measurement data.
In the present detection method, the count N of the notches 11C and the time T that has elapsed after the notch was detected last are used to determine the starting position of acquiring this measurement data. By doing so, the measurement start position can be accurately determined.
In addition to the above, the waveform during setup measurement and the waveform of the measurement data during machining may be compared, and phases may be finely adjusted based on the shapes of the waveforms, for example, detection signal derived from the notch 11C as shown in
Since the time T is originally short because it is the time elapsed after the notch was detected last, and the rotation is almost stable, there is almost no deviation in the time T between during setup and during machining which will be described later. Similarly, there is no difference in the count N until the rotation becomes stable between during setup and during machining which will be described later.
By determining the measurement data acquisition start position as described above, the accuracy is improved, for example, compared to simply determining the acquisition start position based on the time T0 which is the time to the start of measurement data acquisition from the start of rotation (the time T0 is longer and has higher possibility of occurrence of deviation).
Returning to
Next, the data processing device 3 performs Fourier analysis (FFT analysis) on the interpolated measurement data A during setup and calculates and stores the amplitude and phase of one peak component in the waveform of the measurement data (step S38). A basic eccentricity and basic eccentricity vector are calculated from the obtained amplitude and phase (step S39), and are stored to end the setup.
In addition to the above, using the measurement data during setup and the measurement data during machining (both before interpolation), the phase may be corrected (the 0-degree position may be corrected) based on the detection signal of the notch 11C.
Next, when there is a notch 11C, the data processing device 3 restores a sine wave using the interpolation means from the measurement data during machining obtained in step S46, and stores the sine wave (step S47), similarly to during setup. Next, the data processing device 3 performs Fourier analysis (FFT analysis) on the interpolated measurement data during machining, and calculates and stores the amplitude and phase during machining of one peak component (step S48). A measured eccentricity and a measured eccentricity vector are calculated from the amplitude and phase during machining (step S49).
The data processing device 3 determines a chuck error (attachment abnormality) based on the true eccentricity (step S51). As a result, if it is determined that the chucking is properly performed (true eccentricity≤ allowable value) (step S52), machining is directly started (step S53). If the true eccentricity exceeds the allowable value, it is determined that a chuck error (attachment abnormality) has occurred (step S54). In this case, the data processing device 3 instructs the control device 22 to reattach the tool holder 11 or to confirm the attachment state (step S55).
According to the present embodiment, a chuck error (attachment abnormality) is determined based on the “true eccentricity” obtained by removing the eccentricity inherent in the tool holder 11, so that more accurate detection can be performed. Further, in the present embodiment, since the direction of eccentricity can be specified from the true eccentricity vector, the position of trapped chips and the like can also be specified.
Note that the eccentricity may be calculated from the average value of the pieces of measurement data A and B measured multiple times. In this way, reliability is improved and more accurate determination can be performed.
The measurement data during setup and the measurement data during machining are originally based on the data obtained by the sensor 1 measuring the outer circumferential surface of the flange portion 11B, so they originally have similar waveforms. Therefore, if the measurement data is obtained by matching the count N and time T during setup and machining, the phases of both pieces of measurement data can be corrected without any more complicated processing.
Furthermore, if there are two notches 11C and they are located at 180-degree symmetrical positions, the “OFF” region will appear in the measurement data at a corresponding period. From the waveform of the measurement data, it is difficult to identify from which of the two notches 11C this “OFF” region originates. However, since the data processing device 3 makes the counts N taken to obtain the measurement data during setup and during machining match each other after stopping the tool holder at a predetermined angle, it is possible to differentiate them even in this case. Furthermore, setting the counts N to be the same during setup and during machining is useful for phase adjustment not only when there are two notches 11C, but also when there is one notch 11C, there are three notches 11C at 120-degree intervals, and there are more notches 11C.
In the measurement data, when a shake occurs, the fundamental frequency component (first-order component) obtained by Fourier analysis changes significantly. Further, changes in the measurement data from the sensor 1 shown in
Furthermore, in the present embodiment, the eccentricity is obtained by measuring the displacement of the outer circumference of the tool holder 11, performing Fourier analysis on the measurement data to extract one peak component, and obtaining the amplitude value thereof. However, the method for obtaining the eccentricity is not limited to this method. For example, the maximum value and minimum value of the measurement data may be calculated and the eccentricity may be calculated from the difference between them.
Further, in the present embodiment, the flange portion 11B of the tool holder 11 is used as the measurement point of the sensor 1. However, the measurement point of the sensor 1 is not limited to this, and may be changed appropriately depending on the measurement situation and the like. For example, the measurement point may be the cutting edge of the tool 9 (the part where the workpiece is cut). When the cutting edge of the tool 9 is used as a measurement point, the eccentricity of the part to be directly machined can be measured, and chuck errors can be detected more reliably. In this case, the position of the tool may finally be adjusted based on the measurement data before interpolation.
Furthermore, if the sensor 1 is an eddy current sensor, it is desirable to attach the sensor to the head 27 to which the spindle 26 is attached in order to shorten the measurement distance, but the attachment location of the sensor 1 is not limited to this. In particular, according to the present embodiment, even if the sensor 1 is an optical or laser sensor, which is vulnerable to harsh environments where water, oil, and the like are scattered, the distance d can be increased to fix and attach the sensor 1 at a predetermined position other than the head 27. Therefore, when the sensor 1 is an optical or laser sensor, it can be installed at any position. In particular, the sensor 1 can be easily installed at a position that is not affected by coolant (a position that is not exposed to coolant) in order to ensure more stable and highly accurate measurements.
Further, although the present embodiment has been described as being applied to an MC, it can be applied to any machine tool that uses an ATC device.
The displacement detection device 101 includes a control unit 102, a storage unit 103, a communication unit 104, an input/output unit 105, a phase adjustment unit 106, and a data comparison unit 107.
The control unit 102 includes a processor as hardware, and controls each unit of the displacement detection device 101 by causing the processor to execute a program stored in a storage device of the storage unit 103, which will be described later.
The processor included in the control unit 102 includes a microprocessor, a processor core, a multiprocessor, an ASIC (application-specific integrated circuit), an FPGA (field programmable gate array), a GPGPU (General-purpose computing on graphics processing units), and the like.
The storage unit 103 includes a storage device as hardware, and provides a work area for the processor, stores and reads programs for controlling each unit of the displacement detection device 101, stores and reads the measurement data from the sensor 1, stores and reads the time T and count N and the like.
The storage device included in the storage unit 103 includes, for example, ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), flash memory, SSD (Solid State Drive), and the like.
The communication unit 104 is configured to include a communication interface, and performs transmission and reception of various pieces of data between the displacement detection device 101 and an external network and an external device under the control of the control unit 102. Further, the input/output unit 105 is configured to include an input/output interface, and receives the input of instructions to the displacement detection device 101 and outputs displacement detection results.
The input device connected to the input/output unit 105 may be a keyboard, a mouse, a scanner, a touch panel, or the like. Further, the display device connected to the input/output unit 105 may be a liquid crystal display, an organic EL (Electro Luminescence) display, or the like. Further, the display device may be configured integrally with the input device. In this case, the display device may be a touch panel display that provides a GUI (Graphical User Interface).
Note that the displacement detection device 101 may not have the communication unit 104 and the input/output unit 105.
The displacement detection device 101, which includes a processor, a storage device, a communication interface, and an input/output interface, is typically a computer. Although the displacement detection device 101 is provided separately from a computer (not shown) that controls the machine tool 100, the present invention is not limited to the above, and the displacement detection device 101 may further have a function of controlling the machine tool 100 of the present invention. In other words, the computer that controls the machine tool 100 may have the function of the displacement detection device 101.
Next, the phase adjustment unit 106 is a function realized by the processor of the control unit 102 executing a program stored in the storage device of the storage unit 103.
The phase adjustment unit 106 controls the sensor 1 that measures the outer circumferential shape of the flange portion of the tool holder 11, and adjusts the timing of acquiring the measurement data (measurement data A and B). Note that the structure and function of the sensor 1 are the same as those of the sensor included in the tool holder attachment state detection device 50, and the description thereof will be omitted.
In a reference state (for example, “during setup”), the phase adjustment unit 106 rotates the tool holder after stopping it at a predetermined angle, starts counting the number of notches formed in the flange portion, rotates the tool holder at least once, and then, causes the sensor to acquire the measurement data (measurement data A) in a state where the rotation becomes stable. The phase adjustment unit 106 detects the time T (TA) taken to obtain the measurement data A from the notch detected last and the count N (NA) at that time, and stores them in the storage unit 103.
When detecting the displacement (for example, “during machining”), the tool holder is rotated after being stopped at a predetermined angle, the counting of the number of notches formed in the flange portion is started, and after the tool holder is rotated at least once, the sensor acquires the measurement data B. At this time, the time T taken to obtain the measurement data from the sensor from the notch detected last and the count N at that time are made to match the time TA and the count NA, respectively.
In other words, the measurement data B is acquired by the sensor so that the time T and count N match the time TA and count NA, respectively.
When acquiring the pieces of measurement data A and B, the phase adjustment unit 106 rotates the tool holder after stopping it at a predetermined angle (the same angle), starts counting the number of notches formed in the flange portion, rotates the tool holder at least once, and then, makes the times T taken to obtain the pieces of measurement data from the sensor from the notch detected last (the times T taken to obtain the measurement data from the time when the notch was detected last) and the counts N at that time match each other. As a result, it is not necessary to match the phases of the pieces of obtained measurement data. Note that the details of the above phase matching are the same as those in the tool holder attachment state detection device 50 that has already been described, so the description will be omitted.
The displacement of the tool holder 11 can be detected by measuring a change (shift) in the measurement data from the sensor 1 that measures the outer circumferential shape. However, in order to measure the shift in measurement data, it is necessary to match the phases of these pieces of measurement data.
Since the displacement detection device 101 includes the phase adjustment unit 106, even if pieces of measurement data have mutual changes and it is unclear as to the reference point to compare them, it is possible to easily obtain pieces of measurement data with matched phases without any need to perform difficult phase matching based on waveforms.
The data comparison unit 107 is a function realized by the processor of the control unit 102 executing a program stored in the storage device of the storage unit 103. The data comparison unit 107 compares the measurement data A and the measurement data B to detect a displacement.
As one form of the displacement detected by the data comparison unit 107, it is preferable to be the true eccentricity already described in one embodiment. By calculating the true eccentricity from the pieces of measurement data A and B, the relative displacement can be detected after canceling the eccentricity inherent to the tool holder 11.
Although the method for calculating the true eccentricity from the pieces of measurement data A and B has already been explained, one example thereof will be briefly explained again. The data comparison unit 107 interpolates the measurement data A in a reference state (for example, “during setup”) as necessary, and calculates the amplitude and phase of one peak component by FFT analysis. Further, the data comparison unit 107 calculates an eccentricity vector and an eccentricity, which is the magnitude thereof, from the amplitude and phase of one peak component, for example.
Next, the data comparison unit 107 interpolates the measurement data B during displacement detection (for example, “during machining”) as necessary, and calculates the amplitude and phase of one peak component by FFT analysis. Furthermore, the data comparison unit 107 calculates the eccentricity vector and the eccentricity using the same method as in the processing of the measurement data A.
The data comparison unit 107 calculates the difference with each of the eccentricity vectors by vector calculation, and calculates the true eccentricity (relative eccentricity). The true eccentricity reflects the displacement of the tool holder 11 from the reference state, and for example, by comparing the true eccentricity with a predetermined threshold, it is possible to determine whether the tool holder 11 has been displaced.
Next, a displacement detection method using the displacement detection device 101 will be explained.
First,
The method for acquiring the measurement data A is the same as the method for acquiring the measurement data “during setup” described above.
First, in step S70, the tool holder 11 is stopped at a predetermined angle. The angle at which the tool holder is stopped may be any value, as long as it is the same as the angle at which it is stopped before the acquisition of the measurement data B.
The reference state is a state that should serve as a reference for displacement detection, and for example, the reference state is preferably attained before machining, that is, during setup of the machine tool, but may also be attained after the start of machining.
Next, in step S71, rotation of the tool holder 11 is started. When the tool holder 11 starts rotating, the output of the sensor 1 changes from ON to OFF with passing through the notch, making it possible to count the number of notches. When the rotation of the tool holder 11 is started, counting of the number of notches is also started (step S72).
Next, in step S73, when the rotation of the tool holder 11 becomes stable, the measurement data A is acquired. At this time, the time TA from the detection of the notch detected last to the acquisition of the measurement data is also acquired. In addition, the count NA of notches until the acquisition of the measurement data is also acquired. That is, in this step, the measurement data A, the time T (TA), and the count N (NA) are acquired.
Although the acquisition flow of the measurement data A has been described so far, the displacement detection method according to the embodiment of the present invention may not include the procedure for acquiring the measurement data A described above. That is, the measurement data A, the time TA, and the count NA may be obtained and stored in advance. In this case, the measurement data A, the time TA, and the count NA obtained in advance may be used for displacement detection without newly obtaining the measurement data A. Note that the tool holder 11 used to obtain the measurement data A and measurement data B is the same.
Further, after step S73, the measurement data may be subjected to Fourier analysis (FFT analysis) to calculate the amplitude and phase of one peak component. Furthermore, the eccentricity and the eccentricity vector may be calculated from this amplitude and phase.
First, in step S80, the tool holder is stopped at a predetermined angle. This angle is the same angle as when acquiring the measurement data A.
One form of timing for displacement detection is during or after machining of a workpiece when the measurement data A is acquired during setup. As already explained, in a machine tool such as a machining center (MC), a workpiece is machined while changing tools. In this case, chips or the like may be caught in the chuck portion during or after machining, resulting in a chuck failure, and the tool holder 11 may become eccentric. The present displacement detection method can easily detect the relative eccentricity (displacement) of the tool holder 11 from the reference state as described above with high accuracy.
Next, in step S81, rotation of the tool holder is started, and along with this, counting of the number of notches is also started (step S82).
Next, in step S83, the measurement data B is acquired.
The measurement data B is obtained by making the time T and count N match the time TA and count NB, respectively. That is, after the tool holder 11 is stopped at a predetermined angle, the tool holder starts rotating and rotates until the count NA is reached. The measurement data B is acquired when the time TA has elapsed after the count NA is reached.
Since the present displacement detection method includes step S83, the phases of the acquired measurement data A and measurement data B are matched. If the tool holder 11 is displaced due to a chuck error or the like between during the reference state and during detection, and the waveforms of the pieces of measurement data change, it may be difficult to compare these waveforms and match the phases. However, in this displacement detection method, phase matching can be performed without the need to directly compare the waveforms (pieces of measurement data whose phases are already matched are acquired).
Next, in step S84, the true eccentricity is calculated from the pieces of measurement data A and B. The method for calculating the true eccentricity has already been explained. In this way, the displacement of the tool holder 11 can be detected. The detected displacement (true eccentricity) can be used for determining the attachment state of the tool holder and the like as described above.
As already explained, the true eccentricity can be calculated using various methods. For example, the maximum value and the minimum value of the measurement data may be calculated and the true eccentricity may be calculated from the difference between them.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-051017 | Mar 2022 | JP | national |
| 2022-126105 | Aug 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/031343 | 8/19/2022 | WO |
